Dogs and H5N1

Influenza is primarily a disease of birds but other animals, including mammals, can be infected. Humans are mammals, of course, and we know humans get flu. But there are 144 different subtypes of influenza A and mostly they infect birds. When H5N1 jumped from birds to humans in Hong Kong in 1997 it was a surprise. It was thought the bird viruses needed to acquire human specificity by mixing bird and human viruses in a suitable animal (usually thought to be the pig). Pigs are very lucky. They can be infected by both human and bird viruses. That seemed to be what happened in the 1957 and 1968 pandemics, anyway. The bird flus weren't supposed to infect humans directly. Or so the story went.

As of 1997 we know it isn't true. The 1918 virus may well have been another example of a direct jump from birds to humans, although there is still some uncertainty about where it came from. This might suggest that viruses making the direct jump are particularly dangerous, but we now that H7N2, H7N7 and H9N2, all bird viruses, can also infect humans but the disease is very mild, much milder than the usual seasonal flu we are accustomed to each winter. So there is much we don't know.

One of the many things we don't know is what other animals can get infected by viruses we thought were confined to birds. Just considering the H5N1 subtype, we have seen reports of various felines (large cats and also our smaller domestic variety), dogs and ferrets and mice in the laboratory. A new paper just appeared giving some more information on dogs and H5N1:

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. (Maas R et al., Avian influenza (H5N1) susceptibility and receptors in dogs. Emerg Infect Dis. 2007 Aug)

The authors inoculated dogs in the laboratory with a high path H5N1 isolated from a chicken in 2004. The dogs became infected in both their upper and lower respiratory tracts and shed virus from the nose and mouth. But the dogs didn't become sick and there were no lesions in the respiratory tract. The Dutch authors cite a paper of a colleague that the receptors for the virus in cats and humans is only found in the lower respiratory tract, but as we have noted several times, the evidence doesn't establish this and this experiment is consistent either with the existence of bird receptors in the upper tract of dogs or the necessity of the bird receptor affinity for infection being less important than many claim.

In any event, the asymptomatic infection of dogs is something to ponder. If domestic animals (cats and dogs), living in intimate household contact with humans, can be infected and shed virus, it suggests we need to consider pandemic control measures for companion animals.

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By Jon Singleton (not verified) on 03 Jul 2007 #permalink

I train dogs to retrieve migratory waterfowl that have been shot by hunters. These retrievers carry the killed bird in their mouth back to the hunter, who then takes the bird in his hand. These same dogs are freqeuntly family pets as well, and live in the owner's homes.

When I read this research a few days ago I wrote an article for my local 'Retriever's Club' newsletter breaking it down for simplicity's sake. I have not recieved a reply from the editor. I do know that H5N1 just isn't talked about in my club, nor on the on-line forums that are dedicated to hunting dogs.

AKC statistics indicate 123,760 labs and 42,962 golden retreivers were registered in 2006 alone. This does not include UKC registrations, nor does it include other breeds that are used to retrive upland gamebirds.

Obviously, not all of these dogs will be used to hunt. But, given a hunting dog's career may spane 10 years the accumlative stats for the number of dogs out there retrieveing waterfowland other game birds is probably in the hundreds of thousands.

And nobody involved in hunting, or field trials is willing to discuss the possiblities, and therefor not able to take some simple precautions.

Big elephant, big time denial.


Your comments back up what revere said months ago - and I'll probably botch this up and bring down the wrath of revere, but I'll try anyway - the basic implication I recall was that the Indonesians, and many other cultures, care for and relate to their chickens much in the same way Americans, and many other cultures, care for and relate to their dogs and cats. (Granted, we do not eventually slaughter and eat dogs and cats, nonetheless, they have a connection with their chickens.) We cannot understand why they don't just slaughter their chickens, or at least not let them in the house anymore... Just wait until we are told to euthanize all our dogs and cats... then maybe we will understand how they feel.

Big time denial, indeed!

Bit of overreach here? There are several health concerns for pet owners and benefits as well. Pets lower blood pressure and seem to have life extension benefits as well. We have cohabited with dogs for at least 10,000 years to our mutual benefit.
See also flu wiki.

By Joe Jackson (not verified) on 03 Jul 2007 #permalink

Joe: No over reach. I'm not suggesting we kill dogs. On the contrary. We have a dog and have always had them. Instead I am saying we ought to think about this ahead of time so we don't have vigilantes going around shooting dogs out of fear. To prevent that takes some forethought, which is what I am advocating. Companion animals need to be part of pandemic planning just as we now realize they need to be for other disaster settings.

No over reach indeed. The best way to prevent vigilante 'culling' of pets is with sound information and strategies for mitigating the risk. As Revere said, we need to talk about this ahead of time.

Better watch that someone doesn't decide to cull the humans in a that point we are the vectors spreading it to the dogs and cats rather than visa versa.