Sero-prevalence of brucellosis, Q-fever and Rift Valley fever in humans and livestock in Somali Region, Ethiopia

Abstract

Information on zoonotic diseases in humans and livestock are limited in pastoral/agro-pastoral communities in Ethiopia. A multi-stage cross sectional cluster design study was implemented with the aim to establish the seroprevalence of zoonotic diseases including brucellosis, Q-fever and Rift Valley fever (RVF) in humans and livestock in Adadle Woreda of the Somali Region, Ethiopia. Blood samples were collected from humans and livestock and tested by relevant serological tests. For brucellosis, Rose Bengal test (RBT) and indirect ELISA was used for screening and confirmatory diagnosis respectively. Indirect and competitive ELISA were also used for Q-fever and RVF respectively. The individual seropositivity of Q-fever in livestock was 9.6% (95% CI 5.9–15.1) in cattle, 55.7% (95% CI 46.0–65.0) in camels, 48.8% (95% CI 42.5–55.0) in goats, and 28.9% (95% CI 25.0–33.2) in sheep. In humans, seropositivity of Q-fever was 27.0% (95% CI 20.4–34.0), with prevalence in males of 28.9% vs 24.2% in females (OR = 1.3; 95% CI 0.6–2.5). Camel seropositivity of Q-fever was significantly associated with age (OR = 8.1; 95% CI 2.8–23.7). The individual apparent seroprevalence of RVF was 13.2% (95% CI 8.7–18.8) in humans, 17.9% (95% CI 11.0–27.8) in cattle, 42.6% (95% CI 34.8–50.7) in camels, 6.3% (95% CI 3.3–11.6) in goats and 7.4% (95% CI 4.7–11.5) in sheep. Camels had the highest seropositivity of both Q-fever and RVF. Only a weak correlation was observed between human and livestock seropositivity for both Q-fever and RVF. Only cattle and camels were seropositive for brucellosis by iELISA. The individual seroprevalence of brucellosis was 2.8(0.9–6.4) in humans, 1.5% (95% CI 0.2–5.2) in cattle and 0.6% (95% CI 0.0–3.2) in camels. This study showed the importance of zoonoses in Somali Region and is the first published study to describe RVF exposure in humans and livestock in the country. Even though human exposure to RVF virus was reported, public health sector of Somali Region has not given attention to such zoonoses. Collaboration between public and animal health sectors for further investigation on these zoonoses using the One Health concept is indispensable.

Seroprevalence of brucellosis, Q fever and Rift Valley fever in domestic ruminants in Guinea in 2017–2019

“…Consensus exists that Q fever seroprevalence is higher in goat and sheep is than in cattle [ 53 ]. This is confirmed in Africa by other studies in Chad, Egypt, Ethiopia and Kenya [ 32 , 33 , 37 , 54 , 55 ] while other reported similar Q fever seroprevalence between ruminant species [ 3 , 36 , 56 ]. Only few studies showed a higher cattle seroprevalence as we found in Guinea [ 57 , 58 ].…”

“…Our study confirms a significant seroprevalence in Guinean cattle (51 positives; 11.0%) but no seropositive goats and only 2 sheep. This difference between cattle and small ruminants was already observed in Western Africa and Ethiopia and could result from a more active circulation of B. abortus rather than B. melitensis in Guinea [ 3 , 6 , 33 , 36 , 37 ]. Indeed in Western Africa almost 90% of isolates are B. abortus [ 35 ] while B. melitensis has been associated with brucellosis epidemics in small ruminants mainly in Northern, Eastern and Central African countries [ 6 , 35 , 38 ].…”

“…brucellosis, Q fever and Rift Valley fever (RVF), conducted in a short-time period (2017 to mid-2019) on the same 1357 ruminants: 463 cattle, 408 goats and 486 sheep. Such an extensive comparison of the three NZDs in three different ruminant species has rarely been done in West Africa [ 3 ] and in Africa [ 32 , 33 ]. Consistent with previous studies, we found higher overall seroprevalence of Q fever (9.1%) and RFV (6.3%) than brucellosis (3.9%).…”

“…RVF seroprevalence studies in African ruminants have delivered contradictory results [ 23 ]. Most of them show similar seroprevalence levels between cattle and small ruminants [ 3 , 39 – 43 ] or higher seroprevalence in cattle [ 33 , 44 – 48 ]. Only few reports show higher seroprevalence in goats and sheep [ 49 , 50 ].…”

Rift Valley fever and Brucella spp. in ruminants, Somalia

“…Rift Valley fever (RVF) and brucellosis are important neglected zoonotic diseases with severe negative economic impact as they affect livestock productivity and survival, and threaten human health [ 1 , 2 ]. By reducing the productivity of livestock, these diseases significantly lower the quantity and quality of animal products and consequently erode household nutrition, income and food security [ 3 ].…”