A few studies have come out in the last few years indicating that the parasite Toxoplasma gondii found in and transmitted by cats may cause a host of behavioral changes in humans. A new report raises the possibility that T. gondii may be affecting the sex ratios of human populations.
[P]arasitologist Jaroslav Flegr of Charles University in Prague thinks T. gondii could also be skewing our sex ratios. When he looked at the clinical records of more than 1,800 babies born from 1996 to 2004, he noted a distinct trend: The normal sex ratio is 104 boys born for every 100 girls, but in women with high levels of antibodies against the parasite, the ratio was 260 boys for every 100 girls. Exactly how the parasite might be tipping the odds in favor of males isn’t understood, but Flegr points out that it is known to suppress the immune system of its hosts, and because the maternal immune system sometimes attacks male fetuses in very early pregnancy, the parasite’s ability to inhibit the immune response might protect future boys as well as itself.
On the other hand, this may point to a cheap way for couples to bolster their chances of having a male progeny — raise cats.