Avian Influenza

By James M. Harris, BS, DVM, FRSH
Mayfair Veterinary Clinic, Hobart

Avian influenza is a highly lethal generalized viral disease of poultry. An old name for this was fowl plague. There are three types of Influenza virus: A,B,and C.Type A Influenza viruses are responsible for the disease in birds.

Domestic fowl, ducks, geese, turkeys, guinea fowl, quail, pheasants, and many species of wild birds, (waterbirds and seabirds) are susceptible,but infections in the latter two groups are generally subclinical. There have been 4 outbreaks in Australia. The source of infection probably starts with direct or indirect contact with waterbirds. Many strains of the virus in wild birds are not pathogenic or only mildly pathogenic but may by genetic mutation become virulent. Once established in domestic poultry the disease is highly contagious. The virus is excreted in high concentrations in the faeces, nasal and ocular discharges. It can spread rapidly within a facility from bird to bird and from one location to another by mechanical means from contaminated clothing, shoes, crates, and other objects.

Clinical signs include: sudden death, depression, weakness, staggering gait,combs and wattles may have a cyanotic, swollen appearance with haemorrhage. Watery diarrhoea is frequently present. Birds may show laboured breathing and haemorrhage may occur in the skin. There is a high mortality rate.

Influenza viruses can mutate and adapt to other species. Strains normally confined to birds and pigs can become disease producers in humans. This seems to be the case with the present outbreak of Influenza in Southeast Asia. Ferrets are very susceptible to Influenza virus. And usually die. There is no specific treatment for Influenza. Secondary bacterial infections are addressed with antibiotics.

At the present time Australian Quarantine officials have upgraded their surveillance of poultry and poultry products entering Australia.

Additional reading.
1. Zoonoses and Communicable Diseases Common to Man and Animals: Pan American Health Organization, Second Edition, Washington, D.C.
2. Exotic Diseases: Australian Government Publishing Service,Canberra

Copyright remains with author.