Toxoplasmosis--a global threat. Correlation of latent toxoplasmosis with specific disease burden in a set of 88 countries

Abstract

Background: Toxoplasmosis is becoming a global health hazard as it infects 30-50% of the world human population. Clinically, the life-long presence of the parasite in tissues of a majority of infected individuals is usually considered asymptomatic. However, a number of studies show that this 'asymptomatic infection' may also lead to development of other human pathologies.

Aims of the study: The purpose of the study was to collect available geoepidemiological data on seroprevalence of toxoplasmosis and search for its relationship with mortality and disability rates in different countries.

Methods and findings: Prevalence data published between 1995-2008 for women in child-bearing age were collected for 88 countries (29 European). The association between prevalence of toxoplasmosis and specific disease burden estimated with age-standardized Disability Adjusted Life Year (DALY) or with mortality, was calculated using General Linear Method with Gross Domestic Product per capita (GDP), geolatitude and humidity as covariates, and also using nonparametric partial Kendall correlation test with GDP as a covariate. The prevalence of toxoplasmosis correlated with specific disease burden in particular countries explaining 23% of variability in disease burden in Europe. The analyses revealed that for example, DALY of 23 of 128 analyzed diseases and disease categories on the WHO list showed correlations (18 positive, 5 negative) with prevalence of toxoplasmosis and another 12 diseases showed positive trends (p<0.1). For several obtained significant correlations between the seroprevalence of toxoplasmosis and specific diseases/clinical entities, possible pathophysiological, biochemical and molecular explanations are presented.

Conclusions: The seroprevalence of toxoplasmosis correlated with various disease burden. Statistical associations does not necessarily mean causality. The precautionary principle suggests however that possible role of toxoplasmosis as a triggering factor responsible for development of several clinical entities deserves much more attention and financial support both in everyday medical practice and future clinical research.

Figure 1. Correlation between prevalence of toxoplasmosis humidity, geolatitude and GDP per capita in all 88 countries.

The GDP (1000 $), latitude (°) and relative humidity (%) data are shown only for the region or locality for which latent toxoplasmosis prevalence information (%) is reported.

Figure 2. Correlation of prevalence of toxoplasmosis with various disease-attributed DALY for 88 WHO-member countries.

The x-axes show prevalence of toxoplasmosis (%) in women of childbearing age and y-axes the number years of ‘healthy’ life lost by virtue of being in a state of poor health or disability due to particular disease per 100,000 inhabitants in 2004.

Figure 3. Correlation of mortality and Disability Adjusted Life Year (DALY) with prevalence of toxoplasmosis for all 88 WHO member countries (29 European and 59 non-European countries).

The correlations were estimated with partial Kendall correlation test with GDP per capita as covariate. Positive Kendall Taus (red) correspond to positive and negative Taus (blue) to negative correlations. Significant results (p<0.05) are labeled with yellow and trends (p<0.10) with green colors.

Figure 4. Correlation of mortality and Disability Adjusted Life Year (DALY) with prevalence of toxoplasmosis for all 88 WHO member countries (29 European and 59 non-European countries).

The correlations were estimated with General Linear Model with GDP per capita, latitude humidity, as covariates. Positive B (red) correspond to positive, and negative B (blue) to negative correlations. Significant results (p<0.05) are labeled with yellow and trends (p<0.10) with green colors.