ABSTRACT:A reliable antemortem test is needed to understand the ecology of chronic wasting disease (CWD) in elk (Cervus elaphus nelsoni). We measured the ability of antemortem biopsy samples from the rectal mucosa to detect the abnormal prion protein associated with CWD (PrP CWD ), the relationship between test results from the obex and rectal biopsies at varying stages of CWD progression, and the prevalence of CWD in free-ranging elk from Rocky Mountain National Park, Colorado, USA. We sampled and placed radio collars on 136 adult female elk in the winter of 2007-08. Elk with biopsy samples found positive for PrP CWD by immunohistochemistry (IHC) were euthanized and the obex and retropharyngeal lymph nodes were examined with IHC. We resampled, euthanized, and necropsied 20, 25, and 34 of the remaining study elk in each of the three following winters, respectively. Sensitivity of rectal biopsy samples increased in an asymptotic fashion with follicle count and was maximized at 85% (95% credible limits [CL]560, 98) in the beginning of the study, when a greater proportion of elk were in a detectable stage of prion infection. However, maximum sensitivity was reduced to 72% (CL546, 94) when we included resampled elk, which included recently infected elk that were initially negative using rectal biopsies and IHC. Test results were similar between rectal biopsies and the obex, but the earliest stages of prion infection were only detected by using retropharyngeal lymph nodes. Minimum CWD prevalence was estimated to be 9.9% (CL55.7, 15.7) using rectal biopsies, but this rose to 12.9% (CL58.0, 19.1) when we included four elk that were likely misdiagnosed at initial capture. Our results indicate rectal biopsies can provide a useful research tool for CWD in elk populations, but should be used with caution because they can miss individuals in early stages of infection and underestimate prevalence. Prevalence estimates from this population are the highest reported to date in elk and indicate that under appropriate conditions, CWD may be able to affect the dynamics of high-density elk populations.

f Chronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, was first documented nearly 50 years ago in Colorado and Wyoming and has since been detected across North America and the Republic of Korea. The expansion of this disease makes the development of sensitive diagnostic assays and antemortem sampling techniques crucial for the mitigation of its spread; this is especially true in cases of relocation/reintroduction or prevalence studies of large or protected herds, where depopulation may be contraindicated. This study evaluated the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay of recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens and nasal brushings collected antemortem. These findings were compared to results of immunohistochemistry (IHC) analysis of ante-and postmortem samples. RAMALT samples were collected from populations of farmed and free-ranging Rocky Mountain elk (Cervus elaphus nelsoni; n ‫؍‬ 323), and nasal brush samples were collected from a subpopulation of these animals (n ‫؍‬ 205). We hypothesized that the sensitivity of RT-QuIC would be comparable to that of IHC analysis of RAMALT and would correspond to that of IHC analysis of postmortem tissues. We found RAMALT sensitivity (77.3%) to be highly correlative between RT-QuIC and IHC analysis. Sensitivity was lower when testing nasal brushings (34%), though both RAMALT and nasal brush test sensitivities were dependent on both the PRNP genotype and disease progression determined by the obex score. These data suggest that RT-QuIC, like IHC analysis, is a relatively sensitive assay for detection of CWD prions in RAMALT biopsy specimens and, with further investigation, has potential for large-scale and rapid automated testing of antemortem samples for CWD.T ransmissible spongiform encephalopathies are a group of progressively fatal neurodegenerative diseases caused by infectious proteins known as prions (1). The pathogenesis of prion diseases involves conversion of the endogenous cellular prion protein (PrP C ) present within specific tissues to the abnormal, protease-resistant form (PrP res ) following exposure to an infectious dose of PrP res (1). Chronic wasting disease (CWD), a naturally occurring prion disease of white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), Rocky Mountain elk (Cervus elaphus nelsoni), and moose (Alces alces), is the only known prion disease affecting free-ranging, nondomestic animals (2, 3). CWD was first described nearly 50 years ago as a fatal, wasting, spongiform encephalopathy of cervids in Colorado and Wyoming (4). The disease has since been documented in 23 U.S. states, 2 Canadian provinces, and, via exportation of farmed cervids, the Republic of Korea (5-8). Four of the 23 states (Texas, Iowa, Pennsylvania, and Ohio) were considered CWD free prior to 2012, with primary cases in three of these states reportedly arising in farmed cervids (9-11). With the movement of cervids across state and national borders, these new ep...

Trypanosoma cruzi, the causative agent of Chagas' disease, is a substantial public health concern in Latin America. Although rare in humans and domestic animals in the United States, T. cruzi is commonly detected in some wildlife species, most commonly raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana). To increase our understanding of the reservoir host species range and geographic distribution, 11 species of mammals from six states spanning the known range of T. cruzi (Arizona, California, Florida, Georgia, Missouri, and Virginia) were tested for antibodies to T. cruzi using indirect immunofluorescent antibody testing. In addition, culture isolation attempts were conducted on a limited number of animals from Georgia and Florida. Evidence of T. cruzi was found in every state except California; however, low numbers of known reservoirs were tested in California. In general, the highest seroprevalence rates were found in raccoons (0-68%) and opossums (17-52%), but antibodies to T. cruzi were also detected in small numbers of striped skunks (Mephitis mephitis) from Arizona and Georgia, bobcats (Lynx rufus) from Georgia, two coyotes (Canis latrans) from Georgia and Virginia, and a ringtail (Bassariscus astutus) from Arizona. Culture-based prevalence rates for raccoons were significantly greater than those for opossums; however, seroprevalences of raccoons and opossums from several geographic locations in Georgia and Florida were not different, indicating that exposure rates of these two species are similar within these areas. For both raccoons and opossums, seroprevalence was significantly higher in females than in males. No difference was detected in seroprevalence between adults and juveniles and between animals caught in urban and rural locations. Our results indicate that T. cruzi prevalence varies by host species, host characteristics, and geographic region and provides data to guide future studies on the natural history of T. cruzi in the United States.

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Bighorn sheep (Ovis canadensis) populations commonly experience pneumonia outbreaks caused by Pasteurella spp. that result in a partial or complete dieoff. Although several factors can contribute to Pasteurella spp. transmission or infectivity in bighorn sheep, to date the importance of such factors in population declines has not been rigorously examined. We evaluated the relationship between pneumonia-induced dieoffs in bighorn sheep and environmental and biological factors by analyzing demographic information for 99 herds across the species' geographic range. Our analysis revealed that 88% of pneumonia-induced dieoffs occurred at or within 3 years of peak population numbers, which implies that density-dependent forces such as food shortage or stress contribute to bighorns' susceptibility to pneumonia. There were few differences in the growth rates of dieoff and non-dieoff populations, suggesting that pneumonia did not manifest itself demographically prior to an outbreak. On average, abundance of lambs was most dramatically reduced post outbreak (-66%) relative to that of either rams (-35%) or ewes (-42%). Deviations in normal precipitation and temperature regimes were not associated with the onset of pneumonia outbreaks, but herds found in proximity to domestic sheep tended to be more susceptible to dieoff. Our results suggest that bighorn sheep herds are rendered vulnerable to pneumonia principally through density-dependent factors, as well as through horizontal transmission of Pasteurella spp. from domestic sheep serving as reservoir hosts.Résumé : Les populations du Mouflon d'Amérique, Ovis canadensis, subissent souvent des épidémies de pneumonie causées par la présence de Pasteurella spp. qui déciment ou éliminent complètement la population. Bien que plusieurs facteurs puissent contribuer à la transmission de Pasteurella spp. ou à la sensibilité des mouflons à l'infection, l'importance de ces facteurs de déclin des populations n'a jamais été examinée rigoureusement à ce jour. Nous avons évalué la relation entre la mortalité attribuable à la pneumonie chez des Mouflons d'Amérique et les facteurs environnementaux et biologiques par l'analyse des informations démographiques obtenues chez 99 troupeaux provenant de l'ensemble de l'aire de répartition géographique de l'espèce. Notre analyse a révélé que 88 % des épisodes de forte mortalité due à la pneumonie se produisent 3 ans ou moins de 3 ans après une période de densité maximale, ce qui suppose que des facteurs reliés à la densité, tels une carence alimentaire ou un stress, contribuent à la sensibilité des mouflons à l'infection. Nous avons enregistré peu de différences des taux de croissance entre les populations affectées par la mortalité et les populations non affectées, ce qui indique que la pneumonie ne se manifeste pas par des différen-ces démographiques avant l'épidémie. En moyenne, ce sont les agneaux qui se trouvent le plus décimés après une épidémie (-66 %) comparativement aux boucs (-35 %) ou aux brebis (-42 %). Les écarts des conditions normales d...