The Protozoa Blood & Tissue Protozoa The Hemoflagellates: The family Trypanosomatidae contains only two genera that parasitize humans. Genus Trypanosoma contains members that may be found either in the circulating blood or intracellularly (in cardiac muscle). African - blood; American - blood & cardiac muscle. Genus Leishmania are always intracellular, principally in cells of the reticuloendothelial system.

The Protozoa Blood & Tissue Protozoa The Hemoflagellates: Originally parasites of insects; these now serve as intermediate hosts. American trypanosomiasis - transmitted by reduviid bugs. African trypanosomiasis - transmitted by Glossina spp. tsetse flies.

The Protozoa Blood & Tissue Protozoa The Hemoflagellates: "Old World” leishmaniasis - transmitted Phlebotomus spp. sandflies. American leishmaniasis - transmitted by Lutzomyia spp. sandflies.

The Protozoa The Hemoflagellates: Trypanosoma brucei Two subspecies: rhodesiense & gambiense Life cycles are essentially identical. Rhodesian form - primarily an animal pathogen, transmitted to humans by Glossina morsitans. Gambian form - transmitted by Glossina palpalis group of tsetse fly. Trypanosoma b. rhodesiense Trypanosoma b. gambiense

The Protozoa The Hemoflagellates: Trypanosoma brucei (both sub-species) Site of infection - organisms multiply in blood early in disease; later found in lymph nodes and in the CNS. Disease - febrile episodes, night sweats, malaise, headache; enlarged cervical lymph nodes (“Winterbottom’s sign”); final stages - uncontrolled desire to sleep. Diagnosis - examine wet mounts of aspirates from sight of insect bite; and/or blood (buffy coat) for presence of trypanosomes (numbers of organisms peak during fever spikes). Morphology - Epimastigote is the developmental form in flies; trypomastigote is the infective stage.

The Protozoa The Hemoflagellates: Trypanosoma cruzi Disease - American trypanosomiasis, Chagas' disease. Transmission - trypomastigote in reduviid bug feces is introduced through the skin following the bug's bite. Morphology - exhibits a characteristic “C” shape with an undulating membrane and anteriorly extending flagellum; the amastigote is oval, averages 3 to 5 microns in diameter and contains a nucleus and rod-shaped kinetoplast.

The Protozoa The Hemoflagellates: Trypanosoma cruzi Trypomastigote and epimastigote forms may be found in humans. The amastigote is a tissue stage; the trypomastigote is blood stage; the epimastigote is a developmental stage in the bug. Pathogenesis - acute phase is 1- 4 month’s duration; chronic phase may last decades. Clinical signs - Edema of eyelids (Romana’s sign). Fever, headache, malaise, myalgia, megacolon, megaesophagus. Cardiac manifestations.

The Protozoa The Hemoflagellates: Trypanosoma cruzi Epidemiology notes: most prevalent in South America especially Brazil, Argentina, Uruguay, Chile, and Venezuela. Has been found in Central America. Five cases have been confirmed in Texas; one in California. There is great concern about transfusion-induced cases in the blood banking industry. Reservoir hosts - many animals including dogs, opossums, cat, armadillos, etc.

The Protozoa The Hemoflagellates: Genus Leishmania Four pathogenic species. Speciation - based on clinical symptoms and manifestations. Diagnosis - finding amastigotes in lesions; clinical signs and symptoms determine the “differential” diagnosis.

The Protozoa The Hemoflagellates: Leishmania tropica Distribution - Mediterranean basin, India, Middle East, Asia & Africa. Disease - Old World cutaneous leishmaniasis; “Baghdad boil,” “Oriental sore.” Diagnosis - identification of intracellular amastigotes in macrophages from active lesions.

The Protozoa The Hemoflagellates: Leishmania tropica Moist ulcers - Incubation period of several weeks to months, followed by rapid development of weeping ulcers that heal within 6 months. Dry ulcers - Incubation period may last for several years before appearance of a slowly developing ulcer that is covered with a scaly crust. May take years to heal. Healing of lesions of cutaneous leishmaniasis signifies cell-mediated, species-specific, lifelong immunity.

The Protozoa The Hemoflagellates: Leishmania mexicana Similar to L. tropica in that it causes cutaneous leishmaniasis. Found in Central America, Mexico, & Texas. Disease - New World cutaneous leishmaniasis, chiclero ulcer. Diagnosis - identification of amastigotes at periphery of lesion. Necrotic area at center of lesion contains bacteria, few if any organisms.

The Protozoa The Hemoflagellates: Leishmania braziliensis Disease - Mucocutaneous leishmaniasis, espundia. Disfigurement - erosion of oral, nasal structures. Affects mainly the mucous membranes and cartilaginous areas of the nasal and oral structures.

The Protozoa The Hemoflagellates: Leishmania donovani Disease - visceral leishmaniasis, kala-azar (“black fever”). Pathogenesis - a viscerotropic form, skin lesion seldom noticed; in reticuloendothelial system, organisms multiply; extensive hyperplasia of parasitized tissue impairs function of organs.

The Protozoa Miscellaneous Others: Toxoplasma gondii Definitive host - felines, domestic cat is most important. Human infections are due to ingestion of infective oocysts from cat feces; ingestion of trophozoites in undercooked or uncooked meat, mother’s milk; congenital transmission has been documented.

The Protozoa Miscellaneous Others: Toxoplasma gondii Infections are usually asymptomatic; immune system keeps infection in check; immunosuppression (HIV, etc.) results in fulminating infection. Dangerous in pregnant women - the organism can cross the placental barrier and infect the fetus. Diagnosis - isolation of organism is difficult; best diagnosed via serological techniques.

The Protozoa Miscellaneous Others: Babesia spp. A widespread zoonosis, transmitted via the bite of infected hard ticks. Sexual reproduction takes place in ticks. Asexual reproduction takes place in a variety of mammalian hosts.

The Protozoa Miscellaneous Others: Babesia spp. Multiplies within red blood cells; can be confused with malaria ring forms. Babesia rings are more pyriform, multiplication results in pairs and tetrads resembling a “maltese cross.” Pathology - Hemolysis is common, resulting in anemia and jaundice. Severe cases progress to renal failure, hypotension, coma and death.

The Protozoa Miscellaneous Others: Pneumocystis carinii Classification of the organism is uncertain (fungus or parasite). Pathology - “Interstitial Plasma-Cell Pneumonia,” a highly fatal complication of AIDS. The organism and infection are widespread, similar to toxoplasmosis. Diagnosis - identification of cysts (containing 8 trophozoites) or free trophozoite forms in lung exudates; sputum (AIDS patients); open lung biopsy, bronchio-alviolar lavage (BAL).