Vexans Arabiensis Research Articles

It’s risky to wander in September: Modelling the epidemic potential of Rift Valley fever in a Sahelian setting

Estimating the epidemic potential of vector-borne diseases, along with the relative contribution of underlying mechanisms, is crucial for animal and human health worldwide. In West African Sahel, several outbreaks of Rift Valley fever (RVF) have occurred over the last decades, but uncertainty remains about the conditions necessary to trigger these outbreaks. We use the basic reproduction number (R0) as a measure of RVF epidemic potential in northern Senegal, and map its value in two distinct ecosystems, namely the Ferlo and the Senegal River delta and valley. We consider three consecutive rainy seasons (July-November 2014, 2015 and 2016) and account for several vector and animal species. We parametrize our model with estimates of Aedes vexans arabiensis, Culex poicilipes, Culex tritaeniorhynchus, cattle, sheep and goat abundances. The impact of RVF virus introduction is assessed every week over northern Senegal. We highlight September as the period of highest epidemic potential in northern Senegal, resulting from distinct dynamics in the two study areas. Spatially, in the seasonal environment of the Ferlo, we observe that high-risk locations vary between years. We show that decreased vector densities do not greatly reduce R0 and that cattle immunity has a greater impact on reducing transmission than small ruminant immunity. The host preferences of vectors and the temperature-dependent time interval between their blood meals are crucial parameters needing further biological investigations.

Identification and RNAi Profile of a Novel Iflavirus Infecting Senegalese Aedes vexans arabiensis Mosquitoes.

The inland floodwater mosquito Aedes vexans (Meigen, 1830) is a competent vector of numerous arthropod-borne viruses such as Rift Valley fever virus (Phenuiviridae) and Zika virus (Flaviviridae). Aedes vexans spp. have widespread Afrotropical distribution and are common European cosmopolitan mosquitoes. We examined the virome of Ae. vexans arabiensis samples from Barkédji village, Senegal, with small RNA sequencing, bioinformatic analysis, and RT-PCR screening. We identified a novel 9494 nt iflavirus (Picornaviridae) designated here as Aedes vexans iflavirus (AvIFV). Annotation of the AvIFV genome reveals a 2782 amino acid polyprotein with iflavirus protein domain architecture and typical iflavirus 5’ internal ribosomal entry site and 3’ poly-A tail. Aedes vexans iflavirus is most closely related to a partial virus sequence from Venturia canescens (a parasitoid wasp) with 56.77% pairwise amino acid identity. Analysis of AvIFV-derived small RNAs suggests that AvIFV is targeted by the exogenous RNA interference pathway but not the PIWI-interacting RNA response, as ~60% of AvIFV reads corresponded to 21 nt Dicer-2 virus-derived small RNAs and the 24–29 nt AvIFV read population did not exhibit a “ping-pong” signature. The RT-PCR screens of archival and current (circa 2011–2020) Ae. vexans arabiensis laboratory samples and wild-caught mosquitoes from Barkédji suggest that AvIFV is ubiquitous in these mosquitoes. Further, we screened wild-caught European Ae. vexans samples from Germany, the United Kingdom, Italy, and Sweden, all of which tested negative for AvIFV RNA. This report provides insight into the diversity of commensal Aedes viruses and the host RNAi response towards iflaviruses.

Host-feeding patterns of Aedes (Aedimorphus) vexans arabiensis, a Rift Valley Fever virus vector in the Ferlo pastoral ecosystem of Senegal.

BackgroundHost-vector contact is a key factor in vectorial capacity assessment and thus the transmission of mosquito-borne viruses such as Rift Valley Fever (RVF), an emerging zoonotic disease of interest in West Africa. The knowledge of the host-feeding patterns of vector species constitutes a key element in the assessment of their epidemiological importance in a given environment. The aim of this work was to identify the blood meal origins of the mosquito Aedes vexans arabiensis, the main vector of RVF virus in the Ferlo pastoral ecosystem of Senegal.Methodology/principal findingsEngorged female mosquitoes were collected in Younouféré in the pastoral ecosystem in the Ferlo region during the 2014 rainy season. CO2-baited CDC light traps were set at six points for two consecutive nights every month from July to November. Domestic animals present around traps were identified and counted for each trapping session. Blood meal sources of engorged mosquitoes were identified using a vertebrate-specific multiplexed primer set based on cytochrome b. Blood meal sources were successfully identified for 319 out of 416 blood-fed females (76.68%), of which 163 (51.1%) were single meals, 146 (45.77%) mixed meals from two different hosts and 10 (3.13%) mixed meals from three different hosts. Aedes vexans arabiensis fed preferentially on mammals especially on horse compared to other hosts (FR = 46.83). Proportions of single and mixed meals showed significant temporal and spatial variations according to the availability of the hosts.ConclusionAedes vexans arabiensis shows an opportunistic feeding behavior depending on the host availability. This species fed preferentially on mammals especially on horses (primary hosts) and ruminants (secondary hosts).

Ecological distribution and population dynamics of Rift Valley fever virus mosquito vectors (Diptera, Culicidae) in Senegal

BackgroundMany zoonotic infectious diseases have emerged and re-emerged over the last two decades. There has been a significant increase in vector-borne diseases due to climate variations that lead to environmental changes favoring the development and adaptation of vectors. This study was carried out to improve knowledge of the ecology of mosquito vectors involved in the transmission of Rift Valley fever virus (RVFV) in Senegal.MethodsAn entomological survey was conducted in three Senegalese agro-systems, Senegal River Delta (SRD), Senegal River Valley (SRV) and Ferlo, during the rainy season (July to November) of 2014 and 2015. Mosquitoes were trapped using CDC light traps set at ten sites for two consecutive nights during each month of the rainy season, for a total of 200 night-traps. Ecological indices were calculated to characterize the different populations of RVFV mosquito vectors. Generalized linear models with mixed effects were used to assess the influence of climatic conditions on the abundance of RVFV mosquito vectors.ResultsA total of 355,408 mosquitoes belonging to 7 genera and 35 species were captured in 200 night-traps. RVFV vectors represented 89.02% of the total, broken down as follows: Ae. vexans arabiensis (31.29%), Cx. poicilipes (0.6%), Cx. tritaeniorhynchus (33.09%) and Ma. uniformis (24.04%). Comparison of meteorological indices (rainfall, temperature, relative humidity), abundances and species diversity indicated that there were no significant differences between SRD and SRV (P = 0.36) while Ferlo showed significant differences with both (P < 0.001). Mosquito collection increased significantly with temperature for Ae. vexans arabiensis (P < 0.001), Cx. tritaeniorhynchus (P = 0.04) and Ma. uniformis (P = 0.01), while Cx. poicilipes decreased (P = 0.003). Relative humidity was positively and significantly associated with the abundances of Ae. vexans arabiensis (P < 0.001), Cx. poicilipes (P = 0.01) and Cx. tritaeniorhynchus (P = 0.007). Rainfall had a positive and significant effect on the abundances of Ae. vexans arabiensis (P = 0.005). The type of biotope (temporary ponds, river or lake) around the trap points had a significant effect on the mosquito abundances (P < 0.001).ConclusionsIn terms of species diversity, the SRD and SRV ecosystems are similar to each other and different from that of Ferlo. Meteorological indices and the type of biotope (river, lake or temporary pond) have significant effects on the abundance of RVFV mosquito vectors.

Aedes mosquitoes in the Republic of the Sudan, with dichotomous keys for the adult and larval stages

ABSTRACTDescriptions of the mosquitoes of the Republic of the Sudan are mostly limited to works published more than 60 years ago. Khartoum State in central Sudan, which encompasses the capital city, has experienced many outbreaks of diseases caused by mosquito-borne pathogens, including Rift Valley fever. In this paper we focus on the composition of Aedes mosquitoes in high-risk areas in and around major agricultural projects. This is based on longitudinal surveillance of adults and larvae during the hot dry and rainy seasons in 2013. A total of 630 adult female mosquitoes were collected. Anopheles mosquitoes were the most abundant (n = 456, 72.4%), followed by Culex (n = 96, 15.2%) and Aedes (n = 78, 12.4%). Only three Aedes species were identified: Aedes caballus (n = 38, 48.7% of the Aedes), Aedes vexans arabiensis (n = 30, 38.5%) and Aedes caspius (n = 10, 12.8%). A total of 42,549 larvae were collected. Aedes larvae were the most abundant (n = 30,936, 72.7%), followed by Culex (n = 9656, 22.7%) and Anopheles (n = 1957, 4.6%). The Aedes larvae included Ae. caspius (n = 21,957, 71.0% of the Aedes), Ae. vexans arabiensis (n = 5577, 18.0%), Aedes quasiunivittatus (n = 107, 0.3%), Aedes dentatus (Theobald) (n = 204, 0.7%) and 3091 unidentifiable larvae (10.0%), denoted as Forms X, Y and Z. We discuss the bionomics of the four identified species of Aedes and provide updated keys for the identification of the mosquito genera and the larvae and adults of the Aedes species recorded from the Republic of the Sudan.

Genetic and phenotypic variation in central and northern European populations of Aedes (Aedimorphus) vexans (Meigen, 1830) (Diptera, Culicidae).

The floodwater mosquito Aedes vexans can be a massive nuisance in the flood plain areas of mainland Europe, and is the vector of Tahyna virus and a potential vector of Dirofilaria immitis. This epidemiologically important species forms three subspecies worldwide, of which Aedes vexans arabiensis has a wide distribution in Europe and Africa. We quantified the genetic and phenotypic variation in Ae. vexans arabiensis in populations from Sweden (northern Europe), Hungary, and Serbia (central Europe). A landscape genetics approach (FST , STRUCTURE, BAPS, GENELAND) revealed significant differentiation between northern and southern populations. Similar to genetic data, wing geometric morphometrics revealed two different clusters, one made by Swedish populations, while another included Hungarian and Serbian populations. Moreover, integrated genetic and morphometric data from the spatial analysis suggested groupings of populations into three clusters, one of which was from Swedish and Hungarian populations. Data on spatial analysis regarding an intermediate status of the Hungarian population was supported by observed Isolation-by-Distance patterns. Furthermore, a low proportion of interpopulation vs intrapopulation variance revealed by AMOVA and low-to-moderate FST values on a broader geographical scale indicate a continuous between-population exchange of individuals, including considerable gene flow on the regional scale, are likely to be responsible for the maintenance of the observed population similarity in Aе. vexans. We discussed data considering population structure in the light of vector control strategies of the mosquito from public health importance.

Prevalence of mosquitoes in Jazan Province, Saudi Arabia

During the period from February 2009 to September 2010, a mosquito (Diptera: Culicidae) survey was conducted in Jazan province the southwestern Region of Saudi Arabia,. A total of 29414 larval and 484 adult mosquitoes were collected from 41 sites, resembling 10 governorates. The collected mosquitoes related to 7 genera and 16 species. The genera were Aedes (A.) (1 species),Stegomyia (St.) (1 species), Aedimorphus (Am.) (1 species), Anopheles (An.) (4 species), Lutzia (L.) (1 species), Culex (Cx.) (7 species), and Culliseta (Cs.) (1species) and the mosquitoes species encountered were A. caspius Pallas, St. aegypti Linnaeus, Am. vexans arabiensis Patton, An. d'thali Patton, An. pretoriensis Theobald, An. Arabiensis Patton, An. turkhudi Liston, L. (Metalutzia) tigripes de Grandpre & de Charmoy, Cx. sitiens Wiedmann, Cx. decens Theobald, Cx. bitaeniorhynchus Giles, Cx. pipiens Linnaeus, Cx. quinquefasciatus Say, Cx. sinaiticus Kirkpatrick, Cx. tritaeniorhynchus Giles, and Cs. longiareolata Macquart. Cx. pipiens is the most prevalent species in Jazan region. It was encountered in 90 % of total collection sites. Cx. tritaeniorhynchus is less prevalent encountering in 80 % of total collection sites but An. Arabinesis was encountered in 70 % of total collection sites. St. aegypti, L. (Metalutzia) tigripes and Cx. sitiens were encountered in 50% of total collection sites. Cx. quinquefascitus, Am. vexans and Cs. longiareolata were encountered in 40 %, 30% and 20% of total collection, sites respectively. An. pretariensis, An. d'thuli, An. turkdi, Cx. decens, A. caspius and Cx. bitaeniorhynchus were the least prevalent mosquitoes in Jazan region encountered in only 10% of total collection sites. Am. vexans was the most abundant 57 % (17121), Culicine spp. 38.2 % (11416) , Anopheline spp. 1.5 % (433), St. aegypti 3 % (749) and each of Aedine, Lutzia and Culleseta were encountered less than 1%.

Identification of wild collected mosquito vectors of diseases using gas chromatography–mass spectrometry in Jazan Province, Saudi Arabia

Thirty-three species of mosquitoes have been reported from the Kingdom of Saudi Arabia. Several of these mosquitoes, Anopheles gambiae Giles s.l., Anopheles stephensi Liston, Culex pipiens Linnaeus, Culex quinquefasciatus Say, Culex tritaeniorhynchus Giles, Stegomyia aegypti (Linnaeus) and Aedimorphus vexans arabiensis (Patton) are known vectors of human and animal diseases. In this study, the cuticular hydrocarbon profiles of eight mosquito species using gas chromatography-mass spectrometry were analyzed. Wild collected fourth-instar larvae were reared, and single, newly emerged, unfed adult females were used for the analysis. A total of 146-160 peaks were detected from the cuticular extracts by gas chromatography. Repeated analysis of variance (ANOVA) and Tukey HSD Post Hoc test was used to test for quantitative differences in relative hydrocarbon quantity. In addition, a linear regression model was applied using Enter method to determine the diagnostic peaks for the eight mosquito specimens. The ANOVA test indicated that relative peaks were significant (P < 0.05) when selected pairs of peaks were compared. Also, seven compounds showed qualitative differences among the five mosquito vectors tested. The classes of constituents present were n-alkanes, monomethylalkanes, dimethylalkanes, trimethylalkanes, alkenes, branched aromatic hydrocarbons, aldehydes and esters. These compounds have a carbon chain length ranging from 8 to 18 carbons. The most abundant compound in all adult mosquito specimens was n-hexylacrylate [retention time (RT) 6.73 min], which was not detected in Cx. pipiens. In Cx. pipiens, the most abundant peak was benzaldehyde (RT 2.98 min). Gas chromatography-mass spectrometry is a suitable method to identify adult mosquitoes, especially from focal areas of public health concern such as Jazan Province, Saudi Arabia. This method allows a wide range of adult collected material to be identified with high accuracy.

The Status of Rift Valley Fever in Animals in Saudi Arabia: A Mini Review

In August-September 2000, an overwhelming outbreak of Rift Valley fever (RVF) struck the southwestern part of Saudi Arabia and adjoining Yemeni territories. During the outbreak, which was the first ever to be recorded outside Africa, around 40,000 animals, mostly sheep and goats, died or aborted and 883 cases, with 124 deaths, were recorded among humans in Saudi Arabia. An additional 1328 human cases, with 166 deaths, were concurrently recorded in northwestern Yemen. Vector studies in Saudi Arabia established Aedes vexans arabiensis and Culex (culex) triteniorynchus as the biological vectors of RVF virus in the region. Both of these species and several others, which could be potential vectors of the virus, occur throughout the Kingdom. Rigorous control measures were implemented, which succeeded in curtailing the infection and preventing its spread to other parts of the country. However, the virus persisted in a cryptic form in the original area of the epizootic, resulting in intermittent diagnosis of few cases throughout the past 10 years. To date, however, no evidence was found of virus activity outside that area. This review provides, from a veterinary perspective, a brief account of the events surrounding the epizootic and its present status in Saudi Arabia and emphasizes the need for vigilance, preparedness, and regular monitoring of the disease by serosurveillance methods.

The mosquito Aedes (Aedimorphus) vexans arabiensis as a probable vector bridging the West Nile virus between birds and horses in Barkedji (Ferlo, Senegal)

Active catches of adult females of Aedes vexans arabiensis Patton, (Diptera: Culicidae) Patton by nets or aspirator, were conducted in 2003 and 2004 in the vegetation at the edge of temporary ponds in Barkedji, Senegalese Ferlo area. Two hundred and forty-one engorged females were captured, dissected and the gut content adsorbed on a Whatman filter paper and analysed using the enzyme-linked immunosorbent assay (ELISA) technique to determinate the bloodmeal origin. Results indicated that Ae v. arabiensis fed primarily on mammals, including horses (35.7% of the bloodmeals), but also on birds (10%). Moreover, associations between horses and birds accounted for 42% of the mixed bloodmeals. These results show an opportunistic feeding behaviour and suggest that Ae v. arabiensis is a probable vector bridging the West Nile virus between horses and birds hosts in the Ferlo area.

Classification of ponds from high-spatial resolution remote sensing: Application to Rift Valley Fever epidemics in Senegal

During the rainy season the abundance of mosquitoes over the Ferlo region (Senegal) is linked to dynamic, vegetation cover and turbidity of temporary and relatively small ponds. The latter create a variable environment where mosquitoes can thrive and thus contribute to diffusion and transmission of diseases such as the Rift Valley Fever (RVF, with Aedes vexans arabiensis and Culex poicilipes mosquitoes) in the Ferlo. The small size and complex distribution of ponds require the use of high-spatial resolution satellite images for adequate detection. Here the use of SPOT-5 images (10 m-resolution) allows for detailed assessment of spatio-temporal evolution of ponds, through two new indices: i.e., the Normalized Difference Pond Index (NDPI), and the Normalized Difference Turbidity Index (NDTI). Small ponds less than 0.5 ha dominate whatever the time period. For example they represent nearly 65% of the total ponds during the peak of the rainy season, up to 90% at the end of the same season. Moreover, another product is proposed: the Zone Potentially Occupied by Mosquitoes (ZPOM). During the apex of the summer monsoon, it is found that RVF mosquitoes occupy 25% of the Ferlo region, while only 0.9% of the same area is covered by ponds. Overlapping areas occupied by grazing cattle and mosquitoes, enhance RVF virus transmission. The remotely sensed operational indices and products presented here are meant to better understand the mechanisms at stake and to contribute to the development of early warning systems in a changing climate and environment.

Rainfall triggered dynamics of Aedes mosquito aggressiveness

Inspired by Davidson method of estimating daily survivals of a structureless population of mosquitoes, we present a model which describes the behavior of floodwater mosquitoes in terms of emergence functions following a rainfall event, blood feeding frequency and parous stages, and survival at various stages. As a generalization of the Davidson formula, we have developed an approach for dealing with the dynamics of structured population of mosquitoes, and derived various formulas allowing assessment of demographic parameters like durations of gonotrophic cycles and (apparent) daily survivals. The method was subsequently applied to field data of floodwater mosquitoes Aedes vexans arabiensis, potential vectors of Rift Valley fever in West Africa, collected during the 2003 rainy season in Barkedji, Senegal. We found that mosquitoes emerged about 3 to 4 days following an efficient rainfall, and mosquito emergences, described by a bell shaped function, lasted for about 2 days. The mean duration of the gonotrophic cycle was 3 days and the apparent daily survival about 0.87 .

Rift Valley Fever Potential, Arabian Peninsula

To the Editor: Rift Valley fever (RVF) virus causes severe disease, abortion, and death in domestic animals (especially young sheep, cattle, and goats) in Africa and the Arabian Peninsula. Humans are infected by mosquitoes, which maintain epizootic transmission, or through exposure to infected animal tissue. Although human disease may be mild, sometimes severe retinitis, meningoencephalitis, or hemorrhagic fever syndromes may develop in patients. In Africa, epizootics and associated human epidemics usually follow heavy rainfall (1). RVF was first confirmed outside Africa in September 2000. The outbreak in southwestern coastal Saudi Arabia and neighboring coastal areas of Yemen resulted in an epizootic with >120 human deaths and major losses in livestock populations from disease and slaughter (2,3). RVF virus isolated from the floodwater mosquito Aedes vexans arabiensis during the outbreak was closely related to strains from Madagascar (1991) and Kenya (1997), which suggests that the virus was imported through infected mosquitoes or livestock from East Africa (3). The Arabian outbreak followed increased rainfall in nearby highlands that flooded the coastal areas and created ideal environments for mosquito populations similar to those found in RVF-endemic regions of East Africa (4). Most RVF activity was associated with flooded wadi agricultural systems; no cases were reported in the mountains or in dry sandy regions, where surface water does not accumulate long enough to sustain mosquito breeding. To provide early warning of conditions favorable for RVF epidemics, the National Aeronautics and Space Administration (NASA) and the Department of Defense Global Emerging Infections Surveillance and Response System (DoD-GEIS) monitor the satellite-derived normalized difference vegetation index (NDVI), which reflects recent rainfall and other ecologic and climatic factors (5–7). NDVI anomalies in the highlands east of affected areas during the 2000 outbreak (Figure A1 panel A) showed a spatial pattern (although of lower magnitude) similar to recent anomalies in those areas (Figure A1 panel B). Greater than normal NDVIs (20%–60%) were seen in the Sarawat Mountains, from just northeast of Djeddah, Saudi Arabia, and southwestward beyond Jizan and into Hodeidah governorate in Yemen during May and June 2005. Figure A1 Figure A1. Systeme Probatoire pour l'Observation de la Terre vegetation sensor 1 km normalized difference vegetation index (NDVI) anomaly images of the Arabian Peninsula region during June 2000 (A) and June 2005 (B). Data are the percentage deviation ... Satellite-derived rainfall estimates show that widespread rainfall occurred over most of western Saudi Arabia and Yemen from mid-April to mid-June 2005 (8) and accounts for the high magnitude and spatial pattern of observed NDVI anomalies in May and June 2005. Rainfall was concentrated in the mountainous regions east of the Red Sea coast, and was heaviest in the areas east of Djeddah and Jizan, with rainfall totals as high as 120 mm and 60–80 mm, respectively, during April 2005, compared with the same period in 2000 (10–50 mm) (Figure A1 panels C and D) and in southwestern Yemen, with totals as high as 120 mm during May. In the area east of Djeddah, total rainfall in April 2005 was 150 mm above the long-term average for that month. Flooding was reported in Hodeidah Governorate, Yemen during May (9) and could be expected in other Red Sea coastal areas following such heavy rainfall. This created habitats appropriate for breeding of mosquitoes capable of transmitting RVF, as occurred in 2000. No human cases of RVF have been reported in Saudi Arabia and Yemen since the 2000 outbreak, but in September 2004 the Saudi Ministry of Agriculture reported that 5 RVF-seropositive sheep had been identified during routine surveillance in Jizan where most infected persons were exposed during the outbreak in 2000 (2). The primary infection was estimated to have occurred in April 2004 (10). The NDVIs and rainfall patterns alerted the Yemen and Saudi Arabia Ministries of Health and Ministries of Agriculture to conduct field investigations with the Food and Agriculture Organization and the World Health Organization. Since RVF virus can be maintained in mosquito eggs for extended periods and transmitted under favorable conditions (6), the high magnitude of NDVI and rainfall patterns reported should prompt heightened veterinary and human surveillance for RVF in coastal Arabia and mass vaccination of susceptible animals. The current RVF model (7) is indicative of conditions that would promote vector breeding and could result in an outbreak of mosquitoborne diseases.

Isolation and genetic characterization of Rift Valley fever virus from Aedes vexans arabiensis, Kingdom of Saudi Arabia.

An outbreak of Rift Valley fever in the Kingdom of Saudi Arabia and Yemen in 2000 was the first recognized occurrence of the illness outside of Africa and Madagascar. An assessment of potential mosquito vectors in the region yielded an isolate from Aedes vexans arabiensis, most closely related to strains from Madagascar (1991) and Kenya (1997).

The 2000 epidemic of Rift Valley fever in Saudi Arabia: mosquito vector studies.

In mid-September 2000, Rift Valley fever (RVF) virus was diagnosed as the cause of infection in humans and livestock in Jizan Region, Saudi Arabia. This is the first time that this arbovirus has been found outside Africa and Madagascar. Collections of mosquitoes (Diptera: Culicidae) were therefore undertaken (from 25 September to 10 October) at eight sites during the epidemic to obtain mosquitoes for attempted RVF virus isolation. Among 23 699 mosquito females tested, six isolations of RVF virus were made from 15 428 Culex (Culex) tritaeniorhynchus Giles and seven from 8091 Aedes (Aedimorphus) vexans arabiensis Patton [corrected]. Minimum mosquito infection rates per 1000 at sites with infected mosquitoes were 0.3-13.8 Cx. tritaeniorhynchus and 1.94-9.03 Ae. v. arabiensis. Viral activity moved northwards as collecting was in progress and collectors 'caught up' with the virus at the two most northerly sites on the last two trapping evenings. Other species occurred in small numbers and were identified but not tested. Both Cx. tritaeniorhynchus and Ae. v. arabiensis were susceptible to RVF virus and transmitted between hamsters, and an additional quantitative test with Cx. tritaeniorhynchus showed that 71-73% of mosquitoes became infected after ingesting 6.9-7.9 log10 FFU/mL of virus; transmission rates were 10% (post-infection day 14) and 26% (post-infection day 20). It was concluded that both species were vectors on grounds of abundance, distribution, preference for humans and sheep, the virus isolations and vector competence tests.