Flea, rodent, and plague ecology at Chuchupate Campground, Ventura County, California

Abstract

Chuchupate Campground in Ventura County, California, was closed to the public for 18 years (1982 to 2000) because of uncontrolled vector fleas and persistent plague antibody titers in rodents. The primary purpose of this study was to clarify the plague ecology of Chuchupate Campground by identifying involved rodents and their vector fleas and by determining many of their ecological parameters: abundance, flea and host preferences and diversities, and flea seasonality. Rodents and fleas were identified to species, some fleas were tested for Yersinia pestis, and rodent bloods were analyzed for the presence of antibodies to Y. pestis. During this study, 20 flea species were identified from 10 rodent and one lagomorph species collected. Five species of rodents were seropositive for plague during 13 of the 17 years in which plague testing was conducted. A likely reservoir species was not determined, but evidence of plague resistance was discovered in Merriam's chipmunks (Tamias merriami) and dusky-footed woodrats (Neotoma fuscipes). The "susceptible" rodent and flea complexes at Chuchupate are the California ground squirrel (Spermophilus beecheyi) and its fleas, Oropsylla montana and Hoplopsyllus anomalus, Merriam's chipmunk and its flea, Eumolpianusfornacis, and the dusky-footed woodrat and its flea, Orchopeas sexdentatus. Host preference, diversity, and seasonality of fleas are discussed, as well as the pivotal role of woodrat houses and nests as foci for hosts, fleas, and plague.