First Report of Isolation of Brucella melitensis, Vaccine Strain Rev.1 as a Source of Cattle Infection in Iran

Brucellosis is a worldwide zoonosis causing reproductive failures in livestock. It is shown that although the vaccine can prevent abortion, it does not provide complete protection against infection. So that vaccination of ewes with Rev.1 biotype can be a source of cattle and even human Brucellosis. The aim of this study was to evaluate possibility of Brucella cross-infection in cattle from Brucella vaccine Rev.1 biotype in Iran. After Brucella vaccination in cattle and ewes in tradition farms in which cattle and sheep are kept close together, 70 aborted cattle fetus samples were collected. The species of Brucella were characterized ant the type of Brucella was studied, by PCR-RFLP method of Pst1 restriction digest of part of Omp2a gene. Of the 70 studied samples, 50 (about 70%) were infected with Brucella Spp. Banding pattern of PCR-RFLP of omp2a gene demonstrated that in 2 of the samples (4%) the source of infection was Rev.1 vaccine. No sample was infected with Rb51 and S19 vaccine strains, which are specific for cattle vaccination. Our results demonstrated that Rev.1 vaccine biotype can cause Brucella infection in cattle. Therefore in places that cattle and sheep are kept close together, ewe vaccination (Rev.1) can be a source of Brucella abortion in cattle. This study has highlighted some of the potential hazards associated with the use of the Rev.1 vaccine in national control programs.