When it comes to the host of dangers that wild deer face, few people think of feral cats. However, a study by researchers at Ohio State University found that feral cats may be responsible for the presence of a dangerous parasite in deer called Toxoplasma gondii. According to the study, which was recently published in the journal Ecohealth, the number of deer infected with the parasite coincided with the number of wild cats in their area. Researchers collected samples from over 400 whitetail deer in the Cleveland, Ohio area and found that almost 60 percent of the animals showed signs of infection. Comparatively, 200 wild cats in the region were tested for the parasite and over 65 percent of the felines were afflicted with the parasite.

“This study documents the widespread infection of deer populations in northeastern Ohio, most likely resulting from feral cats, and highlights the need for consumers of venison to make absolutely certain that any deer meat planned for consumption is thoroughly and properly cooked,” lead author Gregory Ballash told The Billings Gazette.

Hunters are especially warned to take care in cleaning and cooking deer meat, as the parasite is transmissible to humans. Toxoplasmosis is the leading cause of death attributed to foodborne illness in the US. According to the Center for Disease Control, more than 60 million people in the United States—roughly one in five—carry the disease. The Toxoplasma parasite can be suppressed by a strong immune system, but effects may include flu-like symptoms, muscle aches, and in more serious cases, the parasite can even cause eye and brain damage as well as memory loss.

Some animal rights activists contested the study’s findings and argue that other carriers may be responsible for the spread of the parasite. Yet the American Bird Conservancy (ABC), an advocacy group for wild birds, is promoting the study as further evidence of the damage caused to wildlife by feral cats. ABC previously stated that “outdoor” cats kill millions of birds every year, as well as many other species.

“Our Facebook fans already know that ABC supports cats kept indoors because of the huge toll cats take on ‪#‎birds‬,” the group wrote on Facebook. “But there are public and wildlife health concerns too: New study finds that a large percentage of white-tailed deer in Greater Cleveland, ‪#‎Ohio‬, are infected with Toxoplasma gondii, a parasite perpetuated by cats. The findings suggest widespread environmental contamination.”

The greatest number of infected deer documented by the study were urban deer, who tested positive for the parasite at a rate of nearly three times higher than rural animals. This is likely because of the greater quantity of stray cats in urban neighborhoods. Overall, researchers estimate that about 44 percent of Ohio deer are infected with the parasite.

Image from Boksi on the Wikimedia Commons

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2 thoughts on “Study: Dangerous Cat Parasites May Be Infecting Deer

  1. Toxoplasma gondii can only be spread to deer via cat feces. There are only 3 ways for an animal or human to become infected with Tg.

    1) It can be transferred to an unborn fetus if the mother first becomes infected with Tg while she is pregnant.

    2) An animal or human can become infected by eating the meat of another infected animal.

    3) An animal or human can become infected by ingesting an oocyst (egg) of toxoplasma gondii. Microscopic oocysts are shed in the feces of an infected cat by the hundreds of millions per cat. Toxplasma gondii can ONLY complete its life cycle in the gut of a cat, and cats are the ONLY animal that sheds oocysts in its feces. The oocysts remain viable in soil or water (even saltwater) for 18 month or longer. It only takes a single oocyst to become infected. Oocycsts can be transferred from feces to food sources by rodents or insects. In dry conditions the oocysts can become aerosolized and inhaled, causing infection. Oocysts can wash into water sources during rainstorms. If a rain puddle forms where an infected cat has defecated, that water may become contaminated and may infect any animal that drinks from it.

    Deer do not eat meat, so they didn’t get it that way. They could pass it from doe to fawn, but the doe has to become infected some way while pregnant. The only way the deer could have become infected is from oocysts shed by cats.

    Now, the oocysts could have come from native cats, such as cougar or bobcats, but when was the last time anyone saw a cougar roaming around Cleveland? And it is important to remember that domestic house-cats outnumber all native cats in North American combined, by several orders of magnitude.

    1. Thanks for expounding on this subject. So then these oocysts are everywhere then. Life of them (ooocysts) moot point cuz the cats never stop shittin, perpetuating oocysts. Feral cats are at such a rediculous level they are an untold faction of the ecosystem. It’s supposedly illegal to eradicate them because they’re cats. However they can be trapped and “turned in”. They effect the environment in more dramatic ways than coyotes by devastating ground nests and songbird nests, and now apparently their impacting the wildlife in far more comprehensive ways. A huge source to the feral population is “barn cats”. As necessary as they have been for all of time, they are at least of nuisance proportion, and should be controlled as possible. However, I have seen hundreds on trail cameras and from long distances, I have never seen one from a stand or trail. Meaning they probably are an impossible hunt. Not a worthy quarry, but something really needs to be corrected.

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