Sloth fur, research has found, hosts bustling communities of insects, algae, fungi and bacteria, among other microbes, some of which could pose disease risk.

Yet, experts say, the famously slow-moving mammals appear to be surprisingly infection-proof.

"If you look at the sloth's fur, you see movement: you see moths, you see different types of insects... a very extensive habitat," Max Chavarria, a researcher at the University of Costa Rica, told AFP.

"Obviously when there is co-existence of many types of organisms, there must also be systems that control them," he said.

Chavarria and a team took fur samples from Costa Rican two- and three-toed sloths to examine what that control system could be.

They found the possible existence of antibiotic-producing bacteria that "makes it possible to control the proliferation of potentially pathogenic bacteria... or inhibit other competitors" such as fungi, according to a study published in the journal Environmental Microbiology.

'No infection'

The sloth is a national symbol in laid back Costa Rica, and a major tourist attraction for the Central American country.

Both the two-toed (Choloepus Hoffmanni) and three-toed (Bradypus variegatus) sloth species have seen their populations decline, according to the International Union for the Conservation of Nature's Red List of Threatened Species.