Unknowing vectors

Humans may be transmitting new and dangerous viruses to Antarctica

Published: Sunday 31 August 1997

a pathogen generally found in domestic chicken is suspected to have caused large scale deaths of wild penguins in a particular part of Antarctica. Infectious bursal disease virus ( ibdv ) -- antibodies of which have been discovered in a variety of aquatic birds previously -- has infected Adelie penguin chicks ( Pygoscelis adeliae ). This is the first confirmed report of the outbreak of an infectious disease in the penguins.

ibdv is a stubborn pathogen that can resist heat, chemical agents and paucity of water to a great extent. It is contagious and highly infectious by the oral-faecal route. It is most effective in the breeding season of the penguins. One possible reason for the spread of the virus is environmental contamination in Antarctica from careless or inappropriate disposal of poultry products by expiditioners and tourists. This attracts scavenging birds such as the south polar skua ( Catharacta maccormicki ), making way for the virus to enter the food chain. The virus could also have spread through people carrying it in contaminated food, clothing, footwear, vehicles or equipment.

Heather Gardner and her team from the department of environment, Tasmania, Australia, and the Australian Animal Health Laboratory conducted a study on serum samples collected from Adelie penguins and emperor penguins ( Aptenodytes fosteri ). Samples were collected from 52 fledgling emperor penguin chicks that were aged between four and five months from a region of the Antarctic known as Auster Rookery ( Science , Vol 387, No 6630).

The researchers say that ibdv affects lymphoid organs, the organs that are responsible for the development of antibody-producing b -lymphocyte populations. This retards growth and development of the chicks, making them susceptible to infections. Although clinical disease was not noticed in the penguins, investigation into the effect of the virus is very important for numerous reasons. The extent to which expiditioners and tourists threaten the bird populations in Antarctica needs to be ascertained.

A virulent strain of the virus has spread very rapidly in the poultry industry in the northern hemisphere in recent years. Its occurrence in Antarctica bodes ill for the continent that remains one of the last pristine ecological systems of the planet.

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