Detecção de anticorpos anti-Rickettsia spp. em galinhas de criação extensiva de uma região endêmica do estado do Rio Grande do Sul e infecção experimental por Rickettsia parkeri.

Abstract

The aim of this study was to evaluate the natural infection of chickens of extensive breeding of an area considered endemic for spotted fever in the state of Rio Grande do Sul through serological survey, as well as to perform the experimental infection by Rickettsia parkeri these birds. In the first study, 300 blood samples were collected and the sera were tested by indirect immunofluorescence assay (IFA) to identify the presence of anti-Rickettsia spp. antibodies. The occurrence of anti-Rickettsia spp. antibodies observed was 1.33% (4/300), with titers ranging from 64 to 256 for R. parkeri, Rickettsia rickettsii and/or Rickettsia bellii. In the second step, was performed the experimental infection by R. parkeri. 64 chickens were used divided into eight groups which were inoculated with different amounts of the agent by several routes of administration. Group 1 (G1) - inoculated with 2,5 x 105 Vero cells infected with R. parkeri (1 ml) intramuscular (IM); G2 5,0 x 105 Vero cells infected with R. parkeri (2 ml) IM, G3 - 1 ml of inoculum subcutaneously (SC); G4 - 2 ml of inoculum SC; G5 - 1 ml of the inoculum intraperitoneally (IP); G6 - 2 ml of inoculum IP, and G7 and G8 1 ml and 2 ml of culture medium Vero cells IM respectively (negative control groups). The sera of chickens were evaluated at 3, 7, 14 and 21 days post infection (PI) by IFA, to verify the dynamics of antibodies in acute and chronic infection. To identify the multiplication of R. parkeri in tissues during the same period PI, PCR was performed from fragments of spleen and lung of chickens euthanized. Birds of G4 and G3, in order of importance, had the highest average antibody showing the highest levels at seven and 14 days PI. G2, G4 and G6 showed higher mean antibody compared to G1, G3 and G5 respectively, considering the infection dose-dependent. Rickettsial DNA was not detected in the tissues evaluated. The results of both studies suggest that chickens of extensive breeding from endemic area searched do not participate as a reservoir and/or amplifier host in the epidemiology of spotted fever of region and based in the experimental infection, it was verified that birds seroconverted by the challenge by R. parkeri, but no replication of the agent in the tissues analyzed, nor the presence of rickettsemia.