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Wildlife that live near cities are more likely to carry the parasite that causes toxoplasmosis, and domestic cats can play an important role in spreading this parasitic disease to wildlife.
Toxoplasmosis is caused by the pathogen Toxoplasma gondii and can infect any warm-blooded animal, including humans. Between 30 and 50 percent of all people are infected with T. gondii, with most cases being asymptomatic. In humans and animals with weakened immune systems, however, the infection can lead to chronic illness or even death.
“Toxoplasma gondii is a major pathogen for both humans and wildlife because infections are lifelong, associated with several chronic diseases, and are relatively common in both wildlife and humans,” said Amy Wilson of the University of British Columbia in Canada.
Wild and house cats are the primary hosts of T. gondii, which mature and reproduce in these animals. One of the most common ways of spreading toxoplasmosis is through contact with cat feces.
Wilson and her colleagues analyzed 45,079 cases of toxoplasmosis in 238 wild mammal species, using data from 202 published studies. The team compared infection rates with factors such as population density, annual rainfall, and temperature to identify the predictors of the prevalence of toxoplasmosis.
They found a high prevalence of the disease in wild mammals that live near cities. There was also a strong association between warmer temperatures and high infection rates.
Because higher population densities are associated with higher numbers of domestic cats, these results support the suggestion that free-roaming domestic cats are a major cause of these infections, Wilson says.
Urban expansion encroaches on natural habitats and, in some cases, reduces the numbers of wild mammals near cities, making it easier for domestic cats to migrate to these areas without encountering predators, the study authors say.
Wilson says that responsible handling of domestic cats, in addition to preserving natural habitats, could limit the spread of the pathogen while benefiting wildlife and public health.
“The study also shows the value of synthesizing evidence from a large number of painstaking field studies to map disease risk and understand the conditions in which animals and we are at risk of disease outbreaks around the world,” says Konstans Wells of Swansea University in the UNITED KINGDOM.
Journal reference: Proceedings of the Royal Society B: Biological Sciences, DOI: 10.1098 / rspb.2021.1724
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