VECTOR-BORNE AND ZOONOTIC DISEASES Volume 5, Number 2, 2005 © Mary Ann Liebert, Inc. Research Paper Epidemiological Study of Rickettsia typhi Infection in Two Provinces of the North of Spain: Analysis of Sera from the General Population and Sheep L. LLEDO, 1 M.I. GEGUNDEZ, 1 J. MEDINA, 1 J.V. GONZALEZ, 2 R. ALAMO, 2 and J.V. SAZ 1 ABSTRACT Data relating to Rickettsia typhi infection in Spain are scarce. A serological survey of 383 serum samples (184 males, 199 females) from the general population and 120 sera from sheep were studied by immunofluorescence assay (IFA). The human serum samples were collected from the general population of Palencia and Burgos provinces, and sheep serum samples were collected from Palencia province. Of the 383 human serum samples studied, 29 were positive for antibodies against R. typhi (7.5%) No statistical differences were found according to age, sex, origin (rural vs. urban) or geographic distribution, but a significant difference was observed related to occupation. In addition, 69 serums were found positives for R. typhi in sheep samples (57.5%). Our results indi- cated the circulation of R. typhi infectious for humans and sheep in Palencia and Burgos provinces. This study indicates that sheep may be infected with R. typhi, and that animals can, therefore be used as indicators of the presence of this organism. Key Words: Rickettsia typhi—Murine typhus—Epidemiology—Sentinel animals— Sheep. Vector-Borne Zoonotic Dis. 5, 157–161. 157 INTRODUCTION R ICKETTSIA TYPHI usually a mild febrile dis- ease (Azad 1990), although it can also cause severe illness (Dumler et al. 1991). Some diseases that have traditionally been associated with urban environments, such as murine ty- phus, still occur in large city at low or unde- termined frequencies and often go undetected. In addition, alternate transmission cycles have been discovered for R. typhi that differ sub- stantially from their established, classic cycles, indicating that the epidemiology of this agent is more complex than originally thought and may be changing (Comer et al. 2001). The rodents (Rattus rattus and R. norvergicus) are the natural reservoir of the infection, and the oriental rat flea Xenopsylla cheopis is the main arthropod vector. However, other fleas, Ctenocephalides felis and C. canis, have been shown to be a vector for this organism (Dry- den and Rust 1994, Azad et al. 1997, Parola et al. 2003). These fleas are found worldwide and have been reported to parasitize many species of wild and domestic animals like dogs, cats, goats, sheep, horses, opossums (Dryden and Rust 1994, Fagbemi 1982, Obasaju and Otesile 1980, Yeruham et al. 1996). Cats, dogs and opossums produce antibod- ies against R. typhi (Matthewman et al. 1997, Bacellar et al. 1995, Lledó et al. 2003, Sorvillo et al. 1993) and they could act as indicators of the presence of the pathogen; also different authors (Comer et al. 2001, Parola et al. 2003, Adams et 1 Departamento de Microbiología y Parasitología, Universidad de Alcalá, Madrid, Spain. 2 Consejería de Sanidad y Bienestar Social de la Junta de Castilla y León, Spain.