Lower performance of Toxoplasma-infected, Rh-negative subjects in the weight holding and hand-grip tests

Abstract

BackgroundToxoplasma, a protozoan parasite of cats, infects many species of intermediate and paratenic hosts, including about one-third of humans worldwide. After a short phase of acute infection, the tissue cysts containing slowly dividing bradyzoites are formed in various organs and toxoplasmosis proceeds spontaneously in its latent form. In immunocompetent subjects, latent toxoplasmosis was considered asymptomatic. However, dozens of studies performed on animals and humans in the past twenty years have shown that it is accompanied by a broad spectrum of specific behavioural, physiological and even morphological changes. In human hosts, the changes often go in the opposite direction in men and women, and are mostly weaker or non-existent in Rh-positive subjects.MethodsHere, we searched for the indices of lower endurance of the infected subjects by examining the performance of nearly five hundred university students tested for toxoplasmosis and Rh phenotype in two tests, a weight holding test and a grip test.ResultsThe results confirmed the existence of a negative association of latent toxoplasmosis with the performance of students, especially Rh-negative men, in these tests. Surprisingly, but in an accordance with some already published data, Toxoplasma-infected, Rh-positive subjects expressed a higher, rather than lower, performance in our endurance tests.DiscussionTherefore, the results only partly support the hypothesis for the lower endurance of Toxoplasma infected subjects as the performance of Rh-positive subjects (representing majority of population) correlated positively with the Toxoplasma infection.

Faster life history strategy manifests itself by lower age at menarche, higher sexual desire, and earlier reproduction in people with worse health

“…In the Czech population, Rh-negative genotype might serve as such predictor. Five previous studies had shown associations between Rh-negativity and psychomotor or cognitive functions [43][44][45][46][47] and other four studies had demonstrated the existence of a relation between Rh-negativity and health [48][49][50][51] . Another large-scale study concluded that Rh-negative mothers give birth to significantly more girls than boys: secondary sex ratio 1.37 in primiparous mothers and 1.23 in all mothers 52 .…”

Maternal RhD heterozygous genotype is associated with male biased secondary sex ratio

“…Recent results support the hypothesis that the Rhesus factor polymorphism is maintained in human populations due to a higher resistance or tolerance of heterozygotes to specific diseases (see Introduction). The hypothesis was repeatedly supported by empirical data showing that RhD positivity, and especially RhD heterozygosity, protects people against certain negative effects of toxoplasmosis (Flegr et al, 2008(Flegr et al, , 2018Kankova et al, 2010;Novotna et al, 2008). In line with the Trivers-Willard effect (Trivers and Willard, 1973), our working hypothesis was to expect RhD heterozygous mothers, i.e., mothers with supposedly higher health status, to exhibit a higher secondary sex ratio.…”

“…For example, the positive effect of age on performance and intelligence was stronger in RhD positive subjects, whereas the effect of smoking on the number of viral and bacterial diseases was about three times higher in RhD negative subjects. In a different study, Toxoplasma positive RhD negative subjects expressed lower performance in weight-holding and hand-grip tests in comparison with both RhD negative and positive Toxoplasma negative subjects (Flegr et al, 2018). It is clear that faster reaction times or greater stamina conferred a selective advantage in the past, and that they still do in the present.…”

Cognitive Effects ofToxoplasmaand CMV Infections: A Cross-Sectional Study of 557 Young Adults Considering Modulation by Sex and Rh Factor

“…In conjunction with the I-S-T 2000 R session, participants also engaged in two physical performance tests, provided saliva samples for hormone concentration analysis, and underwent ECG recording. These additional data were utilized in an unrelated study [34].…”