Meeting Abstract
Disease is among the leading causes of global amphibian population declines. In North America, parasites are among the factors implicated in precipitous population declines of the giant hellbender salamander (Cryptobranchus alleganiensis), but the incidence of infections and their responses to infections remain poorly studied. We document the prevalence of leech and trypanosome infections in a population of eastern hellbenders and describe hematological and immunological characteristics of hellbenders with these infections. We hypothesized that hellbenders parasitized by trypanosomes would be anemic, that individuals infected with either or both parasites would exhibit shifts in white blood cell counts, and that hellbenders infected with leeches would exhibit altered plasma bactericidal capacity. We found that 24% and 68% of hellbenders were infected with leeches and trypanosomes (respectively), and 20% were co-infected. We found no evidence suggestive of anemia. However, hellbenders infected with either or both parasites exhibited marked shifts in circulating white blood cells that were consistent with adaptive responses to infection. In addition, we found that hellbenders harboring leeches had much higher plasma bactericidal capacity than individuals without leeches, and we offer multiple potential mechanistic explanations for this observation. We also found evidence that cellular and serological immune responses to parasites were less robust in juvenile than adult hellbenders. This finding warrants further investigation in light of the demographic characteristics, specifically the scarcity of juvenile age classes, of hellbender populations where disease is a possible contributor to declines. Our study provides fundamental insights into how hellbenders respond physiologically to endo- and ectoparasites, which could prove useful for their conservation.
