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Toxoplasmosis is one of the most widespread human parasitoses in developed countries. Sexual transmission has been confirmed in several animal species, and indirect evidence suggests it may occur in humans. We compared the seropositivity to Toxoplasma gondii in couples who visited the Center for Assisted Reproduction in Prague from June 2016 to June 2018 and analyzed various risk factors including the serological status of sexual partner. By comparing the risk factors in men and women, we tested the hypothesis of male-to-female sexual transmission of toxoplasmosis. The prevalence of toxoplasmosis in women with infected male partners (25.6%; n = 156) was higher than in women with uninfected male partners (18.2%; n = 477; P = 0.045). Therefore, a partner's seropositivity seems to be a risk factor for infection in women (n = 593; prevalence ratio = 1.418; P = 0.045) but not in men (n = 573; prevalence ratio = 1.058; P = 0.816). Our results support the hypothesis of the sexual transmission of T. gondii from men to women. The risk may seem relatively low, but transmission can occur during unprotected sexual intercourse, which may be at the time of conception. Because of the risk of congenital toxoplasmosis, a lower risk of infection than that observed in our study can represent a serious health problem., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

To determine the risk of toxoplasma infection to individuals exposed to cats in a research institution, we compared the prevalence of toxoplasma antibodies with exposure to cats in university employees. Of 116 employees tested, 42 (36 percent) had toxoplasma antibodies as determined by the indirect fluorescent antibody test. Women and individuals aged 35 years or more had a greater prevalence of antibodies. The antibody prevalence by occupation was 72.1 percent for physicians and those with doctorates, 45.3 percent for animal and veterinary technicians, 33.3 percent for research technicians, 28.2 percent for administrative staff, 25.0 percent for graduate students and fellows, and 13.4 percent for veterinarians. There was no significant positive association between exposure to cats and the prevalence of toxoplasma antibodies. A follow-up of seronegative employees, 6 and 18 months later, revealed no seroconversions indicative of acute toxoplasma infection. We concluded that there was no significant risk of toxoplasma infection in university employees exposed to cats.

In 1970, immunofluorescent toxoplasma dye titers were measured on 265 individuals aged 30 years and older from Washington County, Maryland. Characteristics of the individuals were determined from a private census conducted in this area in 1963. Titers at 1:16 dilution or higher were found in 38.5%. A strong positive association was found with increasing age, possession of farm animals, and residence in an older house; a strong negative association was found with possession of cats. These data are not consistent with laboratory evidence that cate are definitive hosts and disseminators of toxoplasma.

Toxoplasma infection can be transmitted to humans by ingestion of tissue cysts in meat or by ingestion of oocysts in cat feces or fecally contaminated soil. since meat is traditionally well cooked in Costa Rica and the authors were able to exclude meat and eggs from playing a role in transmission, they postulated that ingestions of oocysts should entirely explain transmission. To test this hypothesis, they studied seven populations in Costa Rica and serologically tested 883 people between 15 and 26 years of age. By interviews and surveys, they determined mode of living, soil contact, cat contact, and cat density. The infection rate in cats was studied by stool and serologic examination, and soil availability for defecation was determined from aerial photographs. Antibody was taken as indicating infection and was found to be acquired most actively in children and young cats. In a retrospective analysis, antibody prevalence in humans correlated highly with individual cat contact (both owned and stray), with cat density, with living in houses with wood floors and a crawl space underneath, and with living with cats on a cement floor. antibody prevalence in humans correlated negatively with soil availability to cats for defecation and with soil contact by humans, suggesting that oocysts may be transmitted optimally near house in areas where most terrain is covered by asphalt and concrete and little soil is available for defecation or for human soil contact. Cats acquire infection by eating intermediate hosts; 16% sparrows, 3.5% of mice and 12.5% of rats have been found infected. Favoring transmission are young non-immune cat populations, shade and moisture, older intermediate hosts, a high percentage of which have become infected, and concentration of houses in city blocks. Transmission is diminished when houses are dispersed or arranged along a road in an open rural setting, permitting dispersal of cat fecal deposits.

To further elucidate the epidemiologic factors involved in the transmission of Toxoplasma gondii from cats to humans, veterinarians, animal hospital workers and a selected population of non-contact subjects were questioned about rural or urban residency, pets owned, contact with cats and whether their cats used a litter box in the house. Sera samples were tested at 1:128 dilution for toxoplasma antibodies using indirect fluorescent and hemagglutination techniques. None of the 60 non-contact individuals were seropositive. Of 60 contact subjects, 18.3% were identified as carrying antibodies. Other factors were not significant. Because only one veterinarian was seropositive, we propose that exposure to cats per se does not supply sufficient evidence upon which to expect a risk of toxoplasmosis infection. Direct or indirect association, personal hygiene, duration of exposure and the infectivity of the cats should be considered.