Protozoa are single-celled organisms.  They are the cause of more sickness, death, mutilation, and debilitation in the world than any

other group of disease-causing organisms.  As eukaryotes, protozoa have a membrane-bound nucleus with well-defined

chromosomes.  They also have other cellular organelles that are characteristic of eukaryotes.

Examples of parasitic protozoa:

1.Sarcomastigophora - these include the flagellates and the amoebae. Chief amongst the flagellates are the trypansomes. With one exception trypanosomes are transmitted by vectors, usually by insects.

2.Trypanosomes - are divided into two types stercorarian and salivarian. In stercorarian trypanosomes the trypanosomes are taken up in the blood meal and grow and divide in the hindgut of the insect vector. Infection of the vertebrate host is by contamination, when the insect feeds it defecates and the trypanosomes gain entry through the feeding site or by the skin being scratched.

3. Entamoeba histolytica is one of a number of species of small amoebae which live in the alimentary canal of humans. These are usually harmless protozoa, feeding on bacteria and particles in the intestine. In certain conditions, entamoebae invade the wall of the intestine or rectum causing ulceration and bleeding, with pain, vomiting and diarrhoea, symptoms of amoebic dysentery. The faeces of infected people contain resistant forms, (cysts) of entamoeba.

4. Giardia is a flagellate protozoan that is found in the small intestine. The parasites attach to the intestinal lining causing inflammation, diarrhoea and abdominal pain (giardiasis), though how they do this is not clear. Giardia reproduces by binary fission and at some stage the protozoans produce resistant forms (cysts) which pass out of the alimentary canal in the faeces. These cysts can survive for months.

Plasmodium and MalariaThe malarial parasite, Plasmodium, is another protozoan which lives in the blood stream of humans but, unlike the trypanosomes, the parasites enter the red cells and feed on their cytoplasm. The Plasmodium divides repeatedly inside the red cell which eventually bursts, liberating dozens of new parasites into the circulation. Each of these can invade another red cell and undergo the same cycle. When thousands of red cells all burst simultaneously, releasing parasites and their accumulated waste products, the host suffers from a fever. This cycle of feeding, division and release is repeated regularly, so the fever occurs every 48 or 72 hours, according to which of the four species of Plasmodium has become established.

Leishmaniasis is a disease caused by the protozoa of the Leishmania species, which is transmitted by the bite of a female sandfly. While several ways to classify leishmaniasis (eg, by geography or taxonomy) are available, clinically, it can present itself in various ways, and is more easily classified as cutaneous, mucocutaneous, and visceral leishmaniasis.

Leishmaniasis is found in parts of about 88 countries. Most of these countries are in the tropics and subtropics. It is possible but very unlikely that you would get this disease in the United States. But you should be aware of it if you are traveling to the Middle East or parts of Central America, South American, Asia, Africa or southern Europe

ETIOLOGIC AGENT: 1. Leishmania = is a genus of trypanosome protozoa, and is the parasite responsible for the disease leishmaniasis.[1][2] It is spread through sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents, and humans.

AMEBIC CONJUNCTIVITIS AND KERTOCONJUNCTIVITIS - an amebic infection causing inflammation of the conjunctiva, corneal ulcers, pus formation, and severe pain, can lead to loss of vision

Etiologic agent : Acanthamoeba.

Reservoir and mode of transmission: Ameba-contaminated water.

TOXOPLASMOSISa parasitic disease caused by the protozoan Toxoplasma gondii.[1] The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid (cat) family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself recently been infected, or by transmission from mother to fetus.

1. amebiasis is an intestinal illness that's typically transmitted when someone eats or drinks something that's contaminated with a microscopic parasite called Entamoeba histolytica (E. histolytica). The parasite is an amoeba, a single-celled organism. That's how the illness got its name — amebiasis.

2. Balantidiasis (also known as balantidiosis) is defined as large-intestinal infection with Balantidium coli, which is a ciliated protozoan (and the largest protozoan that infects humans). B coli is known to parasitize the colon, and pigs may be its primary reservoir.

3. Cryptosporidiosis (crypto) is an illness caused by a parasite. The parasite lives in soil, food and water. It may also be on surfaces that have been contaminated with waste. You can become infected if you swallow the parasite.The most common symptom of crypto is watery diarrhea. Other symptoms include:-Dehydration -Weight loss -Stomach cramps or pain -Fever -Nausea -Vomiting

ETIOLOGIS AGENT: Cryptospordium parvum

4. Cyclosporiasis refers to infection by the sporeforming protozoan known as Cyclospora. Protozoa are a group of parasites that infect the human intestine. Parasites are organisms that live in another body, called the host, and get food and liquids from that host. This parasite is a member of the group of protozoa known as coccidia, to which Cryptosporidia also belongs. This group of parasites infects the human intestine, and causes chronic recurrent infections in those with altered immunity or AIDS. Even in people with normal immune function, Cyclopsora can cause prolonged bouts of diarrhea and other gastrointestinal symptoms.

5. Giardiasis is an infection of the small intestine caused by Giardia lamblia (also known as G. intestinalis), a flagellate protozoan. Giardiasis is the most commonly reported pathogenic protozoan disease in the United States. Travelers are the largest risk group for giardiasis infection, especially those who travel to the developing world. Giardiasis is prevalent among hikers and campers, people who swim in public pools, children who attend daycare, and in homosexual males.

1. Trichomoniasis, - one of the most common sexually transmitted diseases (STDs), is caused by a parasite, trichomonas vaginalis, that can live in the urogenital tract of males and females and infect any sexually active person, especially those who are not using protection or who have multiple partners.

1. African trypanosomiasis, - also called sleeping sickness, is a serious tropical disease that is always fatal without treatment. There are two types of African trypanosomiasis, named for the regions in Africa in which they are found: East African trypanosomiasis and West African trypanosomiasis. East African trypanosomiasis is caused by the parasite Trypanosoma brucei rhodesiense. West African trypanosomiasis is caused by Trypanosoma brucei gambiense. The parasites are spread by tsetse flies, found only in Africa.

2. Chagas disease - is a parasitic disease that is an important health problem in Central and South America. Chagas disease is also called American trypanosomiasis. Chagas disease is caused by the parasite Trypanosoma cruzi.

3. Babesiosis is an intraerythrocytic parasitic infection caused by protozoa of the genus Babesia and transmitted through the bite of the Ixodes tick, the same vector responsible for transmission of Lyme disease. While most cases are tick-borne, transfusion and transplacental transmission have been reported. In the United States, babesiosis is usually an asymptomatic infection in healthy individuals. Several groups of patients become symptomatic, and, within these subpopulations, significant morbidity and mortality occur.

4. Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells.

1. PRIMARY AMEBIC MENINGOENCEPHALITIS - The free-living amebae Naegleria fowleri1 , Acanthamoeba species, Balamuthia mandrillari s2 , and Sappinia species3 cause extremely rare and sporadic CNS infections, which were first described in 1965. Typically, N fowleri produces primary amebic meningoencephalitis (PAM), which is clinically indistinguishable from acute bacterial meningitis. The other amebae cause granulomatous amebic encephalitis (GAE), which is a more subacute or chronic infection. The presentation of GAE can mimic a brain abscess, aseptic or chronic meningitis, or CNS malignancy.

2. Toxoplasmosis is a disease caused by the parasite Toxoplasma gondii. More than 60 million people in the U.S.

have the parasite. Most of them don't get sick. But the parasite causes serious problems for some people. These

include people with weak immune systems and babies whose mothers become infected for the first time during pregnancy. Problems can include damage to the brain,

eyes and other organs.

A worm classified as a parasite. (A parasite is a disease-causing organism that lives on or in a human or another animal and derives its nourishment from its host.) One example of parasites that live on humans is lice; bacteria and viruses are examples of parasites that live either on humans or in humans; helminths are examples of parasites that live in humans.

THREE GROUPS OF HELMINTHS:1.NEMATODES OR ROUND WORM

2. CESTODES OR TAPEWORMS

3. TREMATODES OR FLUKES

The nematodes are non segmented helminths and have bilateral symmetry.  They possess a complete digestive tract with oral and anal openings.  They have separate sexes the male being smaller than the female.  They range from a few millimeters to over a meter in length. 

KINDS OF NEMATODES1. Stubby-Root Nematode, Paratrichodorus minor - Paratrichodorus minor was the first ectoparasitic nematode shown to damage plants. On most hosts, feeding by P. minor on cells of root tips causes growth and elongation of roots to cease, and results in stubby-root symptoms.

2. Awl Nematodes, Dolichodorus spp. - Awl nematodes can cause damage as severe as that caused by the sting nematode (Belonolaimus longicaudatus), but because they are generally limited to moist habitats this damage is not as widespread. Awl nematodes have been shown to cause root stunting or reduced yields in many crops including carrots, celery, corn, cotton, beans, cabbage, lettuce, pepper, potato, spearmint and tomato.

3. Lance Nematode, Hoplolaimus galeatus

-In Florida, lance nematodes are right behind sting nematodes as the worst nematode pests of turfgrass. They are very common in home lawns and are the major nematode pest of St. Augustinegrass in the Southeast. Lance nematodes are also an important pest on golf courses and are the most common nematodes causing damage on Bermudagrass putting greens in Florida.

The cestodes or tapeworms found in humans, all have a flat, ribbon like body.  They inhabit the small intestine and are attached to the mucosa by means of a scolex.  The body consists of a chain of segments or proglottids.  The proglottids can be immature, mature or gravid the latter of which contain a fully developed uterus full of eggs.   KINDS OF CESTODES

1. Echinococcus - Echinococcus granulosus - also called the Hydatid worm or Hyper Tape-worm, is a cyclophyllid cestode that parasitizes the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes hydatid disease. The adult tapeworm ranges in length from 2 mm to 7 mm and has three proglottids ("segments") when intact - an immature proglottid, mature proglottid and a gravid proglottid. Like all cyclophyllideans, E. granulosus has four suckers on its scolex ("head"), and E. granulosus also has a rostellum with hooks.

Taenia is a genus of tapeworm that includes some important parasites of livestock. Members of the genus are responsible for taeniasis and cysticercosis in humans. There are more than 100 species recorded. They are morphologically characterized by a ribbon-like body composed of a series of segments called proglottids; hence the name Taenia (Greek tainia meaning ribbon, bandage or stripe). The anterior end of the body is the scolex.

The trematodes or flukes are leaf shaped and covered with a resistant cuticle which may be smooth or spiny. 

KINDS OF TREMATODES1. Clonorchis sinensis - Is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile. These animals, which are believed to be the third most prevalent worm parasite in the world, are endemic to Japan, China, Taiwan, and Southeast Asia, currently infecting an estimated 30,000,000 humans.

2. Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic flatworm of the class Trematoda, phylum Platyhelminthes that infects liver of various mammals, including humans. The disease caused by the fluke is called fascioliasis (also known as fasciolosis). F. hepatica is distributed worldwide and causes great economic losses in sheep and cattle.

3. Paragonimus westermani is a lung fluke and is most prominent in Asia and South America. It was discovered from two Bengal tigers that died in zoos in Europe in 1878. Several years later, infections in humans were found in Formosa.

Derived from the Greek word “helmins,” meaning “worm,” Helminth is a broad categorical term referring to various types of parasitic worms that reside in the body. Parasites get their nourishment from their hosts, causing disease and sickness while continuing to feed off of their environment. Unlike parasites like lice and fleas that live outside their host, Helminths are classified as eukaryotic parasites because they live inside the body.Many helminth infections occur in poverty-stricken and developing countries with warm, moist environments and poor sanitary conditions. Helminths can live in humans and animals and are usually transmitted through contaminated food or water, feces, and unwashed hands or contact with a contaminated object. Helminth infections normally found in livestock can be transferred from animal to man through a process called zoo noses and can then cause increased prevalence among humans. Although few helminth infections lead to death, most of them do cause severe physical impairment.

*Some subtypes of this disease are contagious - spread easily between people, while other subtypes are infectious - transmitted by a pathogenic organism.

1. Onchocerciasis is an infection caused by the nematode Onchocerca volvulus. Humans acquire onchocerciasis through the bite of Simulium blackflies.1,2,3 Because the fly develops and breeds in flowing water, onchocerciasis is commonly found along rivers and is sometimes referred to as river blindness.

1. Trichinosis. Trichinella spiralis is the cause of trichinosis in man. The nematode circulates between rats and pigs with man becoming infected from eating raw or inadequately cooked pork products. Encysted larvae in the meat excyst (hatch) in the intestine and develop into minute adults in the mucosa. These mature and the females deposit larvae that then migrate through the tissues to reach skeletal muscles in which they encysted. Human infections may be asymptomatic but can include fever, orbital edema, myalgia and eosinophilia. In the extreme, infection can be fatal through myocarditis or encephalitis.

2. Dracunculiasis is infection with Dracunculus medinensis, a nematode worm. It is caused by drinking water containing water fleas (Cyclops species) that have ingested Dracunculus larvae.

In the human body, the larvae are released and migrate through the intestinal wall into body tissues, where they develop into adult worms. The female worms move through the person’s subcutaneous tissue, causing intense pain, and eventually emerge through the skin, usually at the feet, producing oedema, a blister and eventually an ulcer, accompanied by fever, nausea, and vomiting. If they come into contact with water as they are emerging, the female worms discharge their larvae, setting in motion a new life cycl

Paragonimiasis is a disease caused by species of lung flukes of the genus Paragonimus. Eight species have been identified which use man as a host, and the disease has a range of Asia, Africa, and the Americas. The most predominant infective species are P. westermani and P. kellicotti.

1. Enterobiasis - Enterobias vermicularis is a small thread-like "pinworm" mainly infecting young children. The female emerges to the perennial region usually at night and lays some 10,000-15,000 eggs and then dies. In the process they cause severe pruritis (itching). The embryonated eggs are infectious on ingestion and hatch in the duodenum. The larvae pass to the caecum where they mature into adults. Because of the pruritis, children often re-infect themselves from eggs under their fingernails.

2. Hydatidosis- This is caused by the tapeworm Echinococcus granulose. The adult worm inhabits the small intestine of dogs from which the eggs of the species are passed. These eggs can be ingested by herbivorous animals and hatch in the duodenum. The embryos enter the circulation where they are carried to various sites to develop into cysts.

Schistosomiasis, or bilharzia, is a parasitic disease caused by trematode flatworms of the genus Schistosoma. Larval forms of the parasites, which are released by freshwater snails, penetrate the skin of people in the water. In the body, the larvae develop into adult schistosomes, which live in the blood vessels. The females release eggs, some of which are passed out of the body in the urine or faeces. Others are trapped in body tissues, causing an immune reaction.

1. Hyposalinity or OST (Osmotic Shock Therapy) is one of the most effective, non-chemical ways to rid fish and an aquarium of saltwater ich and other parasitic diseases, as well as eliminate undesirable pests in saltwater systems, such as aiptasia anemones.

What Hyposalinity Kills ?Osmotic Shock Therapy (O.S.T. or hyposalinity) is one of the most effective, non-chemical ways to rid saltwater fish and aquariums of parasitic ich diseases, as well as can be used to eliminate a number of other pests* that often plague saltwater systems. Unfortunately the downside of using this method to kill bad things you don't want is that it will kill other desirable things as well. This includes, but may not be limited to following animals: Aiptaisia Anemones*Black Spot Disease* (Black Ich/Tang Disease)Brooklynellosis* (Saltwater Ich/Clownfish Disease) Corals Cryptocaryon(Saltwater Ich/White Spot Disease) Non-Shelled Snails/Nudibranchs/Sea Slugs Oodinium•(Saltwater Ich/Velvet, Rust, Coral Fish Disease) •Sea Anemones •Sea Cucumbers •Sea Urchins• Tube Worms (Feather Dusters)

2. Cysteine proteinase inhibitors- Clan CA (papain-like) cysteine proteinases of protozoan parasites are validated targets for the rational design of new anti-parasitic chemotherapies. Peptidyl and peptidomimetic proteinase inhibitors of differing chemistries limit parasite survival in vitro and in vivo. Also, the development of activity-based affinity labels has enabled the identification and characterization of potential cysteine proteinase targets in situ. This article reviews the biology and physicochemistry of parasite proteinases and the ongoing design of peptidyl and non-peptidyl inhibitors to generate anti-parasitic compounds of greater efficacy with decreased toxicity to the host.