Prevalence, herd health and zoonotic implications of brucellosis in communal and smallholder cattle farming areas in north-west province, South Africa

Abstract

Brucellosis is recognized as one of the most important bacterial zoonosis as it is responsible for considerable economic losses in livestock and long-term chronic disease condition in humans, consequently a health-related burden worldwide. This study highlights the need to investigate the prevalence and distribution of brucellosis in the four main districts (Dr Ruth Segomotso Mompati, Dr Kenneth Kaunda, Bojanala platinum and Ngaka Modiri Molema) of the North-West province of South Africa, as well as its zoonotic implications. Specific objectives of this study were to determine the seroprevalence of Brucellosis in cattle though serological analysis, to isolate and identify Brucella from suspected specimens and to assess farm management, herd-health, and husbandry system. A total number of blood (n=770) samples from farmed animals (n=378) and abattoir-slaughtered (n=392) animals were collected for this study. The blood from abattoirs was accompanied by lymph nodes (n=392) corresponding to the blood sample of each animal. In addition to the above, milk samples (n=22) were collected from cows after farmers’ permission. The Rose Bengal Plate Agglutination Test (RBT) was used to detect anti-Brucella antibodies in serum samples followed by confirmation of positive sera with the complement fixation test (CFT). Milk samples were screened by milk ring test (MRT) using B. abortus MRT antigen. Tissue samples corresponding to sero-positive samples were subjected to isolation and phenotypic characterisation of Brucella species by isolation onto Farrell's Medium with 5% bovine serum and penicillin. The same positive tissue samples were subjected to Brucella spp. molecular identification by amplification of the IS711, 16S rDNA and the internal transcriber subunit (ITS) gene fragments. Serological results indicated the overall prevalence for RBT positive samples to be 2% at 95% Confidence Interval (CI). All 770 samples were subjected to screening with the RBT, 18 out of 770 (2.3%) tested positive. Confirmation with CFT revealed that 16 (n=16) out of 18 samples were indeed positive. Sero-positive results were found in Ngaka Modiri Molema and Dr Ruth Mompati districts with the prevalence of 4.65% (95% CI: 2.61 – 8.11) and 2.34% (95% CI: 0.91-5.85) respectively. This resulted in the overall prevalence of 1.95% (95%CI: 1.14 – 3.12) for all four districts combined. Out of the 2.3% (18/770), only 0.90% (7/770) were from slaughtered animals. All 0.90% (7/770) tissue samples tested negative for PCR and cell culture. A questionnaire to determine the abattoir owners and farmers’ general understanding and knowledge on zoonotic diseases was developed and interviews conducted. A multivariate analysis has shown a significant association between participants’ statuses of literacy with the risk of brucellosis in a farm.