Brucellosis in Ethiopia: A comprehensive review of literature from the year 2000–2020 and the way forward

Abstract

Brucellosis is a zoonotic disease of considerable economic and public health significance globally. Despite the limited bacteriological evidence, a large number of serological works revealed that it is prevalent both in livestock and humans in Ethiopia. The current comprehensive review was carried out to provide apparent pooled seroprevalence (APS) estimates at individual animal and herd levels in livestock, and identify factors causing variability between studies conducted over the last two decades, show the spatial distribution, as well as summarizes Brucella species reported from livestock. It also provides APS of brucellosis in humans and evaluates the public health awareness of zoonotic brucellosis. In this review, systematic and synthetic review approaches were followed to summarize the available information. For the systematic review and meta‐analysis, articles were selected based on predefined criteria. Data extracted from these articles were analysed using meta‐analytical approaches to provide APS estimates and in‐between study variations for humans and all livestock species considered. Sensitivity analyses and bias assessments were conducted using influence plot analysis and, Egger's and Begg's statistics along with funnel plots, respectively. Synthetic review approaches were used to summarize data on isolates and public health awareness. Pooled seroprevalence estimate of brucellosis at national level was 2.6% (95% CI: 2.2–3.0) in cattle, 4% (95% CI: 3.1–5.1) in goats, 3% (95% CI: 2.3–3.9) in sheep and 3% (95% CI: 2.4–3.7) in camels. At a herd level, 16.3% (95% CI: 12.9–20.5) of cattle, 12.1% (7.1–19.9) of goat, 13.3% (7.6–22.1) of sheep and 19.7% (13.8–27.4) of camel herds in the country had at least one seropositive animal. Cattle in the pastoral/agropastoral production systems had significantly higher (p < .05) APS compared to mixed crop‐livestock and urban/peri‐urban dairy production systems. Pooled seroprevalence of brucellosis in small ruminants (8.3%, 95% CI: 6.3–10.8) and camels (4.4%, 95% CI: 3.5–5.6) in Afar were significantly higher (p < .05) than in other regions. Reports conducted using ELISA and serial Rose Bengal plate test (RBPT)‐ELISA had higher (p < .05) APS estimates than serial RBPT and complement fixation test. Brucella melitensis and B. abortus were reported from goats and cattle, respectively, from three available reports. The APS of brucellosis in humans was 5% (95% CI: 3.3–7.3). Public awareness of brucellosis was low (18.4%), while, practices that expose humans to Brucella infection were high. Scenario‐based control interventions on regions and production systems using one health approach are suggested.

Seroprevalence of Cattle Brucellosis in Al Gadarif State – Eastern Sudan

“…The overall seroprevalence findings of cattle brucellosis revealed 35.7% (131/367), 38.41% (141/367), 42.8% (157/367) and 8.4% (12/143), using the Rose bengal, modified Rose bengal (1:2), modified Rose Bengal (1:3) and c.ELISA tests respectively. These findings are lower than the prevalence of the disease in Gongli state in South Sudan in which the overall estimated seroprevalence of bovine brucellosis was 31%, however the findings were significantly higher compared to the findings in Khartoum State 25.7% (n=77) using RBPT and 22.7% (n=68) (95% CI : 17.96 to 27.44) using Serum Agglutination test (SAT) [16]. On the other hand seroprevalence estimate of brucellosis in Ethiopia which is the neighbor of Al Gadarif state from east part was 16.3% (95% CI: 12.9-20.5) in cattle [17], this result is obviously lower than the result obtained from the study.Out of the 77 RBPT positive sera, 66.2% (n=51) were confirmed to be positive by c-ELISA (95% CI from 55.63 to 76.77) in Bahr el Ghazal region, South Sudan [1,15].…”

Whole genome sequencing of Ethiopian Brucella abortus isolates expands the known diversity of an early branching sub-Saharan African lineage

“…To date, no brucellosis control strategy, including vaccination, has been implemented in cattle or other livestock species in Ethiopia. As the national herd-level seroprevalence in cattle has been estimated to be 16.3% ( Sibhat et al, 2022 ) it is likely that bovine brucellosis represents an endemic veterinary and public health priority issue in other geographic areas of the country. The successful isolation of Brucella from lymph nodes of the mammary glands highlights the potentially significant public health risk from Brucella abortus infection in cattle, if milk or dairy products are consumed without pasteurisation.…”

“…In Ethiopia, studies from various regions of the country have reported individual-level brucellosis prevalence ranging from 0.06% in commercial intensive dairy production ( Edao et al, 2018 ) to 9.7% in an extensive production system at the livestock-wildlife interface ( Chaka et al, 2018 ). A recent systematic review and meta-analysis reported an estimated seroprevalence of 2.6% (95% CI: 2.2–3.0) in cattle, which increased to 16.3% (95% CI: 12.9–20.5) when herd-level prevalence was estimated ( Sibhat et al, 2022 ). However, only two studies have reported the isolation of Brucella sp.…”

Long ignored but making a comeback: a worldwide epidemiological evolution of human brucellosis

“…Brucellosis is highly prevalent in the Kiboga District, Uganda, and the transmission risk was aggravated by the consumption of unpasteurized milk products and residing in rural settings [ 70 ]. In Ethiopia, the pooled seroprevalence of brucellosis in humans was 5% from 2000 to 2020, during which time the public awareness of brucellosis was low (18.4%), while practices that exposed humans to Brucella infections were high [ 71 ].…”