The Temperature-Associated Effects of Rift Valley Fever Virus Infections in Mosquitoes and Climate-Driven Epidemics: A Review

Abstract

Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic disease within the genus Phlebovirus. Symptoms of the disease in animals range from moderate to severe febrile illness, which significantly impacts the livestock industry and causes severe health complications in humans. Similar to bunyaviruses in the genus Orthobunyavirus transmitted by mosquitoes, RVFV progression is dependent on the susceptibility of the physical, cellular, microbial, and immune response barriers of the vectors. These barriers, shaped by the genetic makeup of the mosquito species and the surrounding environmental temperature, exert strong selective pressure on the virus, affecting its replication, evolution, and spread. The changing climate coupled with the aforementioned bottlenecks are significant drivers of RVF epidemics and expansion into previously nonendemic areas. Despite the link between microclimatic changes and RVF outbreaks, there is still a dearth of knowledge on how these temperature effects impact RVF transmission and vector competence and virus persistence during interepidemic years. This intricate interdependence between the virus, larval habitat temperatures, and vector competence necessitates increased efforts in addressing RVFV disease burden. This review highlights recent advancements made in response to shifting demographics, weather patterns, and conveyance of RVFV. Additionally, ongoing studies related to temperature-sensitive variations in RVFV-vector interactions and knowledge gaps are discussed.

Keywords: Culex and Aedes species; Orthobunyavirus; Phlebovirus; mosquito genetics and immunity; reassortment; temperature effects; transovarial transmission; vector competence; vector-borne diseases.

Figure 1

Overall, temperature can impact the natural habitats of mosquitoes (Section 2) and virus genetics (Section 3). In response to environmental stresses like temperature, mosquitoes exploit inherent gene regulatory systems to preserve fitness and modify their phenotypes (Section 3.1, Section 3.2, Section 3.3, Section 3.4 and Section 3.5) indicated by the red dotted arrows. The black arrows indicate various factors that contribute to mosquito vector capacity and RVF transmission. In effect, temperature can modify key elements of vector competence such as the microbiome (Section 3.5) shifting the balance in favor of increased or decreased virus transmission and persistence via modifications to transmission mechanisms including TOT (Section 2.1). EIP: extrinsic incubation period; TOT: transovarial transmission. This figure was created in BioRender. Lab, K. (2024).