A Venomous Primate Could Help Us Understand Why Some Humans Are Allergic To Cats

When threatened, a slow loris will raise its arms over its head to bring both glands toward the mouth. A quick lick of its highly specialized brachial gland turns saliva venomous. kunanon/Shutterstock

Madison Dapcevich 06 Feb 2020, 10:37

Big-eyed and puppy-sized, slow lorises may look just like a cuddly pet but they're actually equipped with a deadly weapon – venom. This toxin makes the slow loris the world’s only venomous primate, and genetic sequencing of its properties is helping researchers to understand why people are allergic to cats.

Slow lorises have highly specialized brachial glands, a hair-free swelling found on the elbow that produces a strong-smelling fluid. When threatened, a slow loris will raise its arms over its head to bring both glands toward the mouth. A quick lick of the glands turns saliva venomous. The venomous bite from a slow loris will prevent wounds from healing over a long period of time, eventually leading to necrosis, septicemia, lung edema, and cellulitis.  

“Generally slow lorises use their venom to fight with other slow lorises, causing very slow-to-heal wounds. But, when humans are bitten, the victim will display symptoms as if they’re going into allergic shock,” said the University of Queensland’s Associate Professor Bryan Fry in a statement.

Despite their unique defensive tactic, slow lorises (Nycticebus javanicus) remain a “mystery to science”. To fill in some of the gaps, Fry obtained gland secretions from wild slow lories studied at an Indonesian ecological research center over the course of two years. DNA sequencing of the samples revealed a protein found in the brachial gland that presented “remarkable” similarities to proteins present in cat dander. In fact, the two were virtually identical.

“Cats secrete and coat themselves with this protein, and that’s what you react to if you’re allergic to them,” said Fry, adding that if slow lorises use the protein as a defensive mechanism it may come as no surprise that cats do as well. “The fact that so many people are allergic to cats mightn’t be a coincidence. This may have been evolutionarily selected for in the wild as a defense against predators.”

Though it is a claim that will require further investigation, the researchers say that it could be that the two animals separately evolved to carry the protein, a process known as convergent evolution whereby two organisms that are not closely related evolve similar traits as an adaptation to their environment. Allergenic proteins likely play a role in the “defensive arsenal” of endangered slow lorises and cats as well as other mammals that exhibit the venomous traits, including platypuses, vampire bats, and water shrews. Together, these defense mechanisms may have evolved over time to “hijack” a victim’s immune system. 

Several species of slow lorises are critically endangered. Sainam51/Shutterstock
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