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Free-Roaming Cats Spread Deadly Parasite to Wildlife




When domestic cats roam outdoors, they can spread a deadly parasite to wildlife.

New research suggests that free-roaming cats are likely to infect other animals with Toxoplasma gondii, the parasite responsible for toxoplasmosis. This disease is associated with disorders of the nervous system, diseases of the respiratory system, heart and other chronic diseases.

“For a long time, conservationists have emphasized the interdependence between human health and wildlife. Lead researcher Amy Wilson, associate professor in the Department of Forestry at the University of British Columbia, tells Trehuger that Toxoplasma gondii is a great example of this shared fate, as it is one of the most common parasites in the world. It is common worldwide and affects both humans and wildlife.

“It is important to understand the risk factors for this infection because toxoplasmosis can have severe effects in susceptible individuals, but even in healthy individuals, the hosts are infected for life.”

Because research in humans has shown that toxoplasmosis infection can have long-term health consequences with many serious neurological diseases, Wilson and her team wanted to use the vast amount of infection data available in wildlife to better understand the causes of this infection.

In their study, the researchers analyzed more than 45,000 cases of toxoplasmosis in wild animals using data collected from 202 studies. The studies included 238 different species in 981 sites around the world.

They studied data and extraction information for species-specific ecological features, as well as geographic information and human population density in the area where the infection occurred.

They found that wildlife living near areas of high human density were more likely to be infected.

“Because increased human density is associated with increased density of domestic cats, our study suggests that free-roaming domestic cats – whether pets or feral cats – are the most likely cause of this infection,” Wilson says.

“This discovery is important because simply by reducing the free roaming of cats, we can reduce the impact of Toxoplasma on wildlife.”

The results were published in the journal Proceedings of the Royal Society B.

Why domestic cats matter

Only wild and domestic cats (called cats) can spread the infectious form of Toxoplasma into the environment through eggs called oocysts in their faeces.

“There has been a growing recognition that domestic cats are the most likely to be a fauna that causes Toxoplasma infection in the wild,” says Wilson. “Domestic cats outnumber wild cats by many orders of magnitude, so when you consider their population size and can shed millions of long-lived eggs intermittently throughout their lives; the potential for environmental contamination is significant.”

A severely infected cat can secrete up to 500 million toxoplasma eggs within two weeks, and even a single egg sac can cause infection.


Field studies and DNA research have also provided evidence that domestic cats, not wild animals, spread the parasite.

“Our study also supports this role because wild cats avoid human environments and because we found that Toxoplasma infection in wildlife is higher in areas of greater human density, it suggests that domestic cats are the link while the opposite pattern would be if wild cats were the main cause. Source, Wilson says.

Healthy environment

If the animal or person is otherwise healthy, Toxoplasma gondii rarely causes symptoms or harm. However, if the immune system is compromised, the parasite can cause serious illness or even death.

Likewise, if the environment is healthy, streams, forests, and other ecosystems can help filter out potentially dangerous pathogens like these.

“In the case of Toxoplasma gondii, ecosystems with healthy populations of native predators can prevent domestic cats from roaming in ecologically important wildlife areas and reduce pathogen inputs into those environments,” explains Wilson.

“For existing pathogens, plants and healthy assemblies of soil bacteria and invertebrates increase the soil’s ability to filter or inactivate pathogens. When you have bare soil or concrete, pathogens can sit on the surface or be absorbed by runoff and travel directly to aquatic habitats”.

Wildlife protection

The researchers say the results of this study are important because they are a clear example of how human activity increases the risk of parasites in wildlife. Wild animals can also be indicators of human dangers.

One way to reduce this risk is to limit exposure to outdoor pets.

“Freely roaming cats kill billions of wildlife in the United States every year. In the case of birds, losses due to cats are three times higher than all other direct causes combined,” Wilson says. “In the current extinction crisis, we cannot afford to lose wildlife.” for trivial sources.”

She says the greatest danger is from cats who are allowed to roam freely and hunt wildlife.

“The instinct to hunt and the ability to kill wild animals is present in both cats and dogs, but for dogs, owners are expected to offer alternative forms of enrichment, and the same responsibilities should be extended to cat owners. There is a progressive movement among cat owners for supervised access,” says Wilson. Through harness training and downtime, which is very encouraging for this problem and the well-being of the cats.”

“It is critical for people to understand that maintaining healthy ecosystems has benefits not only for the health and resilience of wildlife, but also for human health. Although we may not fully understand all the mechanisms of this advantage, it is imperative that we act quickly to protect everything we can before losing it.


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