Diagnóstico e controle de lentivírus de pequenos ruminantes (LVPR) em caprinos.

Abstract

In Brazil, the Agriculture Animal Husbandry and Supply Ministry (MAPA) has launched a Caprine and Ovine Health Program (PNSCO) which encompasses a National Plan of Control and Vigilance of Small Ruminants Lentiviruses (PNVCLVPR) that the usage of the agar gel immunediffusion(AGID) is recommended as a routine test in the diagnosis of lentiviruses being used anda the western blot (WB) as confirmatory test and for certification purposes, though the last is not available in the country. In this work a WB was standardized for the diagnosis of small ruminants lentiviruses (SRLV) in caprines, using antigen through a simplified purification system, initiated with the concentration by dialysis of the floating of infected corneas cell cultures and followed by centrifugation in continuous sucrose gradient. In the WB, five viral proteins were recognized by the standard positive serum, and showed molecular weights of 14-16, 25, 40, 50 and 70 kDa. When using filed samples of caprine serum, also positive in the immunoblot, at least one viral protein was recognized by all the samples. All serums displayed antibodies against the 25 kDa protein. Positive reaction to gp40 was observed in four animals, with discreet reaction intensity in three of them. Two animals displayed positive reaction to p16, and two to gp50, although not intense ones. It was also standardized an ELISA using G protein as a conjugate, ELISA-G, from an indirect ELISA (ELISA-i). The values of the positive/negative relation (P/N) obtained for the standard serum was significantly superior (P < 0,05) in the ELISA-G (10.9) than in the ELISA-i (4.8). When testing a group of 8 seropositive and 10 seronegative, it was observed, basically, the same behavior, with P/N values, in the ELISA-G of 4.68 and in the ELISA-i of 3.33, showing greater discrimination capacity regarding the ELISA-G, which is highly desirable in immune-enzymatic assays standardization (EEA). These tests are standardized, however the WB needs to be more widely evaluated and the ELISA requires validation (sensibility and specificity estimate), based on the test of a significant number of samples of the caprine and ovine population, representative of different existent epidemiological conditions in Brazil, so that it can be used in the serological diagnosis of lentiviruses in SRLV control programs. Using the WB, in addition to AGID, a serology was performed in animals born through induced labor, separated immediately after birth from their mothers and fed with artificial or treated termally colostrum, these measures, probably, would difficult the transmission of LVSR from the infected goats to their descendents, that would show low or null title of antibodies, however the results of both tests revealed that, although without clinical alterations compatible with infection by SRLV, 27.27% (12/44), all animals, showed antibodies against SRLV, concluding that the handling measures applied were not sufficient to avoid the infection by the SRLV, given that, possibly, an intrauterine infection, and/or failure to inactivate the virus in the colostrum and milk have occurred, besides horizontal transmission.