Contribuições para a epidemiologia e controle da leptospirose em ruminantes do Nordeste do Brasil.

Abstract

This thesis consists of three chapters, in Chapter I, the strategies of control of an outbreak of leptospirosis infection in dairy cattle in the state of Maranhão, Northeastern Brazil, are described. The diagnosis of leptospirosis was based on serology, bacteriological culture and polymerase chain reaction. Of all farm animals, 136 (48.6%) were seropositive for Leptospira sp. Eight of the animals with reproductive problems were PCR positive. Genetic sequencing of a positive PCR sample of vaginal fluid revealed Leptospira borgpetersenii. One year after the adoption of control measures, no reproductive problems were observed. Thus, leptospirosis probably caused reproductive failures in the herd, and the control and prevention measures implemented were efficient in controlling the disease. In Chapter II the serological and molecular characterization of Leptospira sp. in cattle and sheep in semi-arid conditions of Northeast Brazil. Serological, molecular and and attempt isolation of Leptospira sp. of 99 females of reproductive age. Of these 38.4% were reagents in the serological test, being 49% bovine females and 27.1% ovine females. Serogroups detected in cattle were Sejroe, Hebdomadis, Australis, Djasiman, Balum, Pomona and Cynopteri. In sheep, the reactive serogroups were Australis, Balum, Djasiman, Tarassovi, Icterohaemorrhagiae and Cynopteri. In PCR, leptospiral DNA was detected in nine urine samples. Growth of the agent in culture medium was not observed in urine samples. In semi-arid conditions, transmission between animals of the same species seems to be the main form of dissemination of leptospires in sheep and cattle, but the participation of other domestic and wild animals can not be ruled out. It is also suggested that the practice of intercropping cattle and sheep and the close coexistence between them facilitates the dissemination of the agent in the rural properties. Chapter III determined the seropositivity for leptospirosis and the serogroups prevalent in the serological tests carried out at the Transmissible Diseases Laboratory (TDL) of the Federal University of Campina Grande (UFCG), Patos, Paraíba, Northeast Brazil, in cattle, goats, sheep and buffaloes in the period from 2010 to 2017. The records of the serological tests for leptospirosis of 5,594 animals from four Brazilian states were computed. A total of 662 samples were positive in the serological test, resulting in a frequency of 11.8%. Serjoe, Autumnalis and Icterohaemorrhagiae were the most frequent serogroups for all species. The individual frequencies of cattle, goats, sheep and buffaloes were 20%, 8.3%, 7.9%, and 27.9%, respectively. In relation to the most frequent serogroups by animal species, Serjoe predominated in cattle, Autumnalis was the most frequent in goats and sheep and Australis predominated in buffaloes. Leptospira sp. infection, determined by serology, is widespread in ruminants (cattle, goats, sheep and buffalo) in Northeast Brazil, suggesting the existence of alternative transmission routes less dependent on environmental factors, as well as identification of the most frequent serogroups suggests the need to improve sanitary conditions and implement efficient and targeted control measures for the main sources of infection.