From the avian influenza virus (AIV) outbreaks and market surveillance in Viet Nam during November 2011 and March 2012, a total of 196 AIV were isolated, according to Kwang-Il Kim of South Korea's Animal and Plant Quarantine Agency.

With co-authors there and at Viet Nam's National Center for Veterinary Diagnosis, they report in a paper in Poultry Science that although H5N1 highly pathogenic avian influenza (HPAI) was the most prevalent subtype in Viet Nam, 57 low pathogenic avian influenza (LPAI) viruses were identified from mainly domestic ducks and some chickens.

They noted a range of various subtypes of LPAI viruses were isolated from domestic ducks in Viet Nam: H3 (n=16), H4 (n=4), H6 (n=24), H7 (n=1) and H9 (n=10).

Geographically, the LPAI viruses were identified in different regions of Viet Nam.

Phylogenetic analysis of HA and NA genes in LPAIV in Viet Nam showed that some H3 (group I) and H4 subtypes AIV clustered with the viruses of several Asian isolates from domestic poultry and wild birds. However, the H6, H9 and some H3 (group II and III) subtypes AIV were closely related to isolates from domestic poultry in southern China.

Whereas the N2 and N6 subtypes AIV belonged to the Eurasian lineage, the N8 subtype AIV was classified to be both of Eurasian and American lineage.

These findings revealed that the regional trade and wild birds play a key role transmission of LPAIV in domestic ducks in Viet Nam, concluded Kim and co-authors.

Further surveillance at the intercountry level is needed, they added, to understand the epidemiology of these viruses and to cope with emergence of novel AIV types.

Reference

^{Kim K-I., J-G. Choi, H-M. Kang, T.L. To, T.D. Nguyen, B-M. Song, M-S. Hong, K-S. Choi, S-J. Kye, J-Y. Kim, H-S. Lee and Y-J. Lee. 2013. Geographical distribution of low pathogenic avian influenza viruses of domestic poultry in Vietnam and their genetic relevance with Asian isolates. Poult. Sci. 92(8):2012-2023. doi: 10.3382/ps.2013-03105}