Determining the status of Brucella canis in dogs in the Maputo region of Mozambique using various techniques

Abstract

Brucella canis causes canine brucellosis in dogs inducing mainly contagious abortion. Diagnosis of B. canis is based on bacterial isolation that is timeconsuming and inconsistent; serological tests (more than one test) that is ambiguous and lacks specificity; and PCR that may lack sensitivity as bacteraemia may not be constant. Since bacteraemia of B. canis develops 7-30 days after infection, often resulting in a sustained bacteraemia, PCR was investigated for the detection of B. canis in whole blood of dogs. The PCR sensitivity was validated to detect 3.8 fg Brucella DNA mixed with dog DNA as well as 1 x 102 cfu/ml B. canis in dog blood (mock infection) using primers (ITS66 and ITS279) that amplifies the 16S-23S ribosomal DNA intergenic spacer (ITS) region. The PCR assay for the detection of B. canis in whole blood samples was compared with bacterial isolation, serological tests, which include the rapid slide agglutination test (RSAT), 2-mercaptoethanol RSAT (2ME-RSAT) and imunochromatographic assay (ICA). These techniques were used to test 56 dog samples obtained from the Michangulene and Mafavuca villages at the municipality of Changalane, in District of Namaacha in Maputo, Mozambique for B. canis. No B. canis was isolated from dog blood using the classical microbiology isolation and PCR. A sample was only presumed positive if both the 2ME-RSAT and ICA tested positive. None of the samples in this study tested positive using this criterion for serological testing. Results of this study indicated that B. canis was not present in the 56 dogs sampled in the Maputo region of Mozambique using bacteriology, PCR and serological tests (RSAT, 2ME-RSAT and ICA). Due to the discrepancy between serological tests we cannot conclude that B. canis is not present in the Maputo region of Mozambique. In future the accuracy of the serological tests, bacteriology and PCR assay should be assessed using experimentally infected B. canis dogs over a period followed by a surveillance study in Mozambique that includes urine, semen and blood samples collected from dogs.