Inferência sorológica de espécies da ordem Rickettsiales de importância em saúde pública em cães no Sul de Minas Gerais

Abstract

Diseases caused by bacteria of the order Rickettsiales are a major public health challenge. A high fatality rate may be associated with health professionals' lack of knowledge about the patient's clinical and epidemiological history and their circulation in the geographical area. This leads to late diagnosis and treatment. Dogs are host to ticks and sentinels to zoonoses, so investigating the presence of anti-rickettsia and anti-anaplasma antibodies in these is important in regions with no recorded human cases. This study aimed to determine the presence of circulating Rickettsiales pathogens in the city of Lavras/MG, through the Indirect Immunofluorescence Reaction (RIFI), in dogs, considering that there are no reports of animal and/ or human cases in the region. A bank of canine serums stored in the Laboratory of Pathology of the Department of Veterinary Medicine at the Federal University of Lavras, collected in 2010 was used. Serums of ninety-nine urban and hundred rural dogs were tested for anti-Rickettsia amblyommatis antibodies, R. belli, R. parkeri, R. rickettsii and Anaplasma phagocytophilum. Descriptive analysis of all variables was performed, and the association between each diagnosis with urban/rural area, gender and age were tested by the chi-square test, considering the statistical significance of p <0.05 and calculated odds ratios with a confidence interval of 95%. Titers equal or greater than 1:64 and 1: 320 were considered positive for rickettsiae and A. phagocytophilum, respectively. In the case of co-infection between rickettsiae, the final titer agent was four times higher than the others in the IFAT, and was considered as the most likely diagnosis. Of the samples, 61.8% (123/199) were seropositive for rickettsiae. Of these, 26.0% (32/123) had a reaction for more than one species: ten were considered probable for R. parkeri and one as R. rickettsi, the remainders were considered as coinfection. The R. rickettsii species had the highest rate of co-infections 71.9% (23/32), but with titers ranging from 1/64 to 1/256. There was no significant difference (p> 0.05) among areas, gender or age. In this comparison by species, only seropositive for R. parkeri and R. belli showed significant differences between areas, p=0.037 and p=0.017, respectively. However, for R. rickettsii and R. amblyommatis there were no differences between the two groups. In the analysis of the risk estimate (OR), dogs from the urban area had 5.16 (CI=0.13 to 0.85) times more chance of seropositivity for R. parkeri and 3.39 (CI = 0.27 to 0,96) times for R. belli compared to rural animals. Regarding the serological research related to A. phagocytophilum, 19.1% (38/199) were reactive when considering the 1:40 cutoff point, but only two sera (1%), both from rural areas, were positive with titer. four times the cut-off point, ruling out a possible cross-reaction with A. platys. One of the sera positive for A. phagocytophilum was also reactive to R. parkeri. The results indicate the circulation of bacteria of the order Rickettsiales in Lavras/ MG, with dogs seropositive for R. parkeri, R. rickettsii, R. belli, R. amblyommatis and A. phagocytophilum, in this frequency order. Some of it has a similar frequency in endemic regions in Brazil. Consequently, due to the absence of clinical cases, it can be inferred that the region is a silent area for Brazilian Macular Fever and Human Granulocytic Anaplasmosis. The risk and the need to adopt environmental surveillance measures for early diagnosis of possible human cases should be considered.