Plague in Pine Martens

Thirteen pine martens (Martes americana) were sampled periodically from July 1979 to September 1980 for plague (Yersinia pestis) antibodies and their fleas collected and identified. Four individuals were positive for plague antibodies on 8 of 24 sampling occasions. Titer peaks in these individuals occurred simultaneously in early winter but fell to undetectable levels by late spring. A chipmunk flea (Monopsyllus ciliatus) was the most common ectoparasite constituting 55% of all individuals collected. Thirty-one percent of all fleas belonged to Chaetopsylla floridensis, a species previously unreported in California. The remains of ground-dwelling sciurids (chipmunks, Eutamias spp., and ground squirrels, Spermophilus spp.) were very common in marten scats during the period preceding elevated titers. For this reason, and the fact that 92% of all fleas collected from martens during this same period were found more commonly on chipmunks and ground squirrels, these rodents were implicated as the source of the martens' exposure to plague. Plague is an infectious zoonotic disease found primarily in wild rodents in the western United States. Fleas serve as the vector of the disease agent. Carnivores are infected secondarily while feeding upon moribund and dead infected animals (Rust et al. 1971) or from contact with fleas residing in rodent burrows or nests (Eads et al. 1979). Because most carnivores appear to develop only transient clinical signs to plague (Marchette et al. 1962, see Rust et al. 1971, for feline exceptions) and have larger home ranges than rodents, they play an important role in transferring infected fleas to uninfected rodent populations (Eads et al. 1979). Rodent predators also serve as sentinel species for monitoring plague (Poland and Barnes 1979, Messick et al. 1983). Despite their importance, the contribution of rodent predators to the epidemiology of plague is poorly known (Messick et al. 1983). In California, the pine marten feeds primarily on the rodents that are confirmed plague host reservoirs. Plague has been detected in martens elsewhere (Barnes 1982), but little information was available regarding the ecology of the marten population at the site. Presented here are the first records of plague in California pine martens, the flea fauna discovered, and information on marten diets and home ranges. MATERIALS AND METHODS Field work was concentrated in the 40 km Sagehen Creek drainage, located on the eastern side of the Sierra Nevada in Nevada County, California. This area is classified as having "intermediate potential" for epizootic plague (Murray 1964), and evidence of decimation of ground squirrel populations has been documented at nearby Tahoe City (Murray 1971). Thirteen pine martens were captured at least once each from July 1979 to September 1980 and were immobilized with a combined intramuscular injection of ketamine-hydrochloride (Vetalar, 100 mg/ml, Parke-Davis, Detroit, MI) and acetylpromazine maleate (Acepromazine, 10 mg/ml Ayerst Laboratories, Inc., New York, N.Y.). During initial captures, and at several recap tures for those animals trapped often, a toenail was cut to the quick and blood was collected on a paper strip (Wolff and Hudson 1974). These samples were sent to the Plague Branch, Centers for Disease Control, Fort Collins, Colorado, for serological testing. Development of antibody gives evidence of prior infection with plague. Results are reported as a dilution ratio of 1:32 to 1:16,384 with titers • FRQVLGHUHG SRVLWLYH )OHDV ZHUH Department of Forestry and Resource Conservation, University of California, Berkeley, California 94720. Present address: Department of Zoology, North Carolina State University, Raleigh, North Carolina 27650.