• Posted June 22, 2023

Stray Cats Shed Toxoplasmosis Parasites in Cities, Especially in Warm Weather

Wild and feral cats appear to release more toxoplasmosis parasites in places densely populated with people, new research suggests.

These cats also "shed" more when the temperature is warmer, a significant finding given climate change, according to the report published online June 21 in PLOS ONE.

Policymakers could help protect humans from this illness by better managing these stray cat populations, the researchers said.

“Changes from climate or human activities can affect disease transmission in ways that we don't fully understand yet," said study author Sophie Zhu, of the University of California, Davis, and colleagues.

"In our study, we can see how these factors may be associated with changes in Toxoplasma shedding by cats, which in turn can affect the risk of exposure to vulnerable people and wildlife,” the researchers explained in a journal news release.

Toxoplasmosis is a mild-to-severe disease that can be especially dangerous in pregnancy. It is caused by Toxoplasma gondii, which can affect humans and many wild and domestic animals. Cats, sheep, mice, birds and sea otters are among the vulnerable creatures.

Humans can become infected when they accidentally come in contact with an infected cat's feces. This can happen unknowingly while gardening, for example.

While most T. gondii transmission is driven by domestic cats shedding the parasite at a stage of its life cycle known as oocyst, research has tended to focus on domestic rather than wild, stray and feral cats.

The researchers in this study analyzed data from 47 previously published studies on both wildcats, such as cougars and bobcats, and free-ranging domestic cats who did not have owners. These included stray cats fed by humans and feral cats not being fed by humans from around the world.

The investigators looked at a variety of human- and climate-related factors that could potentially be associated with T. gondii oocyst shedding.

Higher average daily temperature fluctuations were associated with more shedding specifically from domestic cats. Higher temperatures in the driest quarter of the year were associated with lower shedding from wild cats.

Combined with evidence from other prior studies, this suggests that rising human population density and temperature fluctuations may create environmental conditions that lead to greater spread of this and other diseases, the study authors concluded.

More information

The U.S. Centers for Disease Control and Prevention has more on toxoplasmosis.

SOURCE: PLOS One, news release, June 21, 2023