Investigating the use of vaccination as a tool for managing pneumonic pasteurellosis in Rocky Mountain bighorn sheep (Ovis canadensis canadensis)

Currently one of the greatest threats to bighorn sheep (Ovis canadensis) populations across western North America is respiratory disease and the associated population-level impacts accompanying the illness. While lungworm (Protostrongylus spp.) and various bacteria and viruses likely contribute to the respiratory disease complex, probably the single most harmful group of pathogens is bacteria in the family Pasteurellaceae. It is well documented that these bacteria can and do cause disease, likely because of the leukotoxin (Lkt) produced by the bacteria which is toxic to ruminant leukocytes. Few ways exist to mitigate this problem, and to date, attempts by wildlife managers to intervene have been ineffective.;Previous research has focused on vaccines to protect bighorns from Pasteurellaceae and the associated Lkt produced by those species. Such vaccines have proven to be effective in domestic livestock and, while less research has been conducted with bighorn sheep, some vaccines have been shown to provide a degree of protection. Because of this potential, I focused on evaluating 2 different Pasteurellaceae vaccines in bighorn sheep. One of those vaccines is an autogenous vaccine developed specifically for the Colorado Division of Wildlife (CDOW) for use in bighorn sheep while the other is a commercially available cattle vaccine (One ShotRTM ). Both vaccines were evaluated experimentally in captive Rocky Mountain bighorn sheep (Ovis canadensis canadensis), while the commercial vaccine was also evaluated in a free-ranging herd of bighorns where it was administered along with a suite of other health-related treatments.;Chapter 1 of my thesis is devoted to the evaluation of an autogenous vaccine manufactured by Newport Laboratories (Worthington, MN) and developed specifically to protect Rocky Mountain bighorn sheep in Colorado from several presumed pathogenic strains of Pasteurellaceae. In this chapter, I focused on serum antibody concentration responses to vaccination in ewes and lambs, the safety of vaccination, and passive transfer of maternal antibodies from ewes to their lambs.;This vaccine evaluation was carried out using Rocky Mountain bighorn sheep that were part of the CDOW's captive research herd in Fort Collins, Colorado, USA. All bighorn ewes were vaccinated approximately 1 month prior to expected parturition, and were boostered 6 months later, while lambs were vaccinated once at approximately 3 months of age. After vaccination, all animals were observed daily for signs of pneumonia or other adverse reactions to the vaccine. Serum samples were collected periodically from the ewes after vaccination and booster. Serum samples were also collected periodically from all lambs after birth and following vaccination. Colostrum samples were collected from 6 of the 9 study ewes within approximately 30 hours of parturition. All serum samples were assayed for both Lkt neutralizing and Mannheimia haemolytica whole cell antibodies using an enzyme-linked immunosorbent assay (ELISA), while colostrum samples were assayed only for Mannheimia haemolytica whole cell antibodies using ELISA.;In the bighorn ewes, vaccination significantly increased Lkt neutralizing and M. haemolytica whole cell antibody concentrations for a period of less than 4 weeks. In addition, Lkt neutralizing antibodies were increased by an insignificant amount following booster 6 months after the initial vaccination.;No increase in passive transfer of maternal antibodies between ewes and lambs was detected as a result of vaccination. Antibody concentrations at < 30 hours of age were not different between lambs born to vaccinated or unvaccinated ewes. Likewise, antibody concentrations found in colostrum samples were not different between treatment groups.;I did not detect a statistically significant increase in antibodies after vaccinating the lambs. However, I did observe an increase in Lkt neutralizing antibodies from a mean OD value of 0.0011 (SE = 0.00067) to a mean OD value of 0.0044 (SE = 0.0014) after vaccination, and also an increase in M. haemolytica whole cell antibodies from a mean OD value of 0.0076 (SE = 0.0044) to a mean OD value of 0.029 (SE = 0.011) after vaccination.;My work shows that both One Shot and the autogenous vaccine induced immunological responses in Rocky Mountain bighorn sheep in Colorado. Potential applications for these vaccines include vaccinating high-risk bighorn herds preventatively or vaccinating bighorn herds that are already experiencing chronic pasteurellosis. While this strategy is likely not feasible in all situations, free-ranging herds do exist where vaccines can be administered, as illustrated by the field evaluation of One Shot. Future research should be conducted to determine if the serological responses that I observed equate to protection from Pasteurellaceae infection and the associated damage caused by Lkt. Additionally, I suggest that future work should evaluate the efficacy of simultaneously administering both of these and potentially other Pasteurellaceae vaccines to provide broader protection against varied strains of Pasteurellaceae. (Abstract shortened by UMI.)...