Swine flu in a cat and other matters

Helen Branswell, the Canadian Press's extraordinary flu reporter, is one of the few reporters who could have written the article, "Flu dogma being rewritten by a strange virus no one pegged to trigger a pandemic". She's been following flu for years and has watched as one thing after another we thought we knew about flu has been shown wrong -- by the flu virus. It's a theme we have been sounding as well for almost as long. As scientists we've seen one alleged flu truism after another was stood on its head. A couple of years ago we began to assume anything said about flu was provisional. Some of it might turn out to be true, and some of it might not. If you've been following this blog for a few years, most of Branswell's material will be familiar, but she has pulled it together in one place. So read it (once again: here). But one piece of now outmoded conventional flu wisdom not is in Branswell's article -- because it was only announced Wednesday -- is that our beloved household companion animals (aka, "pets") aren't susceptible to swine flu (example here, with breaking news update to correct it). This may still be flu dogma, but it's no longer flu catma.

From the Iowa Department of Public Health:

The Iowa Department of Public Health (IDPH) and the Iowa Department of Agriculture and Land Stewardship (IDALS) remind Iowans that in addition to protecting their families, friends and neighbors from the spread of the 2009 H1N1 influenza virus, it’s important to remember to protect family pets from the illness, as well. People who are sick with H1N1 can spread the virus not only to humans, but to some animals.

The Departments are sharing this message following the confirmation of a case of H1N1 in an Iowa cat. (IDPH)

Reporter Tara Parker-Pope has more in an excellent article in The New York Times:

A few days after two members of an Ames, Iowa, family came down with the flu, they noticed their 13-year-old cat wasn’t feeling too well either. The cat has since become the first documented case of a feline with the new H1N1 virus, commonly called swine flu.

The unusual case has riveted pet owners and health officials. Companion animals have been known to contract flu from other species — canine influenza (H3N8) originated in horses, and cats contract avian influenza (H5N1) from eating birds. But this appears to be the first time a cat has contracted influenza from a human. Two pet ferrets, one in Oregon and one in Nebraska, have also tested positive for H1N1, and the virus has also been transmitted between humans and pigs.

[snip]

The cat, a 16-pound orange tabby, began acting lethargic and lost his appetite on Oct. 27. He is the only pet in the house and never goes outside. The cat, described as “large framed but not chubby,” stopped eating and drinking and stopped cleaning himself. He also rested by hunching on all four feet, rather than sprawling out on his side as usual, a sign of respiratory discomfort. A few days earlier, two out of three family members in the home had developed flu-like symptoms, with fever and body aches.

The worried pet owner called Dr. Sponseller, a specialist in large animal internal medicine and molecular virology, who happened to be a family friend. At the time, neither Dr. Sponseller nor the pet owner suspected the flu . . .

[snip]

Although cats can contract flu from birds, this cat never left the house and was never exposed to any other pet. At that point, it occurred to the veterinarians that since the family members had been recently ill, they might be seeing a case of flu transmitted from human to cat. The school is the site of a major diagnostic lab, so the veterinarians were able to test the cat and quickly confirm he had H1N1, a finding that was later confirmed by additional testing by the U.S. Department of Agriculture. (Tara Parker-Pope, New York Times)

This was clearly a serendipitous discovery. This cat's household had connections to sophisticated veterinary science. Otherwise we wouldn't know about it. Which means that lots of animals may be getting this virus but we haven't recognized it. Besides humans, the known list includes free-living (i.e.,not in labs) pigs, ferrets, turkeys and cats. So when I read a briefing by WHO entitled, "Infection of farmed animals with the pandemic virus," I no longer take it seriously:

To date, extensive testing by laboratories in the WHO influenza surveillance network has detected no signs that the H1N1 pandemic virus has mutated to a more virulent form. Currently licensed pandemic vaccines closely match circulating viruses and are expected to confer good protection.

Vigilance for changes in the H1N1 virus includes monitoring to detect possible influenza infections in susceptible animals, both mammals and birds, as well as humans. While most influenza A viruses circulating in mammals preferentially infect a single species, cross-species transmission is known to occur. (WHO 2009 briefing note 15)

WHO's proposition that extensive testing in laboratories shows no signs H1N1 has mutated to a more virulent form implies we can recognize when this is occurring. It would be grand news if true, that we could simply read the biology off the genetic sequence. We're nowhere near that point. Trying to predict what this virus will do or not do from looking at genetic sequences is currently beyond our abilities. How do I know this? The virus has told us. Again and again. The second paragraph acknowledges that other species can be involved, but you certainly don't get the idea that this is something likely to happen, just something to watch for. But surveillance in other species is sparse (even for pig viruses there is little surveillance data available, much less other animals, except for birds).

There are some real concerns here. This is the era of industrial farming, with thousands or tens of thousands of susceptible animals (birds and pigs) under great stress crammed together. A virus can become extremely virulent and kill an animal very quickly yet still successfully transmit to another animal under these circumstances. If it's a virus that can also infect humans, this is a public health problem. Yet WHO says:

In addition, pandemic H1N1 infections have been reported in turkeys in Chile and Canada and in a few pet animals in the USA. Again, these infections were isolated events and pose no special risks to human health. (WHO 2009 note 15)

Maybe this is correct. But it's a wish more than an established fact, as the following section of the same note suggests:

When influenza infections are detected in farmed animals, WHO recommends monitoring of farm workers for signs of respiratory illness, and testing for H1N1 infection should such signs appear. FAO and OIE recommend that animals that are showing signs of illness be examined and properly managed, and allowed to fully recover before being transported or marketed.

In addition, samples from infected animals and humans should be taken for full genome sequencing of the influenza viruses to determine if mutations have occurred that could lead to changes in virulence, host range or antiviral resistance. Such sequencing is also important to assess the possible origin of the case or outbreak.

Industrial farming is big business and it is influential with agencies whose task it is to promote agriculture. Here's the (expected) take of the World Organisation for Animal Health: "Recent identification of the virus in different animal species is no additional cause for alarm":

So far, no evidence has suggested that animals play any particular role in the epidemiology or the spread of the pandemic H1N1 2009 virus among humans. Instead, investigations led by competent national authorities point to possible human-to-animal transmission in most cases. For this reason, the OIE considers that it is sufficient to certify the healthy state of animals for international trade during the relevant period before their exportation and maintains its position that no specific measures, including laboratory tests, are required for international trade in live pigs and other susceptible animal species and/or their products. (World Organisation for Animal Health)

You can't get much more explicit than that. In fairness it's followed by recommendations for continued vigilance. Unfortunately it appears as an after thought. The main message is: move along, nothing to see here.

But I can't stop myself from gawking.