Avian influenza caused by influenza A viruses, is a highly contagious disease of poultry which may result in 100% fatality rate. Migratory birds such as wild ducks and geese can carry the virus, often without any symptoms of illness. Domestic poultry flocks, however, are particularly vulnerable to epidemics of a rapid, severe and fatal form of the disease.
Avian influenza caused by influenza A viruses, is a highly contagious disease of poultry which may result in 100% fatality rate. Migratory birds such as wild ducks and geese can carry the virus, often without any symptoms of illness. Domestic poultry flocks, however, are particularly vulnerable to epidemics of a rapid, severe and fatal form of the disease. Avian influenza virus has been classified on the basis of Haemagglutinin (H1-H16) and Neuraminidase (N1-N9). Different combinations of these types are possible. Although direct relationship of type of viruses with pathogenecity does not exist, highly pathogenic avian influenza (HPAI) viruses generally belong to types H5 and H7. The AIV serotype H5N1 (Bird Flu fame) is also of zoonotic importance as this can cross the species barrier and can infect humans. The virus has already infected 285 humans with 152 deaths during 2003-2006. Pakistan had first outbreak of HPAI in December, 1994 which was diagnosed as H7N3 type. The disease was controlled with culling, movement control and vaccination. The second outbreak of AI was seen in 1998 and was diagnosed as H9N2. Another outbreak of H7N3 was seen in 2003-04.
Following HPAI H7N3 outbreak in poultry during 2003-04, a National Programme for Surveillance and Control of Avian Influenza was launched. In this regard a network of 12 AI monitoring labs is working at provincial level with a National Reference Lab. for Poultry Diseases (NRLPD), at NARC. This network covers domestic and commercial
poultry, wild birds and migratory birds throughout the country. State of the art diagnostic facilities for AI (RT-PCR, virus isolation, ELISA) have been developed and are being utilized for this surveillance. During the active surveillance, an H5N1 outbreak was diagnosed in February, 2006 in Pakistan. The disease spread to a few poultry rearing areas. An effective control strategy was implemented with provincial governments which effectively controlled this outbreak. No human case was reported.
The NRLPD has also been declared as a sub regional reference lab for AIV for SAARC countries by the FAO and training activities for lab. staff from SAARC countries has also been conducted at NRLPD. Furthermore, a repository of different isolates of AIV is regularly being maintained at the NRLPD. This lab also continues to be focus of international collaboration on AI.
Key References
Naeem, K. and Sidduqe., N. (2005). Use of Strategic Vaccination for the control of Avian Influenza in Pakistan. Dev. Biol. (Basel); 124: 145-150.
Naeem, K., Naureen, M., Rashid, S. and Bano, S. (2003). Seroprevalence of avian influenza virus & its relationship with high mortality and dropped egg production. Avian Pathology, 32(3):285-289.
