When humans have parasites, the organisms live in our bodies, co-opt our resources, and cause disease. However, it turns out that parasites themselves can have their own co-habitants.

Viral infections appear red in this photo of the parasite Leishmania; the parasites’ nuclei are blue. These infections may help Leishmania cause more harm when it infects animal and human hosts.

Trichomona Vaginalis trophozoite.