“It confirms that Toxo has pretty strong effects on mammal behavior”-possibly including ours. The study “is a game-changer,” says Stefanie Johnson, a researcher at the University of Colorado who studies how Toxoplasma impacts people and wasn’t involved in the hyena research. One of the study’s limitations, Holekamp and Laubach say, is that it’s unknown whether the hyena cubs were also bolder around other predators, feline or otherwise-a question they’re already investigating. These differences disappeared after the cubs turned one, perhaps because the survivors learned not to get too close to the felines. While uninfected cubs stayed an average of 300 feet away from lions, cubs that had Toxoplasma antibodies in their blood had ventured within an average of 142 feet from the predators, a dangerous proximity. Their analysis revealed that a third of cubs studied had been exposed to Toxoplasma, as had 71 percent of juveniles and 80 percent of adults. The researchers turned to the multi-decadal Mara Hyena Project, which records data on individual hyenas’ locations-including their proximity to other animals-as well as cubs’ age, sex, and blood samples, which would show whether they had ever been infected by Toxoplasma, which causes a lifelong infection. (Read how toxoplasmosis is harming endangered seals in Hawaii.) Parasite Infection Erotic text-based adventure of blue alien women, parasites, and spaceships. Since the parasite reproduces in lion intestines, and hyenas are known to be Toxoplasma carriers, Laubach and Holekamp wanted to know whether the parasite would make its hyena hosts behave differently. “This has the benefit of not only shuffling the parasite's genome, but also leads to the production of environmentally stable spores that can infect many additional hosts,” study co-author Zach Laubach, a postdoctoral fellow at the University of Colorado in Boulder, says by email. Over millions of years of evolution, this distant cousin of malaria has acquired a neat trick: Rodents with toxoplasmosis find the smell of cat urine irresistibly alluring, and that can draw them closer to a hungry feline. That can be challenging-after all, why would a prey animal approach a predator? But the parasite can only sexually reproduce in feline intestines. The Toxoplasma parasite can infect many host species, including rodents, birds, and other prey animals, if they ingest contaminated meat or feces. “This parasite doesn't just affect domestic cats and their mouse prey, but it's potentially a much wider-spread phenomenon,” says Holekamp, who has studied hyenas since 1988. The research also shows that the generally nonfatal parasite, which can infect a wide range of animals with a disease called toxoplasmosis, plays a bigger role than previously thought in how wild animals behave. (Read how Toxoplasma takes over human brains.) But this is the first time scientists have documented such effects in large wild mammals. It’s famous for its ability to manipulate its hosts, such as mice, into acting recklessly around felines, such as house cats. Toxoplasma is a single-celled parasite that infects at least one-third of the world’s human population.
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