Parasitology - Hemoflagellates

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These are the hemoflagellates

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African trypanosomes (African sleeping sickness)
Leishmania
Trypanosoma cruzi (Chaga's disease)

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These are shared features of hemoflagellates

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Insect hosts at some point in their life cycles

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Amastigote

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Obligate intracellular stage of hemoflagellates in their vertebrate hosts (African trypanosome does /not/ have an amastigote stage since it is always extracellular)

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Kinetoplast

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Mitochondrion of hemoflagellates that produces the flagellum. Rich in tiny circular DNA. Used in the identification of hemoflagellates

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Transmission of Leishmania

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By blood-sucking insects (as is true for all hemoflagellates)

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This is how we distinguish between the various extracellular forms of hemoflagellates

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By the location of the kinetoplast and flagellum

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These hemoflagellates are always extracellular in the vertebrate host

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African trypanosome (sleeping sickness)

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Diagnostic stage of trypanosomiasis (sleeping sickness)

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Flagellated parasite in blood, LN bx, or CSF

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This parasite multiplies in the blood, lymph, CSF and tissue of humans

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African trypanosome (sleeping sickness)

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A bite by this fly can cause an ulcerating cutaneous lesion

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Tse tse fly. African trypanosome parasite multiplies locally, producing the lesion.

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Definitie host of African trypanosome

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Tse tse fly

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This disease is caused by two subspecies of the same parasite

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Sleeping sickness (Trypanosomiasis)

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Winterbottom's sign

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Lymphadenopathy (esp POSTERIOR CERVICAL LYMPH NODES) seen in sleeping sickness (Trypanosomiasis)

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Signs and symptoms of sleeping sickness (trypanosomiasis)

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Fever, LAD, parasitemia; lethargy, coma, death with invasion of the CSF

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Unlike malaria, it is impossible to develop immunity to this disease

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Sleeping sickness (Trypanosomiasis). The parasite changes its major surface glycoprotein to evade immune system

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This disease is characterized by waves of parasitemia and fever

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Sleeping sickness (Trypanosomiasis). The parasite changes its major surface glycoprotein to evade immune system, so different glycoproteins are favored at different times, resulting in waves

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This parasite undergoes antigenic shift to evade the immune system of its host

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African trypanosome (sleeping sickness)

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Treatment of African trypanosomiasis (sleeping sickness)

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Highly toxic drugs

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This parasite exists in humans as amastigotes (intracellular parasites) in the reticuloendothelial system

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Leishmania

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Diagnostic stage of Leishmaniasis

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Amastigote in cells

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Vector of Leishmaniasis

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Sandfly (Phlebotomus)

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The flagellated form of this parasite enters monos, loses its flagellum and multiplies as an intracellular amastigote

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Leishmania spp.

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The fly vector of this parasite ingests infected macrophages from the human host to propagate the parasite's life cycle

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Leishmania spp.

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How long before the sandfly can transmit Leishmania after it has ingested parasites?

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1-2 weeks. During this time the ingested amastigotes transform into extracellular, flagellated forms

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DTH skin test can be used to test for current or prior infection by this parasite

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Leishmania spp.

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Cause of visceral leishmaniasis (Kala-azar)

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Leishmania donovani

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What three diseases do Leishmania species cause?

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Visceral, cutaneous, mucocutaneous

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T/F: Leishmania is easily treated

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False. Treatment is difficult because many of the availabe drugs are toxic.

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Kala-azar

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Another name for visceral leishmaniasis (caused by L. donovani)

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Geographic distribution of Kala-azar

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(Visceral leishmaniasis) Asia, Africa, Mediterranean basin, South America

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Incubation of Kala-azar

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2-6 months or longer

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Signs and symptoms of Kala-azar (visceral leishmaniasis)

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Insidious onset fever (twice daily), splenomegaly, LAD, hypergammaglobulinemia

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This parasite infection causes hypergammaglobulinemia

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Kala-azar (visceral leishmaniasis)

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Diagnosis of Kala-azar (visceral Leishmaniasis)

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Marrow bx.

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This hemoflagellate infection is notably common in AIDS patients in endemic areas

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Kala-azar (visceral leishmaniasis)

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Humans are the main reservoir for this leishmaniasis

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Kala-azar (visceral leishmaniasis). Caused by L. donovani

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Domestic dogs, rodents and other mammals are the main reservoir for this leishmaniasis

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Cutaneous and mucocutaneous leishmaniasis

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"Oriental sore"

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Lesion found in cutaneous leishmaniasis, often on arm, leg, face (Asia, India, Mediterranean, West Africa)

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"Chiclero ulcer"

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Lesion found in cutaneous leishmaniasis, often on head (Central and South America)

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Signs and symptoms of cutaneous leishmaniasis

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Papules that ulcerate, lasting for months to years

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Incubation of cutaneous leishmaniasis

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2-8 weeks

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Papule that ulcerates at site of bite seen in this disease

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Cutaneous leishmaniasis

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Diagnosis of cutaneous leishmaniasis

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Bx of lesion

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This is a horribly disfuguring disease of leishmania

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Mucocutaneous leishmaniasis

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This disease is characterized by massive necrotizing lesions at mucocutaneous junctions of mouth or nose

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Mucocutaneous leishmaniasis

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Diagnosis of mucocutaneous leishmaniasis

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PCR. Bx of lesion often fails to dx

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Reduviid bug

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Host of T. cruzi

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This parasite enters the human host not via the salivary glands, but via the feces of the vector

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Chaga's disease (Trypanosoma cruzi)

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This parasite enters skeletal and cardiac muscle cells, in addition to reticuloendothelial cells, where it takes on amastigote form

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Trypanosoma cruzi

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Infectious stage of T. cruzi

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Flagellated forms in bug feces

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Diagnostic stage of T. cruzi

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C-shaped extracellular flagellated forms in the blood (only in acute disease). Dx is difficult

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Signs and symptoms of Chaga's disease

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Initial infection mild or subclinical. Heart failure, meningitis in acute phase can kill. Chronically, we see myositis (enlarged heart, CHF); and mega-colon and mega-esophagus due to destrection of autonomic ganglia (probably an autoimmune phenomenon).

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Romana's sign

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Painless swollen lesion near eye, caused by bite of Reduviid bug

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T/F: Chaga's disease can be transmitted transplacentally

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True. 3% of chronic infections in pregnancy will transmit to fetus

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This is the most reliable diagnostic test for Chaga's disease

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Xenodiagnosis. Feed uninfected reduviid bugs patient blood and check bug rectum for fecal parasites 1-2 months later. This will be replaced by PCR.

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C-fixation test

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Used to detect prior infection of T. cruzi (Chaga's disease)

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Diagnosis of this disease is often difficult

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Chaga's disease. Smear, then culture, then inject mice, then feed bug (xenodiagnosis).

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The vector of this disease lives in substandard housing

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Chaga's disease

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This disease is found only in South and Central America and in Mexico

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Chaga's disease

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This disease is transmitted by blood transfusion in South America

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Chaga's disease

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This bug-transmitted disease has been eliminated in these countries.

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Chaga's disease has been elminated from Brazil, Argentina, Chile, and Uruguay.