Parasitic Protozoans

Lecture 4

2- Flagellates

1- Trypanosoma spp.

2- Leishmania spp.

3- Giardia spp.

4- Trichomonas spp.

1- Hemoflagellates 1- Trypanosoma spp.

2- Leishmania spp.

Called Hemoflagellates because they have a flagellum and require blood medium to culture them.

A.K.A. Kinetoplasta Flagellum is attached to an undulating membrane attached to a kinetoplast.

There is evidence for sexual reproduction but when it occurs is not known.

They can also absorb and use foreign DNA.

1- Hemoflagellates

Two host life cycle Humans and their domestics are Definitive Host Insect vectors are the Intermediate Host Four life stages Not all stages occur in all species Certain stages are found in specific hosts

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Epimastigotes and promastigotes in insect IH

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Amastigoes and trypomastigotes in DH

1- Trypanosoma spp.

1- Trypanosoma gambiensi 2- T. rhodesiensi 3- T. curzi 4- T. lewisi

1- Trypanosoma gambiensi 2- T. rhodesiensi

Definitive Host: Humans. Not pathenogenic to any other species. Native ruminates serve as reservoirs for T.b. rhodesiense, but not

T.b. gambiense.

Intermediate Host: Tsetse fly (Glossina) Mode of transmission: Bite of infected tsetse fly Tsetse fly (Glossina)

Geographic Distribution

T. b. gambiense

is found in west central and central Africa.

T. b. gambiense T. b. rhodesiense

found in central and east central Africa

T. b. rhodesiense

Life cycle

1- Trypanosoma gambiensi 2- T. rhodesiensi

Location: and tissues Throughout the body in the blood Pathology: Both subspecies cause African Sleeping Sickness.

T.b. gambiense causes chronic, long-term form.

T.b. rhodesiense causes an acute form.

Starts with a small sore at bite.

Trypimastigotes divide rapidly and spread throughout body

Pathology

Pathology (con’t): Lymph nodes become swollen and congested Particularly the nodes in neck Called Winterbottom’s sign

Pathology

T.b. gambiense

frequently goes to CNS Causes the chronic, sleepiness associated with African Sleeping Sickness

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Apathy, mental dullness, disturbance of coordination Increase in sleepiness, finally to coma, and death.

Death may also occur from malnutrition, falling, or other infections

Pathology

T.b. rhodiensiense

rarely invade the CNS but causes death much faster.

Usually due to invasion of heart tissue Both subspecies produce intermittent periods of fever, particularly in early stages.

Due to antigen shifts of the parasite.

They can also take antigens from host body and put them on their body Much pathology may be due to heightened immune response killing uninfected body cells.

Diagnosis Trypomastigotes in the blood smear.

Can also be in cerebrospinal fluid Serological test available

3- Trypanosoma curzi

Definitive Host: Humans, dogs, cats, opossums, armadillos, and wood rats.

Intermediate Host: Reduviid bugs (Kissing bug or assassin bugs).

Location in the Definitive Host: Throughout the body. Trypomastigotes in blood Amastigotes most common in spleen, liver, and muscles, including heart Mode of Transmission: Host rubs tryps into bite wound.

Geographic Distribution Throughout much of central and South America.

12-19 million infected Annual incidence 561,000 2-3 million with chronic symptoms 45,000 die from disease every year.

A few cases in U.S. in Maryland, Georgia, Florida, Texas, Arizona, New Mexico, California, Alabama, and Louisiana.

Life cycle

2- Leishmania spp.

Leishmania donovani L. tropica.

Leishmania donovani

Definitive Hosts: Humans. Reservoir includes most mammals Intermediate Hosts: Phlebotomus sand fly.

Mode of Transmission: Bite of infected Sand Fly Location in D.H.: Immune system, including spleen, liver, lymph nodes and bone marrow

Geographic Distribution Probably originated in Old World Moved to New World with slave trade

Pathology Causes Visceral Leishmaniasis A.K.A. Kala-azar, Dum-Dum Fever Amastigote is engulfed by macrophage.

Macrophage doesn’t kill amastigote.

Neutrophils and eosinophils will kill amastigotes.

Multiplies, breaks out, and each invades another macrophage.

Also destroys macrophages in the spleen, liver, and lymph nodes Body starts manufacturing macrophages to replace them.

Results in severe wasting and anemia

Pathology Macrophage Infected with amastigotes of Leishmania

Pathology Early symptoms include malaise, vomiting, low grade fevers.

Followed with chronic wasting, anemia, enlargement of abdomen due to greatly enlarged spleen and liver.

Death usually follows in 1-2 years if untreated.

Some people recover spontaneously Related to age and nutrition Some people who were treated later develop Post Kala-azar dermal leishmanoid “Face bumps” Repeat of treatment usually clears up the bumps.

Life Cycle

Diagnosis Amastigotes in liver tissue, macrophages, spleen, other organs.

IFA, ELISA tests have been developed but can’t tell between L. donovani and L.

tropica.

Need to eliminate possibility of typhoid, paratyphoid, malaria, syphilis, tuberculosis, dyssentery, and relapsing fever which cause similar symptoms.

2- Somato-flagellates

1- Genital flagellates

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Trichomonas spp.

2- Intestinal flagellates

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Giardia spp.

Genital flagellates

Trichomonas spp.

Trichomonas vaginalis

Definitive Hosts: Humans. Reservoir includes most mammals and birds Intermediate Hosts: Nothing Mode of Transmission: during sexual inter course by trophozoite

Geographic Distribution

Trichomonas

are found in man, monkeys, rodents, fowls, pigeons, doves, termites and slugs. Distributed in all countries

Pathology Causes milky yellowish irritant vaginal discharge in female Ulceral discharge may occur in male

Life Cycle

Diagnosis In female: Examination of vaqginal discharge for trophozoites and urine sample In male: Examination of prostatic fluid and urine sample

Intestinal flagellates

Giardia spp.

Definitive Hosts: Humans.

Intermediate Hosts: Nothing Mode of Transmission: quadri-nucleated cyst in contaminated food and drink Flies and cockroaches play an important role in transmission

Geographic Distribution

Worldwide, more prevalent in warm climates

Pathology

Children are affected Mucus production, diarrha, dehydration, intestinal pain, weight loss.

Life Cycle

Diagnosis

Microscopic examination of fecal material for identification of trophozoite.

PCR analysis for detection of giardia DNA from both trophozoites and cysts