Domestic cats helping spread dangerous parasite to wildlife, UBC study finds

New research from the University of British Columbia suggests domestic cats are helping spread a dangerous parasite to wildlife. Simon Little / Global News

Should you keep your pet cat indoors? New research from the University of British Columbia is adding ammunition to the argument the answer is “yes.”

The study, led by veterinarian and UBC adjunct forestry professor Amy Wilson, focuses on the parasite Toxoplasma gondii, which is common in cats and potentially harmful to wildlife.

The researchers looked at more than 45,000 cases of toxoplasmosis in wild animals and found a heightened presence of the parasite among wildlife living near dense urban areas.

“Toxoplasma has an interesting life cycle in that cats and domestic cats and wild cats are at the centre of its life cycle,” Wilson said.

“When you see a pattern that you have increased infection rates and with high human densities, then with high human densities, you’re going to see higher numbers of domestic cats. So that’s what we concluded was one of the factors leading to the infection rates because they’re loading the environment with increased numbers of eggs.”

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A single infected cat can shed as many as 500 million Toxoplasma oocysts (eggs) in a two-week period through feces. Those eggs can go dormant and wait years before infecting an animal, she said.

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Animals infected with toxoplasmosis carry the parasite for life, potentially leading to nervous system disorders, cancers, other debilitating chronic illnesses and death in cases where they already have a weakened immune system.

The parasite can also be passed up the food chain to predators that eat infected wildlife, and is a particular threat to aquatic species, according to Wilson.

Humans can also become infected by coming into contact with infected cat feces, with particular danger to people who are pregnant.

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Many organizations, including the BC SPCA, recommend keeping cats indoors both for their own protection and to reduce predation on birds and other wildlife.

Keeping cats indoors, on harnesses or in so-called “catios” or enclosed outdoor spaces can also help prevent the spread of toxoplasmosis, with additional benefits for the cats themselves.

“I just really want to make sure that people understand that they don’t have to get rid of their cats,” Wilson said.

“The message to cat owners is really to start transitioning your cat to a supervised outdoor access — we know that free-roaming cats suffer increased trauma, we know they suffer increased disease,” she said.

Wilson said the study, recently published in Proceedings of the Royal Society B: Biological Sciences, also highlighted the importance of protecting healthy forests and ecosystems, which can help filter out Toxoplasma and prevent the infection of wild animals.

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