EVALUATION OF AN ALTERNATIVE PRODUCT FOR BRUCELLA MELITENSIS VACCINATION IN GOATS

Abstract

Brucellosis is caused by virulent species of Brucella, specifically B. melitensis, which is the top worldwide bacterial zoonotic disease, with more than 2.1 million new cases annually. B. melitensis is the greatest cause of human brucellosis, primarily transmitted from its preferred host in small ruminants. Addressing the disease in animal hosts is the most efficient way to prevent human brucellosis, as people are essentially dead-end hosts. Vaccination of animal reservoirs is the most cost-effective method to control brucellosis, alongside serologic detection and removal of infected animals. The B. melitensis strain Rev1 vaccine has been used to prevent brucellosis in small ruminants since the early 1950s. The vaccine is efficacious but has limitations due to its tendency to cause abortions in pregnant animals, long-term seroconversion in vaccinates that cannot be differentiated from infection with field strains, shedding in milk, and high virulence in humans. This work sought to explore and evaluate an alternative product for B. melitensis vaccination in goats. The overall aim of the dissertation is to develop a B. melitensis vaccine for use in endemic countries that is efficacious and safe in small ruminants. The first chapter provides an introduction, background, and rationale for developing alternative vaccines in small ruminants. Chapter two summarizes the current literature on B. melitensis vaccines and reviews their advantages and disadvantages in order to support the rationale for the need for new or improved small ruminant brucellosis vaccines. Chapter three evaluates the lipopolysaccharide of B. melitensis as a potential vaccine in goats in terms of the immunologic responses and protection against experimental challenge. Chapter four outlines the scientific protocol for conducting a randomized controlled field trial to assess the effectiveness of the B. melitensis vaccines in goats. Chapter five is the conclusion of a doctoral dissertation focused on exploring management strategies for controlling and eradicating brucellosis caused by B. melitensis, including the use of alternatives to Rev1 vaccines for application in small ruminants. When taken together, implementing improved Brucella vaccines together with effective management strategies for controlling and eradicating brucellosis could significantly reduce the global prevalence of the disease and its associated zoonotic infections.