Paper 2 Micro II

FOODBORNE ILLNESS

Lcdo. Moran Z. Jean Pierre.Instituto de Especialización Tecnológica en AlimentosLicenciatura en NutriciónEscuela Superior Politécnica del LitoralCampus Gustavo Galindo, Km 30.5 vía PerimetralGuayaquil – [email protected]

The vast majority of foodborne illnesses are the direct result of microbiological hazards. These hazards are caused by pathogenic microorganisms. Pathogenic organisms can include: bacteria, viruses, parasites, and mold. _________________________________________________________________________________________________

SUMMARY

Each year, millions of people around the world get sick from contaminated food. Common culprits include bacteria, parasites and viruses. Symptoms range from mild to serious. Foodborne disease is extremely costly. Health experts estimate that the yearly cost of all foodborne diseases in the United States is 5 to 6 billion dollars in direct medical expenses and lost productivity.

Foodborne illness usually arises from improper handling, preparation, or food storage. Good hygiene practices before, during, and after food preparation can reduce the chances of contracting an illness. There is a consensus in the public health community that regular hand-washing is one of the most effective defenses against the spread of foodborne illness. The action of monitoring food to ensure that it will not cause foodborne illness is known as food safety. Foodborne disease can also be caused by a large variety of toxins that affect the environment. For foodborne illness caused by chemicals, see Food contaminants.

Additional episodes of illness were caused by unspecified agents, including known agents with insufficient data to estimate agent-specific illness, known agents not yet recognized as causing foodborne illness, substances known to be in food but of unproven pathogenicity, and unknown agents. To estimate these additional illnesses, we used data from surveys, hospital records, and death certificates to estimate illnesses, hospitalizations, and deaths.

Key words: Foodborne, illness, contaminated food, diseases, health, bacteria, viruses, fungi, parasites.

INTRODUCTION

Infectious diseases spread through food or beverages are a common, distressing, and sometimes life-threatening problem for millions of people around the world. There are more than 250 known foodborne diseases. They can be caused by bacteria, viruses, or parasites. Natural and manufactured chemicals in food products also can make people sick. Some diseases are caused by toxins (poisons) from the disease-causing microbe (germ), others by the human body’s reactions to the microbe itself.

Bacteria that cause disease are called “pathogens.” When certain pathogens enter the food supply, they can cause food-borne illness. They can grow in just about any food, but are fond of protein foods, such as meat, poultry, seafood, eggs, and dairy products in particular, as well as high-protein vegetables such as beans and grains.

Parasites may be present in food or in water and can be identified as causes of foodborne or waterborne illness around the world. They range in size, from tiny single-celled organisms to worms visible to the naked eye. Their lifecycle may also vary. While some parasites use a permanent host, others go through a series of developmental phases using different animal or human hosts. The illnesses they can cause range from mild discomfort to debilitating illness and possibly death.

All foodborne viruses originate from the human intestine and contamination of food occurs either by contamination from an infected food handler during

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Summary Introduction Foodborne Illness by Bacteria Foodborne Illness by Viruses Foodborne Illness by Fungi Foodborne Illness by Parasites Conclusions References

ARTICLE CONTENTS

preparation or by contact with sewage, sewage sludge or polluted water. FOODBORNE ILLNESS BY BACTERIA

Food-borne illness often shows itself as flu-like symptoms such as nausea, vomiting, diarrhea, or fever, so many people may not recognize the illness is caused by bacteria or other pathogens on food.

Thousands of types of bacteria are naturally present in our environment. Not all bacteria cause disease in humans. For example, some bacteria are used beneficially in making cheese and yogurt. Bacteria that cause disease are called “pathogens.”

When certain pathogens enter the food supply, they can cause food-borne illness. Only a few types cause millions of cases of food-borne illness each year. Ironically, most cases of food-borne illness can be prevented. Proper cooking or processing of food destroys bacteria. They can grow in just about any food, but are fond of protein foods, such as meat, poultry, seafood, eggs, and dairy products in particular, as well as high-protein vegetables such as beans and grains.

Also bacteria can get in food when:

1. Bacteria may be present on products when you purchase them. Raw meat, poultry, seafood, and eggs are not sterile. Neither is produce such as lettuce, tomatoes, sprouts, and melons.

2. Foods, including safely cooked, ready-to-eat foods, can become cross-contaminated with bacteria introduced on raw products, meat juices, or other contaminated products, or by poor personal hygiene.

Bacteria which will be discussed in this article will be: Clostridium botulinum, Salmonella typhi, Escherichia coli, Listeria monocytogenes and Bacillus cereus.

Clostridium botulinum

TAXONOMY AND CHARACTERISTICS

Clostridium botulinum is a Gran – positive, rod-shaped bacteria that produces several toxins. The best known are its neurotoxins, subdivided in types A-G, which cause a flaccid muscular paralysis seen in botulism. They are also the main paralytic agent in botox. C. botulinum is an anaerobic spore-former, which produces oval, subterminal endospores and is commonly found in soil. The bacteria form spores that allow them to survive in a lag state until they are exposed to conditions that can support their growth. It’s

mobile by peritrichous flagella, doesn’t produce capsule and is proteolytic and lipolytic.

GROWTH AND IDENTIFICATION

Normally grows in the absence of oxygen. Growth rate is reduced under 100% CO2. Toxins of Group I can grows in a optimum temperature of 35 – 40°C, pH minimum of 4.6 and a water activity minimum of 0.94 (10% NaCl). Toxins of Group II can grows in a optimum temperature of 18 – 25°C, pH minimum of 5.0 and a water activity minimum of 0.97 (5% NaCl).Spores and toxins are resistant to freezing temperatures as used for food storage.

Figure 1. Cultivation of Clostridium botulinum on Blood Agar and under Anaerobiosis. Large colonies were observed growing on the first day of cultivation.

CLASSIFICATION

The current nomenclature for C. botulinum recognizes four physiological groups (I – IV). The classification is based on the ability of the organism to digest complex proteins. Studies at te DNA and rRNA lvl support the subdivision of the species into these groups. Group I (proteolytic) or II (non–proteolytic). Group III organisms mainly cause diseases in animals. There has been no record of Group IV causing human or animal diseases.

BOTILISM BY CONTAMINATED FOOD

Clostridium botulinum is one of the most important pathogens associated with food. The organism forms spores that are resistant to many common food process controls. Botulinal neurotoxins (BoNT) produced by vegetative cells of this Gram positive, anaerobic bacterium are among the most potent biological neurotoxins known.


Foodborne botulism is a very severe intoxication, historically caused by eating preserved low acid, low oxygen foods (e.g. canned vegetables, meat and fish) in which C. botulinum had grown and produced BoNT.

TRANSMISSION, SYMPTOMS AND PREVENTION

Cases of foodborne botulism often originate with home-canned foods with low acid content, such as asparagus, green beans, beets, and corn. Clostridium botulinum, the bacterium that causes botulism, thrives in sealed containers because it is anaerobic, meaning it can survive and grow with little or no oxygen. Outbreaks of botulism, however, are often from more unusual sources such as baked potatoes wrapped in aluminum foil but not kept hot, and tomatoes.

Symptoms appear between 12 and 36 hours after consuming the contaminated food, with early nausea, vomiting and diarrhoea followed by paralysis of the eyes, mouth, throat and, progressively, muscles. Infant botulism is an extremely rare toxic-infection that occurs when C. botulinum grows and produces toxins in the intestines of babies; symptoms appear in 3-30 days and include constipation, lethargy, floppiness and breathing difficulties. Not all C. botulinum cause illness in humans. Strains produce one of seven known types of BoNT (A to G).

The prevention of foodborne botulism is achieved by processing food in such a way as to kill spores, and/or inhibit bacterial growth, and/or denature preformed toxin. Since many cases of botulism are associated with home-preserved food, public education about the need for adequate heating, appropriate storage etc is important. A recommended prevention measure for infant botulism is to avoid feeding honey to infants less than 12 months of age. In older children and adults the normal intestinal bacteria suppress development of C. botulinum.

Salmonella typhi


This gram-negative enteric bacillus belongs to the family Enterobacteriaceae. It is a motile, facultative anaerobe that is susceptible to various antibiotics. Currently, 107 strains of this organism have been isolated; many containing varying metabolic characteristics, levels of virulence, and multi-drug resistance genes that complicate treatment in areas that resistance are prevalent.

Salmonella typhi has a complex regulatory system, which mediates its response to the changes in its external environment. Sigma factors, which are global regulators that alter the specificity of RNA polymerase, are examples of such regulation.

Some sigma factors direct transcription to produce stress proteins, which increases the chances of the bacteria surviving environmental changes. RNA polymerase S is produced in response to starvation and changes in pH and temperature. It also regulates the expression of up to 50 other proteins and is also involved in the regulation of virulence plasmids


Diagnostic identification can be attained by growth on Mac Conkey and EMB agars, and the bacteria is strictly non-lactose and non-sacarose fermenting. It also produces no gas when grown in TSI media, but produces H2S and is Indol-negative. It’s also catalase-positive and oxidase-negative and urease-negative. Those characteristics are used to differentiate it from other Enterobacteriaceae.In cultive the colonies have a black coloration, common for species of the genus Salmonella

Figure 2. Tipically cultive of S. typhi on Salmonella – Shigella Agar. Incubation for 3 days at 35°C.

CLASSIFICATION

Salmonella enterica serotype typhi or paratyphi A, B and C include salmonella to the family of Enterobacteriaceae. Morphologically it is non-spore-forming, facultative anaerobic, flagellated and thus moving peritrich gram-negative rods. They can be good study material from human cultured in special culture medium.


To differentiate the various serovars are Lysotypie systems available. In addition come molecular biological methods (eg pulsed-field gel electrophoresis) are used. The serovars have O, K and H antigens. In addition, the Vi capsular antigen (originally from virulence).

TYPHOID, ENTERIC FEVER, SALMONELLOSIS BY CONTAMINATED FOOD

Salmonellosis is a form of food infection that may result when foods containing Salmonella bacteria are consumed. The Salmonella family includes more than 2300 serotypes, but two types, Salmonella enteriditis and Salmonella typhimurium are the most common in the United States and account for half of the infections.

Infection of S. typhi leads to the development of typhoid, or enteric fever. This disease is characterized by the sudden onset of a sustained and systemic fever, severe headache, nausea, and loss of appetite. Other symptoms include constipation or diarrhea, enlargement of the spleen, possible development of meningitis, and/or general malaise. Untreated typhoid fever cases result in mortality rates ranging from 12-30% while treated cases allow for 99% survival.

Salmonella Typhi pass through fecal contaminated food or drinking water in the gastrointestinal tract. Is excreted in the urine or faces. The minimum infectious dose is less than salmonella enteritis. Typhi and parathyroid fever A, B and C are septicaemic disease. After passing through the intestinal wall is the lymphatic and hematogenous spread with secondary settlement in the spleen, liver, bone marrow, bile ducts, skin, and Peyer's patches.


It is transmitted by direct contact or cross-contamination during handling in food processing or home, also sexually.

Symptoms of Salmonellosis include headache, diarrhea, abdominal pain, nausea, chills, fever and vomiting. These occur within 8 to 72 hours after eating contaminated food and may last four to seven days. Arthritis symptoms may follow three to four weeks after onset of acute symptoms. Infants, young children, pregnant women, the elderly or people already ill have the least resistance to disease effects.

The key to avoiding infection by S. typhi is prevention of fecal contamination in drinking water and food supplies. Since the only source of this agent is infected humans, it is possible to control transmission by proper hygiene, waste management, water purification, and treatment of the sick. These measures are attained in developed societies, attributing to the low incidence..

Prevention can also be aided by vaccination to the bacteria; however the effectiveness of this has been questionable. In addition, it is shown that large inoculum sizes can overwhelm the developed immunity and result in disease.

Escherichia coli


Also known by the abbreviation of its name, E. coli, is perhaps the most studied prokaryotic organism for humans. Are large negative bacilli, catalase positive, oxidase negative, non-spore forming, reduce nitrates to nitrites, produce vitamin B and K and measure 0.5 microns wide by 3 microns long. This is an enterobacteria that is usually found in animal intestines, and therefore in the wastewater, but you can find it everywhere, because it is a ubiquitous organism.


Diagnostic identification can be attained by growth on and EMB Agar. The bacteria is non-lactose and non-glucose fermenting. It produces gas when grown in TSI media, but not produces H2S and is Indol-positive. It’s also citrate-negative, lysine-positive and urease-negative.

Figure 3. Cultive of E. coli on Mc Conkey and CLED Agars, incubated for 72 hours at 32°C.

ILLNESS BY CONTAMINATED FOOD


Escherichia coli belong to a family of microorganisms called coliforms. Many strains of E. coli live peacefully in the gut, helping keep the growth of more harmful microorganisms in check. However, one strain, E. coli O157:H7, causes a distinctive and sometimes deadly disease.E. coli can get into meat during processing. If the infected meat is not cooked to160°F (71°C), the bacteria can survive and infect you when you eat the meat. This is the most common way people in the United States become infected with E. coli. Any food that has been in contact with raw meat can also become infected.

Other foods that can be infected with E. coli include:

Raw milk or dairy products. Bacteria can spread from a cow's udders to its milk. Check the labels on dairy products to make sure they contain the word "pasteurized." This means the food has been heated to destroy bacteria.

Raw fruits and vegetables, such as lettuce, alfalfa sprouts, or unpasteurized apple cider or other unpasteurized juices that have come in contact with infected animal feces.


The most common way of contracting these bacteria is by eating meat for burgers that are cooked (not have enough cooking time).Symptoms begin with non-bloody diarrhoea one to five days after eating contaminated food, and progress to bloody diarrhoea, severe abdominal pain and moderate dehydration. In young children, hemolytic uremic syndrome (HUS) is a serious complication that can lead to renal failure and death.

Ground beef is the food most associated with E. coli O157:H7 outbreaks, but other foods also have been implicated. These include raw milk, unpasteurized apple juice and cider, dry-cured salami, homemade venison jerky, sprouts, lettuce, spinach, and untreated water. Infected food handlers and diapered infants with the disease likely help spread the bacteria.

Preventive strategies for E. coli infections include thorough washing and other measures to reduce the presence of the microorganism on raw food, thorough cooking of raw animal products, and avoiding recontamination of cooked meat with raw meat. To be safe, cook ground meats to 160 °F.

Listeria monocytogenes


Bacteria belonging to the genus Listeria are gram-positive short, regular, non-spore or branched, often seen in individual disposition or forming short chains. In old cultures can appear in filaments 6 - 20 mm long. Presented by 1 - 5 peritrichous flagella that give them mobility at 28° C.Responsible for approximately 2,500 illnesses and 500 deaths in the United States (U.S.) annually, listeriosis is the leading cause of death among foodborne bacterial pathogens, with fatality rates exceeding even Salmonella and Clostridium botulinum.


The colonies are small (1 to 2 mm after one or two days of incubation) and smooth. When viewed under magnification with epiiluminación, with an angle of view of 45°- 60°, reflections observed blue-green on a finely granular surface.

Figure 4. Cultive of Listeria monocytogenes on Blood Agar., incubated for 3 days at 35°C

Its optimum growth temperature is between 30° C and 37° C, but can grow at 4° C in a few days.

Listeria spp. are facultative anaerobic, catalase positive and oxidase negative. The Voges-Proskauer reaction and methyl red are positive. Esculin hydrolyzed in a few hours, but not urea or gelatin; not produce indole or SH2.

CLASSIFICATION


The taxonomic classification of Listeria monocytogenes is: Kingdom: Bacteria, Phylum: Firmicutes Class: Bacilli Order: Bacillales, Family: Listeriaceae, Gender: Listeria. It have 13 serotypes and the 95% of the organisms isolated from outbreaks: 1/2a, 1/2b, y 4b.

LISTERIOSIS BY CONTAMINATED FOOD

Listeriosis is a foodborne illness caused by Listeria monocytogenes, a bacterium found in soil and water. You may encounter a variety of raw foods as well as processed foods made from unpasteurized milk. Listeria is unlike many other germs because it can grow even in the cold temperatures of a refrigerator.

There are animals that, even without symptoms, are "carriers" of the bacteria in their intestines may become contaminated meat and dairy products from them obtained.Foods that have been most frequently involved in outbreaks of disease: Salami and sausage with meat and poultry. Dairy products made from unpasteurized milk. Raw vegetables. Raw and smoked fish


The disease primarily affects older adults, pregnant women, newborns, and adults with weakened immune systems. However, rarely, persons without these risk factors can also be affected.

Avoid cross-contamination between raw and cooked or ready to consume, keep them separate during the purchase, preparation and preservation in refrigerator or freezer.Symptoms include fever and chills, headache, upset stomach and vomiting. Anyone can get the disease. But it is more likely to affect pregnant women, fetuses, elderly and people with weakened immune systems. To reduce the risk: Use precooked and ready to eat foods as soon as you

can Avoid milk and unpasteurized dairy products Warm Ready-to-Eat foods and leftovers until

steaming them Wash fresh fruits and vegetables Avoid meats and undercooked seafood

Bacillus cereus


Bacillus cereus is an endemic, soil-dwelling, Gram-positive, rod-shaped, beta hemolytic bacterium. Some strains are harmful to humans and cause foodborne illness, while other strains can be beneficial as probiotics for animals. B. cereus bacteria’s are facultative anaerobes, and like other members of the genus Bacillus can produce protective endospores. Its virulence factors include cereolysin and phospholipase C.

Figure 5. Cultive of B. cereus on Selective Agar for B. cereus, incubated for 3 days at 35°C


It is Gram positive, spore-forming, aerobic or facultative anaerobic, Mobile. The spore is ovoid, central and not distorting. Hydrolysed lecithin and egg yolk does not ferment mannitol. Optimum temperature 30°C to 37°C, its growth temperature 5° C to 55° C and germination temperature 5°C to 8°C. It’s optimum pH 4.5 to 9.3, Aw 0.95 and 7.5% salt concentration.


Bacillus cereus is responsible for a minority of foodborne illnesses (2–5%), causing severe nausea, vomiting and diarrhoea.Bacillus foodborne illnesses occur due to survival of the bacterial endospores when food is improperly cooked.Produces two types of food poisoning: how diarrhoeal and emetic form.

The diarrheal type is associated with a wide-range of foods, has an 8 to 16.5 hour incubation time and is associated with diarrhea and gastrointestinal pain. Also known as the long-incubation form of B. cereus food poisoning, it might be difficult to differentiate from poisoning caused by Clostridium perfringens.


The emetic form is commonly caused by rice that is not cooked for a time and temperature sufficient to kill any spores present, then improperly refrigerated. It can produce a toxin, cereulide, which is not inactivated by later reheating. This form leads to nausea and vomiting 1–5 hours after consumption. It can be difficult to distinguish from other short-term bacterial foodborne pathogens such as Staphylococcus aureus.


In case of Foodborne illness, the diagnosis of B. cereus can be confirmed by the isolation of more than 105 B. cereus organisms per gram form epidemiologically implicated food, but such testing is often not done because the illness is relatively harmless and usually self-limiting.

The rapid time of onset of symptoms of emetic form of the disease, as well as some evidence from food involved, are often sufficient tests to diagnose this type of food poisoning.

Total prevention is nearly impossible, however, cooked foods, heated and stored properly, is generally safe against disease type non-emetic. The greatest risk is cross contamination, which occurs when cooked products come into contact with raw materials or contaminated surfaces (eg. Cutting boards).

FOODBORNE ILLNESS BY VIRUSES

Foodborne viral infections are common, and are often under-diagnosed. Some alternative names for foodborne viral infections are: stomach flu, 24-hour flu, gastroenteritis, and human enteric pathogenic virus infections.

For most enteric viruses (enteric means affecting the stomach or the intestinal tract), the symptoms appear suddenly and strongly, and last for 24 to 48 hours, but they can leave the afflicted person feeling weak for days. The symptoms of foodborne viruses include; vomiting, diarrhoea, stomach or abdominal cramps, with the possibility of fever and malaise. Some specific viral infections can have more severe complications and are discussed below.

Viruses cannot grow in food; they require a host; i.e. human, animal, plant, etc. Food is commonly contaminated with viruses through an infected person preparing the food. Food items and hands can also be

contaminated by washing with contaminated water, or through cross-contamination. Shellfish and other seafood can harbour viruses in their muscles if they were exposed to (fresh or sea) water contaminated with sewage. Because human hands are the most common source for spreading the viruses, adequate hand washing is KEY to minimizing their spread

Following, in this article, are the common and emerging viruses transmitted by food and food environments: Enterovirus, Hepatitis A Virus, Norovirus, Rotavirus and Astrovirus.

Enterovirus


Enteroviruses are a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of antibody neutralization test.

Additional antigenic variants have been defined within several of the serotypes on the basis of reduced or nonreciprocal cross-neutralization between variant strains. On the basis of their pathogenesis in humans and animals, the enteroviruses were originally classified into four groups, polioviruses, Coxsackie A viruses (CA), Coxsackie B viruses (CB), and echoviruses, but it was quickly realized that there were significant overlaps in the biological properties of viruses in the different groups. Enteroviruses isolated more recently are named with a system of consecutive numbers: EV68, EV69, EV70, and EV71, etc


Viral isolation: is the reference technique for the specific diagnosis of enterovirus infections with a sensitivity of 65-75%. It is performed by culture on susceptible cell lines and the difficulty may be related to either cell line is optimal to detect all serotypes, with the titles of enterovirus in CSF are low and the average time to enterovirus in CSF is of 4-8 days.

CLASSIFICATION

Enteroviruses are members of the picornavirus family, a large and diverse group of small RNA viruses characterized by a single positive-strand genomic RNA. The enterovirus genus includes the following twelve species: Enterovirus A, B, C, D, E, F, G, H, J and


Rhinovirus A, B, C. Within these twelve species are the serotypes: Coxsackievirus, Echovirus, and Poliovirus.


Enterovirus infections through food usually produce non-specific gastroenteritis box

Enteroviruses can be transmitted by food to people, animals or from fecal contamination. Are stable at pH 3-10 and following its replication in the pharynx can survive the acidic environment of the stomach and reach the lower intestinal tract where they replicate more intensely. Therefore, it is found throughout the intestine, where food can be transmitted to people, animals or from fecal contamination.

These viruses can pass from the intestinal lumen into our bodies as they reach the lymph tissues and regional lymph nodes (cervical and mesenteric), which constitute a true defensive barrier. From here can pass blood in small quantities, so they can cause a lower viremia, which is usually transient and often goes unnoticed.


Often the person who suffers it have flu or cold symptoms, and in a associated form, is suffering from a picture of gastroenteritis with diarrhoeal stools, usually with cramping abdominal pain and which may be associated vomiting.

Treatment is primarily symptomatic, with adequate hydration, use of antipyretics in febrile

Treatment for enteroviral infection is mainly supportive. In cases of pleurodynia, treatment consists of analgesics to relieve the severe pain that occurs in patients with the disease; in some severe cases, opiates may be needed. Treatment for aseptic meningitis caused by enteroviruses is also mainly symptomatic. In patients with enteroviral carditis, treatment consists of the prevention and treatment of complications, such as arrhythmias, pericardial effusion, and cardiac failure.

Due to the lack of specific treatment for enterovirus infections efforts are directed at prevention. It should pay particular attention to hand washing and hygiene of children and people infected and their cohabitants and inpatient case, observe the same care with hospital staff.

Hepatitis A Virus


Hepatitis A, caused by infection with the Hepatitis A virus (HAV), has an incubation period of approximately 28 days (range: 15–50 days). HAV replicates in the liver and is shed in high concentrations in feces from 2 weeks before to 1 week after the onset of clinical illness. HAV infection produces a self-limited disease that does not result in chronic infection or chronic liver disease.


Hepatitis A virus is culturable in primate cell lines but wild type strains are difficult to culture and generally do not produce cell changes so are not easy to identify by culture alone. It will not grow in food or water.

HAV is very stable, shows high resistance to chemical and physical agents such as heat, acid and solvents and has been shown to survive in the environment for over 3 months.


Worldwide HAV infection is very common. High incidence is linked to poor hygiene and sanitation standards. Risk factors associated with these are generally contaminated foods, water, and exposure to sewage or via person-to-person transmission.

Human faeces are the major reservoir. HAV infects primates including chimps and some species of monkeys. Non-primates are also infected but disease is milder. Transmission via these hosts is unlikely.

Contaminated bivalve shellfish, salads, fresh fruits-vegetables, water, and any manually prepared food products. HAV survived in crème-filled cookies for >1 day at 21ºC. Poor hygiene practices and poor sanitation are major risk factors. Presymptomatic foodhandlers excreting HAV pose a risk. Food is rarely available for analysis because of the long incubation period.

TRANSMISSION

People become infected with hepatitis A when they orally ingest the fecal matter—even just microscopic traces—of infected individuals. This usually happens in one of two ways:


Close contact with an infected person who has not washed his or her hands after using the bathroom

Consuming food or water contaminated with the virus, usually caused by food handlers who are infected and do not thoroughly wash their hands or who wash food with contaminated water

Hepatitis A is common in certain areas of the world where there is poor sanitation. Several outbreaks in the United States and elsewhere have also been associated with injecting and non-injecting drug use.

SYMPTOMS

Initially non-specific symptoms - fever, headache, fatigue, anorexia, nausea and vomiting, then viraemia, jaundice and hepatitis symptoms appear 1-2 weeks later. Virus is present in the blood at weeks 2- 4, and is shed in faeces (>106 particles/g) from the latter 2 weeks of the incubation period for up to 5 weeks. Jaundice is usually evident from weeks 4 to 7, and virus shedding generally continues throughout this period. Overall debility lasting several weeks is common and relapses may occur.

At Risk Groups: All age-groups. The disease is milder in young children under 6 years than older children and adults. Case-fatality risk increases with age so risks are higher for unexposed older people.

PREVENTION

The treatment is to rest and an appropriate low-fat diet. Post-exposure prophylaxis may be recommended for certain groups such as day-care centre staff, military and food industry staff.

Prevention is possible via HAV vaccination for at-risk groups including overseas travellers and for foodhandlers when situations warrant it.

Thoroughly wash your hands often to help protect yourself from infection. Wash after using the toilet, before preparing food or eating, and after changing a baby's diaper. Also, don't share towels, eating utensils or toothbrushes.

Norovirus


Norovirus is a genus of genetically diverse single-stranded RNA, non-enveloped viruses in the Calciviridae family. The known viruses in the genus

are all considered to be the strains of a single species called Norwalk virus.


Noroviruses can accumulate and concentrate in the guts of bivalve mollusks, such as oysters and mussels, growing in sewage-contaminated waters. Depuration processes designed to reduce the bacterial contamination of these shellfish are ineffective for removing viruses. Noroviruses are resistant to acid and can survive gastric acid at pH 3 - 4. They have also been shown to still be infective when exposed to a pH of 2.7 for 3 hours at ambient temperature. The virus can survive in water environments and in shellfish for extended periods (possibly months). It is resistant to drying, and is reported to persist on environmental surfaces, such as carpets, for up to 12 days.

Noroviruses can survive exposure to up to 10 ppm free chlorine, and can therefore survive the usual chlorination processes used to treat public water supplies.

CLASSIFICATION

Noroviruses commonly isolated in cases of acute gastroenteritis belong to two genogroups: genogroup I (GI) includes Norwalk virus, Desert Shield virus and Southampton virus, and II (GII), which includes Bristol virus, Lordsdale virus, Toronto virus, Mexico virus, Hawaii virus and Snow Mountain virus.

Serotypes, strains and isolates include: Norwalk virus Hawaii virus Snow Mountain virus Mexico virus Desert Shield virus Southampton virus Lordsdale virus


Norovirus infection is characterized by nausea, forceful vomiting, watery diarrhoea, and abdominal pain, and in some cases, loss of taste. General lethargy, weakness, muscle aches, headache, coughs, and low-grade fever may occur.


The disease is usually self-limiting, and severe illness is rare. The virus affects around 267 million people and causes over 200,000 deaths each year; these deaths are usually in less developed countries and in the very young, elderly and immuno-suppressed.

Food vehicles for noroviruses are thought to include sewage contaminated bivalve shellfish, foodstuffs that are contaminated by an infected handler, fruits and vegetables contaminated during irrigation or washing, and water (including drinking water and ice).

Infected food handlers can contaminate any foodstuff, and outbreaks of Norovirus infections can be associated with any food that is handled and will be eaten without a further cooking step. Contamination can occur during the preparation of foods as well as during the harvesting of fresh produce such as soft fruits.

TRANSMISSION

Noroviruses are transmitted directly from person to person and indirectly via contaminated water and food. They are extremely contagious, and fewer than twenty virus particles can cause an infection (some research suggests as few as five). Transmission occurs through ingesting contaminated food and water and by person-to-person spread.

SYMPTOMS

The first sign of norovirus is usually a sudden sick feeling followed by forceful vomiting and watery diarrhea.Some people may also have: A raised temperature (over 38C/100.4F) Headaches Painful stomach cramps Aching limbs

Symptoms usually appear one to two days after you become infected but they can start sooner. Most people make a full recovery within a couple of days.Apart from the risk of dehydration, the illness is not generally dangerous and there are usually no long-lasting effects from having norovirus. However, it can be pretty unpleasant while you have it.

PREVENTION

Wash your hands frequently and thoroughly with soap and water, particularly after using the toilet and before preparing food.

Disinfect any surfaces or objects that could be contaminated with the virus. It is best to use a bleach-based household cleaner.

Flush away any infected faeces or vomit in the toilet and clean the surrounding toilet area.

Avoid eating raw, unwashed produce and only eat oysters from a reliable source. Oysters have been known to carry the norovirus.

TREATMENT

There is no specific medicine to treat people with norovirus illness. Norovirus infection cannot be treated with antibiotics because it is a viral (not a bacterial) infection.

If you have norovirus illness, you should drink plenty of liquids to replace fluid lost from throwing up and diarrhea. This will help prevent dehydration.

Rotavirus

TAXONOMY AND CHARACTERISTICSRotavirus, an icosahedral virus in the family Reoviridae, has a distinct morphologic appearance by negative-stain electron microscopy. The major antigenic properties of rotaviruses group, subgroup, and serotype are determined by the viral capsid proteins. Rotavirus has seven major groups (A-G); most human strains belong to group A, although groups B and C have occasionally been associated with human illness.

The morphological and biochemical characteristics of rotaviruses include the following: Mature virus particles are nonenveloped and possess

a multilayered icosahedral protein capsid, of about 75nm in diameter, composed of an outer layer, an inner layer, and a core;

The virus genome consists of 11 segments of double-stranded RNA.

Viral particles contain an RNA-dependent RNA polymerase and other enzymes capable of producing capped RNA transcripts.

Viral replication occurs in the cytoplasm of infected cells.

The viruses are capable of genetic reassortment. Virus particles are formed by budding into the

endoplasmic reticulum and


Mature virion particles are liberated from infected cells by cell lysis.


However, a number of laboratory methods can be used to confirm the diagnosis of rotavirus. Rapid tests using enzyme immunoassay and latex agglutination techniques are widely available, relatively inexpensive, and have good sensitivity and specificity.

These methods are directed at identifying a group antigen common to all Group A rotaviruses, VP6. In general, enzyme immunoassays show greater than 95% sensitivity and 99% specificity while latex agglutination tests have had a lower sensitivity and specificity. Electron microscopy can also be used to identify rotavirus in stool specimens, and indeed, this technique enabled the initial identification of rotavirus. Electron microscopy, however, is not readily available, and although it is highly specific, it lacks the sensitivity of the other methods.

CLASSIFICATION

Rotaviruses are included in the genus Rotavirus, in the family Rotaviridiae. They are classified serologically first into groups (or serogroups) containing viruses that share cross-reacting antigens detectable by serological tests such as immunofluorescence, ELISA and immunoelectro-microscopy.

Six distinct groups (A to F) of rotaviruses have been described. Group A, B, and C rotaviruses have been found both in humans and animals; groups D, E, and F rotaviruses have been found only in animals. Group A rotaviruses have clearly been established as causing severe diarrhoeal disease in young; group B rotaviruses include those viruses associated with animal epidemics of severe diarrhoea primarily in adults in China. Group C viruses have been found sporadic cases and outbreaks of diarrhoea in piglets and children.

Viruses within a serogroup are classified further in to serotypes. Serotypes are defined by Plaque reduction Fluorescent – focus reduction or Neutralization assays by using antisera to purified

virus particles prepared in hyper immunized animals.

The assays measure the reactivity of antibody with the two outer capsid proteins (VP4 and VP7), which induce antibodies with neutralizing activity.


Rotavirus is a virus that causes gastroenteritis (inflammation of the stomach and intestines). The rotavirus disease causes severe watery diarrhea, often with vomiting, fever, and abdominal pain. In babies and young children, it can lead to dehydration (loss of body fluids). Rotavirus is the leading cause of severe diarrhea in infants and young children worldwide. Globally, it causes more than a half a million deaths each year in children younger than 5 years of age.

Rotaviruses are transmitted by the fecal-oral route. Person-to-person spread through contaminated hands is probably the most important means by which rotaviruses are transmitted in close communities such as pediatric and geriatric wards, day care centers and family homes. Infected food handlers may contaminate foods that require handling and no further cooking, such as salads, fruits, and hors d'oeuvres.

TRANSMISSION

Rotavirus is believed to be most frequently transmitted by the fecal-oral route, most commonly from person to person. Transmission via fomites, such as toys and countertops, has also been demonstrated. Although children are at highest risk for rotavirus infection and disease, rotavirus infection can also occur in adults.

Those particularly affected include adults who are in close contact with young children, adult travelers, institutionalized or hospitalized elderly patients, and those in rare outbreaks involving adults.

SYMPTOMS

Rotaviruses cause acute gastroenteritis. Infantile diarrhea, winter diarrhea, acute non-bacterial infectious gastroenteritis, and acute viral gastroenteritis are names applied to the infection caused by the most common and widespread group A rotavirus.

Rotavirus disease is most common in infants and young children, but adults and older children can also become infected with rotavirus. Once a person has been exposed to rotavirus, it takes about 2 days for symptoms to appear.

Vomiting and watery diarrhea may last from 3 to 8 days in a child who is infected with rotavirus. Additional symptoms include loss of appetite and dehydration (loss of body fluids), which can be especially harmful for infants and young children.


PREVENTION

To reduce the spread of rotavirus, wash your hands thoroughly and often — especially after you use the toilet, change your child's diaper or help your child use the toilet. But even strict hand-washing doesn't offer any guarantees.

There are two rotavirus vaccines licensed for use in the United States: RotaTeq® and Rotarix®. These rotavirus vaccines have been shown to be safe and effective at preventing severe diarrhea.

RotaTeq. This vaccine is given by mouth in three doses, often at ages 2 months, 4 months and 6 months. The vaccine is not approved for use in older children or adults.Rotarix. This vaccine is a liquid given in two doses to infants at ages 2 months and 4 months. Clinical trials of the vaccine detected no increased risk of intussusception.

Astrovirus


Astrovirus is a type of virus that was first discovered in 1975 using electron microscopesfollowing an outbreak of diarrhoea in humans.

Astroviruses are 28–35 nm diameter, icosahedralviruses that have a characteristic five- or six pointed star-like surface structure when viewed by electron microscopy. Along with the Picornaviridae and the Caliciviridae, the Astroviridae comprise a third family of nonenveloped viruses whose genome is composed of plus-sense, single-stranded RNA.

Astrovirus has a non-segmented, single stranded, positive sense RNA genome within a non-enveloped icosahedral capsid. Human astroviruses have been shown in numerous studies to be an important cause of gastroenteritis in young children worldwide


Astroviruses were experimentally transmitted to adult volunteers and adapted to growth in human foetal cells. Restrictions on the availability and use of foetal tissue limited the cultivation of astroviruses and therefore studies were confined to a few laboratories that access to electron microscopes.

CLASSIFICATION

Two serotypes of human astroviruses are described. It is proposed that these should be called serotype I and serotype II. Using antisera to these two types, 13 of 15 other community-acquired strains were able to be typed, 12 as serotype I and one as serotype II.


Contaminated water and food have occasionally been implicated as the cause of astrovirus out-breaks.

The likely route of transmission is faecal-oral via food or water. Nevertheless, a direct epidemiological link between eating raw food and astrovirus infection has not been fully demonstrated. Easier availability of molecular diagnostic methods may provide new approaches to clarification of these problems.

TRANSMISSION

Astroviruses are transmitted from person to person by the fecal-oral route. Fecal-oral transmission has been verified by numerous volunteer studies. In 1979, Kurtz and colleagues examined filtrate from a child with mild gastroenteritis by EM and determined that it contained a large number of astrovirus particles.

Contaminated water and food have occasionally been implicated as the cause of astrovirus outbreaks.

SYMPTOMS AND PREVENTION

Symptoms of the astrovirus are similar to those of gastroenteritis. Diarrhea, nausea,vomiting and fevers are common symptoms. Patients may also suffer from malaise and abdominal pain. Such symptoms last for around three to four days before naturally subsiding as the body produces antibodies.

There is no vaccine or anti-viral treatment against the Astrovirus infection but personal hygiene can reduce the incidence of the illness.

Since astrovirus-related gastroenteritis is usually a mild, self-limiting disease, it generally does not require any specific therapy, hospitalization, extensive outpatient evaluation, or clinic visits. How-ever, in the case where an affected individual becomes dehydrated, oral or intravenous rehydration therapy may be required.

FOODBORNE ILLNESS BY PARASITES


Parasites may be present in food or in water and can be identified as causes of foodborne or waterborne illness in the United States. They range in size, from tiny single-celled organisms to worms visible to the naked eye. Their lifecycle may also vary. While some parasites use a permanent host, others go through a series of developmental phases using different animal or human hosts. The illnesses they can cause range from mild discomfort to debilitating illness and possibly death.

They may be transmitted from host to host through consumption of contaminated food and water, or by putting anything into your mouth that has touched the stool (feces) of an infected person or animal.

Parasites are of different types and range in size from tiny, single-celled, microscopic organisms (protozoa) to larger, multi-cellular worms (helminthes) that may be seen without a microscope. The size ranges from 1 to 2 µm to 2 meters long.

In this article I’m going to talk about: Giardia intestinalis, Cryptosporidium parvum, Trichinella spirialis, Taenia solium and Toxoplasma gondii

Giardia intestinalis


Giardia intestinalis is a flagellated protozoan parasite that colonizes and reproduces in the small intestine, causing giardiasis. The parasite attaches to the epithelium by a ventral adhesive disc, and reproduces via binary fission.

The organism is most likely to be present in the food as a cyst, the protozoan resting stage equivalent to a bacterial spore.

Figure 6. Giardia intestinalis cysts in a wet mount stained with iodine.

In the older literature this organism is referred to as Giardia lamblia and also as Giardia duodenalis.


Growth: The organism does not grow outside of the animal reservoir so controls designed to restrict the growth of bacteria will be ineffective. There is very little information on the survival of the organism on foods or on how cysts present on foods may be destroyed.

Survival: In general the cysts are stable and can last for long periods (months) in the environment. Cool moist conditions favour survival. Cysts have been shown to survive on herbs for 8 days.

Cyst survival in water is better at lower temperatures. Survival was 77 days in distilled water at 8° C, but only 4 days at 37° C. The 0.1-25% survived in river water for up to 56 days.

CLASSIFICATION

Taxonomical classification for G. intestinalis is: Kingdom: Protista; Subkingdom: Protozoa; Phylum: Sarcomastigophora; Subphylum: Mastigosphora; Class: Zoomastigosphora; Order: Diplomonadida; Family: Hexamitidae; Genus: Giardia; Species: intestinalis.

LIFE CYCLE


Figure 7. Life cycle of Giardia intestinalis

Giardia intestinalis lives as active trophozoites in the small intestine. Some trophozoites encyst into cysts which are released in a bowel movement. The feces might contaminate soil, water, food or surfaces such as bathroom sinks. The cyst has a protective shell and it can survive in the environment for many weeks (in cold water many months). You become infected after accidentally swallowing the microscopic cysts. Each cyst releases two trophozoites in the small intestine.

They remain in the lumen where they can feed freely or attached to the mucosa by a ventral sucking disk. After eating enough, they go through another transformation and multiply by binary fission. The trophozoites encyst as they move towards the colon. Cysts are found more often in firm stool whereas both trophozoites and cysts are present in loose stool. Because the cysts become infective almost instantly after being passed out, the disease can be transmitted during anal-oral-sexual intercourse.


Giardia intestinalis, cause of giardiasis (populary known as beaver fever). It attaches to the mucosa and absorbs nutrients that it gets from the intestinal wall. In addition to humans, Giardia intestinalis infects birds, cows, sheep, deer, dogs and cats. Giardiasis is found worldwide mostly in warm climates.

Sources of illness can be by:Human: Asymptomatic carriers may excrete the organism for years. The asymptomatic carriage rate has been estimated at 3-20% in the USA.

Animal: The organism is found in mammals, birds, reptiles and amphibians. However isolates from these sources are not necessarily pathogenic to humans.Food: Agricultural products that have directly or indirectly been subjected to faecal contamination may be a source of cysts. Giardia has been isolated from root crops, lettuces, herbs and strawberries irrigated with wastewater.Environment: Cysts are found in waters which have been faecally polluted

TRANSMISSION

People get giardiasis the following ways: Giardiasis is frequently associated with drinking

contaminated water, but some people might get infected by consuming uncooked meat also contaminated with G. duodenalis cysts (the infective stage of the organism).

By putting anything into your mouth that has touched contaminated surfaces or the stool of a person or animal with giardiasis.

SYMPTOMS

Immunocompetent people who are infected may be asymptomatic or experience gastrointestinal disease. In the immunocompromised the results may be more serious (severe diarrhea and loss of weight), and occasionally life threatening. Malabsorption may be quite severe in diarrhoeal cases.

Symptoms may last from 4 to 6 weeks, and consist of diarrhoea followed by flatulence, foul-smellin stools and cramps.

Chronic infection might lead to dehydration and severe weight loss. Some cases may be without symptoms.

At Risk Groups: Any one may become infected, but the disease is more serious in those who are immunocompromised. Infants and children are more susceptible to infection than adults.

PREVENTION

Ingestion of fecally contaminated food or water is the main mode of transmission. Thus, reducing this contamination is the best method of prevention. Filtering or purifying drinking water (iodine or boiling) in endemic areas is important as is the washing of fruits and vegetables that may have been contaminated.

Cryptosporidium parvum



Coccidian protozoa; sporozoa; sexual and asexual cycles in a single host; sporozoites, trophozoites and merozoites all attach to epithelial cells (generally intestinal cells); mature oocyst contains 4 thin, flat motile sporozoites (2-4 by 6-8µm). C. parvum has gained much attention in the last 20 years as a clinically important human pathogen.

The genome of C. parvum has a relatively small size and simple organization of 9.1 Mb, which is composed of eight chromosomes ranging from 1.04 to 1.5 Mb.

The genome is very compact, and is one of the few organisms without transposable elements. Unlike other apicomplexans, C. parvum has no genes in its plastidsor mitochrondria.

CLASSIFICATION

Taxonomical classification for C. parvun is: Kingdom: Chromalveolata; Phylum: Apicomplexa; Class: Conoidasida; Subclass: Coccidiasina; Order: Eucoccidiorida; Family: Cryptosporidiidae; Genus: Cryptosporidium; Species: parvum.

LIFE CYCLE

Figure 8. Life cycle of Cryptosporidium parvum

Sporulated oocysts, containing 4 sporozoites, are excreted by the infected host through feces and possibly other routes such as respiratory secretions.

Transmision of Cryptosporidium parvum occurs mainly through contact with contaminated water (e.g., drinking or recreational water). Occasionally food

sources, such as chicken salad, may serve as vehicles for transmission. Many outbreaks in the United States have occurred in waterparks, community swimming pools, and day care centers. Zoonotic and anthroponotic transmission of C. pavarum occurs through exposure to infrected animals or exposure to water contaminated by feces of infected animals.

Following ingestion (and possibly inhalation) by a suitable host, excystation occurs. The sporozoites are released and parasitize epithelial cells of the gastrointestinal tract or other tissues such as the respiratory tract. In these cells, the parasites undergo asexual multiplication (schizogony or merogony) and then sexual multiplication (gametogony) producing microgamonts (male) and macrogamonts (female). Upon fertilization of the macrogamonts by the microgametes, oocysts develop that sporulate in the infected host. Two different types of oocysts are produced, the thick-walled, which is commonly excreted from the host, and the thin-walled oocyst, which is primarily involved in autoinfection. Oocysts are infective upon excretion, thus permitting direct and immediate fecal-oral transmission.

Note that oocysts of Cyclospora cayetanensis, another important coccidian parasite, are unsporulated at the time of excretion and do not become infective until sporulation is completed. Refer to the life cycle of Cyclospora cayentanensis for further details.

CRYPTOSPORIDIOSIS BY CONTAMINATED FOOD

Cryptosporidium infection begins when you ingest the cells of one of nearly a dozen species of the one-celled cryptosporidium parasite. The Cryptosporidium parvum species is responsible for the majority of infections in humans. Once a person is infected by the protozoan, the parasite resides in the intestine and then is passed into the stool of the infected person.

Found in food and water that has been contaminated by feces from humans or animals. It is highly resistant to normal levels of chlorine, and can survive in pools and drinking water.

People usually get C. parvum from swallowing contaminated water, eating contaminated food, or coming into contact with contaminated feces. Ingestion of as few as two to ten Cryptosporidium oocysts, or parasites, can cause infection.


Figure 9. Cryptosporidium parvum oocysts in wet mount, under differential interference contrast (DIC) microscopy.

TRANSMISSION

You can become infected with Cryptosporidium parvum by touching anything that has come in contact with contaminated feces. Methods of infection include:

Swallowing or putting something contaminated with cryptosporidium into your mouth

Drinking water contaminated with cryptosporidium Swimming in water contaminated with C. parvum

and accidentally swallowing some of it. Eating uncooked food contaminated. Touching your hand to your mouth if your hand has

been in contact with a contaminated surface or object.

Having close contact with other infected people or animals –especially their feces– which can allow the parasite to be transmitted from your hands to your mouth.

SYMPTOMS

Symptoms of C. parvum infection, or Cryptosporidiosis, generally appear a week after the parasite is swallowed. Signs that one is infected by a cryptosporidium parasite include the following: Diarrhea - diarrhea will be profuse and watery Abdominal cramping Fatigue Fever Nausea Loss of appetite

Symptoms appear 2 to 10 days after ingestion of C. parvum oocysts. The illness usually goes away without medical intervention in 3 to 4 days. For healthy people, symptoms may last up to 2 weeks. For individuals with

weakened immune systems, cryptosporidiosis can be serious, long-lasting, and sometimes fatal.

PREVENTION

There is no specific treatment for cryptosporidiosis, but most healthy people recover within two weeks. Symptoms can be lessened with an anti-parasitic drug and anti-diarrhetic agents. In addition, one should replenish the fluids and electrolytes lost during diarrhea.

Avoiding cryptosporidium is especially important for people with weak immune systems, as the illness caused by cryptosporidiosis can have worse effects on these individuals. In order to prevent the spread of cryptosporidium, one should: Wash hands thoroughly after going to the bathroom,

changing diapers, and before and after eating Wash all raw foods and vegetables before eating

them Be careful of swimming in public areas such as

lakes and swimming pools if contamination is suspected, as cryptosporidium can linger up to six months in water

Wash hands after touching farm animals Avoid exposure to feces during sexual activity

Trichinella spiralis


Trichinella spiralis is a nematode parasite, occurring in rats, pigs, bears and humans, and is responsible for the disease Trichinosis. It is sometimes referred to as the “pork worn” due to it being found commonly in undercooked pork products.

The most widespread and most important species is Trichinella spiralis, which occurs worldwide, but prefers the temperate climate zones. Male Trichinella spiralis are approximately 1-2mm long, the females 2-4 mm.It has sensory papillae on the head region, which are used to help sense the environment.

Another characteristic is that it is histiotrophic, which means that in some stage of its development, they invade tissues and cells


Figure 10. Larvae of Trichinella liberated from bear meat.


Males of T. spiralis measure between 1.4 mm and 1.6 mm long and are more flat anteriorly than posteriorly. The anus can be found in the terminal (side) and they have a large copulatory pseudobursa on each side. The females of T. spiralis are about twice the size of the males and have an anus found terminally. The vulva is located near the esophagus. The single uterus of the female is filled with developing eggs in the posterior portion, while the anterior portion contained the fully developed juveniles.

CLASSIFICATION

Taxonomical classification for Trichinella spiralis is: Kingdom: Animalia; Phylum: Nematoda; Class: Enoplea; Order: Trichurida; Family: Trichinellidae; Genus: Trichinella; Species: spiralis.

LIFE CYCLE

Depending on the classification used, there are several species of Trichinella: T. spiralis, T. pseudospiralis, T. nativa, T. murelli, T. nelsoni, T. britovi, T. papuae, and T. zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involved pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but

animals most often associated as sources of human infection are bear, moose and wild boar.

Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T. pseudospiralis and T. papuae, which do not encyst) of Trichinella species. After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms. Females are 2.2 mm in length; males 1.2 mm.

The life span in the small bowel is about four weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst.

Diagnosis is usually made based on clinical symptoms, and is confirmed by serology or identification of encysted or non-encysted larvae in biopsy or autopsy specimens.

Figure 11. Life cycle of Trichinella spiralis.

TRICHINELLOSIS BY CONTAMINATED FOOD

Trichinella spiralis, cause of Trichinellosis by the colonization of the larvae in muscles where they grow and form cysts.Unlike many parasites that depend on a specific host animal, the Trichinella worm infects nearly all orders of mammals. Rats and wild or domestic pigs are the most common hosts. Animals and humans are infected with


Trichinella spiralis when they ingest infective larvae (juveniles) in raw or undercooked meat. Animals may also become infected when they eat hosts such as rodents, as part of animal feed.

People get Trichinellosis by consuming raw or undercooked meats such as pork, wild boar, bear, bobcat, cougar, fox, wolf, dog, horse, seal, or walrus infected with Trichinella larvae.

TRANSMISSION

Highlighting the incidences of transmission through uncooked portions of meat, specifically pork, Trichinosis impacts the realm of food and culture for its specific regions. The illness is not spread directly from person to person.

SYMPTOMS

The first symptoms are nausea, diarrhea, vomiting, fever, fatigue, and abdominal pain, followed by headaches, eye swelling, aching joints and muscles, weakness, and itchy skin. In severe infections, persons may experience difficulty with coordination and have heart and breathing problems. Death may occur in severe cases.

Abdominal symptoms may appear within 1 to 2 days after eating contaminated meat. Further symptoms (eye swelling and aching muscles and joints) may begin 2 to 8 weeks after infection. Mild cases may assumed to be flu. Symptoms may last for months.

PREVENTION

Infection by Trichinella spiralis is obtained by eating undercooked meat infected with larvae. Thus, cooking the meat (especially pork and bear meat) well to kill the infective larve will prevent one from acquiring an infection.

Taenia solium


Taenia solium, also called the pork tapeworm, is a cyclophyllid cestode in the family Taeniidae. T. solium, commonly known as tapeworm, is a triploblastic aceolomate. It is normally 2 to 3 m in length, but can become very large, over 50 m long in some situations.

Figure 12. Taenia solium eggs in unstained wet mounts.

They are 20 cm in length and have 60 ml of fluid, and 13% of patients might have all three types in the brain. Humans are usually infected through eating infected pork, fostering adult tapeworms in the intestine, and passing eggs through feces, but autoinfection is also possible.

CLASSIFICATION

Taxonomical classification for Trichinella spiralis is: Kingdom: Animalia; Phylum: Platyhelminthes; Class: Cestoidea; Order: Cyclophyllidea; Family: Taeniidae; Genus: Taenia; Species: solium.

LIFE CYCLE

Taeniasis is the infection of humans with the adult tapeworm of Taenia saginata, T. solium or T. asiatica. Humans are the only definitive hosts for these three species. Eggs or gravid proglottids are passed with feces; the eggs can survive for days to months in the environment. Cattle (T. saginata) and pigs (T. solium and T. asiatica) become infected by ingesting vegetation contaminated with eggs or gravid proglottids. In the animal's intestine, the oncospheres hatch, invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal.

Humans become infected by ingesting raw or undercooked infected meat. In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex and reside in the small intestine. Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium. The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day). T. saginata adults usually


have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids.

The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces. T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively.

Figure 13. Life cycle of Taenia solium

CYSTICERCOSIS BY CONTAMINATED FOOD

Taenia solium, cause Cysticercosis. Cysticercosis is a parasitic tissue infection caused by larval cysts of the pork tapeworm. These larval cysts infect brain, muscle, or other tissue, and are a major cause of adult onset seizures in most low-income countries. An individual acquires cysticercosis from ingesting eggs excreted by a person who has an intestinal tapeworm. Cysticercosis is not acquired by eating undercooked pork rather; it is the tapeworm infection that is acquired by eating undercooked pork containing the larval cysts. Pigs become infected by ingesting tapeworm eggs in the feces of the human tapeworm carrier.

Infections with T. solium are for eating undercooked pork and food and water contaminated with human feces.

TRANSMISSION

There are four different ways in which the T. solium infection can be transmitted: Consumption of raw and/or undercooked pork

products. Human-to-human or pig-to-human transfer of T.

solium eggs through direct contact with feces

Human-to-human or pig-to-human transfer of T. solium eggs through consumption of food/water containing fecal matter (indirect).

Autoinfection.

SYMPTOMS

The presence of T. solium worms in the human intestines usually does not cause major problems. Diarrhea, constipation,, indigestion, and other mild stomach symptoms are common. Proglottids may also also crawl out of the anus and cause some discomfort or embarrassment. Also, patients may have higher IgE level in their serum and a low-grade eosinophilia (mostly under 15%).

People with Taeniasis may not know they have a tapeworm infection because symptoms are usually mild or nonexistent.

Taenia solium tapeworm infections can lead to cysticercosis, which is a disease that can cause seizures, so it is important seek treatment.

PREVENTION

It is possible to avoid infection with T. solium by not eating undercooked pork and food and water contaminated with human feces. Extra care should be taken in places with poor hygiene or meat inspection laws. Freezing infested pork for a prolonged period will also kill cysticerci. The following list describes important actions to prevent infection with tapeworm: Meat inspection Health education Adequate sewage treatment and disposal Good hygiene and hand washing after using the

toilet will prevent self-infection in a person already infected with tapeworms.

Improvement of living conditions, especially safe treatment of sewage used for farming.

Toxoplasma gondii


Is an obligate, intracellular, parasitic protozoan that causes the disease Toxoplasmosis. The tachyzoite is often cresent-shaped. Its anterior (conoidal) end is pointed and its posterior end is round. Approximately 2 x 6 um. They measured 4.7 X 2.1 um in size by TEM.T.gondii occurs in three forms; trophozoite, tissue cyst and oocyst.


The trophoziote and tissue cyst represent stages in asexual multiplication (Schizogony). While the oocysts is formed by sexual reproduction (gametogony or Sporogony).

Figure 14. Unsporulated T. gondii oocyst in an unstained wet mount.

CLASSIFICATION

Taxonomical classification for Toxoplasma gondii is: Kingdom: Protista; Subkingdom: Protozoa; Phylum: Amicomplexa; Class: Sporozoasida; Order: Eucoccidiorida; Family: Sarcocystidae; Genus: Toxoplasma; Species: gondii.

LIFE CYCLE

The only known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces. Although oocysts are usually only shed for 1-2 weeks, large numbers may be shed. Oocysts take 1-5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water or plant material contaminated with oocysts. Oocysts transform into tachyzoites shortly after ingestion.

These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts. Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment.

In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the

host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens. Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as PCR.

Figure 15. Life cycle of Toxoplasma gondii.

TOXOPLASMOSIS BY CONTAMINATED FOOD

Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness in the United States. More than 60 million men, women, and children in the U.S. carry the Toxoplasma parasite, but very few have symptoms because the immune system usually keeps the parasite from causing illness.

However, women newly infected with Toxoplasma during pregnancy and anyone with a compromised immune system should be aware that toxoplasmosis can have severe consequences.

Toxoplasmosis may cause flu-like symptoms in some people, but most people affected never develop signs and symptoms. For infants born to infected mothers and for people with weakened immune systems, toxoplasmosis can cause extremely serious complications.

Toxoplasma infection occurs mainly by eating undercooked, contaminated meat (especially pork, lamb, and venison). Or drinking water contaminated with Toxoplasma gondii.

TRANSMISSION

People get toxoplasmosis the following ways:


By consuming foods (such as raw or undercooked meats, especially pork, lamb, or wild game) or drinking untreated water (from rivers or ponds) that may contain the parasite.

Fecal-oral: Touching your hands to your mouth after gardening, handling cats, cleaning a cat's litter box, or anything that has come into contact with cat feces.

Mother-to-fetus (if mother is pregnant when first infected with T. gondii).

Through organ transplants or blood transfusions, although these modes are rare.

SYMPTOMS

Toxoplasmosis is relatively harmless to most people, although some may develop "flu-like" symptoms such as swollen lymph glands and/or muscle aches and pains. In otherwise healthy individuals, the disease is usually mild and goes away without medical treatment. However, dormant non-infective parasites can remain in the infected individual for life. An unborn child may contract the parasite congenitally resulting in severe outcomes including miscarriage or stillbirth.

The time that symptoms appear varies, but generally symptoms will appear 1 week to 1 month after consuming the parasite.Infants infected while still in the womb may show no symptoms at birth, but develop symptoms later in life.

The duration of the illness depends on the health and immune status of the host. Persons with weakened immune systems may experience illnesses of long duration, possibly resulting in death.

PREVENTION

To prevent risk of Toxoplasmosis and other infections from food: Cook food to safe temperatures. A food

thermometer should be used to measure the internal temperature of cooked meat. Do not sample meat until it is cooked. USDA recommends the following for meat preparation.

Freeze meat for several days at sub-zero (0° F) temperatures before cooking to greatly reduce chance of infection.

Peel or wash fruits and vegetables thoroughly before eating.

Wash cutting boards, dishes, counters, utensils, and hands with hot soapy water after contact with raw meat, poultry, seafood, or unwashed fruits or vegetables.

FOODBORNE ILLNESS BY FUNGI

Fungi range in size from microscopic, single-celled organisms to very large, multi-cellular organisms. They are found naturally in air, soil, plants, water and some food. Mold, yeast, and mushrooms are examples of fungi.

Molds share some basic characteristics They spoil food and sometimes cause illness. They grow under almost any condition, but grow

well in acidic food with low water activity. Freezing temperatures prevent or reduce the growth

of molds, but do not destroy them. Some molds produce toxins such as aflatoxins.

While mold cells and spores can be killed by heating them, some toxins are not destroyed by normal cooking methods. Food with molds that are not a natural part of the product should be discarded.

Yeasts are known for their ability to spoil food rapidly. Carbon dioxide and alcohol are produced as yeast slowly consumes food. Yeast spoilage may, therefore, produce a smell or taste of alcohol. Yeast may appear as a pink discoloration or slime and may bubble. They grow well in acidic food with lower water content such as jellies, jams, syrup, honey, and fruit juice. Food that has been spoiled by yeast should be discarded.

Cryptococcus neoformans


Cryptococcus neoformans grows as yeast (unicellular) and replicates by budding. C. neoformans makes hyphae during mating, and eventually creates basidiospores at the end of the hyphae before producing spores. Under host-relevant conditions, including low glucose, serum, 5% carbon dioxide, and low iron, among others, the cells produce a characteristic polysaccharide capsule. When grown as yeast, C. neoformans has a prominent capsule composed mostly of polysaccharides. Microscopically, the India ink stain is used for easy visualization of the capsule in cerebral spinal fluid.


Method of diagnosis: Encapsulated budding forms of the fungus may be seen in the CSF, urine or pus using Indian ink staining. Cryptococcal antigens may also be detected in the CSF and serum.


The diagnosis is confirmed by culture (CSF, blood, sputum or andurine) or by histopathology (Mayer’s mucicarmine staining). Pulmonary cryptococcosis in non-HIV infected persons usually manifests as a nodule which must be distinguished from a malignancy.

CLASSIFICATION

Taxonomical classification for Cryptococcus neoformans is: Kingdom: Fungi; Phylum: Basidiomycota; Class: Tremellomycetes; Order: Tremellales; Family: Tramelleceae; Genus: Cryptococcus; Species: neoformans.

Figure 16. Cultive of C. neoformans on Bird Seed Agar for 48 hours at 35°C.

CRYPTOCOCCOSIS BY CONTAMINATED FOOD

Cryptococcus neoformans is the fungus that causes this disease. It is usually found in soil. If you breathe it in, it infects your lungs. The infection may go away on its own, remain in the lungs only, or spread throughout the body (disseminate). This infection is most often seen in people with a weakened immune system, such as those with HIV infection, taking high doses of corticosteroid medications, cancer chemotherapy, or who have disease of Hodgkin

C. neoformans spores are typically found in bird droppings (especially pigeon droppings) or in soil contaminated with bird droppings. Humans can become infected after inhaling microscopic, airborne fungal spores from the environment. Cryptococcosis is not known to be spread from person to person, from animal to animal, or from animals to humans

TRANSMISSION

Transmission of C. neoformans seems to transmit mainly via inhalation of the bird feces, or consuming food that was in touch with these feces.

SYMPTOMS

Infection with C. neoformans may cause a pneumonia-like illness. Symptoms include shortness of breath, cough, and fever. C. neoformans can also infect the central nervous system and cause inflammation of the brain and meninges, which is called meningo encephalitis.

Symptoms of a central nervous infection may include fever, headache, or a change in mental status. If you experience symptoms that you think may be related to Cryptococcus neoformans, it is important to see your doctor right away.

PREVENTION

It is difficult to prevent exposure to C. neoformans because it is present throughout the environment. Most people breathe in small amounts of many different types of fungal spores every day but never become sick.

However, people who have weakened immune systems should avoid areas contaminated by bird droppings, and should avoid contact with birds. If you have symptoms that you think may be caused by C. neoformans, you should see a doctor.

Candida albicans


Taxonomical classification for Candida albicans is: Kingdom: Fungi; Phylum: Ascomycota; Class: Saccharomycetes; Order: Saccharomycetales; Family: Saccharomycetaceae; Genus: Candida; Species: albicans.

It normally resides in the intestinal tract, mouth, throat and genitals, however it can burrow holes in the intestinal tract, enter the blood stream and then make it's way into any organ of the body. To make matters worse it emits over 70 different toxins into the body. Some people may even become allergic to the yeast itself.


Figure 17. Cultive of Candida albicans on CHROM Agar.

CANDIDIASIS BY CONTAMINATED FOOD

Candidiasis is a fungal infection caused by yeasts that belong to the genus Candida. There are over 20 species of Candida yeasts that can cause infection in humans, the most common of which is Candida albicans.

Candida yeasts normally live on the skin and mucous membranes without causing infection; however, overgrowth of these organisms can cause symptoms to develop. Symptoms of candidiasis vary depending on the area of the body that is infected. Steroids and some cancer medications weaken the immune system and can allow yeast to flourish.

Tea, pepper, coffee, coffee substitutes, many spices and tobacco acquire molds or yeast in their drying processes. Left-overs from a previous meal should be frozen for future use, as they will become mold-containing within 24 hours. Brown spots on any food are yeasts and molds that have begun their job of breaking down that foods nutrients for their own survival.

Other foods that encourage Candida Albicans are baked goods, breads, biscuits and pancake mixes, soda crackers and any other foods requiring the use of baker's yeast. Ice cream, candy, malted milk drinks and soda fountain drinks contain sugar yeast.


Most of the time, Candida infections of the mouth, skin, or vagina occur for no apparent reason. A common

cause of infection may be the use of antibiotics that destroy beneficial, as well as harmful, microorganisms in the body, permitting Candida to multiply in their place. The resulting condition is known as candidiasis moniliasis, or a "yeast" infection.

Candida can cause the following problems depending upon the organ infected: In the kidneys can cause blood in the urine In the heart can cause murmurs and valve damage In the lungs can cause bloody sputum (mucus

discharge) In the eyes can cause pain and blurred vision In the brain can cause seizures and acute changes in

mental function or behavior

Keeping skin clean, dry, and free from abrasions or cuts can help prevent skin candida infections.Antifungal drugs usually clear up the trouble; the infection can recur, sometimes as a result of reinfection by a sexual partner. Hence, treatment of both partners is sometimes necessary.

Fusarium graminearum


Taxonomical classification for Fusarium graminearum is: Kingdom: Fungi; Phylum: Ascomycota; Class: Sordariomycetes; Order: Hypocreales; Family: Nectriaceae; Genus: Fusarium; Species: graminearum.


For wheat, brown, dark purple to black necrotic lesions form on the exterior surface of the florets and glume. Although these lesion symptoms sometimes are referred to as scab, they are not formally related to the hyperplasia and hypertrophic epidermal growth associated with other scab diseases such as apple scab. Peduncles immediately below the inflorescence may become discoloured brown/purple.

With time, tissue of the inflorescence often becomes blighted; appearing bleached and tan, while the grain within atrophies. Awns often become deformed, twisted and curved downward. In barley, infections are not always readily apparent in the field. Infected spikelets may show a browning or water-soaked appearance. Infected barley kernels show a tan to dark brown discolour ation that can be similar to that caused by other kernel blighting organisms.


Figure 18. Cultive of F. graminearum on PDA


F. graminearum is best known as a plant pathogen. It causes various diseases of cereal grains, such as gibberella ear rot in corn and Fusarium head blight or scab in wheat and other grains.

Toxic metabolites of the mold have been found to be toxigenic in humans and animals. The major mycotoxins produced by F. graminearum are deoxynivalenol (DON) and Zearalenone.

Some of the clinical symptoms of zearalenone in swine as reported by Trenholm et al. in 1984 include swollen or enlarged red vulva, vaginal prolapse in swine, and fertility problems. In the same study, it was reported that DON may cause decreased feed intake in swine and at very high concentrations, vomiting and feed refusal.

In humans DON has been found to be potentially immunosuppressive, and may result in kidney toxicity. Zearalenone may cause estrogenic issues in humans resulting in mild to severe reproductive effects.

The FDA has set advisory levels for DON of 1ppm in finished wheat products that may potentially be consumed by humans, and 10 ppm DON on grains and grain by-products destined for ruminating beef and feedlot cattle (1993.) There have been no advisory levels set as of yet for Zearalenone.

Alternaria alternata


Taxonomical classification for Alternaria alternata is: Kingdom: Fungi; Phylum: Ascomycota; Class:

Dothideomycetes; Subclass: Pleosporomycetidae; Order: Pleosporales; Family: Pleosporaceae; Genus: Alternaria; Species: alternata.

The genus Alternaria is characteristic by the large conidia. They are produced on chains, light brown to brown, ovoid or obclavate shaped muriform and divided by transverse and vertical walls, with or without beak at the tip (Fig 19). The hyphae and conidiophore are light brown and septate. The dark pigment can prevent the fungal organism from damage caused by UV-radiation.

Figure 19. Alternaria alternata spores


Allergic reactions caused by fungal mold have been recognized since 1726. In the past 300 years, it is reported that many fungi can cause the allergic reactions, such as Penicillium, Chaetomium, and wheat rust. Deuteromycetes has been recognize to contain most of the allergenic fungi; of which Alternaria alternata is one of the most important fungi that can cause asthma and rhinitis.

Not only the intact spores can produce and transfer the allergens, the fragmented hyphae and spores also can transfer the allergens. And, they can cause more asthma than intact spores because they can respiratory tract. And, allergy content in the spores can vary with the developmental conditions


Alternaria fruit spots are characterized by depressed, circular to oval, lesions that eventually become black as a result of mass sporulation by the pathogen. Lesons are restricted to the surface of the fruit and do not cause extensive rotting of the flesh. However, lesions from


multiple infection sites can coalesce as they expand and eventually cover the entire fruit surface.

Aspergillus parasiticus


Aspergillus parasiticus is a mold known to produce aflatoxin, although strains of it that do not produce this carcinogen exist. It is sometimes found on black olives.

Taxonomical classification for Cryptococcus neoformans is: Kingdom: Fungi; Phylum: Basidiomycota; Class: Tremellomycetes; Order: Tremellales; Family: Tramelleceae; Genus: Cryptococcus; Species: neoformans.


Aspergillus parasiticus Speare growth and aflatoxin production in black and white pepper and the penetration of the fungus in black pepper corn over various incubation periods were studied. Also, the effects of piperine and pepper oil on growth and aflatoxin production were studied.

Under laboratory conditions, black and white pepper supported aflatoxin production over 30 days of incubation (Fig 20).

Figure 20. Colonies of Aspergillus parasiticus after one week on MEA.

ASPERGILLOSIS BY CONTAMINATED FOOD

Aspergillus is a common fungus that can be found in indoor and outdoor environments. Most people breathe in Aspergillus spores every day without being affected. Aspergillosis is a disease caused by this fungus and usually occurs in people with lung diseases or weakened immune systems. The spectrum of illness

includes allergic reactions, lung infections, and infections in other organs.

Figure 21. Aspergillus ear rot of corn is caused by Aspergillus parasiticus.

These fungi may colonize only a few kernels on each ear but the colonization is a cause for concern nevertheless because these fungi produce aflatoxin, a potent carcinogen. The disease is most sever in areas with high temperatures and drought.

Aflatoxin B1, and naturally occurring mixtures of aflatoxins, identified as potent human carcinogens by IARC. Adverse effects in various animals, especially chickens. These Aflatoxins contaminate maize and peanuts (Fig 21).

SYMPTOMS

The different kinds of aspergillosis can cause different symptoms. Symptoms of allergic bronchopulmonary aspergillosis (ABPA) may include: Wheezing Coughing Fever (in rare cases)

Symptoms of invasive aspergillosis may include: Fever Chest pain Coughing Shortness of breath Aspergilloma, or “fungus ball”

Other symptoms may develop if the infection spreads beyond the lungs. When invasive aspergillosis spreads outside of the lungs, it can cause symptoms in almost any organ. If you have symptoms that you think are related to aspergillosis, contact your doctor.

PREVENTION

It is difficult to avoid breathing in normal levels of Aspergillus spores.


For people with weakened immune systems or severe lung diseases, there are steps that can be taken to help reduce exposure, including: Wear an N95 mask when near or in a dusty

environment such as construction sites Avoid activities that involve close contact to soil or

dust, such as yard work or gardening Use air quality improvement measures such as

HEPA filters Take prophylactic antifungal medication if deemed

necessary by your healthcare provider Clean skin injuries well with soap and water,

especially if the injury has been exposed to soil or dust

CONCLUSIONS

On balance, foodborne illness are given by a variety of microorganisms, some more dangerous than others, which contaminate a wide range of foods, among which the vast majority are those who we consume daily.

In most cases the microorganisms reach the food due to the lack of hygiene when handling, this being a vector very important for contamination of the food and something harmful to the consumer.The most common presenting symptoms of these diseases are: diarrhea, vomiting, fever and nausea, which occur after a few hours of eating the food.

Usually recommended to avoid eating foods that present a poor appearance on the surface, odor or showing a bad taste when consume them, being that in some cases contamination may not provoke visible changes in the food.

If for some reason you eat a contaminated food, it is recommended to visit the doctor immediately and avoid self-medication that can lead to even more serious problems.

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