Presentation on theme: "Tropical, Vector-borne and Zoonotic Infectious Disease Pathology M. Kent Froberg, MD 2009."— Presentation transcript:
Tropical, Vector-borne and Zoonotic Infectious Disease Pathology M. Kent Froberg, MD 2009
Purpose To learn the etiological agents and life cycles of the major tropical, vector-borne and zoonotic parasites. To learn the major pathology associated with the important tropical, vector-borne and zoonotic pathogens.
CHAGAS’ DISEASE (AMERICAN TRYPANOSOMIASIS) TRYPANOSOMA CRUZI Organism: hemoflagellate (motile) Vector: Triatoma infestans (reduviid, kissing or assassin bug) Transmission: Vector lives in thatched or mud houses, biting sleeping victim at night, depositing infected feces in wounds. Zoonosis: between mammals and vector Dx: finding trypomastigotes in blood
Characteristic “U” or “C” shape of T. cruzi in peripheral blood Nuclei (green) and kinetoplasts(black) are stained blue with Geimsa
Chagas Disease is most common in Central America and northern South America. Chagas is also a transfusion risk in the United States from infected blood donors who have immigrated from Latin America.
Reduviid “kissing” bug infects skin or mucous membranes of bite or other wounds by defecting in wound following a blood meal
CHAGAS’ DISEASE (2) Clinical: –Stage 1: Chagoma (local, transient inflammatory lump) at site of bite –Stage 2: Dissemination: Myocarditis; enlarged spleen, liver, & lymph nodes –Stage 3: Years later (10-30% infected persons): cardiac inflammation and fibrosis, dilated cardiomyopathy, apical aneurysm
CHAGAS’ DISEASE (3) Myenteric plexus damage aperistalsis mega-esophagus + mega-colon Prevalence: –Only in western hemisphere. –Most common cause of heart failure in Latin America –Up to 1/2 million in USA transfusion hazard
Romana’s sign from acute conjunctival T. cruzi infection Dliated cardiomyopathy with destruction of the ventricular wall and an apical aneurysm 2 to Chagas Diseases
Virulence Factors Produces homolog of decay-accelerating factor (DAF) that inhibits formation of C3 convertase & blocks alternate pathway of complement Produces neuraminidase that cleaves sialic acids from host proteins lining lysosomes - destabilizes organelle Produces hemolysins that form pores in lysosomal membranes Burst host cells in going from amastigote to trypomastigote forms
ONCHOCERCA VOLVULUS (FALARIAL NEMATODE) Transmission: Black flies: genus Simulium (tropical Africa) Cycle: Adult worms mate in skin local infl. nodule microfilariae eye keratitis and retinitis blindness Rickettsia-like bacteria of genus Wolbachia live within nematode-probably cause pathology
Ring granuloma in Q fever Pt presenting with FUO
EPIDEMIC TYPHUS (1) Rickettsia prowazekii, ~worldwide Vector: body louse (Pediculus corporis) Louse lives only on humans or in human clothes Clinical: fever, vasculitis rash, cerebral damage Mortality 5-25%
EPIDEMIC TYPHUS (2) Pathology: –skin necrosis & gangrene –heart, lungs, etc. ecchymosis –brain typhus nodule Epidemiology: prevalence if clothing not changed –war, poverty Brill-Zinsser: recurrent typhus after long latent interval
Vascular occlusion (typhus nodule) in CNS of Pt with RMSF
Anaplasmosis (Ehrlichiosis) Ehrlichia canis, Anaplasma phagocytophilum, E. ewingii, E. chaffeensis, U.S. Vector: ticks (deer, wood, dog) Reservoir: unknown Clinical: like RMSF: F, HA, rash 20% Pathology: like RMSF but less severe, thrombocytopenia Dx: “purple blobs” in WBCs
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