# 950
For two years, we've had anecdotal reports of dogs and cats dying in unusual numbers in and around bird flu outbreaks. Dr. C. A. Nidom, studying cats in Indonesia, tested 500 of them and discovered 20%, or nearly 100, had antibodies to the H5N1 virus, indicating exposure.
There are rumors that in some areas of Indonesia, the cat population has been decimated, presumably by the virus. Again, anecdotal.
We now have a study, which will be published in August, showing that dogs can be infected by the H5N1 virus, and at least in some cases, remain asymptomatic and shed the virus.
In Avian Influenza (H5N1) Susceptibility and Receptors in Dogs (Maas R, Tacken M, Ruuls L, Koch G, van Rooij E, Stockhofe-Zurwieden N. Avian influenza (H5N1) susceptibility and receptors in dogs. Emerg Infect Dis. 2007 Aug; [Epub ahead of print]), researchers have determined that dogs have susceptible receptor cells in their upper and lower respiratory tracts, and can shed the virus while not manifesting clinical symptoms of the disease.
Inoculation of influenza (H5N1) into beagles resulted in virus excretion and rapid seroconversion with no disease. Binding studies that used labeled influenza (H5N1) showed virus attachment to higher and lower respiratory tract tissues. Thus, dogs that are subclinically infected with influenza (H5N1) may contribute to virus spread.
Their conclusion was:
Our results demonstrate that dogs are susceptible to infection with avian influenza (H5N1) virus and can shed virus from the nose without showing apparent signs of disease. Moreover, receptors for avian (H5N1) virus are present not only in the lower part of the respiratory tract of dogs but also in their trachea and nose, which are potential portals of entry for the virus.
While not unsuspected, this study adds weight to the idea that dogs may become infected with the H5N1 virus, and that some may remain asymptomatic, but could become vectors of the disease. We've seen other reports where dogs have died from the infection. The outcome may depend on the clade of the virus, the initial viral load, and the dog's overall health.
In any event, dog owners will probably need to take precautions in areas where H5N1 has been reported in birds, and they should be cognizant of the possibility that their dogs could catch the virus from people, should a pandemic erupt.
While dogs and cats are unlikely to be major vectors if a human-to-human form of the virus breaks out, people who are avoiding contact with other people during a pandemic, but own dogs or cats, will probably want to keep them home as well.
More evidence that the H5N1 virus isn't strictly a disease of birds. That it can jump the species barrier, apparently with relative ease. And that it needn't necessarily produce symptoms in carriers.
And that isn't good news.
