From Science Daily :
About 100 million years ago, the bacterium Wolbachia came up with a trick that has made it one of the most successful parasites in the animal kingdom: It evolved the ability to manipulate the sex lives of its hosts.This particular bug only parasitises insects, mites, spiders and nematodes. That doesn't mean to say that it can't affect us though:
Exactly how the bacteria alters its hosts' reproductive systems to its advantage remains a matter for future study. But scientists have identified the bacteria's basic strategies. Depending on its host, the bacteria either:
* Kills infected males;
* Feminizes infected males so they develop as females or infertile pseudo-females;
* Induces parthenogenesis: the reproduction of infected females without males;
* Makes the sperm of infected males incompatible with the eggs of uninfected females or females infected with a different Wolbachia strain.
Although the ubiquitous bacteria cannot trick the human immune system, it does have an adverse impact on human health. For example, it infects many species of nematodes, including the filarial nematodes that infect more than 200 million people worldwide, causing debilitating inflammatory diseases, such as river blindness and elephantiasis.I'm not concerned about this particular bug. But what one bug can do to invertebrates, it may not be completely impossible for another bug to do to quite different species.
In the last 10 years scientists have realized that it is actually the bacterium, not the nematode, that is responsible for most of the symptoms produced by these illnesses. Although Wolbachia can only survive about three days in the human body, the parasitic nematodes act as a continuing source of the bacteria that cause most of the damage. This surprising insight into the disease pathology has improved the treatment of these illnesses: They are now treated with an antibiotic that kills the bacteria and is less toxic than anti-nematode medications.
It would be an astounding coincidence though if such a hypothetical beastie - one whose existence may well be impossible - just happened to infect someone who was transsexual. So one wasn't involved. Any such change would be the result of just a particularly rare intersex condition. Something likely genetic. Probably. I think.
From Incidence of a new sex-ratio-distorting endosymbiotic bacterium among arthropods. Weeks AR, Velten R, Stouthamer R. Proc Biol Sci. 2003 Sep 7;270(1526):1857-65.
Many intracellular micro-organisms are now known to cause reproductive abnormalities and other phenomena in their hosts. The endosymbiont Wolbachia is the best known of these reproductive manipulators owing to its extremely high incidence among arthropods and the diverse host effects it has been implicated as causing. However, recent evidence suggests that another intracellular bacterium, a Cytophaga-like organism (CLO), may also induce several reproductive effects in its hosts. Here, we present the first survey of arthropod hosts for infection by the CLO...No, it's not the only one. *SIGH*