Unpacking the bird flu outbreaks in South Africa

Shahn Bisschop, a senior lecturer and specialist poultry veterinarian at the University of Pretoria, explains what's behind the current chicken crisis and what must be done about it.

- Shahn Bisschop

An outbreak of avian influenza, a highly contagious viral infection that affects wild birds as well as poultry, has hit poultry farms in South Africa. Two different strains are causing outbreaks in the country, namely H5N1 and H7N6.

THE STRAIN THAT HAS BROKEN OUT

The outbreak caused by a highly pathogenic (HPAI) strain of H7N6 avian influenza is causing the most concerning at present.

The strain was first confirmed in chickens near Delmas, east of Johannesburg, at the beginning of June this year.

This virus is a novel mutation of a strain which originated from wild birds at or near the location of the original outbreak.

The strain is well-adapted to chickens in preference to other avian species, infects them easily and replicates in them effectively. This means it spreads easily between birds and farms. An estimated 10 million birds have already become infected, while six million died from H5N1 earlier in the year.

The conventional control measures (collectively known as biosecurity) have been less effective than usual in limiting the spread of the disease. The main measures taken on poultry farms include strictly limiting human and vehicle movement. People entering farms will typically take measures to limit disease transmission such as showering, changing clothes and disinfecting footwear when moving between different parts of the farm. Because wild birds are associated with the spread of bird flu, measures are taken to ensure they are completely excluded from all chicken sheds.

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