From 2speccers2tools wiki

After a group of Devilbruh found themselves in the reproductive organs of other species, they began becoming less predatory, instead living more on their own spite and dead cells, and have become like an std. They are most commonly transmitted via sex, though can also get dispersed by mere ejaculation, which means they can infect things that eat it, penetrating through their entire body until they find its reproductive organs. The odd thing about them is that other than maybe some internal bleeding depending on how one gets infected, there aren't many symptoms, that is, until a few days after being infected and the Transbruhs start releasing a very odd form of spite that begins making the host's body change gender. This transformation occurs differently for different species, though always ends the same way, that being the individual now being the opposite sex in nearly every way. This spite carries a chemical that not only nullifies the said spite's effects, but also causes things in the host's brain to trigger, causing this transformation to occur.