Toxoplasma gondii Serointensity and Seropositivity: Heritability and Household-Related Associations in the Old Order Amish

Abstract

Toxoplasma gondii (T. gondii) is an intracellular parasite infecting one third of the world’s population. Latent T. gondii infection has been associated with mental illness, including schizophrenia and suicidal behavior. T. gondii IgG antibody titers were measured via ELISA. The heritability of T. gondii IgG was estimated using a mixed model that included fixed effects for age and sex and random kinship effect. Of 2017 Old Order Amish participants, 1098 had positive titers (54.4%). The heritability for T. gondii serointensity was estimated to be 0.22 (p = 1.7 × 10−8 and for seropositivity, it was estimated to be 0.28 (p = 1.9 × 10−5). Shared household environmental effects (i.e., household effects) were also determined. Household effects, modeled as a random variable, were assessed as the phenotypic covariance between any two individuals who had the same current address (i.e., contemporaneous household), and nuclear household (i.e., the phenotypic covariance between parents and children only, not other siblings or spouses). Household effects did not account for a significant proportion of variance in either T. gondii serointensity or T. gondii seropositivity. Our results suggest a significant familial aggregation of T. gondii serointensity and seropositivity with significant heritability. The shared household does not contribute significantly to family aggregation with T. gondii, suggesting that there are possible unmeasured non-household shared and non-shared environmental factors that may play a significant role. Furthermore, the small but significant heritability effects justify the exploration of genetic vulnerability to T. gondii exposure, infection, virulence, and neurotropism.

Rosuvastatin revert memory impairment and anxiogenic-like effect in mice infected with the chronic ME-49 strain of Toxoplasma gondii

“…gondii) [ 1 ]. It is estimated that one-third of the world’s population is infected by this parasite [ 2 – 4 ]. Felids are the definitive hosts that eliminate millions of oocysts (sporozoites) in their feces.…”

Toxoplasma gondii, Suicidal Behavior, and Intermediate Phenotypes for Suicidal Behavior

“…Washing the kitchen knives infrequently after preparation of raw meat prior to handling another food item, cleaning the cat litter box, incompletely washed fruits and vegetables, and consumption of raw or undercooked meat have been specifically reported to be factors elevating the risk of T. gondii infection in pregnant women (40,224). Similarly, endophenotypes for suicidal behavior, such as impulsivity, represent risk factors for T. gondii seropositivity as well as future suicidal behavior, and, given the significant heritability of T. gondii (225), it may be possible that this increased impulsivity is brought about via genetic factors for exploratory or self-neglectful behavior. It is important to note that secondarily adjusting for history of mental illness and suicidal behavior in the parents (that would potentially reduce the effect of heritable elements mentioned above) had only a minor effect on the findings, making it unlikely that the results are mainly driven by heritable hidden variables related to preexisting subclinical conditions, which would cause rather than be the consequence of T. gondii infection.…”

Risk factors forToxoplasma gondiiseropositivity in the Old Order Amish

“…Second, response rates were high for both the AWS questionnaire and the ATRFQ. Third, to counteract the possibility that the participants' close family and household aggregation could have produced spurious associations, the study adjusted post-hoc for heritability and household [ 32 ], without any loss of statistical significance for any of the positive findings reported in our study.…”

“…Concentrations of ⩾12 IU/ml were defined as seropositive, and of 8–12 IU/m as equivocal. The equivocal samples were tested a second time, and if the second testing yielded samples that tested positive for concentrations of ⩾12 IU/ml on the second test, they were also considered positive as previously reported [ 32 ].…”