Clinical, culture, serology, and histopathology outcomes of bighorn sheep experimentally infected with Brucella ovis.

Disease caused by Brucella ovis has not been previously reported in bighorn sheep (BHS; Ovis canadensis canadensis). Antibodies to B. ovis, however, are occasionally detected in free-ranging BHS, and this has been a concern for managers involved in translocation programs. To investigate the pathogenesis of B. ovis infection in this species, 20 BHS (10 male, 10 female) were inoculated intraconjunctivally (IC) with 5.4 × 10(8) colony forming units (cfu) B. ovis. Six BHS (three male, three female) received 1 mL phosphate-buffered saline IC and served as in-contact control animals, and eight BHS (one male, seven female) received 1 mL phosphate-buffered saline (PBS) IC and served as noncontact controls. In addition, 14 domestic sheep (Ovis aries, nine male, five female) were inoculated IC with 5.4 × 10(8) cfu B. ovis (positive controls), and five domestic sheep (three male, two female) received 1 mL PBS IC (contact controls). All domestic sheep were housed separately from BHS. Bighorn sheep experimentally infected with B. ovis became antibody and culture positive and developed clinical signs of B. ovis infection including abortion and epididymal and testicular swelling. Lesions in BHS were consistent with, and in some cases more severe, than those observed in domestic sheep. Antibodies against B. ovis were detected within 4 wk postinoculation and remained positive until the end of the study. These findings have important implications for BHS management.

A Review of Hypothesized Determinants Associated with Bighorn Sheep (Ovis canadensis) Die-Offs.

Multiple determinants have been hypothesized to cause or favor disease outbreaks among free-ranging bighorn sheep (Ovis canadensis) populations. This paper considered direct and indirect causes of mortality, as well as potential interactions among proposed environmental, host, and agent determinants of disease. A clear, invariant relationship between a single agent and field outbreaks has not yet been documented, in part due to methodological limitations and practical challenges associated with developing rigorous study designs. Therefore, although there is a need to develop predictive models for outbreaks and validated mitigation strategies, uncertainty remains as to whether outbreaks are due to endemic or recently introduced agents. Consequently, absence of established and universal explanations for outbreaks contributes to conflict among wildlife and livestock stakeholders over land use and management practices. This example illustrates the challenge of developing comprehensive models for understanding and managing wildlife diseases in complex biological and sociological environments.

Factors associated with failure in breeding soundness examination of Western USA rams.

Breeding-soundness examination (BSE) and eradication of Brucella ovis infection in rams are critical components of flock-health programs. The aims of this retrospective, cross-sectional study were to describe the results of BSE in a large sample of rams in the Western USA and to determine the association between BSE outcome and the semen collection method (penis manually extended vs. retained in the preputial cavity), ram body-condition score (BCS), the presence of ulcerative posthitis, and the size of the flock of origin. We evaluated the first BSE in a given year for rams from Colorado, Wyoming, and Utah, USA, from 2000 through 2007. Breeding-soundness examination consisted of physical examination, scrotal circumference and BCS measurement, semen collection by electroejaculation, and microscopic examination of semen motility, morphology, and leukocyte concentration. We assigned a reason for failure to each failed BSE and used multivariable logistic and Poisson regressions to measure associations between ram and flock variables and the risk or reason for failure on BSE. A non-random, owner-selected subset of rams was tested for antibodies to B. ovis by serum indirect ELISA (iELISA). The Rogan-Gladen corrected B. ovis seroprevalence was measured. Of the 14,667 BSEs performed on 11,804 rams, 29.0% were classified as "failed;" the most common reason for failure was substandard semen parameters (43.8%). Breeding-soundness examinations were more likely to have been categorized as failure for inflammatory causes when performed on rams from medium-sized flocks (OR 1.6; 95% CI 1.1, 2.3) and large flocks (OR 1.4; 95% CI 1.0, 1.9) (P=0.02), suggesting that larger flocks are at higher risk of contagious diseases. The adjusted seroprevalence of B. ovis antibodies among tested rams in this study was 10.0%. Of 233 rams seropositive to B. ovis, 125 (53.6%) were subclinical, a finding that supports the importance of this test in ram BSE. We found that emaciation in rams was associated with an increased risk of BSE failure from substandard semen parameters (P<0.001), but ulcerative posthitis and the semen collection method were not (P=0.09 and 0.34, respectively). However, collection of semen with the penis retained in the preputial cavity resulted in greater odds of leukospermia relative to semen collection with the penis extended (OR 4.1; 95% CI 2.9, 5.9; P<0.001), presumably from contamination of the semen sample with preputial leukocytes. For ram BSE, therefore, semen collection with the penis manually extended from the sheath is recommended to limit leukocyte contamination of the sample.

Shared Bacterial and Viral Respiratory Agents in Bighorn Sheep (Ovis canadensis), Domestic Sheep (Ovis aries), and Goats (Capra hircus) in Montana.

Transmission of infectious agents from livestock reservoirs has been hypothesized to cause respiratory disease outbreaks in bighorn sheep (Ovis canadensis), and land management policies intended to limit this transmission have proven controversial. This cross-sectional study compares the infectious agents present in multiple populations of bighorn sheep near to and distant from their interface with domestic sheep (O. aries) and domestic goat (Capra hircus) and provides critical baseline information needed for interpretations of cross-species transmission risks. Bighorn sheep and livestock shared exposure to Pasteurellaceae, viral, and endoparasite agents. In contrast, although the impact is uncertain, Mycoplasma sp. was isolated from livestock but not bighorn sheep. These results may be the result of historic cross-species transmission of agents that has resulted in a mosaic of endemic and exotic agents. Future work using longitudinal and multiple population comparisons is needed to rigorously establish the risk of outbreaks from cross-species transmission of infectious agents.