Part I Protozoans

Parasitism:Two organisms living together

One benefits from the relationship at the expense of the other

 

 Three groups of parasites Protozoan Metazoan Exoparasites

All the parasites are eukaryotes.

All protozoans have 2 important stages of life:

Trophozoite – active, free swimming state of protozoan

Cyst – dormant phase. In most cases this is the infective stage.

Classified by the way they move.

Amoeba (sarcodina)

Flagellates (mastigophora)

Ciliates (ciliophora)

Sporozoans (apicomyplexa)

Sarcodina the largest phylum (11,500 living species) of protozoans.

It comprises the amebas and related organisms; which are all solitary cells that move and capture food by means of pseudopods, temporary

extensions of the cell.

Most sarcodines are free living; others are parasitic. One of these parasites is the causative organism of amebic dysentery.

Most sarcodines are free living; others are parasitic. They are found in aquatic

and terrestrial habitats.

Entamoeba histolytica is the causative agent of

dysentery.

Acanthamoeba is the etiology of amoebic keratitis and encephalitis.

Encephalitis is caused by Acanthamoeba entering cuts or through the nares and spreading to the central nervous system.

Most of the approximately 1,500 species of Mastigophora are propelled by one or more flagella, and members of the group are referred to as flagellates.

Giardiasis, infection of the small intestine

by a protozoan, Giardia lamblia.

Giardia is spread via the fecal-oral route, most commonly by eating food contaminated by the unwashed hands of an infected person or by drinking groundwater polluted by the feces of infected animals such as dogs and beavers (hence the nickname "beaver fever" ).

It attaches itself to the walls of the small intestine and there multiplies

quickly.

Trichomoniasis is caused by a Trichomonas vaginalis and is passed almost 100% of the time through sexual contact.

Trichomoniasis is primarily an infection of women's vaginal and urinary tracts.

A woman is most susceptible to infection just after having completed her menstrual period.

Men also may carry the organism unknowingly, since infection in men may cause mild or no symptoms.

Human African Trypanosomiasis,

also known as sleeping sickness,

is a vector-borne parasitic

disease.

The parasites concerned are protozoa

belonging to the Trypanosoma Genus.

They are transmitted to humans by

tsetse fly (Glossina Genus) bites

which have acquired their infection

from human beings or from animals

harbouring the human pathogenic

parasites.

Chagas diseases occurs in 15 Central

and South American countries.

The symptoms of Chagas disease vary

over the course of an infection. In the

early, acute stage, symptoms are mild

and usually produce no more than

local swelling at the site of infection.

As the disease progresses, over the

course of many years, serious chronic

symptoms can appear, such as heart

disease and malformation of the

intestines. If untreated, the chronic

disease is often fatal.

The ciliates are a group of protistscharacterized by the presence of hair-like organelles called cilia.

Cilia are identical in structure to Flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella.

Infection occurs when a host ingests a cyst, which usually happens during the consumption of contaminated water or food.

Once the cyst is ingested, it passes

through the host’s digestive system.

The Apicomplexa are a large group of protists, most of which possess a unique organelle called apicoplast and an apical complex structure involved

in penetrating a host's cell.

They are unicellular, spore-forming, and exclusively parasites of animals.

They are non-motile protozoans and rely on the fluid structures of the body for movement.

Malaria is a vector-borne infectious disease caused by a eukaryotic protist of the genus Plasmodium.

It is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa.

Each year, there are approximately 350–500 million cases of malaria,

killing between one and three million people, the majority of whom are

young children in Sub-Saharan Africa.

.

Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. 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 faces of a cat that has itself recently been infected,

or by transmission from mother to fetus.

Cats have been shown as a major reservoir of this infection.

Cryptosporidiosis, also known as crypto, is a parasitic disease caused

by Cryptosporidium, a protozoan parasite in the phylum Apicomplexa.

It affects the intestines of mammals and is typically an acute short-term infection.

It is spread through the fecal-oral route, often through contaminated water; the main symptom is self-limiting diarrhea in people with intact immune systems.

In immunocompromised individuals,

such as AIDS patients, the symptoms

are particularly severe and often fatal.

Cryptosporidium is the organism most

commonly isolated in HIV positive

patients presenting with diarrhea.

Treatment is symptomatic, with fluid

rehydration, electrolyte correction and

management of any pain. Despite not

being identified until 1976, it is one of

the most common waterborne diseases

and is found worldwide.

The parasite is transmitted by

environmentally hardy microbial cysts

(oocysts) that, once ingested, exist in the

small intestine and result in an infection of

intestinal epithelial tissue.