A comparative study of diagnostic assays and risk factors associated with human brucellosis transmission in Baringo county, Kenya

Abstract

Brucellosis is a zoonotic disease of public health and economic significance in many developing countries. Clinical diagnosis of human brucellosis is a challenge because of its non specific clinical symptoms. Laboratory diagnosis is based on bacteria isolation from clinical specimens, serological testing for detection of anti-Brucella antibodies and molecular methods for detection of Brucella DNA. This study was three-fold: first it compared the rapid diagnostic kits (RDTs) used in healthcare facilities in Kenya for brucellosis diagnosis and Rose Bengal Test (RBT) to competitive-enzyme linked immunosorbent assay (c-ELISA), second it identified Brucella species infecting humans and third it determined the risk factors associated with transmission of brucellosis in humans in Baringo County, Kenya. This was a cross-sectional laboratory based study, conducted in three healthcare facilities in Baringo County; Kabarnet district hospital (KDH), Marigat district hospital (MDH) and Eldama Ravine district hospital (EDH). Patients 18 years and older that the attending clinicians suspected to have brucellosis were consented, filled a questionnaire that sought to identify risk factors associated with brucellosis and provided blood specimens. Serum was used to test for brucellosis using the rapid diagnostic kits (RDTs), RBT and c-ELISA. Deoxyribonucleic acid (DNA) extracted from the blood clots was used for identification of infecting Brucella species by polymerase chain reaction (PCR) assays. The percentage positivity for each assays was; c-ELISA, 9.6% (16/166), RDTs, 26.5% (44/166), RBT, 10.2% (17/166). The overall sensitivity of RDTs was 37.5% while the specificity was 74.7% when compared to c-ELISA. The positive predictive value of the RDTs was 13.6% while the negative predictive value was 91.8%. The RDTs used in the healthcare facilities were not able to differentiate between B. abortus and B. melitensis infection. Brucella abortus was the species detected and the risk factors associated with Brucella transmission were handling sick animals without gloves and drinking unboiled xiv milk. Half of the participants were aware that brucellosis could be transmitted through unboiled/unpasteurized milk and 40% of the participants were aware of other ways in which brucellosis could be transmitted. The study, demonstrated the presence of brucellosis in Baringo County, B. abortus was detected and it demonstrated that the RDTs used had low sensitivity and specificity. There is need to use diagnostic tests that are more sensitive and specific for diagnosis of brucellosis for effective treatment. In addition there is need to educate the community on brucellosis and brucellosis preventive measures.