The risk of Rift Valley fever virus introduction and establishment in the United States and European Union

Abstract

Rift Valley fever virus (RVFV) is an arthropod-borne disease resulting in severe morbidity and mortality in both human and ruminant populations. First identified in Kenya in 1930, the geographical range of RVFV has been largely constrained to the African continent, yet has recently spread to new regions, and is identified as a priority disease with potential for geographic emergence. We present a systematic literature review assessing the potential for RVFV introduction and establishment in the United States (US) and European Union (EU). Viable pathways for the introduction of RVFV include: transport of virus-carrying vectors, importation of viremic hosts and intentional entry of RVFV as a biological weapon. It is generally assumed that the risk of RVFV introduction into the US or EU is low. We argue that the risk of sporadic introduction is likely high, though currently an insufficient proportion of such introductions coincide with optimal environmental conditions. Future global trends may increase the likelihood of risk factors for RVFV spread.

Encephalitic Arboviruses: Emergence, Clinical Presentation, and Neuropathogenesis

“…CEV and LACV cause an average of 75 cases of meningitis, encephalitis, or meningoencephalitis per year with the majority of disease due to LACV [34]. RVFV has caused periodic outbreaks in Kenya, Somalia, Tanzania, Saudi Arabia, and Yemen [35]. Outbreaks in endemic areas have occurred with up to 20,000 cases and > 500 deaths [36].…”

A dynamic, climate-driven model of Rift Valley fever

“…These eggs require inundation of water in order to hatch but must first undergo a dehydration period. If required, Aedes eggs can remain viable by resisting desiccation in dry conditions for months before rehydration occurs (Mondet et al, 2005;Pepin et al, 2010) and therefore have the potential to act as resevoirs of RVF (Porphyre et al, 2005) via transovarial transmission (Davies and Highton, 1980;Rolin et al, 2013). Culex lay their eggs directly on the surface of water bodies and as such increase greatly in abundance during periods of heavy rainfall and flooding and can also therefore amplify any RVF transmission (Bird et al, 2009;Anyamba et al, 2010).…”

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]. The presence of competent vectors and hosts is essential but must coincide with multiple factors such as sufficient livestock density, rainfall providing vector breeding sites, and Epidemic/epizootic cycle During epizootics, RVFV is maintained by horizontal transmission (HT) between ruminants and mosquitoes ( Fig.…”