Browsing by Author "Snowden, Karen F"

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    Disease Risks to Whooping Cranes (Grus americana) Determined by Non-invasive Sampling and Use of the Sandhill Crane (Grus canadensis) as a Surrogate
    (2016-07-27) Bertram, Miranda Rose; Hamer, Sarah A; Hamer, Gabriel L; Snowden, Karen F; Hartup, Barry K
    The only self-sustaining wild population of endangered whooping cranes (Grus americana) has grown to approximately 308 individuals. However, the population growth is not consistent with species recovery goals, and the impact of parasite infection on whooping crane populations is largely unknown. Our goal was to quantify the prevalence of fecal parasites and hemoparasites in whooping cranes and to compare the prevalence of infection between whooping and sandhill cranes (Grus canadensis). 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. Across both years, 26.5% (n=328) of fecal samples were positive for Eimeria based on microscopy. We noted nematode eggs in 30% (n=327) and 2.7% (n=75) of whooping and sandhill crane fecal samples, respectively. However, sequences from these samples aligned with soil-dwelling nematodes, indicating environmental contamination. We noted trematode eggs in 11.1% (n=63) and 50% (n=20) of whooping and sandhill crane samples, respectively. We identified three species of trematode, one cestode, one acanthocephalan, and one nematode in sandhill cranes on necropsy. Orchipedum jolliei was the most common trematode and was noted in 42% (n=108) of sandhill cranes. The prevalence of O. jolliei was significantly higher in sandhill cranes wintering along the Texas Gulf Coast than in the Texas panhandle or New Mexico. We used three different PCR assays to screen samples for Haemosporida and detected an infection prevalence of 59.5% (n=163) across all birds. Infection prevalence was high in whooping cranes and sympatric sandhill cranes, but significantly lower in allopatric sandhill cranes. Haemoproteus antigonis was present in 46% of samples from both crane species and was phylogenetically distinct from other avian Haemosporida. We demonstrate that non-invasive fecal collections combined with PCR and DNA sequencing techniques provides a useful tool for monitoring coccidia and helminth infection in cranes. We also document a high prevalence of H. antigonis in whooping cranes and sympatric sandhill cranes, supporting the use of sandhill cranes as a surrogate species for understanding health threats to the endangered whooping crane.
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    Ecoepidemiology of Trypanosoma cruzi in Texas
    (2016-10-14) Curtis-Robles, Rachel; Hamer, Sarah A; Wozniak, Edward; Coulson, Robert N; Hamer, Gabriel L; Snowden, Karen F
    This dissertation focused on elucidating factors affecting Trypanosoma cruzi transmission in the southern US, using triatomine, canine, and wildlife samples. Collection of triatomine vectors from 2012-2015 included standard entomological sampling, as well as submissions through a citizen science program. The insects were identified to species, dissected, and tested for T. cruzi infection. T. gerstaeckeri and T. sanguisuga were the most abundant species in the collection. Kissing bugs were captured primarily April-October, and peak activity varied by species. A T. cruzi infection prevalence of 58.9% was found in 1,226 triatomines of 6 species, and infection prevalence varied by species. Amplification and sequencing of the TcSC5D gene revealed Triatoma gerstaeckeri was approximately equally infected with TcI and TcIV, and 10 individuals showed mixed TcI/TcIV infections. In contrast, Triatoma sanguisuga was more frequently found infected with TcIV than TcI. Relative abundance of parasite DTUs varied spatially, with both TcI and TcIV co-circulating nearly equally in vectors in central Texas, while TcIV predominated in northern Texas. A study of T. cruzi infection in dogs in south central Texas using paired IFA and Chagas Stat-Pak serological testing showed a seroprevalence of 57.6%. The odds of being seropositive were greater for dogs older than 6 years of age than dogs less than 2 years of age. PCR analyses of blood revealed 26.7% of dogs, including both seronegative and seropositive dogs, harbored parasite DNA in their blood. Sequencing of the TcSC5D gene from blood and tissue samples showed TcI and TcIV were present, including a co-occurrence of both DTUs in an individual dog. Cardiac tissue and blood were collected from wildlife—including raccoons (Procyon lotor), coyotes (Canis latrans), gray foxes (Urocyon cinereoargenteus), and bobcats (Lynx rufus)—from central Texas. PCR analyses found 2 bobcats (14.3%), 12 coyotes (14.3%), 8 foxes (13.8%), and 49 raccoons (70.0%) were positive for T. cruzi in at least one sample (right ventricle, apex, and/or blood clot). Strain typing revealed raccoons infected with DTU TcIV, and a single raccoon with TcI/TcIV