Toxoplasma seroprevalence in a rural population in France: detection of a household effect

Emmanuelle Gilot Fromont,Muriel Rabilloud,Benjamin Riche

doi:10.1186/1471-2334-9-76

Abstract

BackgroundToxoplasma gondii, the agent of toxoplasmosis, has a complex life cycle. In humans, the parasite may be acquired either through ingestion of contaminated meat or through oocysts present in the environment. The importance of each source of contamination varies locally according to the environment characteristics and to differences concerning human eating habits and the presence of cats; thus, the risk factors may be determined through fine-scale studies. Here, we searched for factors associated with seropositivity in the population of two adjacent villages in Lorraine region, France.MethodsAll voluntary inhabitants filled out a questionnaire and gave a blood sample. The seroprevalence was estimated globally and according to the inhabitants' ages using a cubic spline regression. A mixed logistic regression model was used to quantify the effect of individual and household factors on the probability of seropositivity.ResultsBased on serological results from 273 persons, we estimated seroprevalence to be 47% (95% confidence interval: 41 to 53%). That seroprevalence increased with age: the slope was the steepest up to the age of 40 years (OR = 2.48 per 10-year increment, 95% credibility interval: [1.29 to 5.09]), but that increase was not significant afterwards. The probability of seropositivity tended to be higher in men than in women (OR = 2.01, 95% credibility interval: [0.92 to 4.72]) and in subjects eating raw vegetables at least once a week than in the others (OR = 8.4, 95% credibility interval: [0.93 to 72.1]). These effects were close to statistical significance. The multivariable analysis highlighted a significant seroprevalence heterogeneity among households. That seroprevalence varied between 6 and 91% (5th and 95th percentile of the household seropositivity distribution).ConclusionThe major finding is the household effect, with a strong heterogeneity of seroprevalence among households. This effect may be explained by common exposures of household members to local risk factors. Future work will quantify the link between the presence of oocysts in the soil and the seroprevalence of exposed households using a spatial analysis.

Highlights

Toxoplasma gondii, the agent of toxoplasmosis, has a complex life cycle
Toxoplasma gondii (T. gondii), the agent of toxoplasmosis, is one of the most widespread parasite species worldwide: in 2000, Tenter et al estimated that one third of the human population might be parasitized [1]
The life cycle of T. gondii is complex: post-natal human infection may result from ingestion of tissue cysts contained in raw or undercooked meat from intermediate hosts or from ingestion or inhalation of oocysts shed by definitive hosts and disseminated in soil and water

Summary

Introduction

Toxoplasma gondii, the agent of toxoplasmosis, has a complex life cycle. The parasite may be acquired either through ingestion of contaminated meat or through oocysts present in the environment. Most children with congenital toxoplasmosis have no symptoms at birth but are at risk of developing retinal diseases or neurological abnormalities later in life [3]. The life cycle of T. gondii is complex: post-natal human infection may result from ingestion of tissue cysts contained in raw or undercooked meat from intermediate hosts or from ingestion or inhalation of oocysts shed by definitive hosts (felids) and disseminated in soil and water. Because virtually all mammals and birds may serve as intermediate hosts and because of the high resistance of T. gondii sporulated oocysts in the environment [5], possible sources of infection are multiple

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