To examine the seroprevalence of Toxoplasma gondii, serum samples and surveys were collected from 342 pet cats that visited veterinary clinics during 2010 and 108 that visited 2005 to 2007. The surveys investigated such issues as current and past housing, presence of other pets in the home, outdoor access, hunting behavior, type of food offered, contact with kittens, general demographic information, and vaccination status. Almost 20% tested positive for antibodies to T gondii. Seroprevalence was higher in cats younger than 6 months of age than in those between 6 months and 1 year. Beyond 1 year of age, seroprevalence rose steadily with time until age 4, at which time it remained around 25%.

Only 4 risk factors for T gondii infection were identified. Sharing a household with a dog was associated with a 2.1-fold increase in seropositivity, and being fed raw meat increased the odds of a positive antibody response to T gondii by 2.7 times. Cats that were formerly strays were 3.3 times more likely to show antibodies to T gondii. The greatest risk factor for T gondii–seropositive status was observed hunting behavior of cats, which led to a 4.1-fold increase compared with animals that were never observed to hunt.

Commentary
The identified risk factors make better sense if the life cycle of T gondii is understood. The parasite is transmitted to cats via infected tissue of a secondary host (small rodents), so hunting behavior and prior stray status are potential risks for infection acquisition. This study confirmed prior findings demonstrating higher prevalence in outdoor cats versus exclusively indoor animals. One recent paper also linked raw meat diets to increased parasite infection. However, the USDA has demonstrated that only a miniscule amount of inspected farmed meat contained T gondii, while the level of T gondii in hunted game meat was notoriously high. If owners wish to feed their pets raw meat, they should be advised to only provide meat that is USDA inspected.—Carly Jordan, PhD

Source
Seroprevalence and risk factors for Toxoplasma gondii infection in domestic cats in The Netherlands. Opsteegh M, Haveman R, Swart AN, et al. PREV VET MED 104:317-326, 2012.