Sleeping sickness and its kin may have arrived via beehives

AS RECENT EVENTS have made abundantly clear, new viral diseases in people often start as spillovers from infections affecting other species. But viruses are not the only pathogens to do so. Leishmaniasis, sleeping sickness and Chagas’ disease, three potentially lethal illnesses caused by single-celled creatures called trypanosomes, are probably in this category, too. Not only are they spread by insects (sand flies, tsetse flies and kissing bugs respectively), they presumably originated in insects, too (though not necessarily their current vectors)—for most known trypanosomes are insect parasites. That raises the question of how they leapt the species barrier. A study just published in the , by Evan Palmer-Young of America’s Department of Agriculture, suggests the answer may be “bees”.Dr Palmer-Young’s starting-point was the observation, made a few years ago, that , a trypanosome once thought exclusive to honeybees, was turning up in mammals. Marmosets (a type of New World monkey), coatis (small carnivores related to raccoons), fruit bats, crab-eating foxes and ocelots are all now known to host it. He therefore wondered if there was something special about this particular trypanosome that allowed these leaps into mammals to happen—and whether, if there was, its adaptation to honeybees might be that something.