Leptospirose bovina: abordagens para o diagnóstico sorológico individual e do rebanho

Abstract

Bovine leptospirosis is a worldwide disease. In Brazil, bovine leptospirosis is a major disease, causing economic damage to livestock. In addition, the disease is an important one health risk since asymptomatic cattle can eliminate leptospires through urine for long periods. Currently, the microscopic agglutination test (MAT) is recommended as the main tool for the diagnosis of leptospirosis in cattle herds. In recent years, Rio Grande do Sul (RS) has consolidated as an important exporter of live cattle, directly reflecting on the national economy. In this context, our study aimed to: (1) Determine the prevalence of anti-Leptospira antibodies, through MAT, in cattle awaiting export in the city of Pelotas, RS; (2) Standardize and test an indirect ELISA, using the serovar Hardjo as antigen, comparing the results with the MAT; and (3) Standardize and test a Dot-ELISA in an initial evaluation for the individual and rapid diagnosis of bovine leptospirosis, using the serovar Hardjo as an antigen, comparing the results with the MAT. A representative sample was calculated from 4,552 animals housed in Pelotas, from 34 municipalities in RS, blood was drawn, and the microscopic agglutination test (MAT) performed for serological analysis. Indirect ELISA was performed with 60 randomly sera, of which 21.6% were reagents in MAT. For Dot-ELISA, 34 bovine sera, being 17 reagents and 17 non-reagents in MAT, were used. No animals included in the study had a history of vaccination against leptospirosis. Of the 355 animals sampled, 24 (6.76%; 95% CI 4.58-9.86) were reactive for at least one of the MAT antigens. The serovars Hardjo and Icterohaemorrhagiae had a prevalence of 2.53%, followed by Canicola with 1.97% and Grippotyphosa with 1.12%. Of the 60 bovine sera analyzed in the ELISA, six (10%; 95% CI 4.6-20.1) sera were considered reactive. According to the statistical analysis performed, it was possible to detect a high specificity in the test (97.87%), but a low sensitivity (38.46%). On the other hand, Dot-ELISA was able to detect antiLeptospira antibodies in 16 (sensitivity = 94%) of the 17 bovine sera reactive in MAT. A sample of young cattle aged 24 months or less, the prevalence found indicates the need for preventive measures, such as vaccination of herds. In addition, our results show cattle exposure to the agent, which in turn can lead to one health problems. Future research may use our results to plan epidemiological studies aiming at describing the status of leptospirosis in cattle herds in Rio Grande do Sul. Although the results are promising, additional tests are necessary in order to standardize the technique for large-scale use, aiming at the rapid screening of leptospirosis cases in cattle.