Coccidian Parasites and Conservation Implications for the Endangered Whooping Crane (Grus americana)

摘要

While the population of endangered whooping cranes (Grus americana) has grown from 15individuals in 1941 to an estimated 304 birds today, the population growth is not sufficient tosupport a down-listing of the species to threatened status. The degree to which diseasemay be limiting the population growth of whooping cranes is unknown. One disease of potentialconcern 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, thesecrane-associated species may multiply systemically and cause a potentially fatal disease.Using a non-invasive sampling approach, we assessed the prevalence and phenology ofEimeria oocysts in whooping crane fecal samples collected across two winter seasons (November2012?April 2014) at the Aransas National Wildlife Refuge along the Texas Gulfcoast. 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 basedon microscopy. Although the sensitivity of PCR for detecting Eimeria infections seemed tobe 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 microscopyin the second year of the study (27.6% and 20.8%, respectively). The proportionof positive samples did not vary significantly between years or among sampling sites. Theproportion of Eimeria positive fecal samples varied with date of collection, but there was noconsistent pattern of parasite shedding between the two years. We demonstrate that non-invasivefecal collections combined with PCR and DNA sequencing techniques provides auseful tool for monitoring Eimeria infection in cranes. Understanding the epidemiology ofcoccidiosis is important for management efforts to increase population growth of the endangeredwhooping crane.