April 2 (Bloomberg) -- A bird flu virus that killed dogs in South Korea can spread from one dog to another, showing that the disease is capable of crossing species and causing widespread sickness in mammals, a study found.    

A cocker spaniel and a miniature schnauzer were among dozens of dogs in South Korea sickened by an H3N2 strain from birds, researchers said in a study published in the May issue of Emerging Infectious Diseases journal. Viruses taken from the sick canines were used in an experiment later to see if pathogens were capable of spreading from dog to dog.    

The findings add to scientific understanding of how flu viruses evolve in animals and the risks they pose to humans. A separate bird flu strain called H5N1 has killed 236 people worldwide by spreading primarily from birds to humans. If a deadly H5N1 strain evolved like the strain in today's study to spread from one human to another, it could kill millions.    

``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,'' the Korean researchers said.    

The study, led by Daesub Song, Bokyu Kang and Chulseung Lee of the   Green Cross Veterinary Products Co. and   Daewoong Pharmaceutical Co. at Yong-in, outside Seoul, followed cases of severe respiratory disease last year in dogs at three veterinary clinics in Kyunggi province.    

Close Resemblance    

Tests on specimens collected from three of the dogs showed they were infected with H3N2 viruses closely resembling those found in chickens and doves in South Korea in 2003. The pathogens may have been transmitted from birds to dogs fed raw, minced meat from infected ducks and chickens, the authors said.    

``In South Korea, untreated duck and chicken meats, including internal organs and heads, have been widely used to feed dogs for fattening in local canine farms or kennels,'' they said.    

Dog is regarded by some Koreans as a delicacy. Seoul city officials will ask the national government to include the animal in the legal definition of livestock, the Chosun Ilbo newspaper reported last week.    

A variant of the H3N2 virus causes seasonal flu in humans. A canine strain was linked to an outbreak among 13 dogs at an animal hospital and later reported at a kennel in Jeolla province, where as many as 52 canines were infected, most likely as the virus spread from dog to dog, the Korean researchers said.    

Seal, Dogs    

Avian flu viruses are known to transmit to unrelated mammalian species only rarely, the researchers said. Bird-derived H7 and H4 flu viruses were reported in seals in the early 1980s, and the H5N1 bird-flu strain was found in a dog that fed on a duck infected with the virus in Thailand in 2004, according to the study.    

Large cats, including tigers and leopards, kept in capacity and fed on infected poultry carcasses, have also been infected and developed severe disease. Almost two of every three human H5N1 cases were fatal, according to the World Health Organization.    

``This is an important and interesting study because previous avian-to-mammal influenza infection by H5 or H7 were not efficient in subsequent human-to-human or cat-to-cat transmission, whereas this study shows an outbreak of 13 dogs in addition to sporadic cases,'' said Yuen Kwok-yung, a microbiology professor at the University of Hong Kong.    

Not Unexpected    

``Efficient mammal-to-mammal transmission'' of H3N2 viruses isn't unexpected since variations of the strain regularly infect humans and pigs, Yuen said in an interview today.    

Dogs may be more susceptible to flu strains carried by birds because both canines and birds share a type of virus-binding site in their respiratory systems that is less common in humans.    

The bird-like H3N2 virus may be capable of spreading between dogs because it was excreted in nasal discharges and caused sneezing of experimentally infected beagle puppies, the study found. The virus wasn't active in their feces.    

Evidence of avian flu in pet dogs ``raises the concern that dogs may be become a new source of transmission of novel influenza viruses, especially where avian influenza viruses are circulating or have been detected,'' the authors said.

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