Download Parasitology Part I Protozoans

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 protists
characterized 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 selflimiting 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.