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Group to tackle avian cholera
13/01/2004 14:11 - (SA)
Cape Town - Western Cape nature conservation authorities are establishing a special group to tackle avian cholera which is cutting a swathe through the Cape cormorant bird colony on Dyer Island near Hermanus.
"In early February we will be setting up a specialist working group to investigate methods to try and understand avian cholera better, because research into this outbreak is urgently required to see how it's spread and to look at possible control mechanisms," said Gail Cleaver, Overberg manager for the Western Cape Nature Conservation Board on Monday.
Cleaver said the current outbreak was petering out and had affected about 4 00 cormorants.
"At the moment we are still getting between 40 to 50 birds per day, but it has dropped considerably and we believe we are coming to the tail-end of the outbreak," she said.
Cleaver said that this particular outbreak was the third in recent years, and for the first time targeted specifically fledglings. A previous outbreak in 2002 saw about 7 00 cormorants die, mostly adults.
Cleaver said another reason why setting up a research team was important, was because it seemed as if the bacterium causing avian cholera lay inert in the soil before becoming active again.
"A major concern is that we believe the bacterium can lay dormant in the island's soil for up to four months. What we've seen is that if we have lots of rain on the island, then the bacteria seem to be activated," she said.
The latest outbreak killed about 20% of the island's cormorant population of 20 000, but was fortunately host-specific and did not transfer to, for example, penguins.
The disease was highly contagious and had a 100% fatality rate in affected birds, usually within 24 hours.
Cleaver said that if the outbreaks continued to occur on a more or less frequent basis, it could have disastrous consequences for the cormorant population on Dyer island.
She said the last volunteers on the island were being removed, and this also highlighted the delicate balancing act conservationists have to follow in responding to such outbreaks.
"There are difficulties in the clearing up operations... we don't want to disturb birds nesting close by, which might be more endangered than the cormorants. It is a delicate balance," Cleaver said.
- SAPA
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