Citation:

Egorov, A., R. Converse, S. Griffin, J. Styles, E. Klein, E. Sams, E. Hudgens, AND Tim Wade. Environmental risk factors for Toxoplasma Gondii infections and the impact of latent infections on allostatic load in residents of Central North Carolina. BMC Infectious Diseases. BioMed Central Ltd, London, Uk, 18(1):142, (2018). https://doi.org/10.1186/s12879-018-3343-y

Impact/Purpose:

The objectives of this study were to evaluate environmental risk factors of Toxoplasma gondii infections in the population of central North Carolina, and to assess subclinical effects of chronic infections on health using biomarker-based measure of physiological disregulation known as allostatic load. The study demonstrated that individuals living in a greener residential environment were more likely to be infected after adjusting for covariates. The results suggest that contacts with soil contaminated with cat feces (e.g. through gardening) was a likely infection pathway. In infected individuals, the parasite was linked with elevated allostatic load. In contrast, the effect of greener environment was positive - a reduced allostatic load. This study shows that while contacts with natural living environments should be promoted, it is important to avoid potential detrimental effects such as transmission of zoonotic disease.

Description:

Background: Toxoplasma gondii infection can be acquired through ingestion of infectious tissue cysts in undercooked meat or environmental oocysts excreted by cats. This cross-sectional study assessed environmental risk factors for T.gondii infections and an association between latent infections and a measure of physiologic dysregulation known as allostatic load. Methods: Serum samples from 206 adults in the Durham-Chapel Hill, North Carolina area were tested for immunoglobulin (IgG) responses to T. gondii using commercial ELISA kits. Allostatic load was estimated as a sum of 15 serum biomarkers of metabolic, neuroendocrine and immune functions dichotomized at distribution-based cutoffs. Vegetated land cover within 500 m of residences was estimated using 1 m resolution data from US EPA’s EnviroAtlas. Results: Handling soil with bare hands at least weekly and currently owning a cat were associated with 5.3 (95% confidence limits 1.4; 20.7) and 10.0 (2.0; 50.6) adjusted odds ratios (aOR) of T. gondii seropositivity, respectively. There was also a significant positive interaction effect of handling soil and owning cats on seropositivity. An interquartile range increase in weighted mean vegetated land cover within 500 m of residence was associated with 3.7 (1.5; 9.1) aOR of T. gondii seropositivity. Greater age and consumption of undercooked pork were other significant predictors of seropositivity. In turn, T. gondii seropositivity was associated with 61% (13%; 130%) greater adjusted mean allostatic load compared to seronegative individuals. In contrast, greater vegetated land cover around residence was associated with significantly reduced allostatic load in both seronegative (p < 0.0001) and seropositive (p = 0.004) individuals. Conclusions: Residents of greener areas may be at a higher risk of acquiring T. gondii infections through inadvertent ingestion of soil contaminated with cat feces. T. gondii infections may partially offset health benefits of exposure to the natural living environment. Keywords: Toxoplasma gondii, Seroprevalence, Vegetated land cover, Biomarkers, Allostatic load

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