Abundance of rodents and fleas as related to plague in Lava Beds National Monument, California.

Abstract

Plague was found in dead pack rats (Neotoma cinerea) in Lava Beds National Monument. This finding prompted an investigation of the ecology of plague in the area and initiation of subsequent control measures. Eighteen species of mammals were collected and 25 species of fleas were taken. Peromyscus maniculatus and Neotoma cinerea were taken most frequently in the caves. Comparison of species composition and numbers of fleas on these hosts in the caves and on the surface revealed substantial differences in the fleas on these hosts depending upon where they were captured. Fleas from rodent nests taken in caves and on the surface reflected somewhat the same proportion of species on hosts from respective environments. Also most fleas were more numerous on their hosts in caves than on the surface. Some fleas, such as Phalacropsylla allos which are considered rare because few are normally encountered even in museum collections, were found in abundance in the caves. Of notable significance is the variety and abundance of hosts and their fleas in the area and the apparent conducive cave environment for production of fleas. Plague was isolated from specimens of Phalacropsylla allos, Malaraeus sp., Opisodasys keeni, and Orchopeas sexdentatus.