Infectious disease update (Proceedings)


Infectious disease update (Proceedings)

Aug 01, 2010

     • Bordetella bronchiseptica...IN v. SQ
     • Canine Leptospirosis
     • Canine Influenza Virus

1. Bordetella bronchiseptica vaccination: IN or SQ?

Closely related to Bordetella pertussis, the cause of "whooping cough" in humans, Bordetella bronchiseptica is a gram negative, aerobic coccobacillus particularly well adapted to colonize the ciliated respiratory epithelium of dogs and cats. (NOTE: it's known today that B. bronchiseptica is the progenitor of all 9 recognized Bordetellae). Today, this organism is regarded as a principle etiologic agent in what is now being termed "canine infectious respiratory disease" or CIRD (the term canine infectious tracheobronchitis (ITB) is 'out'). In the clinical setting, however, B. bronchiseptica infection should not be regarded as synonymous with CIRD. Dogs infected with canine parainfluenza virus (CPiV), canine influenza virus (CIV), or canine adenovirus-2 (CAV-2) are expected to experience more severe respiratory disease when co-infected with B. bronchiseptica than with any these agents alone. Canine bordetellosis, i.e. B. bronchiseptica infection in the absence of either CPiV, CIV, or CAV-2, is known to occur and can be associated with acute, fatal pneumonia in young dogs. B. bronchiseptica is transmitted through aerosolization of respiratory secretions. Bacteria can also be transmitted directly by contaminated dishware, human hands, and other fomites. Because B. bronchiseptica possesses several intrinsic mechanisms for evading host defenses, it is recognized for its role as a significant complicating factor in dogs with multiple-agent respiratory infections.

Several commercially licensed canine vaccines for protection against B. bronchiseptica, CAV-2, and CPiV are available. At this time, there is only one vaccine licensed for protection against feline B. bronchiseptica infection. Canine vaccines are available for topical (intranasal); currently there is only one parenterally administered vaccine for protection of dogs against B. bronchiseptica. Regardless of the route of administration, vaccinated dogs experience substantially less coughing when compared to control dogs following bacterial challenge. Beyond that, however, recent studies conducted on B. bronchiseptica vaccine since 2005 have shed new light on existing products and (fortunately) provided good clinical evidence to refute old paradigms.

New: While both parenteral and topical vaccines prevent signs of illness in exposed dogs, there are significant differences between the two products. First: in the only comparative challenge study published to date, it was shown that dogs vaccinated with a single dose of a topical (intranasal) vaccine were protected from infection and bacterial shedding. Dogs previously vaccinated with 2 doses of the parenteral (SQ) vaccine, then challenged with B. bronchiseptica, shed bacteria in the same concentration that control dogs did. These findings are particularly important among kennel-housed dogs. Parenterally vaccinated dogs still represent a risk to other, unvaccinated dogs.

New: While it was conventional knowledge that the onset immunity following topical (IN) vaccination was faster than parenteral vaccination, 2 studies have documented this fact in dogs challenged following initial vaccination. Onset of immunity following a single dose of IN vaccine is 72 hours (and...probably faster); onset of immunity to the parenteral vaccine, on initial dosing, does require 2 doses, at least 2 weeks apart then at least 7-10 days after the second dose. Onset of immunity following an annual 'booster' inoculation is not known. It is probably similar for both vaccines (within 7 days) after a single dose.

New: Conventional recommendations for B. bronchiseptica re-vaccination (booster) have been anecdotally reported as "every 6 months in dogs with sustained risk of exposure". However, until recently, there have been no studies that confirmed or refuted that information. Conventional challenge studies with the topical vaccines have shown 12 to 14 month duration of protective immunity. Based on these studied, "annual booster" seems appropriate for most dogs. It is this author's opinion that booster inoculations every 6 months for dogs facing frequent (weekly) exposure (dog day-care, frequent trips to dog parks, boarding, etc) are justified twice yearly. Dogs with minimal risk of exposure need only be vaccinated annually.

Another fact that generally favors topical vaccine over parenteral vaccine is the fact that parainfluenza virus (CPiV) is combined with virtually ALL topical vaccines currently on the market today. In fact, most authors agree that the best way to protect against parainfluenza virus infection (the infection that best characterizes the disease called "Kennel Cough") is via topical (also called, IN or intranasal) vaccination. Parenteral (SQ) vaccination against CPiV induces no mucosal (or local) immunity.