Plague in a Colony of Gunnison’s Prairie Dogs ( Cynomys gunnisoni) Despite Three Years of Infusions of Burrows with 0.05% Deltamethrin to Kill Fleas.

  At Valles Caldera National Preserve in New Mexico, US, infusing Gunnison’s prairie dog ( Cynomys gunnisoni) burrows with an insecticide dust containing 0.05% deltamethrin killed fleas which transmit bubonic plague. The reduction in the number of fleas per prairie dog was significant and dramatic immediately after infusions, with a suggestion that the reduction persisted for as long as 12 mo. Despite the lower flea counts, however, a plague epizootic killed >95% of prairie dogs after 3 yr of infusions (once per year). More research is necessary for a better understanding of the efficacy of insecticide dusts at lowering flea counts and protecting prairie dogs from plague.