Host-specificity, freeze tolerance and infections of Hepatozoon blood parasites in wood frog, Rana sylvatica
LE3 .A278 2013
Bachelor of Science
Hepatozoon catesbianae and Hepatozoon clamatae are apicomplexan blood parasites of frogs and mosquitoes. These parasites are known to naturally occur in bullfrogs, Rana catesbiana, and green frogs, Rana clamitans, but only H. catesbianae has been found to naturally occur in wood frogs, Rana sylvatica. There is also variability in prevalence and parasitaemia levels for H. catesbianae infections amongst these host species. To investigate the host-specificity of these two parasites in wood frogs, mosquitoes were allowed to feed on green frogs infected with both parasites and then fed to laboratory-raised wood frogs once parasites were mature. Wood frogs are capable of surviving for long periods of exposure to subzero temperatures, and it is hypothesized that there may be some interaction between these episodes and parasitaemia levels of infections with H. catesbianae. A cohort of frogs infected from host-specificity experiments was acclimated to low temperatures before being frozen at -3 C for 48 hr, and another cohort remained unfrozen as controls. Samples taken after the frozen frogs were thawed were used to assess any changes in parasite intensity. Data from this study was combined with research from previous years to reveal that H. catesbianae occurred at a significantly higher prevalence (12 of 25 inoculated frogs) compared to H. clamatae (2 of 25 inoculated frogs). The effects of subzero temperatures on parasitaemia of H. catesbianae infections are still inconclusive due to low intensity of infections in many of the infected frogs and to small sample sizes overall. However, there is evidence of a downward trend in parasitaemia following freezing episodes in experimental groups compared to unfrozen controls.
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