# 2439
The H5N1 virus has shown an ability to infect a surprisingly wide range of hosts. Many species of birds are susceptible, of course. But we've also seen infections in cats (including tigers), dogs, martens, civets, and of course humans.
Researchers have successfully infected cattle with the H5N1 virus, along with ferrets and mice for testing.
Today we get an early look at two new studies. One where foxes were exposed to the H5N1 virus, and another where raccoons were tested for various influenza antibodies.
The first study we'll look at:
Hall JS, Bentler KT, Landolt G, Elmore SA, Minnis RB, Campbell TA, et al. Influenza infection in wild raccoons. Emerg Infect Dis. 2008 Dec; [Epub ahead of print]
involves the seroprevalence study of raccoons in the wild, looking for influenza antibodies and the lab infection of raccoons with avian and human influenza strains.
The results are a bit surprising. Here is the abstract, slightly reformatted for easier reading.
ABSTRACT
Raccoons (Procyon lotor) are common, widely distributed animals that frequently come into contact with wild waterfowl, agricultural operations, and humans.
Serosurveys showed that raccoons are exposed to avian influenza virus. We found antibodies to a variety of influenza virus subtypes (H10N7, H4N6, H4N2, H3, and H1) with wide geographic variation in seroprevalence.
Experimental infection studies showed that raccoons become infected with avian and human influenza A viruses, shed and transmit virus to virus-free animals, and seroconvert.
Analyses of cellular receptors showed that raccoons have avian and human type receptors with a similar distribution as found in human respiratory tracts. The potential exists for co-infection of multiple subtypes of influenza virus with genetic reassortment and creation of novel strains of influenza virus.
Experimental and field data indicate that raccoons may play an important role in influenza disease ecology and pose risks to agriculture and human health.
Now, the percentage of wild raccoons with avian influenza antibodies was relatively low, but significantly high enough to raise questions as to how big a role they may play in the harboring of influenza viruses.
Laboratory experiments showed that raccoons could be infected by a variety of influenza viruses, and would shed the virus for days, and apparently even passed the virus on to an uninfected animal caged in the same room.
The second study involves foxes, which were fed infected chicken carcasses, to see if they would become infected with the H5N1 virus.
Reperant LA, van Amerongen G, van de Bildt MWG, Rimmelzwaan GF, Dobson AP, Osterhaus ADME, et al. Highly pathogenic avian influenza virus (H5N1) infection in red foxes fed infected bird carcasses. Emerg Infect Dis. 2008 Dec; [Epub ahead of print]
Here is the abstract, reformatted for readability:
Eating infected wild birds may put wild carnivores at high risk for infection with highly pathogenic avian influenza (HPAI) virus (H5N1).
To determine whether red foxes (Vulpes vulpes) are susceptible to infection with HPAI virus (H5N1), we infected 3 foxes intratracheally. They excreted virus pharyngeally for 3–7 days at peak titers of 103.5–105.2 median tissue culture infective dose (TCID50) per mL; they became ill with severe pneumonia, myocarditis, and encephalitis.
To determine whether foxes can become infected by the presumed natural route, we fed infected bird carcasses to 3 other red foxes. These foxes excreted virus pharyngeally for 3–5 days at peak titers of 104.2–104.5 TCID50/mL, but only mild or no pneumonia developed.
This study demonstrates that red foxes fed bird carcasses infected with HPAI virus (H5N1) can excrete virus while remaining free of severe disease, thereby potentially playing a role in virus dispersal.
Once again, a non-avian species not normally thought of as being a potential carrier of influenza viruses has been show, in laboratory experiments, to be a competent host.
In this case, foxes fed infected bird carcasses became infected, shed the virus, but did not become seriously ill.
They were, basically, asymptomatic carriers of the virus.
Both of these studies raise the issue as to whether there might be competent non-avian reservoirs of avian influenza viruses in the wild.
This could explain why, even after extensive poultry culling and farm disinfection, the H5N1 virus has a bad habit of returning to certain areas of the world.
