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H3N8 Widespread in Companion Dogs in the United States
September 27, 2005
August 2004, 6 pet dogs in the same household were examined at a southwest Florida veterinary clinic for respiratory disease. The dogs ranged in age from 6 months to 10 years and included a German Shepherd Dog, a rat terrier, and 4 terrier cross breeds. The 4 terrier
cross breed dogs had been adopted from an animal shelter facility in south Florida 1 week earlier.......
Serum collected from the 6 dogs was tested for antibody to canine/FL/04 (H3N8) by HI. The 3 dogs that had clinical disease for at least 7 days were seropositive with antibody titers ranging from 64 to 512.......
Serum samples collected from 16 dogs with clinical disease for < 5 days were negative for antibody to canine/FL/04 (H3N8) by HI. Of the 42 dogs that had clinical disease for =7 days, 40 had HI antibody titers ranging from 32 to >1024 to canine/FL/04 (H3N8).
The descriptions above demonstrate that H3N8 is widely detected in companion dogs. Reports in the summer of 2004 indicated H3N8 was being found in greyhounds at racetracks in Florida. This year there were more reports of fatal infections in Florida and New England in the Boston area. There were also reports of H3N8 being found in companion dogs.
The latest examples indicate H3N8 is easily spread in kennels and shelters and is now in many states. In the past H3N8 was frequently found in horses, and the latest report indicates that the H3N8 is most closely related to the H3N8 from horses.
However, H3N8 has H3, which is the most common human serotype, so the potential for the H3 in H3N8 to become involved in human infections is very real. H3N8 has also been isolated from wild water fowl as well as pet birds, but the rapid spread of H3N8 through pet dogs in the United States probably poses the greatest threat for human infections, since the pets a popular and frequently kept indoors with frequent encounters with adults and children.
Although H3N8 has not been reported in humans, the dramatic expansion of the host range and geographical range by H3N8 could create new opportunities for genetic exchange of information via reassortment or recombination. This could also impact dual infections by H5N1. There have been some reports of H5N1 in dogs in Thailand, so H3N8 in dogs could offer a new species for acquisition of a human receptor binding domain by H5N1 avian influenza.
Plans had been announced for collection of serum samples from animal handlers in contact with racing dogs. The widespread detection of H3N8 in companion dogs suggests such screening should be expanded.