Lec.No.1 Prof.Dr.Abdulsalam Al-Mukhtar

Medically Important Helminths In contrast to the protozoa one cell parasites (unicellular). Helmthins are worm -like parasites (multicellular) causing diseases to human.

They are characterised with:

(1)complex reproductive systems.

(2) life cycles involving intermediate hosts or soil for the development of larval stages and a definitive host for the adult worm.

(3)Adults may be with separate sexes or hermaphroditic which mean both sexes in one parasite.

The helminthic infection is world wide in distribution , such as Ascaris, hookworms, and Trichuris trichiura and schistosomes.  

 The classification of medical helminths is:

1.Nematodes ( Roundworms )

Adult roundworms are bisexual, cylindrical worms and they have Lips, teeth or dental plates,and filariform extremities. They inhabit intestinal and extra-intestinal sites.

  

2.Cestodes (Tapeworms )

Adult tapeworms are elongated, segmented, hermaphroditic flatworms and they have oral sucker and hooks.They inhabit the intestinal lumen.   

3.Trematodes ( Flukes ) Adult flukes are leaf-shaped flatworms. They

have oral and ventral suckers .

Flukes are hermaphroditic except for blood flukes, which are bisexual .

The life-cycle includes a snail intermediate host.

Ascaris lumbricoides(Ascariasis)

The infections are usually asymptomatic, especially if the number of worms is small .

Morphology

It is the largest nematode (roundworm) parasitizing the human intestine,the male smaller than female . Adult females about 20 to 35 cm.long.

Adult male about 15 to 30 cm.long .

Adult worm

Eggs of A.lumbricoides

Symptoms or Clinical Features 1.Ascaris takes most of its nutrients from the partially digested food in the intestine.

2. If the number of worms are few, patients can remain asymptomatic for very long periods of time.

3.Chilidren are more likely than adults to develop gastro-intestinal symptoms because they have smaller intestines and are at greater risk of developing intestinal obstruction.

4.As larval stages travel through the body, they may cause inflammation, and pneumonia and the patient suffer from: Loss of appetid ,

Fever, wheezing .

5 .In haevy infections may cause nutritional deficiency.

6.Complications, sometimes fatal, include obstruction of the intestine by a large number of worms especially in children .and also may cause obstruction with following symptoms:

Vomiting Shortness of breath Swelling of the abdomen Sever abdominal pain.

EpidemiologyAscariasis is the most common intestinal worm infection. World wide distribution. It is found in association with:

poor personal hygiene, poor sanitation, and in places where

human feces are used as fertilizer.

The source of transmission is from ingestion of infective eggs from contaminated hands with infected human feces or contaminated vegetables and water is the primary source of infection.

Laboratory Diagnosis Microscopic identification of eggs in the stool is ithe most common method for diagnosing  ascariasis.

The procedures are :1.Direct method by drop of ioden and

drop of stool.

.Concentration method .

3.The diagnosis is easy when the host passes a worm in the stool or larvae in vomit. 4.Larvae may be found in sputum during migration of larvae through the lung.

5.Blood counts may demonstrate peripheral eosinophilia.

Prevention 1.Improved sanitation and hygiene in developing countries will reduce the risk in those areas. 2.preventive (prophylactic) treatment with deworming medications may be advised. The following methods are very important to do :

3.Food and hands should be protected from contamination of infected dirt and soil.

4.Washing of vegitable by running water is very important for cleaning from contaminated infective eggs .

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Treatment Albendazole or mebendazole which are the drugs of choice. If there is a blockage of the intestine caused by a large number of worms, endoscopy or, rarely, surgery may be needed.

Lec.2 .

Enterobius vermicularis :

E.vermicularis is nematode (previously called Oxyuris vermicularis) also called human pinworm also known as threadworm or seat worm.  Humans are is the only host of .E.vermicularisE vermicularis is a common human intestinal parasite infecting the cecum, especially in children. The disease is known as enterobiasis, or sometimes called

oxyuriasis . 

Morphology 1.The adult pinworm appears as a white,

small and delicate nematode. 2.The adult female has a sharply pointed posterior end, is 8 to 13 millimeters long. 3.The adult male is smaller, measuring 2 to 5 millimeters long , and it has a

curved posterior end .

4.The egg are translucent, and may contain a developing embryo or a fully developed larva. The eggs are oval in shape with thick outer shell is flattened on one side, and measure 50 to 60 micrometers by 20 to 30

micrometers .

Life cycle

The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. 

The life span of the adults is about two months. 

  The females migrate during the night outside the anus and oviposit while crawling on the skin of the perianal area.   The larvae developed inside the eggs which become infective in 4 to 6 hours under optimal conditions .

 

Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum and then migrate up to the final habitate the cecum.

Geographic Distribution:

The human pinworm Enterobius vermicularis is being estimated that over 200 million people are infected with this parasite. It is more common in the temperate and tropical regions of Asia, Europe and North America.

 

Worldwide, with infections more frequent in school- or preschool- children and in crowded conditions.

Unlike many other intestinal parasites, the pinworm does not enter the bloodstream or any other organs besides the intestines.  

Transmission usually occur from person-to -person, also occur through handling of contaminated clothes or bed.  

 

Enterobiasis may also be acquired from contaminated environment with pinworm eggs which inhaled and then it reach the pharynx and pass down the oesophagus and migrate to the large intestine(cecum).

Clinical Features: Enterobiasis is frequently asymptomatic.  The most typical symptom is perianal pruritus, especially at night, which may lead to bacterial superinfection.

Except for itching, pinworm infestation does not usually cause any direct damage to the body. 

Other symptoms include anorexia, irritability, and abdominal pain.

However, the scratching of the itch can spread germs from the fingers to other parts of the body. Sleep disturbance may arise from the itching or crawling sensations of the worns.

Some case reports proved that severe infestation may be associated with an increased risk for appendicitis.

Laboratory Diagnosis:  1. Microscopic identification of eggs collected in the perianal area is the method of choice for diagnosing enterobiasis.  

This must be done in the morning, before defecation and washing, by pressing transparent adhesive tape ("Scotch test", cellulose-tape slide test) on the perianal skin and then examining the tape placed on a slide. 

2.Eggs can also be found, but occasionally, in the stool .

3 .Diagnosis is often made clinically by

observing the female worm (or many worms) in the stool, or perianal area .

4.Self-diagnosis is also possible with observing worms around the anus. Crawling sensations inside the anus indicate female pinworm migration,this crawling sensations caused by large numbers of pinworms in the lower rectal area, simply by manually removing some of

them .

Prevention and control 1. All the patients sould be treated.

2.Personal hygiene should be proved to prevent reinfection and also clothes and bedding sheets, should be washed with hot water and cleaned.

3.The nails of the patient should be cut.

4.The hands always wased with water and remain clean.

 

Treatment:

The drug of choice is pyrantel pamoate.

Other Antihelmintic drugs albendazole, mebendazole, Piperazine are also used to treat pinworms. The person being treated should receive a second course after two weeks.  

Lec. No.3 Dr.Abdul Salam M.Al-Mukhtar

Hookworm: These worms are parasitic nematode worm that lives in the small intestine of human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus and causing .Ancylostomiasis

Ancylostomiasis, is the disease caused by hookworms. It is caused when hookworms, present in large numbers, produce an abdominal pain and iron deficiency anemia by contineous sucking blood from the host's intestinal walls.

There are other species of ancylostoma infect animals like A. braziliense species which infect cats, while A. caninum infects dogs.

Morphology of Adult ,Egg

Pathology and Symptomatology

The incubation period can vary between a few weeks to many months and is largely dependent on the number of the parasites, usually the infection is generally considered to be asymptomatic, The hookworm is an extremely dangerous infection because its damage is “silent and insidious. There are general symptoms that appear soon after infection:

1 .Ground-itch, which is an allergic reaction at the site of parasitic penetration of the skin and entry. 2. Cough and pneumonitis may result as the larvae begin to break into the alveoli and travel up the trachea. 3. Then once the larvae reach the small intestine of the host and begin to mature, the infected individual will suffer from diarrhea and other gastrointestinal discomfort.

4 .However, the “silent and insidious” symptoms are mainly related to chronic, heavy-intensity hookworm infections. 5.Major morbidity associated with hookworm is caused by intestinal blood loss, iron deficiency anemia, and protein malnutrition. They result mainly from adult hookworms in the small intestine ingesting blood, rupturing erythrocytes, and degrading hemoglobin in the host.

6.The children who suffer from chronic hookworm infection can suffer from growth retardation. 7. The symptoms can lead to inflammation in the gut stimulated by feeding hookworms, such as nausea, abdominal pain and intermittent

diarrhea, and to progressive anemia .

8 -Blood examination in early infection often show a rise in numbers of eosinophils. 9-Falling blood hemoglobin levels will be seen in cases of chronic or prolonged infection with anemia.

Epidemiology

It is estimated that between 576-740 million individuals are infected with hookworm today .

A. duodenale is found in Europe and the Mediterranean. Most infected individuals are concentrated in Africa and East Asia/the Pacific Islands. A majority of these infected individuals live with poor sanitation.

Prevention

1-Hookworm infection results because of non-hygienic practices and fecal contact in the soil,so the low sanitation should be proved. 2- Fecal matter should be chemically treated, and the sewage or untreated 'night soil' should not used as fertilizer in agriculture befor

chemically treated .

3-The infective larvae develop and survive in an environment of dirt, sandy or loamy and moist soil, so this type of soil should be desciccated to kill the larvae.. 4-Wearing shoes can prevent penetration of the worms into the skin of the feet.

5-Contaminate water with larvae can also transmit the infection. Therefore, swimming and washing and any other contact with the water should be avoided until it's treated or boiled to kill the larvae .

Diagnosis of hookworms :

1.It depends on finding characteristic worm eggs on microscopic examination of the stools .

The eggs are oval, measuring 60 µm by 40 µm, colourless, and with a thin transparent hyaline shell membrane. When released by the worm in the intestine, the egg contains an unsegmented ovum. During its passage down the intestine, the ovum develops and thus the eggs passed in feces have a segmented

ovum, usually with 4 to 8 blastomeres .

2-Recent research has focused on the development of DNA-based tools for diagnosis of infection .

Treatment1-The most common treatment for Hookworm are 2-Benzimidazoles (BZAs), specifically albendazole and mebendazole.

2- It is also recommended that if the patient also suffers from anemia that ferrous sulfate (200 mg) be administered 3/day at the same time as anthelmintic treatment; this should be continued until hemoglobin values return to normal.

3- High protein diet should be given wich can improve the protein lack in patient.

The different between A.duodenale and N.americanus:

1 .N. americanus is very similar in morphology to A. duodenale. N. americanus is generally smaller than A. duodenale with males usually 5 to 9 mm long and females about 1 cm long .

2. A. duodenale possess two pairs of teeth, N. americanus possesses a pair of cutting plates in the buccal capsule. Additionally, the hook shape is much more defined in Necator than in Ancylostoma.

3.The eggs of both Ancylostoma and Necator are indistinguishable.

4.A. duodenale can infect both through penetration as well as orally,while N. americanus larvae only infect through penetration of skin.

5.Necator tends to cause a chronic infection, generally 1–5 years. Ancylostoma adults are short lived, surviving on average for only about 6 months.

6.The entire process from skin penetration to adult development takes about 5–9 weeks.

7.The number of eggs released by female of N. Americanus about 9,000-10,000 eggs/day

and A. duodenale 25,000-30,000 eggs/day .

8 -The ground itch is more common in patients infected with N. americanus .

9-N. Americanus is found in Americas, Africa, and Asia. A. duodenale is found in Europe and the Mediterranean areas .

10.The eggs of both Ancylostoma and Necator are morphologically indistinguishable .

11.The treatment is the same for hookworm

are 2-Benzimidazoles (BZAs), specifically albendazole and mebendazole .

Lecture No.5 Dr.Abdul Salam M.Al-Mukhtar

Strongyloides stercoralisAims

To provide core knowledge of Strongyloides stercoralis relevant to the morphology, life cycle,diagnosis and management (drug of choice),prevention and control of infectious diseases.

Learning ObjectivesOur goal is to help students become skillful and caring physicians with the knowledge and compassion to prevent, diagnose, and treat infectious diseases.

Lecture No.5 Dr.Abdul Salam M.Al-MukhtarStrongyloidiasis:

Causal Agent: The nematode (roundworm) Strongyloides stercoralis.  Other Strongyloides include S. fülleborni, which infects chimpanzees and baboons and may produce limited infections in humans.

The Strongyloides life cycle is more complex than that of most nematodes with its alternation between free-living and parasitic cycles, and its potential for autoinfection and multiplication within the host.  Two types of cycles exist:

Free-living cycle: The rhabditiform larvae passed in the stool (see "Parasitic cycle" below) can either molt twice and become infective filariform larvae (direct development)

or molt four times and become free living adult males and females that mate and produce eggs from which rhabditiform larvae hatch .  The latter in turn can either develop into a new generation of free-living adults (as represented in ), or into infective filariform larvae .  The filariform larvae penetrate the human host skin to initiate the parasitic cycle (see below)

Parasitic cycle: Filariform larvae in contaminated soil penetrate the human skin , and are transported to the lungs where they penetrate the alveolar spaces; they are carried through the bronchial tree to the pharynx, are swallowed and then reach the small intestine. In the small intestine they molt twice and become adult female worms . 

The females live threaded in the epithelium of the small intestine and by parthenogenesis produce eggs , which yield rhabditiform larvae. 

The rhabditiform larvae can either be passed in the stool (see "Free-living cycle" above), or can cause autoinfection .

  In autoinfection, the rhabditiform larvae become infective filariform larvae, which can penetrate either the intestinal mucosa (internal autoinfection) or the skin of the perianal area (external autoinfection); in either case, the filariform larvae may follow the previously described route, being carried successively to the lungs, the bronchial tree, the pharynx,

and the small intestine where they mature into adults; or they may disseminate widely in the body.  To date, occurrence of autoinfection in humans with helminthic infections is recognized only in Strongyloides stercoralis and Capillaria philippinensis infections.  In the case of Strongyloides, autoinfection may explain the possibility of persistent infections for many years in persons who have not been in an endemic area and of hyperinfections in immunodepressed individuals.

Person-to-person transmission can also occur through handling of contaminated clothes or bed linens.  Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting ). Some small number of eggs may become airborne and inhaled.