Avian influenza
The etiological a gentisa via ninfluenz a type A virus und e r the family Orthomyxoviridae. Avian influenza pandemics in Pakistan, Nepal and Myanamar (1995) and in India (2006 and 2008) have caused concern and anxiety among the scientists and poultry farmers.
The virus, however, exists in a variety of feral migratory birds viz. fowl, duck and turkey in subclinical form. In domesticated poultry the pathogenicity of the virus ranges from non-clinical forms to a fulminant respiratory syndrome with a high rate of mortality, the latter form being designated as 'Fowl plague' in view of its devasting nature.
Epidemiology: The virus spreads rapidly both by direct and indirect contacts.Migratory birds ducks, pig and turkey act as reservoirs and play a major role in viral transmission to poultry. Eggs laid at active stage of infection are contaminated both outside and inside. The incubation period is short ranging from a few hr to 3 days depending on the dose, age of the bird and the virus strain.
Diagnosis: T he disea se is d ia gno sed by se r olo gic al co nfir ma tio n using haemagglutination inhibition (HI) test with convalescent sera, AGID with nucleo protein or matrix protein monoclonal antibody, single radial haemolysis test or by ELISA using nucleo-protein monoclonal antibody. The virus is successfully isolated in embryonating hen eggs by inoculating processed nasopharyngeal or cloacal swab samples collected from clinical cases.
Control: The disease can be controlled by using inactivated vaccines and applying other control measures, viz. (i) physical separation of healthy birds from ailing birds, (ii) minimizing the contact of poultry with feral and migratory birds, (iii) proper disposal of carcasses, (iv) creating a disease-free zone at international borders by de-population, (v) banning importation of biologicals, reagents, poultry, pigs and their products from disease reporting countries, and (vi) periodical screening of poultry for maintaining the disease-free status.