Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Veterinary Medical Sciences - Pathobiological Sciences

First Advisor

Thomas R. Klei

Abstract

This dissertation describes studies on three Trypanosoma cruzi isolates from Louisiana mammals with particular reference to infectivity to dogs. Isolates from an opossum (Tc-O) and armadillo (Tc-A) were obtained during a blood culture survey of these animal populations in Louisiana. Prevalence of T. cruzi were 37.5% and 1% in opossums and armadillos respectively. Further, 48% opossums had myocarditis suggestive of T. cruzi infection. Rural dogs with known contact with T. cruzi hosts, housed rural dogs, urban animal shelter dogs and household pets showed 4.7, 0, 2.3 and 0% serological prevalence to T. cruzi respectively. Tc-O and Tc-A (wild isolates) displayed similar in vitro characteristics, growth rate in liquid media, protein profiles on SDS-PAGE and zymodeme types. An isolate from a dog (Tc-D) displayed markedly different parameters. Slight differences in infectivity to 6 inbred mouse strains were noted between wild isolates, but marked differences occurred between wild isolates and Tc-D. Wild isolates, but not Tc-D, produced high parasitemias, weight changes, and muscle pathology in CF1 mice. Wild isolate infected dogs developed high parasitemias and acute myocarditis 2 to 3 weeks post infection. Survivors of acute disease developed chronic dilated cardiomyopathy within 9 months of infection. Tc-D infected dogs showed no clinical signs and low parasitemias. Wild isolate but not Tc-D, infected dogs developed electrocardiographic abnormalities associated with conduction disturbances during acute disease, and ventricular based arrhythmias and cardiac function loss as measured by echocardiography. Tc-D and Tc-O infected dogs had similar antibody and lymphocyte blastogenic responses to T. cruzi epimastigote antigens. Western blot analysis showed similarities and differences between infected dog serum and T. cruzi epimastigote antigens from both isolates. Wild isolate infected dogs had severe granulomatous myocarditis, mild encephalitis and myositis during acute disease, and biventricular dilation, fibrosis and mild myocarditis during chronic disease. Minimal pathology was seen in Tc-D infected dogs. Results indicate the wild T. cruzi isolates are similar, are virulent to dogs, and may constitute a model for human Chagas' disease. Tc-D is different from the wild isolates, and infective but non-virulent to dogs.

Pages

286

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