How a wildlife biologist became a plague-chaser in the American Southwest

FLAGSTAFF, Ariz. — When there’s a suspected outbreak of plague in this college town among the pines, the authorities know to call David Wagner. He’s a tall man, with the square-jawed looks of the sheriff in a spaghetti Western, and one of his jobs is to determine whether these flare-ups are indeed caused by the same bacteria as the Black Death. He pulls on long pants and long sleeves — preferably white, so it’s easier to spot the dark speck of a flea — and drives out to the scene.

Usually, the corpses are already underground, not because they’ve been buried, but because they are prairie dogs. In the throes of plague, they crawl down into their burrows to die at home. Wagner isn’t there for their bodies. He’s more interested in the fleas that transmitted plague in the first place. Sometimes, like their dead hosts, they too are beneath the earth, and he needs to coax them out. At other times — when he’s investigating what he’d call a “hot site” —  the blood is gone from the corpses, the fleas have begun to starve, and they’ve jumped their way to the surface to wait for another mammal to pass by. “You can just see them popping around looking for something to feed on,” Wagner said. “It’s pretty creepy.”

The creepiness stems in part from the fact that a bite, , could give Wagner lumps the size of chicken eggs; make him bleed from his mouth, nose, and rectum; turn his extremities a gangrenous black; and kill him within days. The prospect doesn’t worry him much. He carries prophylactic antibiotics, which he’ll take if he starts to feel his muscles aching or his throat getting sore. He wears latex gloves. And really, more than a liability, his access to fleas full of