The pathobiology and molecular epidemiology of reptilian hemosporozoa and other selected hemoprotozoa of medical or veterinary importance
Abstract
The goals of this study were to explore the range of vectors of reptilian hemosporozoa, to characterize pathologic and immunologic aspects of hemogregarine-unnatural host relationships, and to devise a molecular assay to type isolates. These studies are important in zoological medicine because of the high potential for inter-specific transmission between captive specimens. Surveys of wild and captive colubrid, boid, and viperid snakes by blood film examination demonstrated a high prevalence of hemogregarine infections. Blood stages were consistent with hemogregarine gametocytes, with morphometrically similar, non-dividing, fusiform, intraerythrocytic protozoa with single round compact nuclei. Erythrocytic infection was associated with variable hypertrophy, alterations in sedimentation coefficients, cytoplasmic pallor, and erythrocytic protein depletion. Hemogregarine parasites from several colubrid and viperid snakes completed sporogony within Aedes aegypti mosquitoes in 14-18 days, and produced oocysts typical of Hepatozoon sp. All lizards experimentally inoculated per os with mosquito-borne oocysts developed Hepatozoon sp. infections. No sporogonic development was demonstrated in any Ornithodoros turicata ticks (Argasidae) fed on parasitemic snakes. None of the lizards inoculated by tick developed Hepatozoon sp. infections. Molecular characterization of several hemogregarine isolates, two lizard Plasmodium species, and several species of Leishmania and Trypanosoma at the ribosomal DNA (rDNA) locus by PCR amplification and restriction enzyme analysis demonstrated detectable molecular differences between genera, species and isolates. Within unnatural lizard hosts multifocal accumulations of heterophilic leukocytes with intralesional Hepatozoon meronts were observed within the liver and lungs. The accompanying clinicopathologic changes in unnatural hosts included a marked leukocytosis with heterophilia, increases in plasma liver enzyme activities, and mild increases in the serum gamma globulin fraction. No meront-associated inflammation or significant clinico-pathologic changes were noted in naturally infected snakes despite numerous pulmonary and hepatic meronts. Assay of unnatural host serum for anti-Hepatozoon antibody by ELISA, IFA, and Western blot demonstrated post-infection increases in lizards sampled at 38 days post-infection and beyond. Stage-specific antibody directed against surface antigens of infected erythrocytes with a moderate orthochromatic erythroblastosis, was demonstrated only in parasitemic lizards. Molecularly distinct hemogregarines in different snake species and evidence of parasite-associated disease in unnatural hosts, suggest host-parasite coadaptation in nature.
Degree
Ph.D.
Advisors
McLaughlin, Purdue University.
Subject Area
Animal diseases|Entomology|Veterinary services
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