A serological and molecular (PCR) survey on abortions caused by Brucella melitensis Rev-1 vaccine strain in sheep herds of Tabriz-Iran

Sheep and goats brucellosis is a zoonotic infection with important effects on both public and animal health and is widespread in many areas of the world, including Iran. The main purpose of this study was to determine of seroprevalence of brucellosis among the aborted ewes and in the same time, detection of bacterial DNA in the aborted fetal tissues by the PCR protocol. From October 2010 to March 2011, peripheral blood samples were taken from 100 ewes aborted in the farms of Tabriz (North-West of Iran) and their sera separated by centrifugation. Serum samples analyzed by ELISA (Pourquire-ELISA Kit manufactured by France). At the same time, tissue samples were taken from the abomasal fluid, liver, kidney, spleen, lung, heart and brain of the aborted fetuses and dam’s placenta and tested by PCR. Twelve out of 100 dams (12%) were seropositive to the Brucella spp. and twelve out of 100 aborted fetuses (12%) showed positive reaction to the Brucella melitensis Rev-1 vaccine strain by the PCR. None of the aborted fetuses showed positive reaction to the B. melitensis standard strain (ATCC 23457). Statistical analysis did not show any significant difference between two diagnostic methods (PCR and serological tests). However, PCR protocol is preferred to the serological tests due to its ability to differentiate of the Brucella strains. In conclusion, both serological and particularly PCR tests are recommended for diagnosis of Brucella strains in the ewes subjected to abortion. According to our PCR test results, vaccination with Brucella melitensis Rev-1 vaccine strain could be abortive in pregnant ewes.