Identifying Areas Suitable for the Occurrence of Rift Valley Fever in North Africa: Implications for Surveillance

Abstract

Rift Valley fever (RVF) is a vector-borne zoonotic disease that has caused widespread outbreaks throughout Africa and the Arabian Peninsula, with serious consequences for livestock-based economies and public health. Although there have never been any reports of RVF in Morocco, Algeria, Tunisia and Libya, it is a priority disease in the Maghreb, due to the threat of introduction of the virus through transboundary livestock movements or infected mosquito vectors. However, the implementation of surveillance activities and early warning contingency plans requires better knowledge of the epidemiological situation. We conducted a multicriteria decision analysis, integrating host distribution with a combination of important ecological factors that drive mosquito abundance, to identify hotspots and suitable time periods for RVF enzootic circulation (i.e. stable transmission at a low to moderate level for an extended period of time) and an RVF epizootic event (i.e. a sudden occurrence of a large number of infected animals over a large geographic area) in the Maghreb. We also modelled vector species distribution using available information on vector presence and habitat preference. We found that the northern regions of the Maghreb were moderately suitable for RVF enzootics, but highly suitable for RVF epizootics. The vector species distribution model identified these regions as the most favourable mosquito habitats. Due to the low density of animal hosts and arid conditions, the desert region showed low RVF suitability, except in oases. However, the presence of competent vectors in putative unsuitable areas underlines the need for further assessments of mosquito habitat preference. This study produced monthly RVF suitability maps useful for animal health managers and veterinary services involved in designing risk-based surveillance programmes. The suitability maps can be further enhanced using existing country-specific sources of information and by incorporating knowledge - as it becomes available - on the epidemiology of the disease and distribution of vectors in the Maghreb.

Prevalence and identification of arthropod-transmitted viruses in Kassala state, Eastern Sudan

“…RVFV causes epizootic outbreaks in tropical areas, mainly in Africa, including Sudan, which is the largest country in Africa [12][13][14][40][41][42]; however, we detected only five infections in adult patients in this study. Another study conducted on 290 patients in eastern Sudan revealed the presence of highly seropositive RVFV IgG [18].…”

“…Dengue, yellow fever, chikungunya, Rift Valley fever, alkhurma haemorrhagic fever, and Sindbis viruses have been reported in more than 34 countries in sub-Saharan Africa and Middle East [10][11][12][13][14]. YFV originated in Africa and spread with the slave trade dating back to at least 1650 [15,16].…”

Rift Valley fever virus: strategies for maintenance, survival and vertical transmission in mosquitoes

“…Potential routes of entry of RVFV into Europe and the USA have been identified [22][23][24] and the risk of establishment into North Africa [25], Italy [26], the Netherlands [27] and Spain [28] reviewed. The conclusions collectively identify a need to determine competence in local vectors to accurately evaluate risks, and guide control and surveillance activities [23,24].…”

A scoping review of importation and predictive models related to vector-borne diseases, pathogens, reservoirs, or vectors (1999–2016)

“…Not all publications included parameters on the vector, despite all publications investigating VBDs. These publications were focused on transmission in humans and reservoirs [41,42].…”