Potential solutions to problems posed by the offspring sex ratios of people with parasitic and viral infections

Abstract

i have hypothesized that mammalian offspring sex ratios (proportions male at birth) are partially controlled by the hormone levels of both parents around the time of conception. recently data have been published (privately) which impugn suggestions of mine (based on that hypothesis) relating to the offspring sex ratios of people who are carriers of hepatitis B virus; and (publicly) to hormone profiles of women who are infected with the protozoan parasite Toxoplasma gondii. Here these data are reviewed in the light of data on offspring sex ratios of people infected with hepatitis c, and cytomegalovirus and T. gondii; and of mice with T. gondii and the trichostrongyline nematode Heligmosomoides polygyrus. three proposals are made viz: 1. Women infected with T. gondii may have high oestrogen levels. this would potentially explain reports of their high offspring sex ratios, long gestations and (perhaps) behavioural traits. 2. some of these infective organisms may 'prefer' a particular endocrine environment in their host (in the sense that it facilitates replication or transmission or both). 3. some of these organisms apparently cause changes in that endocrine environment as a consequence of their presence. if both the latter two proposals were correct, it could explain recent puzzling data on the offspring sex ratios of hepatitis B carriers. and if this solution turns out to be correct, it would suggest new endocrine means of combating hepatitis B infection. Keywords: cytomegalovirus cMV, Heligmosomoides polygyrus, hepatitis B virus HBV, hepatitis c virus HcV, sex ratio at birth, Toxoplasma gondii 115 to be low in cMV-seropositive women: hence ex hypothesi, their low offspring sex ratio. i know no evidence on whether the virus, once present, alters oestrogen levels in women, nor on whether offspring sex ratio alters with duration of infection. Hepatitis C virus (HCV)i know only one published set of data on the sexes of offspring born to women infected with hepatitis c. the European Paediatric Hepatitis c Virus Network (2005) reported 802 boys and 668 girls born to infected women. this sex ratio (proportion male) of 0.546 yields a chisquared value of 6.2, with 1 df, p < 0.02, tested against an expected contemporary European live birth sex ratio of 0.513 (Parazzini et al. 1998). the difference between these two sex ratios (0.033) is small but typical of much established human sex ratio variation. the evidence is weak, but one might speculate that this unusual offspring sex ratio has an endocrine basis (as would be suggested by my hypothesis). analogously, Blumberg (2006) noted sex differences in morbidity and mortality from hepatitis B which he suggested might have endocrine bases. other evidence is that hepatitis c (like hepatitis B) is a powerful risk factor for hepatocellular cancer (Hcc) (Kumada et al. 2009). Moreover, men who are destined to develop HCC have significantly higher T levels than controls (Yuan et al. 1995, Yu et al. 2001). so it is suggested here that (at least at the time infection is in...

Host Manipulation by Parasites: Cases, Patterns, and Remaining Doubts

“…As a possible explanation, he suggested publication bias, that is, an initial euphoria concerning the intensity of manipulation effects became replaced by more realistic estimates over time (Poulin, 2000). More recently, other authors have stressed that alternative explanations need to be considered-and excluded-to provide conclusive empirical support for an assumed case of manipulation (Klein, 2005;Thomas et al, 2005;James, 2010;Cator et al, 2012Cator et al, , 2015Lafferty and Kuris, 2012;Worth et al, 2013). Alternatively, such alterations can: (1) represent mere side-effects of the pathology that is associated with infection; (2) form part of the successful immune response of the host to parasitization; or (3) represent traits that were inherited from ancestors but represent maladaptations in the present host-parasite combination (Klein, 2005;Thomas et al, 2005).…”

“…Similarly, several different mechanisms could cause the frequently reported association of elevated levels of testosterone in males with latent toxoplasmosis (Flegr et al, 2008;Shirbazou et al, 2011). Rather than indicating an alteration that is elicited by T. gondii, high levels of testosterone could be a causal reason for infection and represent an intrinsic trait of certain individuals that: (i) causes more risktaking behavior and thereby leads to higher infection risk, or (ii) simply provides the parasite with a "preferred endocrine environment in the host" (James, 2010). Even when T. gondii can unambiguously be shown to actively enhance the levels of testosterone in its host it remains an open question whether this capacity has primarily evolved for the manipulation of host immunity, in which case it would mainly serve infection, rather than transmission.…”

Differences in onset of disease and severity of psychopathology between toxoplasmosis‐related and toxoplasmosis‐unrelated schizophrenia

“…The last line shows similar partial correlation between probability of the brief psychotic disorder diagnosis and the concentration of anti-Toxoplasma antibodies. Indirect evidence also exists for increased concentration of oestrogens in the Toxoplasmainfected women (58,59). Statistically, women get infected with T. gondii later than men in the Czech Republic.…”

“…further incidence increase is seen in women during the peak fertility between the age of 25 and 35 (41). Kanˇkova´et al (58) and James (59) reported that infected women are more likely to produce sons than uninfected mothers and that the offspring sex ratio (proportion of males) increases with the concentration of anti-Toxoplasma antibodies in T. gondii-positive mothers. Difference in mean age of Toxoplasma infection in men and women may be one of the factors that can help to explain the gender-associated difference in onset of schizophrenia.…”

Study of Latent Toxoplasma gondii Role in Level of Testosterone, DHEA, Cortisol and Prolactin Hormones of Young Persons

“…There were no significant differences in prolactin and DHEA level in these individuals. An explanation for the observed increase in the level of testosterone in latent toxoplasmosis is that individuals with high testosterone levels are more susceptible to any infection including toxoplasmosis (James, 2010). Hirsutism, acne, alopecia are clinical expressions of testosterone in women of reproductive age (Karrer-Voegeli et al, 2009).…”