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.
Highlights
The whooping crane (Grus americana) experienced a severe population decline in the first part of the 20th century and has been listed as endangered since 1967
The Aransas-Wood Buffalo population (AWBP), which nests in Wood Buffalo National Park, Alberta and Northwest Territories, Canada and winters among coastal marshes in and around the Aransas National Wildlife Refuge in Texas, USA, is the only self-sustaining wild population of whooping cranes
We document that nearly one-third of fecal samples collected from the only wild migratory population of whooping cranes on their wintering grounds harbor Eimeria species coccidian parasites, based on visualization of oocysts and PCR analysis of voided fecal samples
Summary
The whooping crane (Grus americana) experienced a severe population decline in the first part of the 20th century and has been listed as endangered since 1967. The species has rebounded from a low of 15 individuals in 1941 to a total of 451 wild birds, including reintroduced populations, and 157 captive birds in 2013 [1]. The Aransas-Wood Buffalo population (AWBP), which nests in Wood Buffalo National Park, Alberta and Northwest Territories, Canada and winters among coastal marshes in and around the Aransas National Wildlife Refuge in Texas, USA, is the only self-sustaining wild population of whooping cranes. One criterion for down-listing the species requires the AWBP to maintain a population of at least 1000 individuals [3]. A second criterion relaxes this requirement to at least 400 individuals in the AWBP if a second self-sustaining flock is established [3]. The species remains endangered and is highly susceptible to stochastic events that could decimate the population
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