Oropharyngeal bacteria, with respect to animal health classification, and viral serology of Montana bighorn sheep (Ovis canadensis) and domestic (Ovis aries) near to and distant from the wildlife/domestic animal interface

Abstract

Respiratory disease outbreaks attributed to pasteurellosis have lead to conflict at the wildlife/domestic interface, where domestic sheep have been hypothesized to be a reservoir of Pasteuerellaceae strains that cause disease in bighorn sheep. This dissertation compares bighorn sheep ( Ovis canadensis) and domestic sheep ( O. aries) oropharyngeal Pasteurellaceae biovariants from animals classified as diseased and healthy. It also compares bacteriology and viral serology of populations of these species near to and distant from the wildlife/domestic livestock interface. A retrospective study of clinical submissions (1990 - 2004) indicated that 94 Pasteurellaceae biovariants have been associated with domestic sheep classified as diseased. A second retrospective study (1989 - 2004) indicated that 37 Pasteurellaceae biovariants have been associated with bighorn sheep classified as diseased. A prospective study of domestic and bighorn sheep near to and distant from the wildlife/domestic interface indicated that Pasteurellaceae biovariants commonly associated with disease in the retrospective studies were also common in healthy animals, and that there was extensive interspecific sharing of biovariants. This suggests that a simple agent/disease relationship may not exist for Pasteurellaceae in these host species. In addition, it is not clear that either species serves as a reservoir for Pasteurellaceae that are pathogenic for the sympatric species. However, unstated assumptions that single samples represent an animal's Pasteurellaceae microflora are questionable, based on the minimal concordance of biovariants of individual domestic livestock (n = 118) sampled six months apart. Based on the populations in the prospective study, bighorn sheep populations were naive to Mycoplasma, and both Ovis species were largely naive to infectious bovine rhinotracheitis and bovine virus diarrhea 1 and 2. This suggests that these agents may cause outbreaks if introduced into these populations. Cluster analysis of Pasteurellaceae and viral serology results identified four different clusters (P < 0.0001), but these did not closely correspond to species and location categories. The results from this study suggest that emphasis on single determinants for causes of respiratory disease outbreaks in domestic and bighorn sheep, rather than determination of risk factors for multiple determinants, may not provide results that are useful for managing disease in these species.