Abstract
Simple SummaryRift Valley fever (RVF) is a mosquito-borne disease caused by the Rift Valley fever virus (RVFV) transmitted by various genera of mosquitoes usually classified into primary vectors and secondary vectors. The former, belonging to the genus Aedes, are known for their ability to lay drought resistant eggs that can maintain the virus on dry soil for many years in geomorphic structures in the form of shallow depressions. After heavy rains, mosquitoes hatch from these eggs, some of which are infected and transmit the virus to neighboring animals. The secondary vectors, mainly mosquitoes of the genera Culex, Anopheles, and Mansonia, can colonize these sites, reproduce in abundance, and subsequently spread RVFV. Although the northern regions of Cameroon host more than half of the country’s cattle, sheep, and goat populations, there is a dearth of information on the occurrence and transmission of RVFV and its vectors. The very common transhumance of animals during periods of drought leads to contact between domestic and wild animals and creates opportunities for cross-transmission of the virus. It also increases the possibilities of exposure of herds to vectors, in particular at water points. In addition, rare heavy rainfall, flooding, and irrigation-based agricultural practices in these regions provide conditions for vector proliferation and increase the risk of the spread of vector-borne diseases, including RVF. Therefore, this study aimed to determine species diversity and spatial distribution of potential RVFV vectors in the North Region of Cameroon. The study revealed the presence of potential primary and secondary vectors of RVFV with an abundance and a diversity varying according to the ecological sites studied. This presence of potential vectors with their variable number per trap, per night, or per site may create areas of variable risk for disease transmission to susceptible hosts. Molecular analysis (PCR) tests for RVFV RNA research and viral isolation methods on these vectors to determine their role in the epidemiology and control of RVF cannot be overemphasized.Rift Valley fever (RVF) is a major viral zoonosis transmitted by mosquitoes. The virus is endemic in most parts of sub-Saharan Africa and can affect humans, livestock, and wild ungulates. Knowledge of the biology of vectors of Rift Valley fever virus (RVFV) is essential for the establishment of effective control measures of the disease. The objective of this study was to determine the species diversity and relative abundance of potential RVFV vectors in the North Region of Cameroon. Adult mosquitoes were trapped during the wet and dry seasons from December 2017 to January 2019 with “EVS Light” traps with CO2 baits placed at selected sites. The captured mosquitoes were identified using dichotomous keys according to standard procedures. The abundance was calculated with regard to site, zone, and collection season. A total of 27,851 mosquitoes belonging to four genera (Aedes, Anopheles, Mansonia, and Culex) and comprising 31 species were caught (including 22 secondary vectors (98.05%) and nine primary vectors (1.94%). The total number of mosquitoes varied significantly depending on the locality (p-value < 0.001). The average number of mosquitoes collected per trap night was significantly higher in irrigated areas (p-value < 0.001), compared to urban and non-irrigated areas. The study revealed the presence of potential primary and secondary vectors of RVFV with varying abundance and diversity according to locality and ecological site in the North Region of Cameroon. The results showed that the genus Mansonia with the species Ma. uniformis and Ma. africana formed the dominant taxon (52.33%), followed by the genera Culex (45.04%) and Anopheles (2.61%). The need for molecular analysis (PCR) tests for RVFV RNA research and viral isolation methods on these vectors to determine their role in the epidemiology and control of RVF cannot be overemphasized.
Highlights
Rift Valley fever (RVF) is an infectious disease of many wild and domestic animal species [1,2]caused by an RNA virus belonging to the order Bunyavirales, family Phenuiviridae, genus Phlebovirus [3,4].The virus is transmitted by mosquitoes of several genera, including Aedes and Culex [5,6] and it was first isolated in 1931 during an outbreak in Kenya [7]
The need for molecular analysis (PCR) tests for Rift Valley fever virus (RVFV) RNA research and viral isolation methods on these vectors to determine their role in the epidemiology and control of RVF cannot be overemphasized
This study revealed the presence of potential primary and secondary vectors of RVFV with an abundance and a diversity varying according to the ecological sites studied
Summary
Rift Valley fever (RVF) is an infectious disease of many wild and domestic animal species [1,2]caused by an RNA virus belonging to the order Bunyavirales, family Phenuiviridae, genus Phlebovirus [3,4].The virus is transmitted by mosquitoes of several genera, including Aedes and Culex [5,6] and it was first isolated in 1931 during an outbreak in Kenya [7]. Rift Valley fever (RVF) is an infectious disease of many wild and domestic animal species [1,2]. Caused by an RNA virus belonging to the order Bunyavirales, family Phenuiviridae, genus Phlebovirus [3,4]. The virus is transmitted by mosquitoes of several genera, including Aedes and Culex [5,6] and it was first isolated in 1931 during an outbreak in Kenya [7]. Infection with the virus causes abortions and high mortality in young animals. Animals are mainly infected through bites of infected mosquitoes, while humans are typically exposed when they come into direct contact with infected bodily fluids and tissues of infected animals. Transmission to humans via mosquito bites has been associated to a milder disease and asymptomatic infections [8]
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