Infecção experimental por leptospira sp. em ovinos deslanados da Raça Santa Inês e mestiços no Semiárido Nordestino.

Abstract

Most of the information on leptospirosis was obtained from experimental rodent infections, which, while relevant, do not provide all the answers about the pathogenesis of the disease in animals and humans. It is known that to advance in the control and prevention of leptospirosis it is necessary to know better on the interaction between the agent and each animal host. Thus, we sought to contribute to the understanding of host-parasite interaction, disease transmission and the carrier role of Santa Inês and crossbred sheep experimentally infected with Leptospira sp., as well as to register clinical and hemato-biochemical changes that may help in the previous diagnosis of the disease in this species. For this purpose, this Thesis is composed of three chapters. In Chapter I an experimental infection with Leptospira interrogans serogroup Pomona serovar Kennewicki was carried out in sheep, seeking to analyze a natural model of infection and the behavior of the agent-host interaction according to the breed of challenged sheep. In total, 12 sheep were used, six crossbred and six Santa Inês breed. The ewes were compared on the basis of serology, molecular and microbiological diagnosis. In Chapter II, the objective of the study was to reproduce the acute disease in Santa Inês sheep and crossbred ewes by intraperitoneal inoculation of L. interrogans serogroup Pomona serovar Kennewicki, verifying possible differences in response to infection in challenged ewes. In total, 10 ewes were used, five crossbred and five Santa Ines. The ewes were compared on the basis of serology, molecular and microbiological diagnosis. In Chapter III, the influence of infection by L. interrogans serogroup Pomona serovar Kennewicki on clinical and haematobiochemical parameters was determined according to the route of inoculation and the breed of experimentally infected sheep. Twenty-four sheep were used to carry out this experiment, which were divided into two groups: crossbred (group A) and Santa Inês (group B). In both groups the animals were challenged intraperitoneally and conjunctivally. The ewes were compared on the basis of clinical signs, blood count, serum biochemistry and urinalysis. Both the conjunctival and intraperitoneal routes were efficient in reproducing the infection in the infected sheep, but the intraperitoneal route presented more strong alterations in hematological and biochemical parameters. Santa Inês sheep presented higher concentration and duration of the antibody titers. No sheep presented clinical signs compatible with Leptospira sp. infection, so clinical evaluation was insufficient to reliably determine infected animals. The findings emphasize the importance of the genital tract as an extra urinary infection site and indicate the possibility of venereal transmission in the species. It is possible that both Santa Inês and crossbred sheep can exercise a resistance relationship and be able to participate in the transmission of strains of the Pomona serogroup, with the crossbred sheep seeming to be more resistant to infection.