Click for abstract
Background: Latent toxoplasmosis, a lifelong infection with the protozoan Toxoplasma gondii , has cumulative effects on the behaviour of hosts, including humans. The most impressive effect of toxoplasmosis is the ‘‘fatal attraction phenomenon,’’ the conversion of innate fear of cat odour into attraction to cat odour in infected rodents. While most behavioural effects of toxoplasmosis were confirmed also in humans, neither the fatal attraction phenomenon nor any toxoplasmosis-associated changes in olfactory functions have been searched for in them. Principal Findings: Thirty-four Toxoplasma -infected and 134 noninfected students rated the odour of urine samples from cat, horse, tiger, brown hyena and dog for intensity and pleasantness. The raters were blind to their infection status and identity of the samples. No signs of changed sensitivity of olfaction were observed. However, we found a strong, gender dependent effect of toxoplasmosis on the pleasantness attributed to cat urine odour (p = 0.0025). Infected men rated this odour as more pleasant than did the noninfected men, while infected women rated the same odour as less pleasant than did noninfected women. Toxoplasmosis did not affect how subjects rated the pleasantness of any other animal species’ urine odour; however, a non-significant trend in the same directions was observed for hyena urine. Conclusions: The absence of the effects of toxoplasmosis on the odour pleasantness score attributed to large cats would suggest that the amino acid felinine could be responsible for the fatal attraction phenomenon. Our results also raise the possibility that the odour-specific threshold deficits observed in schizophrenia patients could be caused by increased prevalence of Toxoplasma -infected subjects in this population rather than by schizophrenia itself. The trend observed with the hyena urine sample suggests that this carnivore, and other representatives of the Feliformia suborder, should be studied for their possible role as definitive hosts in the life cycle of Toxoplasma .
Click for abstract
Toxoplasma gondii infection may cause a variety of symptoms involving virtually all organs. Little is known of the epidemiology of T. gondii infection in different patient groups in Mexico. We sought to determine the prevalence of T. gondii infection and associated epidemiological characteristics in 472 patients in Durango, Mexico. Participants were tested for T. gondii IgG and IgM antibodies. In addition, sociodemographic, clinical, and behavioral characteristics from each participant were obtained. Seroprevalences of T. gondii IgG antibodies were found in 7 (8.2%) of 85 patients with hearing impairment, 5 (10.0%) of 50 patients with hemodialysis, 28 (12.0%) of 234 patients with visual impairment, and 7 (6.8%) of 103 at risk of immunosuppression. In total, 47(10%) of 472 subjects had IgG T. gondii antibodies; 6 (1.3%) of them also had IgM anti T. gondii antibodies. Patients born in Durango State had a significantly lower prevalence of T. gondii infection than patients born in other Mexican states (9.0% vs. 21.4%, respectively: P < 0.05). Multivariate analysis showed that T. gondii infection was significantly associated with consumption of undercooked meat (adjusted odds ratio [OR] = 2.95; 95% confidence interval [CI]: 1.18-7.35) or raw cow's milk (adjusted OR = 2.52; 95% CI: 1.28-4.96), presence of cats at home (adjusted OR = 2.01; 95% CI: 1.06-3.78), raising animals (adjusted OR = 2.44; 95% CI: 1.06-5.63), or eating away from home (adjusted OR = 2.70; 95% CI: 1.03-7.11). In the group of patients with visual impairment, those with reflex impairment had a significantly higher frequency of T. gondii infection than those with normal reflexes (19% vs. 9.4%, respectively: P = 0.04). Results of the present study are the first step in the design of prevention programs to avoid the sequelae of toxoplasmosis.