Identification of the Excretion of Brucella Melitensis Vaccine Strain Rev.1 in Lactating Ewes and the Assessment of Antibody Response in their Lambs

 Brucellosis is a zoonotic disease and humans get the infection mostly through consumption of raw milk. Vaccination is the best way to control brucellosis and Iran uses Rev.1 vaccine in sheep and goat flocks. It is evident that the vaccine may shed through milk so it can infect humans. The objective of the present study is to assess the shedding of the vaccine in lactating ewes and its possible immunity in their lambs through milk feeding. 

 In a two-month period post-parturition, reduced dose Rev.1 vaccine was injected to 50 parturited ewes. From the first day of vaccination, mixed milk samples were collected and continued for 2 months. Then the samples were tested by PCR method and the sera from 70 lambs of the examined ewes were tested by modified Rose Bengal test while they were feeding milk.

 From the 6th day until the 27th day post-vaccination, PCR represented the DNA of Rev.1 in the milk samples. All the lamb’s sera were negative in the serological test. 

 As the presence of Rev.1 in milk was confirmed in this study, it is important to consider the role of the vaccine strain as a risk of infection in humans. Moreover, as the serological response in the lambs was negative, it seems that the vaccine strain didn’t immunize the lambs through milk feeding so the vaccination of lambs is necessary in small ruminant’s flocks.