Pasteurellosis Prevention

Regulations about antibiotic use in rabbit production are expected to tighten, thus there is urgent need for infection-control alternatives. Pasteurella multocida, a serious bacterial infection in rabbits, causes significant economic losses. Improved husbandry and culling of affected animals reduces morbidity and mortality but at considerable cost. Vaccines do not provide complete protection. β-glucans are cell wall constituents of bacteria, fungi, and plants that act as biological-response modifiers, and positively influence the immunological response in mammalian cells. This study evaluated the effects of a β-glucan dietary supplement on P multocida infection in rabbits. 

Clinically healthy rabbits (n = 35) were divided into 5 groups of 7, including 1 control group and 4 experimental groups (positive controls, enrofloxacin-treated [10 mg/kg], low-dose β-glucan [5 mg/kg], and high-dose β-glucan [50 mg/kg]). There were 3 physiological model groups inoculated intranasally (IN) and 4 supraphysiological groups inoculated both IN and intramuscularly (IM). Subjects were evaluated clinically and via necropsy. All infected rabbits developed clinical signs within 24 hours. IN-challenged (positive) controls had minor changes found on necropsy; β-glucan-treated animals had healthy tissues, similar to negative controls. In the supraphysiologically challenged group, β-glucan treatment did not mitigate necropsy findings or reduce death rate but postponed death by several days, both at low and high doses. This delay may allow antibiotic intervention in field conditions, as the study found enrofloxacin treatment effective. Overall, results indicate that oral β-glucan may prevent naturally acquired pasteurellosis in rabbits.

Commentary

This report suggests the possibility of using oral β-glucan, a non-specific stimulant of the innate immune systems, to prevent P multocida infection in rabbits. The importance of P multocida in the lab, rabbit meat, or pet trade cannot be overstated. Although many diseases have been eradicated from lab rabbits, P multocida is still a scourge because of its communicability, carrier state, and ability to cause fatal disease arising in numerous organs. In the current climate of antibiotic resistance, the use of such easily administered alternatives will only increase in importance.—Bruce Williams, DVM, DACVP