Seroprevalence of rift valley fever virus and risk factors among domestic ruminants at the human- livestock- wildlife interfaces of Lake Mburo-Nakivale and Pian-Upe conservation areas

Abstract

Rift Valley Fever (RVF) is one of the major zoonotic diseases in Uganda, affecting livestock, wildlife, and humans, and transmitted by mosquitoes. Although wildlife potentially harbors RVF virus (RVFV) strains, livestock exposure to RVFV at human-livestock-wildlife interfaces remains underexplored. This cross-sectional study was conducted in Satellite Research Sites (SRS) within Lake Mburo-Nakivale Conservation Area (LMCA) and Pian-Upe Conservation Area (PUCA). Using a 2- stage sampling design, livestock herds were randomly selected from the selected villages within the SRS. Blood samples and qualitative data were collected. A total of 1,572 livestock were sampled from both LMCA and PUCA. Serum samples were analyzed using a validated indirect ELISA RVF virus Nucleoprotein (NP) protocol to determine the seropositivity of anti-RVFV IgG antibodies. Descriptive, crude, and adjusted logistic regression analysis was performed on both laboratory and field data. Overall RVFV seroprevalence was 34.7% (546/1572), (95% CI, 32.4-37.1%). RVFV Seropositivity per conservation area was 38.3% (297/775) in LMCA, and 31.2% (249/797) in PUCA. RVFV Seropositivity per species was 41.3% (66/160) in sheep; 33.3% (290/870) in cattle and 35.1% (190/542) in goats. Multivariate logistic regression indicated that being over 5 years old (AOR = 1.4; 95% CI, 1.1-1.8; p=0.005), grazing in park and farm areas (AOR = 4.9; 95% CI, 1.7-14.2; p=0.003), and animals watered with piped water (AOR = 3.7; 95% CI, 1.1-12.0; p=0.030) or from rivers/streams (AOR = 2.3; 95% CI, 1.3-4.2; p=0.009) were significantly associated with RVFV exposure. There was high RVFV seropositivity reported among the domestic ruminants sampled in this study. More RVFV seropositive animals were distributed in herds closest to the national parks, and natural resources (lakes and rivers) in the areas. Animals older than 5 years, and herds which utilized both park and farm as grazing pattern, as well as those which were watered using piped water, and rivers or streams were seropositive at multivariate logistic regression analysis. These findings could guide in the development of effective RVF control strategies in these high risk areas of Uganda.