Plague in the U.s.: Present and Future

An increasing trend in the frequency of human bubonic plague cases in the United States, the principal sources of human infection, and emerging control techniques are described. Development of an integrated control program involving public health education, citizen participation in plague surveillance, and insecticidal control of flea vectors in response to evidence of plague and potential human exposure substantially reduced human plague cases in a Bernalillo County, New Mexico, hyperendemic plague area. Permethrin 0.5% dust (Pyraperm 455) applied at a rate of 7 g per burrow was found to provide effective control of flea vectors for at least 6 weeks. Proc. 14th Vertebr. Pest Conf. (L.R. Davis and R.E. Marsh, Eds.) Published at Univ. of Calif., Davis. 1990. INTRODUCTION Bubonic plague (Yersinia pestis infection) is widespread among an array of rodent hosts and flea vectors in the western United States from the Pacific Coast eastward to about the 97th Meridian (Fig. 1). The disease also has been recorded (from animals) in Alberta (Brown 1944) and British Columbia, Canada (unpubl. data, British Columbia Ministry of Health and CDC records), and from the northern State of Coahuila, Mexico (Verela and Vasques 1954). Figure 1. Geographic distribution of human and animal plague in the United States by county of origin 1970-1988. From 1925 (following the last urban plague epidemic in the United States) until 1965, human cases-all from wild rodent sources-averaged fewer than two per year. With an outbreak of seven cases on the Navajo Reservation in northwestern New Mexico in 1965, the number of cases per year began an increase that continued into the 1980s with peaks about every 5 to 8 years, reaching highs of 40 cases in 1983 and 31 in 1984 (Fig. 2). Following the 1983-84 outbreaks in New Mexico and northern Arizona, the number of cases gradually diminished, reaching a low of four cases in 1989. Figure 2. Human plague and plague pneumonia cases in United