VETgirl Q1 2021 Beat e-Newsletter

VACCINATION FOR BORDETELLA BRONCHISEPTICA IN DOGS: THE ARGUMENT FOR PRIME-BOOST VACCINATION STRATEGIES DR. STEPHAN CAREY, DVM, PHD, DACVIM Michigan State University

KEY HIGHLIGHTS

1 CIRD OVERVIEW Canine Infectious Respiratory Disease (CIRD) is a complex, highly contagious respiratory infection caused by numerous bacterial and viral pathogens that are spread primarily through aerosolized respiratory secretions. The communicable nature of CIRD makes it a frequent cause of morbidity in shelters, kennels, boarding facilities, pet day care centers, veterinary clinics, and other locations where commingling of dogs can occur. Most cases of CIRD result in mild upper airway symptoms including coughing, sneezing, and nasal discharge, that are self-limiting. However, some cases can cause more complicated disease resulting in more extensive lower airway injury, and even death in vulnerable populations. 2 RESPIRATORY DEFENSES AGAINST CIRD The respiratory defense system against CIRD can be divided into three components. Mechanical barriers, including the airway epithelium and the overlying mucus layer, serve to prevent inhaled pathogens from attaching to the epithelial surface, thereby inhibiting their ability to infect the host. If inhaled pathogens are able to bypass the mechanical barriers and engage the epithelial surface, the innate immune system, can become activated. The innate immune response is a non- specific, local immune response triggered by binding of pathogens to receptors on leukocytes and epithelial cells on the airway surface.

Binding of these receptors stimulates the release of immune mediators, including interferons, enzymes, and chemoattractant molecules, which function to inhibit infection and prime or amplify adaptive immunity. Thus, the innate immune response serves as an important bridge toward the development of the adaptive immune response. The adaptive immune system involves antigen presentation to T-helper lymphocytes in lymphoid tissues, which subsequently drive development of local IgA and systemic IgG-producing plasma cells and antigen-specific cytotoxic T-lymphocytes (CTL). It is the adaptive immune response that provides both immunologic specificity and immunologic memory. Vaccination against CIRD pathogens is a common and important strategy designed to stimulate and maintain adaptive immunity in patients at risk of disease. 3 THE ROLE OF BORDETELLA BRONCHISEPTICA IN CIRD Bordetella bronchiseptica , an aerobic, gram negative bacterium, is one of the most frequently identified bacterial causes of CIRD 1,2 . Bordetella bronchiseptica expresses virulence factors including a tracheal cytotoxin, transcellular secretion mechanisms, and adhesion molecules that facilitate bacterial attachment and mediate injury to ciliated cells in the upper respiratory tract 3,4 . These unique functions contribute to the ability of Bordetella bronchiseptica to serve

as both a principal pathogen and an important contributor to co-infections with other CIRD pathogens 5,6 . 4 BORDETELLA BRONCHISEPTICA VACCINATION Because of its important role as a co-factor in the CIRD complex, considerable attention has been devoted to the development of vaccination options for Bordetella bronchiseptica . Multiple Bordetella bronchiseptica vaccination types are available, including subcutaneous, non- adjuvanted cellular antigen extract, modified live intranasal (monovalent and multivalent combinations) and modified live monovalent oral. (continued)

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