To western sensibilities, the raising of dogs (and cats) as food (or for their skins) is both cruel and barbaric, but for thousands of years these animals have been used for these purposes in many places around the world. (see IBTimes article China proposes ban on dog meat, will South Korea follow suit?).
As with any livestock raised in close quarters, shipped unregulated cross-country, or kept under less than humane conditions, there is the potential for the introduction and spread of disease.
Today (h/t Tetano on FluTrackers) we’ve a study that looks at the seroprevalence of avian-origin H3N2 among farmed dogs in China.
But first, a little background on the virus.
In July of 2011, in a blog called Korea: Interspecies Transmission of Canine H3N2, I wrote about a study that reported on a recently emerged canine H3N2 influenza virus that had been observed to infect and sicken domestic cats at an animal shelter in South Korea.
This emerging canine H3N2 was of a different lineage than human H3N2 which appeared in the 1968 pandemic. It first appeared in Korea in 2007 – and unlike the other canine flu (H3N8) -which jumped from equines to dogs, this strain appears to have emerged directly from an avian source.
Earlier this year, in Interspecies Transmission Of Canine H3N2 In The Laboratory, we saw another study that showed that cats (and to a far lesser degree, ferrets) were susceptible to this canine H3N2. Thus far, these new canine viruses haven’t shown the ability to infect humans.
But viruses, particularly promiscuous ones that jump species, have ample opportunities to evolve and mutate. Which led the author of a 2008 EID study - Transmission of Avian Influenza Virus (H3N2) to Dogs - to point out:
Transmission of avian influenza A virus to a new mammalian species is of great concern, because it potentially allows the virus to adapt to a new mammalian host, cross new species barriers, and acquire pandemic potential.
Su S, Li HT, Zhao FR, Chen JD, Xie J, Chen ZM, Huang Z, Hu Y, Zhang M, Tan L, Zhang GH, Li SJ.
College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province 510642, People's Republic of China.
Since 2006, more and more cases of the infectious H3N2 canine influenza virus (CIV) in pet dogs have been reported in southern China. However, little is known about the prevalence situation of H3N2 CIV infections in farmed dogs in China. This is the first systematic epidemiological surveillance of CIV in different dog populations in southern China.
Two virus strains (A/canine/Guangdong/1/2011(H3N2) and A/canine/Guangdong/5/2011(H3N2) were isolated from canine nasal swabs collected at one dog farm in Guangzhou and the other farm in Shenzhen. Sequence and phylogenetic analysis of eight gene segments of these viruses revealed that they were most similar to the newly isolated canine H3N2 viruses in dogs and cats from Korea and China, which originated from avian strain.
This indicates that H3N2 CIV may be a common pathogen for pet and farmed dog populations in southern China at present. Serological surveillance has shown that the infection rate of this avian-origin canine influenza in farmed dogs and in pet dogs were 12.22% and 5.3%, respectively; as determined by the ELISA. The data also suggested that transmission occurred, most probably by close contact, between H3N2 CIV infected dogs in different dog populations in recently years.
As H3N2 outbreaks among dogs continue in the Guangdong province (located very close to Hong Kong), the areas where is densely populated and with frequent animal trade, there is a continued risk for pets H3N2 CIV infections and for mutations or genetic reassortment leading to new virus strains with increased transmissibility among dogs.
Further in-depth study is required as the H3N2 CIV has been established in different dog populations and posed potential threat to public health.
A recurring theme in this blog is that nature’s lab is open 24/7, and is constantly trying out new genetic experiments.
For a virus, successfully jumping to a new species is akin to hitting the lottery. A fresh supply of hosts not only increases its odds of long-term survival, it may also provide new opportunities for evolution.
Which is why we give these species jumps considerable attention.