Antibodies to alpha-protobacteria in humans, domestic animals and rodents of Parque Nacional El Rey, Argentina

MASTROPAOLO, M; BALDI, CJ; MACEDO, AC; ORDUNA, GM; ORCELLET, VM; PERALTA, JL; FOLEY, J; BELDOMENICO, PM

Ouro Preto

Congreso; XIII Congresso Brasileiro de Parasitología Veterinária e I Simpósio Latino-Americano de Rickettsioses; 2004

Visitors of Parque Nacional El Rey (PNER) report frequent tick bites. Last decade, a cluster of 6 cases of rickettsial fever was documented in the region . The ecology of these diseases in the southern-cone is unknown, and studying host exposition to alpha-protobacteria is needed for its better understanding. To estimate the seroprevalence of alpha-protobacteria in humans, domestic animals and rodents of PNER, blood samples were collected from 16 humans, 18 horses, 3 dogs, and 195 rodents during november 2000, march and june 2001; and immunofluorescence assays were conducted using Anaplasma phagocytophilum, Ehrlichia canis and Rickettsia rickettsii antigens. To find associations between rodent prevalence status and environmental and host factors, parasitism and seasonality, chi-square tests and loglinear analysis were conducted. Humans, mainly parasitized by Amblyomma spp. , were serologically negative for the three pathogens. Horses, parasitized predominantly by Amblyomma spp. and by Haemaphysalis juxtakochi2, had a prevalence of 94%, 89%, and 22% for R. rickettsii, A. phagocytophilum and E. canis, respectively. Dogs were mainly parasitized by Amblyomma spp.2; two reacted positively to R. rickettsii, and only one to A. phagocytophilum and E. canis. Regarding rodents, primarily parasitized by Ixodes pararicinus2, had an overall prevalence of 28%, 1.5%, and 0% for R. rickettsii, A. phagocytophilum and E. canis, respectively. Seroprevalence to R. rickettsii varied significantly with the seasons in rodents, being 0% in spring, 15% in summer, and 51% in autumn. It also varied with age, with 21% for juveniles, 51% for young, and 18% for adults. The prevalence was higher in the transitional region (51%) between Chaco (15%) and Cloudforests (30%). Hosts harboring ticks had lower seroprevalence (17.5%) than those not parasitized (34%). Analyzing biome, age, season, and tick infestation together in a loglinear model, seroprevalence to R. rickettsii was associated with biome, season, and tick parasitism, but not with age.