Evaluation of serological tests for the diagnosis of brucellosis in Brucella melitensis experimentally infected dromedary camels

Fifteen non pregnant female dromedaries of different age were intra-tracheally and intra-nasally infected with a Brucella melitensis strain belonging to the genetic group East Mediterranean (former African group). The development of Brucella antibodies in the infected dromedaries was investigated over a period of 12 months by comparing 15 different serological tests. Three uninfected control dromedaries remained negative during the entire experiment. Our investigations revealed that only 2 serological tests were characterised by a high degree of sensitivity for the diagnosis of brucellosis in dromedaries. These two tests are a Rose Bengal Test (RBT) from Vircell, Spain and a competitive ELISA (cELISA) from Ingenasa, also from Spain. The blood culture revealed that all tested sodium citrate blood samples were negative. Results of the enriched citrate blood samples of the infected 15 dromedaries fluctuated and became positive for a short time, but at the end of the experiment only one remained positive. Direct examination by PCR did not show any evidence of the pathogen in the EDTA blood of the 15 infected dromedaries. Also, all nasal swabs taken up to a period of 3 months post infection remained negative in both PCR and microbial culture.