Ecological and subject-level drivers of interepidemic Rift Valley fever virus exposure in humans and livestock in Northern Kenya

Abstract

Nearly a century after the first reports of Rift Valley fever (RVF) were documented in Kenya, questions on the transmission dynamics of the disease remain. Specifically, data on viral maintenance in the quiescent years between epidemics is limited. We implemented a cross-sectional study in northern Kenya to determine the seroprevalence, risk factors, and ecological predictors of RVF in humans and livestock during an interepidemic period. Six hundred seventy-six human and 1,864 livestock samples were screened for anti-RVF Immunoglobulin G (IgG). Out of the 1,864 livestock samples tested for IgG, a subset of 1,103 samples was randomly selected for additional testing to detect the presence of anti-RVFV Immunoglobulin M (IgM). The anti-RVF virus (RVFV) IgG seropositivity in livestock and humans was 21.7% and 28.4%, respectively. RVFV IgM was detected in 0.4% of the livestock samples. Participation in the slaughter of livestock and age were positively associated with RVFV exposure in humans, while age was a significant factor in livestock. We detected significant interaction between rainfall and elevation's influence on livestock seropositivity, while in humans, elevation was negatively associated with RVF virus exposure. The linear increase of human and livestock exposure with age suggests an endemic transmission cycle, further corroborated by the detection of IgM antibodies in livestock.

Exploring community-based reporting of livestock abortions for Rift Valley Fever surveillance in Uganda: A pilot study

“…Regarding brucellosis, goats had the highest prevalence than cattle. These findings align with previous research conducted in Uganda and Keny (Birungi et al, 2021;Kabami, 2023;Ndumu et al, 2021;Nyakarahuka et al, 2018aNyakarahuka et al, , 2023aNyakarahuka et al, , 2023bNyakarahuka et al, , 2023cNyamota et al, 2023;Tumusiime et al, 2023b).…”

“…Multiple reports/samples taken from the same farm could have skewed distribution towards cattle, or it may be that farmers were more likely to report cattle due to their value. Previous studies in Uganda (Nyakarahuka et al, 2018(Nyakarahuka et al, , 2023a(Nyakarahuka et al, , 2023c and neighbouring countries like Kenya (Hassan et al, 2020;Muturi et al, 2023) have also found surprisingly low rates of reports of abortions in sheep. However, the small number of sheep included in the study, means we could not measure the (relative) risk of infection infection in this species.…”

“…In leu of the potential for RVF to cause economic disruptions, the World Health Organisation (WHO) and Food Agricultural Organisation and World Organization for Animal Health (WOAH) have prioritized it among the key zoonotic diseases that have pandemic potential (Jenkin et al, 2023). The African Union Commission (AUC) has ranked it among the priority diseases for Africa, while in Uganda it is ranked third on the list of priority zoonotic diseases (PZDs) together with other viral haemorrhagic fevers (VHFs) including Ebola, Marburg and Crimean-Congo Haemorhagic fever (Sekamatte et al, 2018) by the Global Health Security Agenda (Kabami, 2023; Muturi et al, 2023). In some African countries like Sudan, Uganda, RVF has been reported as causing 10% mortality among adult livestock and abortions in ∼ 80-90% pregnant animals (Bird et al, 2009; Birungi et al, 2021; Hassan et al, 2020).…”

“…In addition to the lost foetuses, abortion poses an additional excess mortality risk for female animals (Muma et al, 2006). Livestock owners lose the potential financial benefits that would be achieved through the sale of lost animals and animal products including beef, hides, skins and milk (Kabami, 2023; Muturi et al, 2023).…”

MERS-Coronavirus across Kenya: a spatial examination of social and environmental drivers

“…In East Africa, changes in climate (i.e., hotter and drier trends) and agricultural land-use change have increased the likelihood of infectious disease emergence and transmission, such as Ebola virus, Flaviviruses, Usutu viruses, Chikungunya and O’nyong-nyong viruses, Bunyaviruses, and Rift Valley Fever and Crimean-Congo haemorrhagic viruses (Duygu et al, 2018; Fanelli & Buonavoglia, 2021; Fenollar & Mediannikov, 2018; Muturi et al, 2023; Pandit et al, 2022). Further, a combination of climate, agricultural and economic changes are supporting the spread of emerging pathogens from East Africa into the Middle East and Europe (Ryan et al, 2019; Xiao et al, 2015).…”