Toxoplasma gondii is a common parasite that causes an infection called toxoplasmosis in approximately one-third of humans, so research in this area is important to human health. T. gondii's lifecycle is curiously complex, and it has gained infamy for it's tendency to reproduce in the intestines of cats. The reason for this exceptional specificity has previously been unknown. Now, a study published in PLOS Biology in August has identified the exact molecular components in the feline intestine that create the conditions necessary for the parasite to reproduce. 

The research found that a chemical called linoleic acid is necessary for the sexual lifecycle of T. gondii. An enzyme in the intestines of most mammals called delta-6-desaturase usually helps convert linoleic acid to arachidonic acid. But cats are the only mammal known to lack this enzyme in their guts –  therefore, their guts maintain high enough levels of linoleic acid to allow for the parasite to reach sexual maturation. After the researchers figured this out, they found a way to stop the activity of delta-6-desaturase in mice, which means that in the future they may be able to stop using cats – a point of contention with animal rights activitists – in the lab. Eventually they may even be able to grow T. gondii in cell culture to learn more about this common (and, some say, mind-controlling) parasite.