RESUMEN
Anaplasma phagocytophilum is a zoonotic tick-borne rickettsial pathogen that causes granulocytic anaplasmosis (GA) in humans, horses, and dogs. In California, dusky-footed woodrats (Neotoma fuscipes) are a putative reservoir host, and Ixodes pacificus is a vector for transmission from rodents to humans, dogs, and horses. Cases are clustered in coastal and Sierra Nevada foothill regions, but not necessarily in proximity to infected woodrats. This study was designed to compare exposures and active infections of A. phagocytophilum in multiple rodents at a fine spatial scale in a hyperenzootic area and to evaluate the spatial clustering of infections. Of 331 rodents, the seroprevalence was 14.5%, with 60% in tree squirrels (Sciurus griseus and Tamiasciurus douglasii), 29% in woodrats, 14% in flying squirrels (Glaucomys sabrinus), and 5% in chipmunks (Tamias senex). No seropositive ground squirrels (Spermophilus beecheyi) were detected. The seroprevalence was significantly higher west of the Trinity River (23.1%) than east (11.8%) of the river. One Douglas squirrel and one western gray squirrel were polymerase chain reaction (PCR) positive. There was more spatial clustering among seropositive animals compared with all animals tested across the spatial scales evaluated, and this clustering was significantly greater than expected by chance alone. A significant cluster of 24 seropositive animals was found west of the Trinity River, with a population of 56 animals considered within the 50% population-at-risk, and a radius of 362.8 meters. The diversity of cricetine and sciurid rodents infected suggests that squirrels and chipmunks may be underappreciated contributors to A. phagocytophilum ecology in the western United States. The spatial clustering of exposed animals suggests interesting underlying spatially heterogeneous environmental variables that could facilitate the persistence of A. phagocytophilum in nature.
Asunto(s)
Anaplasma phagocytophilum/aislamiento & purificación , Vectores Artrópodos/microbiología , Ehrlichiosis/epidemiología , Ixodes/microbiología , Enfermedades de los Roedores/epidemiología , Roedores/microbiología , Anaplasma phagocytophilum/patogenicidad , Animales , Anticuerpos Antibacterianos/sangre , California/epidemiología , Análisis por Conglomerados , Reservorios de Enfermedades/microbiología , Reservorios de Enfermedades/veterinaria , Ehrlichiosis/transmisión , Femenino , Humanos , Masculino , Enfermedades de los Roedores/transmisión , Estudios Seroepidemiológicos , Sigmodontinae/microbiologíaRESUMEN
Epidemic typhus, caused by Rickettsia prowazekii, is maintained in a southern flying squirrel (Glaucomys volans) sylvatic cycle in the southeastern United States. The northern flying squirrel (Glaucomys sabrinus) has not been previously associated with R. prowazekii transmission. A second rickettsial pathogen, Anaplasma phagocytophilum, infects dusky-footed woodrats (Neotoma fuscipes) and tree squirrels in northern California. Because northern flying squirrels or their ectoparasites have not been tested for these rickettsial pathogens, serology and polymerase chain reaction (PCR) were used to test 24 northern flying squirrels for R. prowazekii and A. phagocytophilum infection or antibodies. Although there was no evidence of exposure to R. prowazekii, we provide molecular evidence of A. phagocytophilum infection in one flying squirrel; two flying squirrels also were seropositive for this pathogen. Fleas and ticks removed from the squirrels included Ceratophyllus ciliatus mononis, Opisodasys vesperalis, Ixodes hearlei, Ixodes pacificus, and Dermacentor paramapertus.