Testing for Antibodies to Brucella abortus in Milk From Consumers and Market Agents in Kenya Using Milk Ring Test and Enzyme Immunoassay

Abstract

Over 85% of all milk sales on Kenya pass through informal channels. The extent of the risk posed by the sale of this raw milk to human health in respect to brucellosis is unknown. This paper presents the results of a study on the occurrence of antibodies to Brucella abortus in milk from households consuming raw unpasteurized milk and market agent selling the same. Four hundred thirty four (434) raw milk samples from consumer households and 508 from informal market agents were collected between January 1999 and January 2000 from Nakuru /Narok and Nairobi/Kiambu. Milk agents sampled included co-operative societies, milk collecting centers and self-help groups, milk bars, shops and kiosks and mobile traders on foot, bicycle or motorized transport. In addition, 147 samples from the formal market chain (pasteurized) were collected. All the samples from the samples were screened for antibodies to Brucella abortus using ELISA and Milk Ring Test (MRT), except for the formal milk that was tested using ELISA only. Five percent of the consumer household samples and 4% of the samples form informal milk market agents tested positive on ELISA. There was poor agreement between the two antibody surrogate tests (Kappa =0.40, 95% confidence interval =0.19-0.60). ELISA detected 3.2% more samples from consumer households and 0.4% from informal market agents than MRT. Of the formal market samples, 16.4% were positive. Ways of reducing the risk of contracting brucellosis from drinking raw milk are proposed.