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Canine infectious disease update (Proceedings)


1. Bordetella bronchiseptica…IN v. SQ
2. Canine Influenza Virus
3. Canine Leptospirosis

Bordetella bronchiseptica infection and prevention

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.

Canine Influenza Virus (CIV) infection

The clinical disease

In January 2004, an outbreak of respiratory disease occurred in 22 racing greyhounds at a Florida racetrack. Since then, dogs, mostly in shelter environments throughout the US have been confirmed with CIV infection.

Two clinical syndromes are reported:

1. a mild cough, with fever, lasting 10-14 days with subsequent recovery (14 dogs), and…
2. peracute death associated with extensive lower respiratory tract hemorrhage (8 dogs…36%) involving the lungs, mediastinum, and pleural space. Histology of the lungs revealed suppurative bronchopneumonia as well as bronchiolitis, and tracheitis.
3. about 10% or so of cases are sub-clinical…dogs are infected yet do not develop clinical signs and remain healthy. Subclinical infections appear to be common among infected dogs today.

Canine influenza is NOT a highly fatal disease; 80% of infected dogs develop nasal discharge, cough, mild fever and recover spontaneously. Several others will show NO CLINICAL SIGNS whatsoever. What makes this disease particularly problematic, clinically speaking, is the fact that it is contagious from dog-to-dog. Susceptibility rates, obviously, are very high.

Co-infection with other viruses and/or bacteria have not been studied. CIV infection in a dog with concurrent bacterial infection (B. bronchiseptica would be a likely candidate!) of the lower respiratory tract could pose a significant health threat to the affected dog(s).

Mortality in dogs is estimated to be from 6% to 8%. In clinical practice, this number may be much lower.

Occurrence of Canine Influenza in Dogs

Blood samples collected from 70 dogs with respiratory disease in shelters in Florida and a variety of veterinary practices in Florida and New York City showed 97% were positive for antibody to the influenza virus (ie, past exposure). This study demonstrated that canine influenza virus infection was not unique to the greyhound breed. Over 30 States and the District of Columbia have confirmed infections in dogs…shelter-housed dogs predominate.