Treat ’em rough, keep ’em tough

Conservationists need to leave parasites well enough alone.

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Leaving biting mites and slimey tapeworms to feed on critically endangered animals may be in conservation’s best interests, according to a study published in Trends in Ecology & Evolution.

While it’s common practice to deworm and delouse species such as takahē, kiwi and kākāpō during reintroduction to the wild, research led by University of Otago professor Hamish Spencer suggests that most types of parasites bolster the animals’ immune system and ultimately benefit them.

In humans, this benefit is known as the ‘hygiene hypothesis’. It maintains that infections during childhood stimulate the development of the immune system so that in later life it does not overreact to low doses of allergens and other foreign agents.

There are limits, however.

“We are arguing against what we see as standard practice,” says Spencer. “But it is important to realise that there are some parasites and diseases that seem unequivocally bad for their hosts. These latter cases would still need to be controlled.”

Plus, says Spencer, there’s also conservation value in the parasite itself as a potentially rare species and an important element of an endangered host’s normal environment. In 1904, for example, the tapeworm Stringopotaenia psittacea was discovered in kākāpō but has never been seen since, thought to have gone extinct as its host became endangered, or perhaps eradicated as a side effect of the conservation effort itself.

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