# 4104
It was only last month that that a study in Eurosurveilance sought to reassure us that Turkeys weren’t particularly susceptible to the H1N1 virus.
Below is just an excerpt.
Eurosurveillance, Volume 14, Issue 41, 15 October 2009
Rapid communications
C Terregino1, R De Nardi1, R Nisi1, F Cilloni1, A Salviato1, M Fasolato1, I Capua ()1
Our findings suggest that in its present form, the pandemic H1N1 influenza virus is not likely to be transmitted to meat turkeys and does therefore not represent an animal health or food safety issue for this species.
Despite this study (which has an excellent pedigree in Ilaria Capuam, noted virologist for the OIE/FAO in Italy), over the past few months we’ve had reports of infected turkeys in Chile (see FAO: Concerns Novel H1N1 May Spread In Poultry and Chile: H1N1 Jumps To Turkeys) and Canada (see Update On Ontario H1N1 Infected Turkeys).
Now, a US turkey farm in the the state of Virginia is reporting an H1N1 infection in a flock. A hat tip goes to Indigo Girl on Allnurses pandemic forum and celvin11 on FluTrackers for the link.
This report from Reuters.
U.S. finds pandemic H1N1 virus in turkey flock
Mon Nov 30, 2009 5:53pm EST
WASHINGTON (Reuters) - The pandemic H1N1 flu virus was confirmed in a flock of breeder turkeys in Virginia -- the first U.S. case involving turkeys, the U.S. Agriculture Department said on Monday.
The virus also has been found in hogs, three house cats, pet ferrets and a cheetah in California. USDA said infections of turkeys have been reported in Canada and Chile.
"This is the first detection of 2009 pandemic H1N1 influenza in turkeys in the United States," said a USDA spokesperson.
We’ve chronicled a number of species jumps involving the H1N1 virus, and the Reveres at Effect Measure took on the subject of promiscuous flu viruses in their blog today (see Dogs, cats and swine flu's promiscuity).
I confess I’m unaware of the `cheetah story’ alluded to in the above story, and a quick Google search didn’t turn up anything.
We will no doubt be reminded by the USDA that these infections pose no food safety issues, but the ultimate threat of an ever widening host range for the H1N1 virus is less clear.
There are a couple of trains of thought here.
One is that when the virus broadens its host range, it has more opportunities to mutate or to reassort with other viruses.
One might, after all, reasonably expect that the H1N1 virus has a better chance to meet up and reassort with an H5 or H7 avian virus in a turkey, than in a human host.
There is another theory, however, that states that viruses don’t tend to mutate as long as they have a large number of susceptible hosts.
Virologist John Oxford has suggested that mutations in the H1N1 virus are less likely to occur until a certain amount of herd immunity is achieved. There have been studies that indicate that vaccination pressure may actually drive antigenic drift in flu viruses.
Avian influenza: genetic evolution under vaccination pressure
Magdalena Escorcia, Lourdes Vázquez, Sara T Méndez, Andrea Rodríguez-Ropón, Eduardo Lucio and Gerardo M Nava
Virology Journal 2008, 5:15doi:10.1186/1743-422X-5-15
As a population gains herd immunity (through vaccines or exposure), the virus must either evolve (mutate) away from the established immunity or die off for a lack of suitable hosts.
But, if the virus has a wider host range (say humans, pigs, and birds), or a ready natural reservoir, then there is less evolutionary pressure on it to mutate.
Of course this second theory doesn’t help much with relatively rare, but major antigenic shifts (reassortments), but deals mostly with the far more common antigenic drift (minor mutations).
Which theory is correct?
It’s entirely possible that both are correct, as they are not mutually exclusive.
As to what happens with this promiscuous pandemic H1N1 virus?
That’s the $64 question, and no one has a good answer yet.
Stay tuned.
