Coccidian Parasites and Conservation Implications for the Endangered Whooping Crane (Grus americana)
Abstract
While the population of endangered whooping cranes (Grus americana) has grown from 15
individuals in 1941 to an estimated 304 birds today, the population growth is not sufficient to
support a down-listing of the species to threatened status. The degree to which disease
may be limiting the population growth of whooping cranes is unknown. One disease of potential
concern is caused by two crane-associated Eimeria species: Eimeria gruis and E.
reichenowi. Unlike most species of Eimeria, which are localized to the intestinal tract, these
crane-associated species may multiply systemically and cause a potentially fatal disease.
Using a non-invasive sampling approach, we assessed the prevalence and phenology of
Eimeria oocysts in whooping crane fecal samples collected across two winter seasons (November
2012–April 2014) at the Aransas National Wildlife Refuge along the Texas Gulf
coast. We also compared the ability of microscopy and PCR to detect Eimeria in fecal samples.
Across both years, 26.5% (n = 328) of fecal samples were positive for Eimeria based
on microscopy. Although the sensitivity of PCR for detecting Eimeria infections seemed to
be less than that of microscopy in the first year of the study (8.9% vs. 29.3%, respectively),
an improved DNA extraction protocol resulted in increased sensitivity of PCR relative to microscopy
in the second year of the study (27.6% and 20.8%, respectively). The proportion
of positive samples did not vary significantly between years or among sampling sites. The
proportion of Eimeria positive fecal samples varied with date of collection, but there was no
consistent pattern of parasite shedding between the two years. We demonstrate that non-invasive
fecal collections combined with PCR and DNA sequencing techniques provides a
useful tool for monitoring Eimeria infection in cranes. Understanding the epidemiology of
coccidiosis is important for management efforts to increase population growth of the endangered
whooping crane.
Department
EntomologyVeterinary Integrative Biosciences
Veterinary Pathobiology
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