A study that I saw a couple of days ago posted by Ironorehopper on his website was re-tweeted this morning by @Dutchy123 and posted on FluTrackers.
It looks at the susceptibility of dogs to the H5N1 `bird flu’ virus, and it seems like good fodder for a blog on this long 4th of July weekend.
First the abstract from PubMed.gov, then some background.
Virology. 2010 Jun 25. [Epub ahead of print]
Dogs are highly susceptible to H5N1 avian influenza virus.
Chen Y, Zhong G, Wang G, Deng G, Li Y, Shi J, Zhang Z, Guan Y, Jiang Y, Bu Z, Kawaoka Y, Chen H.
Animal Influenza Laboratory of the Ministry of Agriculture and National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, 427 Maduan Street, Harbin 150001, People's Republic of China.
Replication of avian influenza viruses (AIVs) in dogs may facilitate their adaptation in humans; however, the data to date on H5N1 influenza virus infection in dogs are conflicting.
To elucidate the susceptibility of dogs to this pathogen, we infected two groups of 6 beagles with 10(6) 50% egg-infectious dose of H5N1 AIV A/bar-headed goose/Qinghai/3/05 (BHG/QH/3/05) intranasally (i.n.) and intratracheally (i.t.), respectively.
The dogs showed disease symptoms, including anorexia, fever, conjunctivitis, labored breathing and cough, and one i.t. inoculated animal died on day 4 post-infection. Virus shedding was detected from all 6 animals inoculated i.n. and one inoculated i.t.
Virus replication was detected in all animals that were euthanized on day 3 or day 5 post-infection and in the animal that died on day 4 post-infection. Our results demonstrate that dogs are highly susceptible to H5N1 AIV and may serve as an intermediate host to transfer this virus to humans. Copyright © 2010 Elsevier Inc. All rights reserved.
PMID: 20580396 [PubMed - as supplied by publisher]
Although there’s not been much in the way of direct research done with dogs and avian flu, over the years we’ve seen several reports that suggest that dogs are susceptible to the virus.
Dogs are not normally considered vulnerable to influenza viruses, although in recent years an equine H3N8 influenza has jumped species to canines and has spread across the country (see the CDC’s Key Facts about Canine Influenza (Dog Flu)).
However, last December we saw a report of a dog from the Katonah Bedford Veterinary Center in Bedford Hills, New York, tested positive for the pandemic H1N1 virus (US: Dog Tests Positive For H1N1).
Prior to that, we saw reports out of China where two dogs had been infected with the H1N1 virus as well (see China Reports 2 Dogs With H1N1).
So, while probably not very common, dogs can apparently contract the new H1N1 virus.
Regarding the more virulent H5N1 `bird flu’ virus, we have reports as well, including this 2006 Dispatch to the CDC’s EID Journal.
Volume 12, Number 11–November 2006
Fatal Avian Influenza A H5N1 in a Dog
Thaweesak Songserm,* Alongkorn Amonsin,† Rungroj Jam-on,* Namdee Sae-Heng,* Nuananong Pariyothorn,† Sunchai Payungporn,† Apiradee Theamboonlers,† Salin Chutinimitkul,† Roongroje
Avian influenza H5N1 virus is known to cross the species barrier and infect humans and felines.
We report a fatal H5N1 infection in a dog following ingestion of an H5N1-infected duck during an outbreak in Thailand in 2004. With new reports of H5N1 virus continuing across Asia, Europe, and Africa, this finding highlights the need for monitoring of domestic animals during outbreaks.
The following year, in:
Avian Influenza (H5N1) Susceptibility and Receptors in Dogs
(Maas R, Tacken M, Ruuls L, Koch G, van Rooij E, Stockhofe-Zurwieden N. Avian influenza (H5N1) susceptibility and receptors in dogs. Emerg Infect Dis. 2007 Aug; [Epub ahead of print]),
Researchers determined that dogs have susceptible receptor cells in their upper and lower respiratory tracts, and can shed the virus while not manifesting clinical symptoms of the disease.
Their conclusion was:
Our results demonstrate that dogs are susceptible to infection with avian influenza (H5N1) virus and can shed virus from the nose without showing apparent signs of disease.
Moreover, receptors for avian (H5N1) virus are present not only in the lower part of the respiratory tract of dogs but also in their trachea and nose, which are potential portals of entry for the virus.
Different viruses have an affinity for different types of cells. That is why most viruses are selective as to what organ systems they attack, or even what species are susceptible.
This explains why a virus might affect a dog, or a cat, or a bird, yet not affect humans. This species selectivity is known as a `host range'.
Most viruses generally have a fairly narrow host range (there are exceptions, of course. Like rabies).
The receptor binding domain (RBD) of the H5N1 virus is that area of its genetic sequence that allows it to attach to, and infect, host cells. Much like a key into a padlock, the RBD must `fit' the host cell in order for it to bind.
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.
When it comes to infecting hosts, the H5N1 virus isn't apparently very particular.
Which may help explain the persistence of the virus in endemic areas, even after eradication and culling of avian hosts has taken place.