Two news reports in recent days added another dimension to the already worrisome seasonal resurgence of H5N1. First, there is little doubt that the current spate of human cases is just what we expect to see at this time of year, based on past experience. This doesn't mean that the increase is "just" seasonal, however. It can easily be masking or being accompanied by a change in the virus that makes this year different than last year, just as perhaps previous years were different than the ones before. To say this is a the usual seasonal resurgence is more descriptive than explanatory. It is typical of the usual January increase, but that doesn't tell us what is causing it. What are the extra dimensions?
More reports of infections in cats and pigeons. Neither is truly new in the sense we haven't seen it or talked about it before (see posts here, here, here, here, here, and here, among others). As we have more experience with this virus and some events begin to repeat themselves the picture starts to change. Whether it clearer or not is hard to say. But the continued reports that the virus is infecting feral cats and pigeons is something to watch because both animal species live in close contact with urban dwellers throughout the world. Widespread distribution of backyard poultry is not a feature of North American or European cities, as it is in asia and southeast asia, but cats and pigeons are found everywhere in those countries and could become an equivalent endemic focus of the virus.
The latest cat news is somewhat provisional. C. A. Nidom, who first reported finding H5N1 in Indonesia from swabs from pigs, now says a convenience sample of 500 stray cats in the vicinity of Indonesian poultry markets (where presumably the cats were feasting on bird carcasses) showed 100 of them (20%) had antibodies against the virus. This is some evidence that the cats had become infective at some point in the past, not that they were currently infected or that they were ever infective to other animals. Even this evidence has yet to be verified, as Nidom acknowledges. But for almost a year, now, we have been hearing about H5N1 in feral cats in Indonesia and FAO's Peter Roeder was supposedly doing a study similar to Nidom's. Why we haven't seen any other information is unsettling, as is the Indonesian Health Ministry's apparent refusal to look more seriously into what it characterizes as unproven "rumors." The pigeon reports come from Thailand, where a die off of wild birds included four pigeons. The pigeon story is not new, either.
So the fact that pigeons and cats can be and have been infected with H5N1 is not new. But given the increasing geographic spread of this virus, we should be taking a much closer look to see whether these two species and perhaps others might be potential new enzootic foci of the virus in a new ecologic niche, the cities of the temperate zone.
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Revere, I agree that both species have a potential niche. However, I'm not sure they represent the missing reservoir we've talked about for some time. H5N1 shows an extraordinary range with regard to mammals.
Marissa: I don't know if there is a missing reservoir or not. Possibly. My point, here, though, was that an enzootic in pigeons and cats would be a North American/European counterpart to the backyard poultry issue elsewhere, i.e., a source of virus very close to and in close contact with the human population. People eat and sleep with their cats and cats prowl the outdoors and eat pigeons (who also drop feces all over the city). As of now there is no evidence of an enzootic in cats and pigeons anywhere. But my concern is that the lack of evidence may simply be a function of failure to look.
disappointing, that we have no pigeon sequence from
Jakarta. Now they are culling the chickens - but
the chicken viruses don't match the human viruses
I have never been one of those who consider a pandemic by H5N1 inevitable. But the incursion of this virus into cats as well as pigeons probably takes it one big step further in that direction.
When the cat and tiger deaths first started in 2004, we could have said that those might be one-off events. A couple of years later, we have reports of cat infections from multiple countries, and, more worryingly, from both clade 1, and at least 2 subclades of clade 2 viruses, assuming we haven't seen any reports of cat infections from China. Which probably means that the ability to infect cats is not due to a rogue mutation but something almost intrinsic to this virus.
The ability to infect cats and transmission between them are both scientifically well established, although we don't know how often or how efficiently that happens. So in terms of whether we might have an enzootic focus in urban population centers in western countries, it becomes IMHO a matter of when not if, before some infected migratory bird in Europe, for example, encounters our family cats.
The infection of pigeons, however, takes this to yet another level of risk, if it become established. One could in theory take care to avoid cats in our daily lives but pigeons and their droppings are impossible to avoid if you live in European cities. I suspect it's not that different in the Americas.
The bigger danger is the exposure of cats to pigeons, which will happen far more frequently. There is indeed something almost iconic about cats and pigeons, in that, more than many other species, they both roam freely and willfully among humans in concrete jungles, but each is the nemesis to the other! Their frequent contact is almost guaranteed.
At present, one might take some (false) comfort from the low rate of human infections compared to exposure, but this could easily change if cats instead of poultry becomes the major source of human infections. Some speculate that is what is happening in Indonesia, but we don't know.
For the west, if pigeon infections become widespread, then the virus is going to be among us far sooner than we are prepared for.
we could however cull the pigeons more easily than the
chickens, I assume. I mean, with fewer economical loss.
About Nidom and the cats, we chould wait for confirmation from Japan, it's not clear which tests he did.
Culling feral pigeons is beyond the reach of man. In NYC and other cities, we call them flying rats. I remember sitting in an open window forty floors up in mid-town once, at dawn, watching the squadrons of pigeons waking up and launching into their special three-dimensional world. They are their own tribe, and I like to think of them as other than rats. However, if they become reservoirs in out cities, God help us.
I have been fascinated with the mystery of other reservoirs, mammal or not. Having lived in south Asia in a rural area for two years, I remember the ubiquitous sparrows, always cheeping in the courtyard and flying in and out of the windows. All around, stealing grain, crumbs, whatever they could find. Whatever the mystery reservoir is, my theory is that it is so common that it is invisible.
As our raptor population increased over the last 15 years, our pigeon population has plummeted. We used to have two or three large flocks but I haven't seen a pigeon in town in two years. Most of the pigeon fanciers rarely fly their birds anymore, at least not anything they can't afford to lose.
Almost nothing included in the following article from AP, via the CattleNetWork, is in any way, unexpected.
It can still have a chilling effect on the reader though, who is told about a recent experiment on monkeys, using a recreated version of the 1918 pandemic flu virus and it's devastating effect on the unfortunate primates.
Here is a taster:
"The experiment was supposed to last 21 days, but after eight days the monkeys were so sick - feverish, in pain and having difficulty breathing - that ethical guidelines forced the researchers to euthanize them.
"There was some surprise that it was that nasty," University of Washington virologist and study co-author Michael Katze said. "It was the robustness of the immune system that helped victimize them."
The virus was simply overwhelming, researchers said.
....No other flu virus is deadly to monkeys, and the speed in its spread and the overwhelming immune system response is only similar to those in the H5N1 bird flu, Kawaoka said."
Full article here:
http://www.cattlenetwork.com/content.asp?contentid=98421
JM
Given the written 1918 accounts I think it was unethical to duplicate the results again, by infecting the primates...
It's not like proving 1918 and H5N1 kill the young and healthy has yet motivated any politician to upset the VIP apple cart early, and get the public preparing their households and communities against a deadly panflu year or two.
crfulmoon: Thee are no written accounts of the cytokine/chemokine effects of 1918 in primates. There is a great deal of new information in this paper not available anywhere. What is unethical about it? It is this kind of information that might allow us to piece together a rational thearapy for H5N1.
Susan C: ...it becomes IMHO a matter of when not if, before some infected migratory bird in Europe, for example, encounters our family cats.
That's already happened, hasn't it? In Germany:
http://www.fao.org/AG/AGAInfo/subjects/en/health/diseases-cards/avian_c…
T42, Yes, it has. I meant in a large scale manner.