HISTORY OF AVIAN INFLUENZA (BIRD FLU) IN PAKISTAN

Investment in poultry sector in Pakistan is about one billion dollars. Every family in rural areas and every fifth family in urban areas is associated directly or indirectly with poultry production activities in one way or the other (Sadiq., 2000). Poultry industry in Pakistan and all over the world is a major contributor of animal proteins substitute. Pakistan poultry industry is facing various managemental problems along with infectious diseases including avian influenza avian influenza (Alexander., 2000). Economics losses from avian influenza have varied depending on strain of virus, species of bird infected, number of farms involved, control methods used, and speed of implementation of control or eradication strategies. Direct losses in HAPI outbreak have included disposal costs, high mortality and morbidity losses, quarantine and surveillance costs and indemnities paid for elimination of marketing birds (Swayne., 2003).

In Pakistan outbreak of AI was first recorded in October 1994. The disease affected broiler breeder in Mansehra, Abbotabad, Rawalpindi and adjoining areas, killing approximately one million birds. The causative agent was confirmed as avian influenza a virus H7N3 (Naeem and Hussain.,1995).

In 1996, outbreak of AI broiler breeder and commercial layer was suspected in various areas of the Punjab. This outbreak did not cause considerable loss but was responsible for low production and immunosuppression. The causative agent was isolated and characterized as avian influenza virus H9N2. Keeping in view the virulence of this virus for poultry, this was also included in locally prepared vaccine. The AI vaccines containing locally isolated H7N3 have been extensively used since 1996 (Muhammad et al., 1997).

However, due to poor bio security and congested poultry colonies, the problem of AI started reappearing in Karachi in 1999 mainly in broilers. The disease was controlled by vaccination and strict bio security measures. However, later on due to poor bio security and no usage of vaccine the avian influenza was endemic in Karachi by the end of 1999 (Naeem et al.,1999).

In 2001, outbreak of a respiratory syndrome in broiler and layer, in Karachi and Abbotabad was recorded. The morbidity upto 100 percent and mortality was upto 50 percent. The HA agent was confirmed as avian influenza (H9 subtype) by using HI with AIV-H9 specific antis era (Muhammad et al., 2001). In 2003, the occurrence of avian influenza virus (AIV) infection in broiler, layer and broiler breeder flocks were reported in |Southern Pakistan. Data from this survey showed high levels of AIV antibodies, indicating unrecognized AIV infection occurring in these flocks. Based on this information, a second investigation was undertaken in selected broiler breeder, broiler and layer flocks. In this investigation, nine H9N2 AIV isolates were recovered. Chicks with the previous history of respiratory tract infection and some without overt clinical respiratory signs, had seroconverted to H9N2 (Naeem et al., 2003).