JACKSON, Wyo. — The parasite Toxoplasma gondii (T. gondii) is present in Yellowstone National Park (YNP) and can spread to both canines and humans.
According to a 2022 research article, 51.6 percent of the 62 YNP mountain lions tested positive for T. gondi antibodies, meaning that those animals have been exposed to the parasite. The research also utilized 26 years of gray wolf data to confirm that YNP wolves are exposed to transmission due to their overlap in territory with infected mountain lions. The study confirms the wolves contract the parasite either through direct contact with infected cougars or the cats’ feces.
The research also reveals that wolves with the antibody marker for T. gondii actually change their behavior to become bigger risk-takers. The behavior analysis results show that YNP wolves classified as dispersers, those that venture out from their pack, had almost double the T. gondii marker prevalence than non-dispersers, for both sexes. The research also confirms that wolves with T. gondii markers are more than 46 times more likely to become pack leaders.
According to the study, dispersal can allow wolves to find increased opportunities for reproduction and fill gaps in unoccupied territories by establishing new breeding populations. However, dispersal is also considered a “risky” behavior that sees higher mortality rates in the wolves that attempt it.
According to Dan Stahler, wildlife biologist for YNP, blood samples from live-captured wolves and cougars during radio-collaring events in the Park are collected as part of annual baseline monitoring. This data continues to be submitted for disease screenings that include exposure to T. gondii, along with data collection on wolf and cougar survival, reproduction, behavior and distribution overlap.
Stahler tells Buckrail that more time is needed to collect data before the 2022 results can be updated or new patterns can be evaluated.
“Given the widespread presence of T. gondii worldwide, the park has no specific concerns with prevalence levels in Yellowstone’s wildlife population or risk of exposure at this time,” Stahler says.
T. gondii is a common parasite in developed countries, with roughly 50 percent of the global population experiencing exposure. Primarily, Stahler says this exposure comes from consumption of uncooked meat or living in close proximity to domestic cats, although Stahler notes that YNP visitors should always be aware of the possible risk of exposure.
“Most people infected with toxoplasmosis have no symptoms, but it can affect those with compromised immune systems, may cause miscarriage and birth defects during pregnancy and affect young infants more significantly,” Stahler says. “There is some evidence that toxoplasmosis has neurological effects that influence behavior in both animals and humans.”
Preliminary research shows that toxoplasmosis-associated changes in humans influence executive functions, such as inhibition and working memory, in addition to improving cognitive control in healthy adults, creating deficits in goal-directed behavior of healthy elderly and reducing sensitivity towards motivational effects of rewards in otherwise healthy young adults.
According to Stahler, YNP visitors can take precautions against exposure by avoiding drinking untreated water, not handling scat of wild or dead animals and washing hands with soap and water after touching anything like soil or sand that might be contaminated by felid feces containing T. gondii.
