Bovine Brucellosis in Gauteng, South Africa: Seroprevalence amongst Cattle Handlers and Variables Associated with Seropositive Cattle Herds, 2014–2016

Abstract

In South Africa, the prevalence of cattle handler exposure to Brucella on cattle farms is unknown and risk factors and cattle symptoms associated with infected cattle herds are unavailable. To address this gap, a case-control study of cattle herds was conducted in Gauteng province and farm workers and veterinary officials were tested for exposure to Brucella. Seroprevalence amongst farm workers exposed to case herds ranged from 4.0% (BrucellaCapt®) to 16.7% (IgG ELISA®), compared to those exposed to control herds, where seroprevalence ranged from 1.9% (BrucellaCapt®) to 5.7% (IgG ELISA®). Seroprevalence amongst veterinary officials was significantly greater compared to farm workers exposed to case herds for the outcome RBT+ IgM- IgG+ (OR = 11.1, 95% CI: 2.5–49.9, p = 0.002) and RBT- IgM- IgG+ (OR = 6.3, 95% CI: 2.3–17.3, p < 0.001). Risk factors associated with being an infected herd were: being a government-sponsored farm vs. private farm (OR 4.0; 95% CI: 1.4–11.3; p = 0.009), beef vs. dairy herd (OR 7.9; 95% CI: 1.4–44.9; p = 0.020), open vs. closed herd (OR 3.3; 95% CI: 1.1–10.4; p = 0.038) and the presence of antelope on the farm (OR 29.4; 95% CI: 4.0–218.2; p = 0.001). Abortions (OR = 5.1; 95% CI: 2.0–13.3; p < 0.001), weak calves in the herd (OR = 8.0; 95% CI: 2.6–24.4; p < 0.001), reduction in number of calves born (OR = 9.0; 95% CI: 2.1–43.6; p < 0.001), reduction in conception rate (OR = 3.9; 95% CI: 0.8–18.3; p = 0.046), hygromas in cattle (p = 0.011) and farmers reporting brucellosis-like symptoms in their farm workers or in him/herself (OR = 3.4; 95% CI: 1.3–8.7; p = 0.006) were more likely to be associated with Brucella infected herds than control herds. This evidence can be used in strategic planning to protect both human and herd health.

Brucellosis Seropositivity Using Three Serological Tests and Associated Risk Factors in Abattoir Workers in Gauteng Province, South Africa

“…The associated risk to workers to brucellosis will be influenced by the brucellosis infection in livestock with which the workers have had contact. This is reflected by the low to moderate brucellosis seroprevalence (4.0% (BrucellaCapt) to 16.7% (IgG ELISA)) of farm workers on brucellosis infected farms compared to low seroprevalence [1.9% (BrucellaCapt ® ) to 5.7% (IgG ELISA ® )] on farms free of brucellosis in South Africa (27). In South Africa, we have limited data on the brucellosis prevalence in animals.…”

“…These studies were conducted in various countries/regions, each with its unique zoonotic disease profile in abattoir facilities that determine the risk factors identified in each study. In South Africa the only published record focusing on occupational workers exposed to brucellosis is the seroprevalence amongst farm workers exposed to brucellosis case farms that are higher, ranging from 4.0% (BrucellaCapt ® ) to 16.7% (IgG ELISA ® ), compared to those exposed to brucellosis negative control farms where seroprevalence ranged from 1.9% (BrucellaCapt ® ) to 5.7% (IgG ELISA ® ) (27). There are no empirical data or published reports on brucellosis seroprevalence and risk factors in abattoir workers in South Africa.…”

Prevalence and occupational exposure to zoonotic diseases in high-risk populations in the Free State Province, South Africa

“…Limited studies have reported BB’s prevalence or incidence rate in South Africa cattle populations. Previous findings have reported on the seroprevalence of BB in Gauteng, Mpumalanga (Mnisi area), and KwaZulu Natal and determined seroprevalence of 2.33, 0.88, and 1.3%, respectively, with the latter two focusing on communal cattle in municipal dip tanks ( Matekwe, 2011 ; Chisi et al, 2014 ; Govindasamy et al, 2021 ). Moreover, introducing compulsory calf vaccinations in South Africa has considerably decreased the overall BB prevalence from approximately 10.5% in 1976 to 1.4% in 1988 ( Godfroid et al, 2004 ).…”

Serological Evidence and Coexposure of Selected Infections among Livestock Slaughtered at Eastern Cape Abattoirs in South Africa

“…Te diagnostic performance characteristics of ELISAs and FPA are comparable with or better than that of the CFT, and as they are technically simpler to perform and more robust, their use may be preferred [10]. Te problem with SA partial brucellosis scheme focusing only on bovines is once the disease has been established in a herd, it is difcult to control as it has variable incubation periods ranging from several months to at least two years and even nine years as reported [15]. Tese problems make control and elimination from herds costly and difcult as it takes a minimum of two years after removal of infected animals to declare a herd free and decades to declare countries free of brucellosis [15].…”

“…Te problem with SA partial brucellosis scheme focusing only on bovines is once the disease has been established in a herd, it is difcult to control as it has variable incubation periods ranging from several months to at least two years and even nine years as reported [15]. Tese problems make control and elimination from herds costly and difcult as it takes a minimum of two years after removal of infected animals to declare a herd free and decades to declare countries free of brucellosis [15]. As human brucellosis is mainly caused by contact with Brucellainfected animals that could be asymptomatic [16], their secretions and carcasses result in occupational public health risks for those workers in contact with animals such as abattoir workers, animal handlers, and veterinarians.…”