Potential Vector Species Research Articles

Larval development and emergence sites of farm‐associated Culicoides in the United Kingdom

Culicoides biting midges (Diptera: Ceratopogonidae) are the biological vectors of internationally important arboviruses of livestock including bluetongue virus (BTV). Information on the habitats used by Culicoides for larval development is valuable for establishing targeted vector control strategies and for improving local scale models of vector abundance. This study combines emergence trap collections of adult Culicoides identified using molecular markers and physiochemical measurements of habitats to investigate larval development sites of Palaearctic Culicoides in South East England. The known range of larval habitats for several Culicoides species is extended and the potential BTV vector species C. obsoletus and C. scoticus are confirmed to co-occur in many larval habitats. The presence of emerging C. obsoletus was favoured by increasing substrate moisture level [odds ratio (OR) 6.94 (2.30; 20.90)] and substrate pH [OR 4.80 (1.66; 13.90)] [bias-corrected Dxy : 0.68; area under the curve (AUC): 0.86] rather than any particular larval habitat type, as expected for a species with relatively wide larval habitat preference. Of the newly emerged sub-genus Avaritia individuals collected, 23% were observed to have a degree of abdominal pigmentation commonly inferred to indicate parity. If consistent across species and locations, this observation represents a potential source of error for age structure analyses of Culicoides populations.

Introduction to the Special Issue on Epidemiology and Ecology of Parasitic Diseases

Human African Trypanosomiasis (HAT), commonly known as sleeping sickness is a vector-borne parasitic infection caused by protozoa of the genus Trypanosoma. It can be fatal if left untreated. HAT is found in sub-Saharan Africa, but is restricted to the range of its tsetse vector. In recent decades, the foci of HAT infections have changed and it has been suggested that climate change and changes to the habitats of the tsetse vectors have influenced the observed changes. The paper by Tongue et al. clearly demonstrates the effects of habitat change on the transmission of African trypanosomiasis. Certain subspecies of Glossina have adjusted to the decrease in natural habitats by exhibiting peri-domestic behaviors that allow them to live in urban and suburban habitats near humans. The increase in urban and suburban habitats for subspecies of the tsetse vector Glossina has reduced the effectiveness of efforts to control, much less eliminate, transmission of the causative species Trypanosoma brucei rhodesiense (causes the acute form of the disease) and Trypanosoma brucei gambiense (causes the chronic from of the disease). This study provides a cautionary tale about the influence of habitat changes and climate change on the future of HAT transmission (and other pathogens), assuming these changes continue to occur. In the next study, we move west off of the continent of Africa to consider a species of mosquito in the genusCulex and its possible role in the transmission of Dirofilaria immitis, the primary causative agent of heartworm disease. Although the Canary Islands are a known endemic focus of Dirofilaria immitis, the mosquito vector on the island has, heretofore, not been identified. This article by Morchon Garcia et al. provides convincing evidence that they found the mosquito species that serves as the vector of D. immitis on the islands. Five potential vector species of mosquitoes were collected on the islands. Using molecular biological techniques, the authors identified one species of mosquito, Culex theileri, which was infected with D. immitis. Recent studies in Iran [4] and Spain [5] suggest that C. theileri is a competent vector species. In addition, comparing analyses of the mtDNA in the cox1 gene between C. theileri populations in the Canary Islands and Iran suggest that the two populations are molecularly similar. Although the results of this study are supportive of the role of C. theileri in the transmission of D. immitis in the Canary Islands, the authors caution that additional studies are required to conclusively support their suggestions. Our next study takes us to Asia and consideration of the status of Visceral Leishmaniasis (VL) in Iran. In his review, Mohebali combines his personal experience with numerous (>3,000) cases of leishmaniasis in Iran with results obtained from a search of databases from 1996 through 2010. The author’s results suggest that canids serve as the primary reservoir hosts of infection of humans a result found in previous studies [6]. Several species of Phlebotomus serve the insect vectors in Iran. In Iran, VL appears to be a disease of the young as children 12 years of age and younger made up 92.8% of the reported cases of VL during the time span under review. Mohebali found that the direct agglutination test was an effective means of detecting antiLeishmania antibodies and recommended it as a surveillance tool. The author concluded that VL is a serious zoonotic threat in Iran with sporadic prevalence in most geographic zones while being endemic in northwestern and southern Iran. Finally, we go further east and north to Mongolia where Papageorgiou et al. examined the epidemiology of tick-borne pathogens in two of the country’s provinces (aimags). Livestock were investigated using serology and PCR to identify exposure and infection

Exploratory analysis of the interrelations between co-located boolean spatial features using network graphs

Visual data mining of spatial data is a challenging task. As exploratory analysis is fundamental, it is beneficial to explore the data using different potential visualisations. In this article, we propose and analyse network graphs as a useful visualisation tool to mine spatial data. Due to their ability to represent complex systems of relationships in a visually insightful and intuitive way, network graphs offer a rich structure that has been recognised in many fields as a powerful visual representation. However, they have not been sufficiently exploited in spatial data mining, where they have principally been used on data that come with an explicit pre-specified network graph structure. This research presents a methodology with which to infer relationship network graphs for large collections of boolean spatial features. The methodology consists of four principal stages: (1) define a co-location model, (2) select the type of co-association of interest, (3) compute statistical diagnostics for these co-associations and (4) construct and visualise a network graph of the statistic from step (3). We illustrate the potential usefulness of the methodology using an example taken from an ecological setting. Specifically, we use network graphs to understand and analyse the potential interactions between potential vector and reservoir species that enable the propagation of leishmaniasis, a disease transmitted by the bite of sandflies.

Comparison of two trapping methods for Culicoides biting midges and determination of African horse sickness virus prevalence in midge populations at Onderstepoort, South Africa

Culicoides biting midges (Diptera: Ceratopogonidae) are vectors of a variety of pathogens including African horse sickness virus (AHSV), a member of the family Reoviridae, genus Orbivirus. AHSV causes African horse sickness (AHS), an endemic disease of equids with an extremely high mortality rate in horses in sub-Saharan Africa. Culicoides (Avaritia) imicola Kieffer is considered to be the principal vector of AHSV and is the dominant Culicoides species in South Africa. Due to the global distribution of Culicoides vectors, there is a potential risk of AHS spreading from endemic areas to areas traditionally free of the disease, which could have a severe economical impact on the affected equine industry. As part of any risk assessment it is essential to monitor known vectors as well as potential vector species. In the present study, sampling of Culicoides insects was compared using overnight collections in the conventional Onderstepoort light trap and mechanical aspiration of midges at sunset from bait horses. Culicoides imicola was confirmed as the predominant species using both trapping methods. Other species, mainly Culicoides (Avaritia) bolitinos Meiswinkel and Culicoides (Avaritia) gulbenkiani Caeiro, were highly underrepresented in the light trap collections, but made a significant contribution to the mechanical aspiration catches. The time for optimal collection differed between the trapping methods, leading to the conclusion that mechanical aspiration is a useful addition to conventional light trap collection and possibly the better choice when investigating insect vectors. An infection rate of 1.14% was calculated for the midge population based on real-time quantitative reverse-transcription polymerase chain reaction (RT-qPCR) assays of collected Culicoides midges, which exceeds previous estimates. This is probably due to the increased sensitivity of the RT-qPCR assay used in this study as compared to the virus isolation assays used in previous studies. RT-qPCR-positive midges were present in midge pools obtained from both light trap and mechanical aspiration. Seven of the positive pools consisted of C. imicola only, four contained mixed species and one pool contained no C. imicola, suggesting the presence of AHSV in midges of other species.

Information-theory-based model selection for determining the main vector and period of transmission of Potato virus Y

Potato virus Y (PVY, genus Potyvirus, family Potyviridae) is transmitted non-persistently by aphids. It causes major losses in potato production (Solanum tuberosum), especially following seed tuber-borne infection of plants. To limit the risk of PVY infection, seed potato production is located preferably in regions where vector pressure is low. The northern-most high-grade seed potato production area (HG zone) of Europe is in Finland. The aim of this study was to determine the incidence of aphid species with documented ability to transmit PVY and to use a modelling approach to determine their relative importance as vectors of PVY in the HG zone of Finland. Winged aphids were caught from six to seven potato fields in each of three growing seasons (2007–09) using yellow pan traps that were examined twice a week. Identification of more than 30 000 individuals indicated that 37% of the aphids belonged to nine species reported to transmit PVY. Incidence of PVY in seed lots was low (0–5.6%) and the seasonal increase of PVY incidence was also low in the potato crops. No potato-colonising aphids were found on the plants in any of the years. The seasonal increase in PVY incidence was modelled using aphid counts in traps, the relative vector efficiencies of the aphids, virus resistance of cultivars, and the initial infection rate of the seed tubers as explanatory variables in generalised linear mixed modelling. Akaike's information criterion was employed to find the best set of explanatory variables for PVY in harvested tubers. Results of this modelling approach showed that the incidence of seed-borne PVY infection and the early-season vector flights are the most important factors contributing to the incidence of PVY in the yield. Compared to models with data from all potential vector species, models containing data from Aphis fabae only showed a better model fit with regard to the incidence of PVY in the harvested tubers. The explanatory power of the models was lost when A. fabae was omitted from the vector data, suggesting that other species play a negligible role as vectors of PVY in the HG zone of Finland. Results can be used to devise appropriate strategies for enhanced control of PVY.

Influence of season and meteorological parameters on flight activity of Culicoides biting midges

Summary1. Culicoides biting midges are vectors of internationally important arboviruses including bluetongue virus (BTV). The ecological constraints imposed by the small body size of these insects strongly influence the epidemiology of the diseases they can carry. Bluetongue virus recently emerged in northern Europe, and atmospheric dispersion models have subsequently been employed to simulate vector movement (and hence likely spread of BTV). The data underlying such models, however, have hitherto either been obtained from small‐scale studies or from outside the north‐western Palaearctic.2. The effects of seasonality and local meteorological conditions upon the daily presence and abundance of Culicoides vectors were examined using 2760 samples collected across a network of 12 different habitat types in England during 2008. Over 50 000 individuals were estimated to be in the samples with males constituting 62% of the total collection, allowing straightforward comparison between potential vector species in terms of their activity rates and seasonality. Culicoides abundance was linked to livestock density and land use. Farm‐associated Culicoides species were recorded at all sites including species thought to be restricted to this ecosystem by larval habitat, suggesting a greater potential for dispersal over land than previously thought.3. Synthesis and applications. The model developed has already been applied in a functional dispersion model to predict disease risk from wind‐borne infected Culicoides incursion into the UK and elsewhere. The study has expounded the long‐distance dispersal potential of Culicoides, essential for future prediction of the incursion and spread of Culicoides‐borne pathogens. It has additionally contributed to the understanding of the ecology of highly dispersive insect vectors.

Laboratory and Field-Based Tests of Deltamethrin Insecticides Against Adult Culicoides Biting Midges

Bluetongue virus (BTV) is an economically important arbovirus of ruminants transmitted by Culicoides biting midges. Vector control using residual spraying or application to livestock is recommended by many authorities to reduce BTV transmission; however, the impact of these measures in terms of both inflicting mortality on Culicoides and subsequently upon BTV transmission is unclear. This study consisted of a standardized World Health Organization laboratory assay to determine the susceptibility of European Culicoides species to deltamethrin and a field trial based upon allowing individuals of a laboratory strain of Culicoides nubeculosus Meigen to feed upon sheep treated with Butox 7.5 pour-on (a deltamethrin-based topical formulation). Susceptibility in the laboratory trial was higher in colony C. nubeculosus (24-h LC90 = 0.00106%), than in field populations of Culicoides obsoletus Meigen (24-h LC90 = 0.00203%) or Culicoides imicola Kieffer (24-h LC90 = 0.00773%). In the field, the pour-on formulation was tested with a total of 816 C. nubeculosus specimens fed upon on the thigh of treated sheep. The study revealed a maximum mortality rate of 49% at 4 d postapplication, and duration of lethal effect was predicted to be as short as 10 d, despite testing being carried out with a highly susceptible strain. The reasons for this low efficacy are discussed with reference both to the potential for lack of spread of the active ingredient on the host and feeding patterns of the major potential vector species on the sheep host. Practical implications for vector control strategies during BTV incursions are also detailed.

Detection ofOrientia tsutsugamushi, the Causative Agent of Scrub Typhus, in a Novel Mite Species,Eushoengastia koreaensis, in Korea

To identify potential vector species of scrub typhus in the Republic of Korea (ROK), chigger mites were harvested from wild rodents captured at nine localities in October 2005. The bodies of the chigger mites were individually punctured with a fine pin, squeezed out internal contents, and examined for Orientia tsutsugamushi DNA by nested polymerase chain reaction. The exoskeleton of associated chiggers was mounted on glass slides with polyvinylalcohol (PVA) medium for identification. Among 830 individuals belonging to 4 genera and 14 species, O. tsutsugamushi was detected from 22 chiggers of six species, with an overall infection rate of 2.7%. The infection rate was highest for Leptotrombidium palpale (5.3%), followed by Neotrombicula japonica (4.3%), Leptotrombidium scutellare (3.7%), Leptotrombidium orientale (3.6%), Eushoengastia koreaensis (1.9%), and Leptotrombidium pallidum (1.5%). This study first reported O. tsutsugamushi infection from N. japonica and E. koreaensis larvae in the ROK. The population densities of L. pallidum (33.4 chiggers/rodent), historically confirmed as a primary vector of scrub typhus in the ROK, were high, whereas its infection rate was relatively low (1.5%). However, E. koreaensis was only collected from 154 individuals at seven collection sites and its infection rate was demonstrated relatively high (mean 1.9%). Additional studies are needed to determine the role of vector species in the epidemiology of scrub typhus.

Novos registros e potencial epidemiológico de algumas espécies de mosquitos (Diptera, Culicidae), no Estado do Rio Grande do Sul

Entomological surveillance has proven to be an important strategy for monitoring culicidae fauna, aimed at predicting the risk of exposure to pathogen vector species. The present work reports species identified for the first time in the State Rio Grande do Sul and discusses the epidemiological potential displayed by mosquito species occurring in Maquiné municipality and in other regions of the State. Mosquitoes were collected with Nasci vacuum and CDC light traps between December 2006 and December 2008, in the wild, rural and urban areas of Maquiné. Fifty-five species were verified, of which 22 were registered for the first time in the state and 10 are potential vector species for the Saint Louis, Oropouche, Aura, Trocara, Ilhéus, Rocio, Una, West Nile, and eastern equine encephalitis viruses. These data demonstrate the importance of entomological surveillance as a tool for gathering information and promoting Health Surveillance actions.

Monitoring of biting midges (Diptera: Ceratopogonidae: Culicoides Latreille) on farms in Sweden during the emergence of the 2008 epidemic of bluetongue

In light of the emergence of bluetongue in northern Europe, populations of Culicoides species were monitored in 2007-2008 by means of Onderstepoort blacklight suction traps operating at livestock farms in Sweden. The location of the 22 sampling sites ranged from about latitude 55 degrees N to about 68 degrees N. A total of 61,669 male and female Culicoides were captured, of which, 52,319 were trapped outside the farms and 9,350 in byres or livestock sheds. Thirty-three Culicoides species were recorded, of which, 30 were new to Sweden. The species and their relative abundance and spatial distribution on sites are presented. Two species incriminated as vectors of bluetongue virus, viz. Culicoides obsoletus (about 38%) and Culicoides scoticus (about 36%), were predominant and common in the environment of livestock farms practically all over the Swedish mainland, penetrating far north to at least 65 degrees N. The two species were also recorded from the island of Gotland. Culicoides pulicaris, another potential vector species, accounted for about 9% of all Culicoides captured.

A distinct tospovirus causing necrotic streak on Alstroemeria sp. in Colombia

A tospovirus causing necrotic streaks on leaves was isolated from Alstroemeria sp. in Colombia. Infected samples reacted positively with tomato spotted wilt virus (TSWV) antiserum during preliminary serological tests. Further analysis revealed a close serological relationship to tomato chlorotic spot virus (TCSV) and groundnut ringspot virus (GRSV). A major part of the S-RNA segment, encompassing the nucleocapsid (N) protein gene, the 5′ untranslated region and a part of the intergenic region 3′ of the N gene, was cloned and sequenced. The deduced N protein sequence showed highest amino acid identity (82%) to that of TCSV, indicating that the virus represents a new tospovirus species, for which the name Alstroemeria necrotic streak virus (ANSV) is coined. Phylogenetic analysis based on the N protein sequence revealed that this Alstroemeria-infecting tospovirus clustered with tospoviruses from the American continent. Frankliniella occidentalis was identified as potential vector species for ANSV.

Bionomics of Anopheles spp. (Diptera: Culicidae) in a malaria endemic region of Sukabumi, West Java, Indonesia

A 15-month bionomic study of Anopheles species was conducted in two ecologically distinct villages (coastal and upland) of Sukabumi District, West Java, Indonesia from June 2006 to September 2007. Mosquitoes were captured using human-landing collections at both sites. During the study, a total of 17,100 Anopheles mosquitoes comprising 13 Anopheles species were caught: 9,151 at the coastal site and 7,949 at the upland site. Anopheles barbirostris, Anopheles maculatus, and Anopheles vagus were the predominant species caught at the coastal site, and Anopheles aconitus, Anopheles barbirostris, and An. maculatus predominated in the upland site. Overall, species were exophagic at both sites, but there was variation between species. Anopheles aconitus was endophagic at the coastal site, exophagic at the upland site, collected most often in April 2007 and had a peak landing time between 22:00 and 23:00. Anopheles sundaicus was only collected at the coastal site, exophagic, collected most often in October 2006, and had a peak landing time between 19:00 and 20:00. Potential malaria vector species such An. aconitus, An. maculatus, and An. sundaicus were present throughout the year. None of the 7,770 Anopheles tested using CSP-ELISA were positive for malaria, although the risk for malaria outbreaks in Sukabumi district remains high.

Introduction and Establishment of the Exotic Mosquito SpeciesAedes japonicus japonicus(Diptera: Culicidae) in Belgium

The establishment of the potential vector species Aedes (Finlaya) japonicusjaponicus (Theobald) (Diptera: Culicidae) in southern Belgium is reported. The species was most likely introduced through the international trade in used tires. It was first collected in 2002 on the premises of a second-hand tire company and was sampled using different sampling methods in the two consecutive years (2003-2004). It was only in 2007 and 2008, during a national mosquito survey (MODIRISK), that its presence as adults and larvae at the above-mentioned site and at another tire company in the area was confirmed based on morphological and molecular identification. This discovery is the first record for Belgium of an exotic mosquito species that established successfully and raises the question on the need for monitoring and control. Considering the accompanying species found during the surveys, we also report here the first observation of Culex (Maillotia) hortensis hortensis (Ficalbi) in Belgium.

Molecular characteristics of phytoplasmas associated with Flavescence dorée in clematis and grapevine and preliminary results on the role of Dictyophara europaea as a vector

A survey was conducted over several years in Italy and the Balkans in order to gain an understanding of the relationship between the Flavescence dorée (FD) phytoplasma isolates found in clematis and grapevine. A total of 399 clematis and 107 grapevine samples were analyzed. The results showed that 36% of the Clematis vitalba plant samples were infected by phytoplasmas which, in grapevine, are associated with FD, a quarantine disease in Europe. Infected clematis plants were also found in areas where FD phytoplasma had never previously been reported to infect grapevine, such as Macedonia, Croatia and some areas of Italy and Serbia. Molecular data from three phytoplasma genomic fragments showed the presence of different FD phytoplasma isolates, all belonging to the 16SrV‐C subgroup, including the Italian FD‐C isolate, the isolate found in Serbia, an isolate similar to the French FD2000 and a new isolate typical of central Italy. A few clematis plants were infected with single nucleotide polymorphism, insertion or deletion mutants of the FD‐C isolate. Of all the potential Hemipteran vector species surveyed in Italy and Serbia, only 18 of 527 Dictyophara europaea individuals tested proved to be infected with the FD phytoplasma. Preliminary transmission experiments showed that this species is able to transmit the FD phytoplasma from clematis to grapevine. The presence of FD‐infected clematis and of D. europaea could, therefore, constitute a risk for FD epidemics in the European viticultural regions.

Bluetongue Virus Detection by Real-Time RT-PCR inCulicoidesCaptured During the 2006 Epizootic in Belgium and Development of an Internal Control

After the emergence of bluetongue (BT) in Belgium in 2006, two types of entomological surveys were initiated, the one to identify the local vector species, and the other to study their population dynamics. In the vector study, Culicoides were captured near farms with recently infected cattle or sheep; in the population study Culicoides were captured in two meadows situated in the BT-affected region. A total of 130 pools of parous, non-blood engorged female midges (with a mean of 7.5 midges per pool) were analysed with real-time reverse transcription PCR (RT-qPCR) targeting bluetongue virus (BTV) segment 5. To ensure the RNA integrity of the samples, all pools were also tested in a second RT-qPCR targeting Culicoides 18S rRNA, which served as an internal control. Seventeen pools with negative results for both 18S and BTV were excluded, most of which originated from the population survey. In the vector survey near outbreak sites, female midges of the obsoletus complex, including C. obsoletus, C. scoticus, C. dewulfi and C. chiopterus, dominated the black-light trap collections with 19 of 89 pools being BTV-positive. Moreover, all the collections from the vector survey included at least one positive pool of the obsoletus complex compared with only 20% collections (C. obsoletus/C. scoticus) in the population survey. The current study also revealed the presence of BTV RNA in one of five pools of C. pulicaris females captured near recent BT outbreaks, suggesting that this species might have played a role in transmission. Finally, the use of RT-qPCR for the recognition of new potential BTV vector species and the impact of an appropriate monitoring method and internal control are discussed.

Deux années de comparaison de pièges à <em>Culicoides</em> dans les îles Baléares

Several types of light traps are being used in different European countries to help determine the potential vector species of blue­tongue virus (BTV). The four traps compared in this study were: i) the Onderstepoort trap – black light trap, with 8 W ultraviolet light tube used in the United Kingdom and Italy; ii) mini-CDC – black light, model 912, with 4 W UV light tube, used in Spain and Portugal; iii) Rieb trap, white light model, with 4 W UV light tube, used from 2000 to 2006 in France; iv) UK trap, with 4 W standard white incandescent bulb, used in the past in the UK and other European countries for African horse sickness surveillance. All traps included a downdraught suction fan. Tests were conducted from 18 Oct. to 19 Nov. 2007, from 18 Feb. to 4 June 2008, and from 1 Oct. to 28 Nov. 2008. During at least nine non-consecutive nights the traps were placed following a randomized block design in four different positions on a cattle farm located on the island of Mallorca (Balearic Islands, Spain). In 2008, only three traps (Onderstepoort, UK and mini-CDC) were tested. Results showed major differences in collecting Culicoides. The Onderstepoort trap showed the best performance in terms of total number of Culicoides captured in autumn both in 2007 and 2008. The UK trap, and especially the Rieb trap showed the lowest efficacy in terms of captures. In autumn 2008, the Onderstepoort trap cap­tured on average 90 Culicoides per night, whereas the mini-CDC captured on average 27. During spring 2008, however, the mini- CDC performed better as it captured on average 180 Culicoides per night, against 84 captured by the Onderstepoort. However, Fisher’s least significant difference test showed no statistically sig­nificant differences between the traps (P < 0.05). No remarkable difference was observed between the four traps as they all cap­tured a similar range of species. Captures of Culicoides newsteadi were greater during the autumn, and those of C. obsoletus in the spring. Finally, the Onderstepoort trap showed a higher sensitiv­ity in catching Culicoides midges in low population levels of the vector, especially during the winter season.

Especies de Lutzomyia en un foco urbano de leishmaniasis visceral y cutánea en El Carmen de Bolívar, Bolívar, Colombia

A focus of leishmanias transmission was reported in the municipality of El Carmen de Bolívar in the province of Bolívar, Colombia, where both cutaneous and visceral leishmaniasis cases have occured. Vector identification, ecology and behavior of potential vector species have not been characterized in this region, however. Sand fly species of the genus Lutzomyia were identified, patterns of behavior were established, and their possible roles in leishmaniasis transmission were evaluated. CDC light traps were used in several different habitats; in addition, monthly collections were made with human bait as attraction inside houses as well as outdoor Shannon trap collections. The collection data were compared with independent variables including precipitation, temperature, relative humidity and wind velocity by means of a Pearson correlation matrix to estimate levels of association and to determine the influence of the climatic conditions on the density of adults of Lutzomyia evansi and L. gomezi in each of the habitats. Five species of Lutzomyia were captured: L. evansi, L. cayennensis cayennensis, L. gomezi, L. dubitansi, and L. walkeri. Lutzomyia evansi and L. gomezi presented a significant relationship in the abundance of adults indoors with respect to outdoor wind velocity. The Lutzomyia species captured showed an anthropophagic behavior with a constant activity between the 18:00 and 20:00 hrs. Lutzomyia evansi and L. gomezi are inversely proportional in relationship to wind velocity-when the wind diminishes, the activity of these species increases.

Social and epidemiological determinants of Chagas disease: basic information for a surveillance and control policy in the Southern Cone

1. Which are the neglected or emerging aspects inthe discussed issue that need information and addi-tional knowledge for the formulation of a policy forsurveillance and Chagas disease control?Vector control - There are two recognized basic strat-egies for vector control and prevention of Chagas dis-ease. The first one is the destruction of intra andperidomiciliary foci of triatomines through chemicalcontrol with insecticides and the other is to avoid theinstallation of vectors inside dwellings by improvinghousing conditions and/or using tools of early detectionof triatomine populations that make possible theirprompt elimination (Schofield 1985, 1992, Schofield& Dias 1991, Rojas de Arias 1995, Rios 1997, Rojas deArias et al. 1999, 2005).The first strategy currently leads initiatives of tria-tomine elimination in the countries of the Southern Coneand Central America focused in the application of insec-ticide mass campaigns with different modalities accord-ing to the country’s plans. The latter is focused in theestablishment of a surveillance program in the hands ofthe communities themselves and case-finding with toolsof early detection of triatomines in order to avoid re-infestations. This surveillance phase implies monitor-ing and supervision with technology transfer that shouldgive sustainability to the actions. Additionally, there isthe fundamental importance of the coverage and qualityachieved in the application of insecticides and the dura-bility of their effect at different post-application times(Diotaiutti & Texeira Pintos 1991, Gurtler et al. 1994,Ferro et al. 1995, Rojas de Arias 1995, 2004, 2005,Guillen et al. 1997). The surveillance phase is longer,expensive and difficult to maintain (Paulone et al. 1988).Besides, there are neglected aspects that need additionalknowledge. The massive insecticide application has re-cently shown the presence of populations with impor-tant levels of resistance in the North of Argentina andSouthern Bolivia. The mechanisms that have triggeredthis resistance are still unknown, as well as the approachsystems for control measures and if the phenomenon ispresent in other regions where massive chemical con-trol has been applied. On the other hand, there are fewstudies that have been performed about the remainingaspects of the early detection of triatomine populations,especially in the peridomiciliary area and the technol-ogy development of new tools that permit the early de-tection and timely elimination.An important advance in entomological surveillancehas been the incorporation of the geographic informa-tion system (GIS) for the location of triatomine infesta-tions, reinfestations, species distribution, and interven-tion monitoring. This tool has made possible a broaderand more dynamic vision of the behaviour of triatominepopulations impacted by control measures. It has alsoshown the behaviour of species that play an importantrole as secondary species.In recent years, there has been much progress in vec-tor genetics and potential vector species. The applica-tion of techniques of advanced cytogenetics, molecularbiology, cuticle hydrocarbons, and biological studies ofstructure, conformation and sensillas, have contributedto the knowledge of different species, especially in theSouthern Cone, where the actions and studies are in moreadvanced stages (SSA-EC 2005). However, potential vec-tor species still remain to be known as well as the vari-ability of the populations in relation to the impact of thechemical control.Transplacentary and transfusional transmission -Concerning other modes of transmission, although a pro-cess of vector elimination will give a significant impacton the transmission of Chagas disease, the transfusionaland congenital transmissions that are independent of thisshould be addressed in a public health context by the re-gional health services. For congenital transmission, thecontrol of chagasic pregnant women and the monitoringand treatment of their infected children should be con-sidered (Russomando et al. 1998). However, there arenot simple and economically accessible techniques thatwould make possible to discard a congenital Chagas in-fection at birth time in those children where parasito-logical infection is not detected. The screening in bloodbanks has been established in all Latin American coun-tries using diagnosis methods with high sensitivity andspecificity but sustainability must be guaranteed.Social aspects - The socio-cultural dimension ofChagas disease is undeniable because there is an asso-ciation between the forms of social organization andprecarious lifestyles. For this reason, it is necessary tostem from a conceptualization of health-disease as well

Incriminating bluetongue virus vectors with climate envelope models

Summary 1 The spread of vector-borne diseases into new areas, commonly attributed to environmental change or increased trade and travel, could be exacerbated if novel vector species in newly invaded areas spread infection beyond the range of traditional vectors. 2 By analysing the differential degree of overlap between the environmental envelopes for bluetongue, a devastating livestock disease, and its traditional (Afro-Asian) and potential new (Palearctic) midge vectors, we have implicated the latter in the recent dramatic northward spread of this disease into Europe. 3 The traditional vector of bluetongue virus, the Afro-Asian midge Culicoides imicola, was found to occur in warm (annual mean 12–20 °C), thermally stable locations that were dry in summer (< 400 mm precipitation). The Palearctic C. obsoletus and C. pulicaris complexes were both found to occur in cooler (down to 7 °C annual mean), thermally more variable and wetter (up to 700 mm summer precipitation) locations. 4 Of 501 recorded outbreaks from the 1998–2004 bluetongue epidemic in southern Europe, 40% fall outside the climate envelope of C. imicola, but within the species’ envelopes of the C. obsoletus and C. pulicaris complexes. 5 The distribution in multivariate environmental space of bluetongue virus is closer to that of the Palaearctic vectors than it is to that of C. imicola. This suggests that Palearctic vectors now play a substantial role in transmission and have facilitated the spread of bluetongue into cooler, wetter regions of Europe. 6 Synthesis and applications. The risk to Northern Europe now depends on how much of the distributions of the widespread, abundant Palearctic midge vectors (the C. obsoletus and C. pulicaris complexes) bluetongue can occupy, perhaps determined by thermal constraints on viral replication. This was highlighted by the sudden appearance in summer 2006 of bluetongue virus at latitudes of more than 50° North – approximately 6° further North than previous outbreaks in southern Europe. Future surveillance for bluetongue and for related Culicoides-borne pathogens should include studies to record and explain the distributional patterns of all potential Palearctic vector species.

A survey of mosquitoes breeding in used tires in Spain for the detection of imported potential vector species

The used tire trade has facilitated the introduction, spread, and establishment of the Asian tiger mosquito, Aedes albopictus, and other mosquito species in several countries of America, Africa, Oceania, and Europe. A strategy for detecting these imported mosquito vectors was developed in Spain during 2003-2004 by EVITAR (multidisciplinary network for the study of viruses transmitted by arthropods and rodents). A survey in 45 locations found no invasive species. Eight autochthonous species of mosquitoes were detected in used tires, including Culex pipiens, Cx. hortensis, Cx. modestus, Anopheles atroparvus, An. claviger, Culiseta longiareolata, Cs. annulata, and Aedes caspius. Dominant species were Cx. pipiens and Cs. longiareolata. Aedes caspius was found in only once, near its natural breeding habitat. Considering the recent discovery of an established population of Ae. albopictus in Catalonia, the increasing commerce of used tires in Spain for recycling, storage, and recapping might greatly contribute to the rapid spread of this species across the Iberian Peninsula.