Avian influenza (AI) also known as bird flu is a serious emerging respiratory disease in poultry industry caused by influenza A virus of Orthomyxoviridae family.
The virus is classified into different subtypes based on the combination of two main surface proteins hemagglutinin (H) and neuraminidase (N). According to the genetic characteristics and the severity of the disease caused among poultry birds, the virus is grouped into 2 broad categories viz. low pathogenic avian influenza (LPAI) causing asymptomatic disease and highly pathogenic avian influenza (HPAI) producing severe fatality.
AI is responsible for the mortality of domestic birds, reduced egg production associated with serious economic loss of the poultry farmers.
The LPAI strain H9N2 was first isolated in the USA in 1966 from turkeys and in 1992 in China and other Asian countries. In 2003 this strain was identified in Indian poultry farms. Although this strain caused less mortality percentage, the birds showed signs like edema, conjunctivitis, trouble breathing and remarkable drop in egg production among the layer birds.
The HPAI strain H5N1 was detected in China in 1997 and in India it was identified in 2006. This strain was observed among the poultry birds causing disease of sporadic to endemic in nature. This highly pathogenic strain caused huge loss in poultry industry leading to immense economic loss among the poultry farmers. The strain H5N1 also transmitted to human population imposing a serious impact on public health. People in close contact with the infected birds especially the farmers were at high risk to get the infection causing severe illness leading to death.
Recently, the United States Department of Agriculture (USDA) has confirmed the presence of HPAI strain in the commercial flock of poultry birds in USA. The infection has been transmitted due to the migratory wild birds carrying the highly infectious strain of the virus. However, no human case of AI has been detected so far.
Strict biosecurity measure should be taken to control AI outbreak in poultry flock. Proper health monitoring is also primary requirement. Vaccination of the healthy flock may be adopted.
