‫المحاضرة الرابعة‬
Parasitology
Phylum: Protozoa
Class Zoomastigophorea
Examples:



Trichomonas
Trypanosoma
Leishmania
Characters of class
zoomastigophorea
1) Motion is by flagella. The flagellum arises from kinetoplast.
The kinetoplast is composed of the blepharoplast and the parabasal body.
2) Vesicular nucleus with central karyosome.
3) Reproduction is by longitudinal binary fission.
4) Complex life cycles include alternation of hosts.
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Intermediate hosts commonly serve as vectors, which transport developing parasites
from one definitive host to another.
 Some species are living in the digestive tract and genitals as Trichomonas
vaginalis. Their transmission does not require a biological vector.

Parasitical species parasites of tissues and blood as Trypanosoma and
Leishmania. Their transmission requires a biological vector.
Trichomonas vaginalis
Parasite: Trichomonas vaginalis
Disease: Urogenital trichomoniasis
Geographical distribution:
cosmopolitan.
Morphology: Trophozoite is a
pear-shaped (7 to 23 micro; m long)
with four anterior flagella and a
fifth forming the edge of an
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Trichomonas vaginalis
‫المحاضرة الرابعة‬
Parasitology
undulating membrane. The axostyle
extends the length of the body.
Host: human
Transmission: by sexual contact;
otherwise (through contact with toilet
seats and towels, for example).
Localization: vagina, urethra, prostate.
Clinical Manifestations: vaginitis in
women, more commonly asymptomatic
in men, but may lead to prostatitis or
urethritis. The main symptoms are
dysuria, pruritis, yellow and frothy
discharge.
Laboratory diagnosis: microscopic
examination of the vaginal fluid,
scrapings, or washing.
Life Cycle of Trichomonas vaginalis
 Trichomoniasis is a sexually transmitted infection caused by a parasite.
 Trichomonas infection can affect women or men.
 Many people who have the infection have no symptoms, but when symptoms
occur, they include vaginal or urethral (in men) discharge that may appear
greenish and frothy, burning on urination, discomfort during sex, and itching
in the genital area.
 Diagnosis is based upon identifying the parasite through miscroscopic exam
in the vaginal or urethral discharge.
 Trichomonas infection can be treated with antibiotics.
 Left untreated, the infection can persist over the long term. It may also recur
following treatment.
 Trichomonas infection during pregnancy can lead to premature birth and low
birth weight.
Trypanosoma
A genus of asexual digenetic
protozoan flagellates that have a
spindle-shaped body with an
undulating membrane on one
side, a single anterior flagellum,
and a kinetoplast; they are
Trypanosoma
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‫المحاضرة الرابعة‬
Parasitology
parasitic in the blood plasma of many vertebrates (only a few being pathogenic) and
as a rule have an intermediate host, a bloodsucking invertebrate, such as a leech,
tick, or insect; pathogenic species cause trypanosomiasis in humans and other
diseases in domestic
animals.
Highly magnified view of Trypanosoma (red arrow)
swimming among red blood cells .
 African sleeping sickness is caused by
T. gambiense and T. rhodesiense, two species
of flagellates transmitted by biting flies of the
genus Glossina, better known as tsetse flies.
Unless treated in early stages, African
sleeping sickness is a potentially fatal disease.
Life Cycle of Trypanosoma
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‫المحاضرة الرابعة‬
Parasitology
Infection and symptoms:
Trypanosoma gambiense is found in 24 countries in west and central Africa.
This form currently accounts for over 98% of reported cases of sleeping sickness
and causes a chronic infection.
A person can be infected for months or even years without major signs or
symptoms of the disease.
When symptoms emerge, the patient is often already in an advanced disease stage
where the central nervous system is affected.
Sleeping Sickness (Trypanosmiasis)
Infection from the flagellate protozoan Trypanosoma brucei gambiense is
transmitted by the tsetse fly.
Sleeping sickness is characterized by fever, inflammation of the lymph nodes, and
involvement of the brain and spinal cord leading to profound lethargy, frequently
ending in death.
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