It is a large-scale study that was conducted for twenty-six years on more than 200 gray wolves from Yellowstone National Park. (United States), and whose results were published by Communications Biology and relayed by Science and Future. The latter suggest changes in the behavior of some wolves, which would be linked to an infection with the parasite Toxoplasma gondii, the agent of toxoplasmosis. This parasite mainly affects felines, which can sometimes accidentally transmit it to wolves or humans. The presence of pumas in Yellowstone Park where these wolves live might therefore well explain this transmission.
The results of the study suggest that wolves infected with the parasite would adapt risky behavior from an early age, leaving the pack prematurely. About 50% of infected male wolves would separate from the pack at the age of only 6 months, when in normal times a young wolf separates from it on average around 21 months. The observation is the same in infected females: 25% of them would separate from the pack at the age of 30 months, instead of 48 months. Also according to the results of the study, an infected wolf would be 46 times more likely to become pack leader, this role going to the most aggressive and reckless individual in the pack.
Affected animals more vulnerable
According to Dan Mcnulty, an American wolf biologist, this study “provides compelling evidence of the profound influence that pathogens can have on the ecology and behavior of wild animal populations”.
Other studies had previously been carried out on the behavior of other animals carrying the infection. In mice, a decrease in their distrust of cats had been observed in particular, due to a change in their reaction to the urine of their predator. A similar trend in hyenas, whose behavior modification increases the risk of being attacked by lions.
50% of French people affected by the parasite?
In humans, infection with the Toxoplasma gondii parasite is extremely common since it would affect 50% of the population in France, without apparent symptoms and without risk for healthy people, specifies theNational Health Security Agency (Anses). However, it can manifest itself in severe forms in immunocompromised patients. Serological screening is also mandatory for pregnant women to avoid the risk of transmission to the fetus.
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