Epidemiology and molecular confirmation of Brucella spp. in cattle in Namibia

Abstract

This study assessed knowledge, attitudes, and practices regarding brucellosis among cattle farmers (n=264), meat handlers (n=143) and medical professionals (n=124); estimated seroprevalence of Brucella infection in cattle (n=49718) (2004-2018) and humans (n=971) (2012-2017) retrospectively, and prospectively (n=304) at a major abattoir in Namibia. Molecular characterisation of Brucella species was performed on DNA extracted from spleen and lymph nodes from seropositive cattle. Overall awareness of brucellosis was 43.50% (231/531), with highest awareness among medical professionals (73.40%, 91/124) and the lowest in meat handlers (14.00%, 20/143). Medical professionals (98.40%, 122/124) did not consider brucellosis in the differential diagnosis of persistent fever in humans. Seroprevalence of human brucellosis was 11.64% (113/971, 95% CI: 9.77-13.81), with positive cases clustered in the 30-40-year age group and in females (64.00%) (z=-5.24, p<0.01). Individual cattle and herd prevalence of brucellosis was 0.49% (244/49718, 95% CI: 0.43%-0.56%) and 9.26% (78/842, 95% CI: 7.49%-11.41%) respectively, with more seropositive communal herds (33.09%) and cattle (10.27%) than commercial herds (4.67%) and cattle (0.24%) (p<0.05). Seroprevalence of brucellosis in the abattoir was 2.30% (7/304; 95% CI: 1.10-4.70%) based on RBT, and 1.64% (5/304; 95% CI: 0.70-3.8%) after confirmation with CFT, while herd prevalence was 9.62% (5/52). Brucella DNA was detected in lymph nodes (6/7, 85.71%) and spleens (6/7, 85.71%) from seropositive cattle using ITS-PCR. From cultures, Brucella abortus isolates were confirmed from lymph nodes (4/7, 57.14%) and spleen (6/7, 85.71%) by AMOS-PCR. Targeted public health education, better enforcement of current control measures and the use of protective gear are recommended to prevent human and animal infection.