Migratory Bird Flu Sequences in Companion Dogs in Korea
Recombinomics Commentary 19:11
April 4, 2008
The recent paper on H3N2 bird sequences in Korean companion dogs cited a close relationship with avian H3N2 isolates from 2003. However, new avian H3 isolates have been described in a new publication, and the sequences from these isolates have been released. The closest match in both HA and NA is a migratory bird isolate, A/aquatic bird/Korea/JN-2/06(H3N2).
This relationship may signal infection through consumption of an infected wild bird. Similar infections have been postulated from H5N1 infections of dogs and cats, raising concerns of co-infection of H3N2 and H5N1 in a common mammalian host.
Evidence of extensive reassortment was presented in the table listing the public sequence with the greatest identity with the canine H3N2 sequence. The relationships raise concerns over frequent co-infections, which can lead to both reasssortment and recombination.
Although the canine sequences are partial, the NA sequence from the above bird isolate is a full sequence and it contains multiple examples of recombination, including sequences related to pandemic H2N2 and H3N2 sequences.
Human sequences raise additional concerns. Although PB2 E627K was first detected in H5N1 from a bird at Qinghai Lake, it had been previously found in H5N1 infected cats and dogs. H5N1 in mammals would grow more efficient if E627K was present, because it is linked to a higher polymerase activity at lower temperatures. The mammalian body temperature, 37 C, is markedly lower than avian, 41C.
Thus, even though the H3N2 in dogs is most closely related to avian H3N2, passage through mammals can lead to the acquisition of mammalian polymorphisms.
The presence of H3N2 in migratory birds, and linkages between H5N1 infection and consumption of H5N1 infected birds, raises concerns of similar infection in mammals eating H3N2 infected wild birds.
It is also of note that many of the polymorphisms in the dog or wild bird H3N2 contain North American polymorphisms, linking birds in Korea with North America.
Widespread screening of companion dogs in Asia and North America would be useful in view of the dog to dog transmission of H3N2 in Korea, and North American polymorphisms in these sequences.
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