A One Health perspective to identify environmental factors that affect Rift Valley fever transmission in Gezira state, Central Sudan

Abstract

BackgroundRift Valley fever (RVF) is a zoonotic viral vector-borne disease that affects both animals and humans and leads to severe economic consequences. RVF outbreaks are triggered by a favorable environment and flooding, which enable mosquitoes to proliferate and spread the virus further. RVF is endemic to Africa and has spread to Saudi Arabia and Yemen. There is great concern that RVF may spread to previously unaffected geographic regions due to climate change. We aimed to better understand the spatiotemporal pattern of the 2007 RVF outbreak at the human–animal–environment interface and to determine environmental factors that may have effects on RVF occurrence in Gezira state, Sudan.Materials and methodsWe compiled epidemiological, environmental, and spatiotemporal data across time and space using remote sensing and a geographical information system (GIS). The epidemiological data included 430 RVF human cases as well as human and animal population demographic data for each locality. The cases were collected from 41 locations in Gezira state. The environmental data represent classified land cover during 2007, the year of the RVF outbreak, and the average of the Normalized Difference Vegetation Index (NDVI) for 6 months of 2007 is compared with those of 2010 and 2014, when there was no RVF outbreak. To determine the effect of the environmental factors such as NDVI, soil type, and RVF case’s location on the Blue Nile riverbank on RVF incidence in Gezira state, a multilevel logistic regression model was carried out.ResultsWe found that the outbreak in Gezira state occurred as a result of interaction among animals, humans, and the environment. The multilevel logistic regression model (F = 43,858, df = 3, p = 0.000) explained 23% of the variance in RVF incidence due to the explanatory variables. Notably, soil type (β = 0.613, t = 11.284, p = 0.000) and NDVI (β = − 0.165, t = − 3.254, p = 0.001) were the explanatory environmental factors that had significant effects on RVF incidence in 2007 in Gezira state, Sudan.ConclusionsPrecise remote sensing and the GIS technique, which rely on environmental indices such as NDVI and soil type that are satellite-derived, can contribute to establishing an early warning system for RVF in Sudan.Future preparedness and strengthening the capacity of regional laboratories are necessary for early notification of outbreaks in animals and humans.

The Emergence of Rift Valley Fever in Gedaref State Urges the Need for a Cross-Border One Health Strategy and Enforcement of the International Health Regulations

“…Several components of a one health strategy might be readily available for application, including limiting the movement of livestock between the RVF-endemic and non-RVF-endemic areas, making the currently available vaccine against RVF (for use on animals) accessible to herd owners, raising the awareness of herd owners about the interconnected health of humans and animals, and how to live safely together. Additionally, implementing national surveys to determine the diversity, transmission, and risks associated with the emergence of zoonotic diseases, and periodically investigating the environmental suitability for emergence, are needed [ 30 ]. In the long term, establishing a molecular surveillance system for the detection of pathogens in vector populations prior to their emergence among humans and animal populations, and developing a national institute in charge of implementing the one health strategy, might be useful for the early detection and responses to emerging zoonotic diseases.…”

Detection of Rift Valley Fever virus inter-epidemic activity in Kilimanjaro Region, North Eastern Tanzania

“…It is also considered an important threat to agriculture in African countries, including Tanzania [7][8][9]. Transmission of RVFV to animals is mainly through bites by infected Aedes and Culex mosquitoes, whereas human transmission is largely accomplished through direct contact with tissues of RVFV-infected animals [10]. Most people infected by RVFV remain asymptomatic, although a small percentage present with clinical disease [11][12][13].…”

Paving the way for human vaccination against Rift Valley fever virus: A systematic literature review of RVFV epidemiology from 1999 to 2021

“…To fully understand the ecology of local transmission such broad-based human studies need to be conducted concurrently with robust animal surveys. Recent reviews and policy papers in the human and animal health RVFV literature call for a greater emphasis on a One Health management approach, both in research and control efforts [127, 209, 210]. A better understanding of viral transmission to all species during interepidemic periods, with an improvement of diagnostic sampling frameworks, are within reach in the next decade.…”

“…In Sudan, males aged 15-29 years were overrepresented among patients who presented with severe disease, as compared to females of the same age [125]. Environmental factors, such as excess rainfall and muddy soil linked to emergence of mosquito blooms have also been linked to severe human disease in both Sudan and Kenya [126,127]. Severity of human RVF was associated with the presence of concomitant coinfections.…”