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Toxoplasma gondii & Human Phenotype

Compendium of Known Effects and Ongoing Research

Secondary sex ratio

The relation of secondary sex ratio and miscarriage history with Toxoplasma gondii infection

August 31, 2018
Shojaee, S.,Teimouri, A., Keshavarz, H., Azami, S. J., Nouri, S.
Bmc Infectious Diseases 2018; 18: 307
Click for abstract
Background: Toxoplasma gondii is a protozoan parasite with worldwide distribution, infecting a broad-range of humans and warm-blooded animals. In the current study, role of this parasite on secondary sex ratio and risk of miscarriage was investigated. Methods: In this cross-sectional study, 850 cord blood samples were collected in Tehran, Iran, 2014-2015. Enzyme-linked immunosorbent assay (ELISA) was used to assess anti-Toxoplasma IgG in samples. Information such as sex of the neonates and age, number of previous pregnancies and history of miscarriage of the mothers were recorded in questionnaires. Logistic regression analysis was used to assess the possible relationship between the latent toxoplasmosis and the highlighted parameters. Results: Logistic regression analysis showed that the odds of having a male neonate in seropositive women is nearly 64% higher than that in seronegative women (OR = 1.64, CI95 = 1.16-2.33, P = 0.005). The odds ratio of having male neonate increased to 2.10 (CI95 = 1.24-3.57, P = 0.006) in high-titer seropositive women, compared to that in seronegative control group. The odds of having a miscarriage history was approximately two and a half times greater in seropositive women than in seronegative ones (OR = 2.45, CI95 = 1.56-3.87, P < 0.001). The odds ratio of having miscarriage increased to 2.76 (CI95 = 1.61-4.73, P < <.001) in low-titer seropositive women, compared to that in seronegative control group. Conclusion: Results of the current study have shown that T. gondii infection affects secondary sex ratio in human offspring and can be addressed as one of the major miscarriage causes in women.

Tagged: abortion, birth, cord blood serum, elisa, humans, latent toxoplasmosis, mice, miscarriage, pregnant women, prevalence, Secondary sex ratio, seroprevalence, Toxoplasma gondii

Reproduction

Do differences in Toxoplasma gondii prevalence influence global variation in secondary sex ratio? Preliminary ecological regression study

September 27, 2016 102 Comments
Dama, S.M., Martinec Nováková, L., Flegr, J.
Parasitology 2016; 143, 1193–1203 doi:10.1017/S0031182016000597
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Sex of the fetus is genetically determined such that an equal number of sons and daughters are born in large populations. However, the ratio of female to male births across human populations varies signi fi cantly. Many factors have been impli- cated in this. The theory that natural selection should favour female o ff spring under suboptimal environmental conditions implies that pathogens may a ff ect secondary sex ratio (ratio of male to female births). Using regression models containing 13 potential confounding factors, we have found that variation of the secondary sex ratio can be predicted by seropreva- lence of Toxoplasma across 94 populations distributed across African, American, Asian and European continents. Toxoplasma seroprevalence was the third strongest predictor of secondary sex ratio, β = − 0·097, P < 0·01, after son pref- erence, β = 0·261, P < 0·05, and fertility, β = − 0·145, P < 0·001. Our preliminary results suggest that Toxoplasma gondii in- fection could be one of the most important environmental factors in fl uencing the global variation of o ff spring sex ratio in humans. The e ff ect of latent toxoplasmosis on public health could be much more serious than it is usually supposed to be.

Tagged: ecological regression, manipulation hypothesis, Secondary sex ratio, toxoplasmosis, Trivers Willard e ff ect

Physical health

Women infected with parasite Toxoplasma have more sons

September 26, 2007 2 Comments
Kanková S., Sulc J. ,Nouzová K., Fajfrlík K., Frynta D., Flegr J.
Naturwissenschaften 94: 122-127, 2007
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The boy-to-girl ratio at birth (secondary sex ratio) is around 0.51 in most populations. The sex ratio varies between societies and may be influenced by many factors, such as stress and immunosuppression, age, primiparity, the sex of the preceding siblings and the socioeconomic status of the parents. As parasite infection affects many immunolog- ical and physiological parameters of the host, we analyzed the effect of latent toxoplasmosis on sex ratios in humans. Clinical records of 1,803 infants born from 1996 to 2004 contained information regarding the mother ’ s age, concen- tration of anti- Toxoplasma antibodies, previous deliveries and abortions and the sex of the newborn. The results of our retrospective cohort study suggest that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii ,can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72, C.I. 95 =(0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of anti- Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be re- sponsible for the enhanced survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis on the human population might be considerable

Tagged: Human sex ratio, Immunosuppression, manipulation hypothesis, Secondary sex ratio, Trivers – Willard hypothesis

Physical healthReproduction

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