AVIAN INFLUENZA

WHAT IS AVIAN INFLUENZA? 

Avian Influenza is caused by an Influenza type A virus. Avian Influenza (AI) – the bird flu – is a virus that infects wild birds’ gallinaceous species (such as ducks, gulls, and shorebirds) and domestic poultry (such as chickens, ducks and geese as well as ostriches). Certain ornamental species are also susceptible to this disease.
AI viruses are classified by a combination of two groups of protein: Hemagglutinin or H proteins of which there are 16 (H1 – H16) and Neuraminidase or N proteins, of which there are 9 (N1 – N9). AI strains also are divided into two groups based upon the ability of the virus to produce disease in poultry: low-pathogenic avian influenza (LPAI) and high-pathogenic avian influenza (HPAI).

HPAI or “high path” avian influenza, is often fatal in chickens. HPAI generally spreads rapidly in an infected flock and has a high death rate in the flock. Up to 100% of diseased chickens die as a result of such infections. Although HPAI strains have infected ostriches in South Africa in the past, it is only in 2017 that such strains have been isolated in chickens. In June 2018 South Africa confirmed its first case of H5N8 in chickens. This HPAI strain continued to persist in wild birds, ostriches and occasionally outbreaks occur in commercial chickens.

Low Pathogenic Avian Influenza (LPAI) or “low path” avian influenza, occurs naturally in wild birds and can spread to domestic birds. In most cases it causes no signs of infection or only minor clinical signs in birds. These strains of the virus are generally accepted to pose little threat to human health, with some exceptions. Most notably in South Africa we have H6N2, a low pathogenic avian influenza strain that affects chickens. Although these viruses cause minor or no clinical signs in poultry they do have the potential to mutate into HPAI and are therefore closely monitored.