Thursday, February 08, 2007

Endangered primates shown to harbour fewer parasites, weakens natural resistance

Primates threatened with extinction harbour fewer parasites than their non-threatened counterparts, a new study shows. It could leave the most vulnerable more susceptible to infectious disease, the researchers say.

Many primate species around the world are in danger of disappearing. Conservation efforts typically focus on habitat loss and poaching, but disease can also pose a danger, especially to populations already in trouble. In particular, outbreaks of Ebola virus are pushing Africa’s remaining gorillas and chimps to the brink of extinction.

Ecologist Sonia Altizer at the University of Georgia in Athens, US, and colleagues wondered if there was a correlation between the diversity of parasites that a species hosts and its status on the Red List of threatened species published by the World Conservation Union.

The team surveyed the data from hundreds of studies with documented cases of primate infection with viruses, bacteria, protozoa, worms and insects.
Natural resistance

In total, the researchers recorded 386 species of parasites from 117 populations of primates. Threatened species hosted fewer species of parasites, probably because disease spreads less readily when animals are scarce, and their populations become geographically isolated, the researchers say.

“People have debated whether endangered species experience higher or lower risk from infectious disease,” says Altizer. “This study suggests it might be lower.”

But she warns that the overall lack of parasite species diversity in threatened primates could lower the animals’ natural resistance, because their immune system will not recognise new pathogens, making them more susceptible to diseases. She hopes her database will inspire field workers to gather more data on what diseases are out there and how they affect primate conservation. “We know depressingly little,” she says.


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