M. A. Miranda

A Broad Assessment of Factors Determining Culicoides imicola Abundance: Modelling the Present and Forecasting Its Future in Climate Change Scenarios

Bluetongue (BT) is still present in Europe and the introduction of new serotypes from endemic areas in the African continent is a possible threat. Culicoides imicola remains one of the most relevant BT vectors in Spain and research on the environmental determinants driving its life cycle is key to preventing and controlling BT. Our aim was to improve our understanding of the biotic and abiotic determinants of C. imicola by modelling its present abundance, studying the spatial pattern of predicted abundance in relation to BT outbreaks, and investigating how the predicted current distribution and abundance patterns might change under future (2011–2040) scenarios of climate change according to the Intergovernmental Panel on Climate Change. C. imicola abundance data from the bluetongue national surveillance programme were modelled with spatial, topoclimatic, host and soil factors. The influence of these factors was further assessed by variation partitioning procedures. The predicted abundance of C. imicola was also projected to a future period. Variation partitioning demonstrated that the pure effect of host and topoclimate factors explained a high percentage (>80%) of the variation. The pure effect of soil followed in importance in explaining the abundance of C. imicola. A close link was confirmed between C. imicola abundance and BT outbreaks. To the best of our knowledge, this study is the first to consider wild and domestic hosts in predictive modelling for an arthropod vector. The main findings regarding the near future show that there is no evidence to suggest that there will be an important increase in the distribution range of C. imicola; this contrasts with an expected increase in abundance in the areas where it is already present in mainland Spain. What may be expected regarding the future scenario for orbiviruses in mainland Spain, is that higher predicted C. imicola abundance may significantly change the rate of transmission of orbiviruses.

Spatial distribution of Culicoides imicola, the main vector of bluetongue virus, in Spain

BLUETONGUE (BT) is a disease caused by a virus of the genus Orbivirus that is mainly transmitted among vertebrate hosts by several species of biting midges of the genus Culicoides (Diptera: Ceratopogonidae) (Du Toit 1944, Mellor and Pitzolis 1979). BT virus (BTV) can replicate in all species of ruminants and causes severe disease in certain breeds of sheep and some species of deer (Taylor 1986, MacLachlan 1994). In Europe, the main vector for BTV is Culicoides imicola Kieffer (Mellor 1996), although species included within the Culicoides obsoletus group have been proposed as the probable vector of BTV in some European areas (Mellor and Wittmann 2002, Savini and others 2003, De Liberato and others 2005). Historically, BTV has made only brief, periodic incursions into Europe (Manso-Ribeiro and others 1957, Mellor and Pitzolis 1979, Jennings and others 1983). However, a large BT epidemic, which started in 1998, has affected many European countries, including several that had not previously experienced the virus, and is still ongoing in some areas. This extension of BTV into Europe appears to be partially linked to the recent northward expansion of C imicola across the Mediterranean European countries – an expansion that seems to be a consequence of recent changes in the European climate (Purse and others 2005). In Spain, during the last BT epidemic, BTV entered the Balearic Islands from eastern Europe in 2003. In late 2004, further incursions occurred from Morocco into south-west Spain, and in late 2005 BTV was spreading northwards in peninsular Spain. Previous studies suggested that the distribution of C imicola in Spain was mainly restricted to southwest peninsular Spain, and the Toledo province was thought to be the northernmost site for the species (Ortega and Holbroock 1994, Ortega and others 1997, 1998, Rawlings and others 1997). In the past five years, however, local surveys have reported, for the first time, the presence of C imicola in the Balearic Islands (Miranda and others 2003), in coastal areas of Catalonia (Sarto i Monteys and others 2003), in Madrid and in the eastern coastal provinces of Alicante and Murcia (Martinez 2004; F. Collantes, personal communication). A national surveillance programme aimed at estimating the spatial distribution of C imicola in Spain was carried out during 2004. The landmass of peninsular Spain was divided into 202 quadrats of 50 x 50 km; 100 evenly distributed quadrats were selected as sampling units, and within each sampling unit at least two livestock holdings or farms were sampled. In addition, seven farms were sampled in the Balearic Islands (three on Majorca, three on Minorca and one on Ibiza), five in the Canary Islands (two each on Tenerife and Fuerteventura and one on Gran Canaria), and one in the town of Ceuta, a Spanish town in northern Africa. Two samplings were carried out: one in spring/summer (April to June) and another in summer/autumn (September to November). Each farm was sampled for two consecutive nights. A 4 W UV light trap fitted with a suction fan (Miniature Blacklight model 1212; John Hock) was placed outside each selected farm but within 30 m of livestock, at between 1·7 and 2·5 m above ground level. The traps were lit from just before dusk until after dawn over both sampling days. Specimens of C imicola were identified on the basis of their wing pattern, as described by Rawlings (1996). In approximately one-quarter of the sampling units more than two farms were sampled; most extra samplings occurred during the summer/autumn period. In total, 364 farms were sampled; 229 during spring/summer and 292 in summer/ autumn; 159 of the farms were sampled in both periods. A total of 12,878 C imicola were trapped over the course of both sampling periods. The species was found on all the farms sampled in the Balearic Islands, with the exception of the one on Ibiza; however, it is known that C imicola is present on Ibiza, albeit in very low numbers (B. V. Purse, M. A. Miranda, personal communication). No C imicola were captured on the farm sampled in Ceuta, and the species was not detected in the Canary Islands. C imicola was found in all the provinces of peninsular Spain where it had previously been reported (Fig 1) except Sevilla, where it was not detected on any of the farms sampled. In addition, C imicola was found for the first time in nine other provinces, mainly located to the north and east of the previously defined distribution area of the species. The highest numbers of C imicola trapped in one sampling session of two consecutive nights in provinces where the species had previously been reported were in Malaga (6304 specimens), Huelva (973 specimens) and Jaen (348 specimens). Among the nine provinces where C imicola was recorded for the first time, the highest catches were in Albacete (480 specimens), Avila (194 specimens) and Granada (66 specimens). All of the sampling sessions with the highest catches occurred during the summer/autumn sampling period. The altitudes of the sampled farms ranged from 5 to 1400 m above sea level. The highest altitude at which C imicola was Short Communications

Host feeding patterns of Culicoides species (Diptera: Ceratopogonidae) within the Picos de Europa National Park in northern Spain.

Blood meal identification can provide information about the natural host-feeding patterns or preferences of Culicoides species. Such information could indirectly provide data indicating which reservoirs are significant in associated vector-borne diseases. We positively identified the host species through DNA sequencing of the cytochrome b gene in 144 of the 170 (84.7%) blood meal specimens tested. In the remaining samples, identification of the blood-meal source was unsuccessful, possibly due to the post-ingestion time prior to sampling or the availability of the species-specific cytochrome b gene sequences in the database. The majority of identified blood meals were derived from mammalian blood (95.8%), and only six contained chicken blood. We identified five species as mammalian hosts for Culicoides spp.: sheep (87.7%), human (6.5%), cattle (3.7%) and Savis Pine Vole (Micrototus savii) (2.1%). The results suggested that large mammals, specifically ruminants, were most frequently fed upon by biting midges (Culicoides spp.), but evidence of opportunistic feeding behaviour was also found. Host feeding behaviour of Culicoides species may also be influenced by the relative abundance of a particular host species in the area being studied. In this sense, Savis Pine Vole, a wild species, was found to be a locally relevant host and a putative reservoir for viruses transmitted by species of biting midges belonging to the Culicoides genus. Finally, feeding on multiple potential host species was observed. One midge acquired blood meals from human and chicken hosts, while four other midges fed on two different sheep.

Protection of livestock against bluetongue virus vector Culicoides imicola using insecticide-treated netting in open areas.

The protection of livestock against Culicoides species (Diptera: Ceratopogonidae) using physical barriers or chemically treated barriers is difficult owing to the small size of these biting midges and animal welfare concerns associated with the reduction of air flow. Culicoides imicola Kieffer is the main bluetongue virus vector in the Mediterranean basin, including the southern Iberian peninsula, where livestock is mainly housed in open pens or sheds which offer no physical protection against C. imicola. In this study we assessed the efficacy of surrounding yearling ewe pens with a canvas barrier or a cypermethrin‐treated canvas barrier in reducing the entry of Culicoides spp. and C. imicola. Analyses were based on comparisons of Culicoides catches in traps in pens with and without barriers, and in traps located outside pens. Although there was no clear reduction in the abundance of Culicoides other than C. imicola in pens with either barrier, the C. imicola presence was markedly reduced by the insecticide‐treated barrier compared with the untreated barrier; the latter did not reduce the abundance of this species in pens. Estimates of the protection conferred against C. imicola by the treated barrier differed depending on whether catch comparisons were based on outside traps or on traps located inside no‐barrier pens. The results suggest that the use of insecticide‐treated barriers may reduce contact between livestock and C. imicola in open areas or sheds. More research is necessary to assess the degree of protection as a function of barrier height, C. imicola abundance, and the size of the area to be protected.

Review of ten-years presence of Aedes albopictus in Spain 2004–2014: known distribution and public health concerns

Ten years have gone by since the Asian tiger mosquito Aedes albopictus was recorded for the first time in Spain. In this paper, all relevant published information about this vector in Spain for the period 2004–2014 is reviewed. The known distribution for 2014 is provided, including all historical records (published and unpublished data) and the results from samplings of the last year. The consequences on public health about the presence of the Asian tiger mosquito in Spain are also highlighted. Further, legal aspects and control plans related to the management and diseases transmitted by this invasive vector species are also discussed.

The impact of indoor residual spraying of deltamethrin on dengue vector populations in the Peruvian Amazon.

Dengue is an important public health problem in the Amazon area of Peru, resulting in significant morbidity each year. As in other areas of the world, ultra-low volume (ULV) application of insecticides is the main strategy to reduce adult populations of the dengue vector Aedes aegypti, despite growing evidence of its limitations as a single control method. This study investigated the efficacy of deltamethrin S.C. applied through indoor residual spraying (IRS) of dwellings in reducing A. aegypti populations. The residual effect of the insecticide was tested by monthly bioassays on the three most common indoor surfaces found in the Amazon area: painted wood, unpainted wood and brick. The results showed that in an area with moderate levels of A. aegypti infestation, IRS dramatically reduced all immature indices the first week after deltamethrin IRS application and the adult index from 18.5 to 3.1, four weeks after intervention (p<0.05). Even though housing conditions facilitated reinfestation with A. aegypti (100% of the houses have open roof eaves, 31.5% lack sewage systems, and 60.4% collected rain in open containers), indices remained low compared to baseline 16 weeks after insecticide application. Bioassays showed that deltamethrin S.C. caused mortalities >80% 8 weeks after application on all types of surfaces. The residual effect of the insecticide was greater on brick than on wooden walls (p<0.05). Our results demonstrate that IRS can have both an immediate and sustained effect on reducing adult and immature A. aegypti populations and should be considered as an adult mosquito control strategy by dengue vector control programs.

Colonization of the Mediterranean Basin by the vector biting midge species #Culicoides imicola#: an old story

Understanding the demographic history and genetic make‐up of colonizing species is critical for inferring population sources and colonization routes. This is of main interest for designing accurate control measures in areas newly colonized by vector species of economically important pathogens. The biting midge Culicoides imicola is a major vector of orbiviruses to livestock. Historically, the distribution of this species was limited to the Afrotropical region. Entomological surveys first revealed the presence of C. imicola in the south of the Mediterranean basin by the 1970s. Following recurrent reports of massive bluetongue outbreaks since the 1990s, the presence of the species was confirmed in northern areas. In this study, we addressed the chronology and processes of C. imicola colonization in the Mediterranean basin. We characterized the genetic structure of its populations across Mediterranean and African regions using both mitochondrial and nuclear markers, and combined phylogeographical analyses with population genetics and approximate Bayesian computation. We found a west/east genetic differentiation between populations, occurring both within Africa and within the Mediterranean basin. We demonstrated that three of these groups had experienced demographic expansions in the Pleistocene, probably because of climate changes during this period. Finally, we showed that C. imicola could have colonized the Mediterranean basin in the Late Pleistocene or Early Holocene through a single event of introduction; however, we cannot exclude the hypothesis involving two routes of colonization. Thus, the recent bluetongue outbreaks are not linked to C. imicola colonization event, but rather to biological changes in the vector or the virus.

Collection of Culicoides spp. with four light trap models during different seasons in the Balearic Islands

Bluetongue (BT) is a viral disease that affects ruminants, being especially pathogenic in certain breeds of sheep. Its viral agent (bluetongue virus; BTV) is transmitted by several species of Culicoides biting midges (Diptera: Ceratopogonidae). Different models of suction light traps are being used in a number of countries for the collection of BTV vector species. To determine the relative effectiveness of different light traps under field conditions, four traps (Onderstepoort, Mini-CDC, Rieb and Pirbright) were compared. These traps were rotated between four sites on a cattle farm in Mallorca (Balearic Islands, Spain) for several non-consecutive nights. Results showed remarkable disparities in the efficacy of the traps for the collection of Culicoides midges. The highest number of midges collected in the Onderstepoort trap (x¯±SD=62±94.2) was not significantly different from that collected in the Mini-CDC (x¯±SD=58±139.2). The Rieb trap collected the lowest number of midges (x¯±SD=3±4.0). Significantly higher mean numbers of midges were collected in the Onderstepoort than in either the Pirbright (P=0.002) or Rieb traps (P=0.008). There were also differences in the Culicoides species composition as determine with the various traps. These results indicate that the Onderstepoort or Mini-CDC traps will be more effective than either the Rieb or Pirbright traps for the collection of large numbers of Culicoides midges.

Detrimental effect of cypermethrin treated nets on Culicoides populations (Diptera; Ceratopogonidae) and non-targeted fauna in livestock farms.

Bluetongue (BT) is an important disease of ruminants which exhibits its most severe clinical signs on cattle and especially on certain breeds of sheep. The known vectors of BT are small insects of the genus Culicoides (Diptera; Ceratopogonidae). Two species from this genus - Culicoides imicola and Culicoides obsoletus - play the major role in the transmission of the disease in Europe. Several prophylactic methods are used to avoid transmission; however, an easy and cost-effective preventive technique would be very useful for the control of the Culicoides populations near the animals. In the present study, the insecticide effect of cypermethrin treated nets on a Culicoides population was evaluated. A polyethylene net sprayed with 1L cypermethrin solution (1%) surrounding a UV light suction trap was placed at a cattle farm in Majorca (Balearic Islands). Collections of Culicoides and other fauna from the trap and floor around the net were compared with a control. Results showed no significant differences in the collection of Culicoides midges between the insecticide-treated net and the control. However, significant differences were observed in the collection of the non-target fauna between the treated net and the control, indicating that the dose used in the present trial was enough to kill most of the arthropods that contacted the net. The reasons for these equivocal findings and means to improve this technique for the control of Culicoides midges are discussed.

Parasitism of Bactrocera oleae (Diptera; Tephritidae) by Psyttalia concolor (Hymenoptera; Braconidae) in the Balearic Islands (Spain)

Psyttalia concolor (Hymenoptera; Braconidae) was introduced to Spain in the early 1970s to control the olive fruit fly Bactrocera oleae. Previous studies showed that P. concolor was poorly adapted to temperate zones, such as the Balearics. In this study, we demonstrate a high rate of natural parasitism of B. oleae by P. concolor in Majorca (Balearic Islands). Surveys were carried out from August to September 2007 in two organically‐farmed olive orchards and two insecticide‐managed orchards. A total of 250 olive fruits were examined weekly from each of the orchards. Olives were kept under laboratory conditions until the emergence of B. oleae pupae, which were collected and placed in Petri dishes until the emergence of B. oleae and/or P. concolor adults. In addition, red sticky spheres and yellow sticky panel traps were placed in every orchard for monitoring adults of P. concolor. Red spheres captured more individuals of the parasitoid when compared with the yellow panels. Seasonal average parasitism levels of B. oleae pupae by P. concolor were high (22.4% and 23.4%) in the two organically‐farmed orchards and 0% in the insecticide treated orchards. The high rates of parasitism by P. concolor found in the organically‐farmed olive orchards supports the use of this parasitoid for the biological control of B. oleae in the Balearic Islands.