Culicoides

Bluetongue virus (BTV) has since 1998 extended its distribution further North than where it has previously been encountered. Changes in the epidemiology of Bluetongue (BT), as well as novel features of recent outbreaks of BTV in Europe, have stimulated research on BTV‑vector‑host interaction. The outbreak of BTV‑8 in Northern Europe from 2006‑2008 is particular noteworthy in this regard, as the European strain of BTV‑8 demonstrated novel properties, including high virulence – especially for cattle – and the capability to cross the ruminant placenta. The virus was in addition transmitted by indigenous European Culicoides species that had not previously been implicated in the widespread transmission of BTV. Recent advances in the scientific understanding of BTV‑vector‑host interaction include increased knowledge of the virus' replication cycle, the role of biotic factors in influencing viral infection of the insect vector, increased knowledge of BTV immunology and pathogenesis in the mammalian host, and increased knowledge of virulence and pathogenicity features of newly discovered serotypes/strains of the virus. New research on aspects of BTV‑vector‑host interaction has been driven in part by developments in molecular biology and experimental infection biology, of which next generation sequencing, the expression of individual viral proteins in cell culture, the establishment of a reverse genetics system for the virus, the development of novel in vitro and in vivo infection models, and refinement of existing BTV experimental infection methodologies have proven instrumental. Moreover, these developments have also provided the opportunity for the development of novel vaccine strategies. This article provides a synopsis of selected recent advances that have been made in the understanding of BTV‑vector‑host interaction, with a particular focus on research that has been conducted in Europe over the last 5 years.

Biting midges from the genus Culicoides (Diptera: Ceratopogonidae) are the vectors of several globally important arboviruses that affect livestock. These include orbiviruses from the bluetongue virus (BTV) and African horse sickness virus (AHSV) groups and members of the Simbu serogroup of orthobunyaviruses, such as the recently emerged Schmallenberg virus. In this article, the authors evaluate several methods for feeding wild‑caught Australian Culicoides on BTV infected preparations of blood and sucrose. Feeding Culicoides on the membrane of embryonated chicken eggs was identified as the preferred feeding method. Although, cotton wool pads soaked in either virus‑infected blood or virus‑sucrose mixtures were also successful. A non‑destructive nucleic acid extraction technique for the detection of viral RNA in Culicoides was also evaluated as it allows for readily differentiating infected from non‑infected Culicoides.

Bluetongue virus (BTV) and Epizootic haemorrhagic disease virus (EHDV) are double-stranded
RNA orbiviruses of the Reoviridae family. Bluetongue virus and EHDV infect domestic and
wild ruminants and they are transmitted by biting midges of the genus Culicoides (Diptera:
Ceratopogonidae). Since 1999, BTV outbreaks have occurred in Tunisia and 4 serotypes, BTV2,
BTV1, BTV4 and BTV3, were involved in 2000, 2006, 2009, and 2016, respectively. Epizootic
haemorrhagic disease was detected for the first time in Tunisia and in other Northern African
countries in 2006. These incursions have caused considerable economic losses. Our study
had the goal to describe diversity, distribution, and seasonal dynamics of Culicoides. Fourteen
sampling sites were chosen throughout the country and 2-night trapping of midges was
performed monthly from June 2006 to July 2008. A total of 11,582 Culicoides specimens
were collected from 336 light traps, comprising 25 species, of which 7 were identified for the
first time in Tunisia, increasing to 35 the total number of Culicoides species now reported in
this country. Twenty-three pools of parous females belonging to the Culicoides imicola and
Culicoides kingi were tested for detection of BTV and EHDV by molecular assays. Both BTV1
and BTV4 were detected in C. imicola.

Light  trapping  for  biting  midges  was  performed  on  cattle  farms  in  3  provinces  of  Western 
Russia in 2013. A total of 9,272, 2,457, and 10,245
Culicoides
midges were collected from farms
in  Smolenskaya,  Pskovskaya,  and  Vladimirskaya  provinces,  respectively.  More  than  99%  of 
collected midges belonged to either the Obsoletus or Pulicaris complexes. Species belonging to the Obsoletus complex were the most abundant in Pskovskaya, whereas species from the Pulicaris complex dominated the catches in Vladimirskaya and Smolenskaya provinces. The seasonal duration of adult activity in all 3 regions was approximately 4.5 months.

Vector-borne diseases are exceptionally sensitive to climate change. Predicting vector occurrence in specific regions is a challenge that disease control programs must meet in order to plan and execute control interventions and climate change adaptation measures. Recently, an increasing number of scientific articles have applied ecological niche modelling (ENM) to study medically important insects and ticks. With a myriad of available methods, it is challenging to interpret their results. Here we review the future projections of disease vectors produced by ENM, and assess their trends and limitations. Tropical regions are currently occupied by many vector species; but future projections indicate poleward expansions of suitable climates for their occurrence and, therefore, entomological surveillance must be continuously done in areas projected to become suitable. The most commonly applied methods were the maximum entropy algorithm, generalized linear models, the genetic algorithm for rule set prediction, and discriminant analysis. Lack of consideration of the full-known current distribution of the target species on models with future projections has led to questionable predictions. We conclude that there is no ideal 'gold standard' method to model vector distributions; researchers are encouraged to test different methods for the same data. Such practice is becoming common in the field of ENM, but still lags behind in studies of disease vectors.

The efficacy of sweep nets and a CDC white light-suction trap for the sampling of
Culicoides
species  (Diptera:  Ceratopogonidae)  were  compared  on  a  livestock  farm  in  Northern  Spain 
during  the  Summer  of  2013.  A  total  of  6,082  specimens  representing  26  species  were 
collected  with  sweep  nets  in  4  areas  at  different  heights  (ground  level,  1.5  m,  and  3  m), 
and  8,463  specimens  representing  28  species  with  a  single  white  light  trap.  Eight  species  - 
Culicoides brunnicans, Culicoides punctatus, Culicoides obsoletus/Culicoides scoticus, Culicoides
lupicaris, Culcoides picturatus, Culicoides achrayi
, and
Culicoides simulator
- were dominant and
accounted for 97.4% and 97.2% of the total specimens collected with both methods, sweep
nets, and light traps, respectively. The sex ratios with sweep netting and light trapping were
strongly female biased (78.4% and 97.1%, respectively). Nulliparous and parous females were
predominantly captured with both methods. A high percentage (17%) of gravid females was,
however,  captured  on  manure  at  ground  level  while  sweeping.  Searches  for  male  swarms 
revealed  the  presence  of  several 
C.  punctatus
  swarms  consisting  of  26  to  196  males  and  3 
swarms of
C. obsoletus
that ranged from 1 to 12 males in size. This study suggested that both
methods are suitable and complementary tools for
Culicoides
sampling.

African horse sickness is a vector-transmitted viral disease that affects equidae. The authors report cases of disease that occurred in Namibia between 2006 and 2008. These were recorded by staff of the Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise 'G. Caporale' and the Central Veterinary Laboratory in Windhoek. All cases described were confirmed by laboratory testing. This study received the support of Namibian state and private veterinarians and horse breeders.

African horse sickness is a vector-transmitted viral disease that affects equidae. The authors report cases of disease that occurred in Namibia between 2006 and 2008. These were recorded by staff of the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise ‘G. Caporale’ and the Central Veterinary Laboratory in Windhoek. All cases described were confirmed by laboratory testing. This study received the support of Namibian state and private veterinarians and horse breeders.

Résumé:
De nombreuses espèces de moustiques sont susceptibles de jouer un rôle dans la transmission de divers agents pathogènes responsables des maladies infectieuses humaines et animales. D'autres, outre leur rôle vecteur, sont un véritable fléau par les piqûres douloureuses qu’ils occasionnent, et constituent de ce fait un grand problème de nuisance. L'identification précise et la connaissance de la biodiversité fonctionnelle des vecteurs est un pas essentiel pour la compréhension du risque de (ré)-émergence et la dynamiques des maladies vectorielles. Le présent travail est une étude rétrospective des inventaires des Culicidae réalisés sur le terrain dans la région du M’Zab (Ghardaïa, Algérie) durant les années 2008 à 2011. Un aperçu sur le rôle vectoriel des espèces signalées dans la région et leur importance au niveau de la santé médicale et vétérinaire sont présentés à partir des données bibliographiques. Les espèces potentiellement vectrices d’arbovirus (Virus de Nile occidentale et Virus de la Vallée du Rift) et de protozoaires (Plasmodium spp) qui peuvent causer des problèmes épidémiologique au niveau de la région du M’Zab sont Cx. pipiens sl L., 1758, Cx. theileri Theobald, 1903, Ochlerotatus caspius Pallas, 1771, Anopheles sergentii Theobald, 1907, An. dthali Patton, 1905 et An. multicolor Cambouliu, 1902.

Mots-clés :
Moustique, Culicidae, Biodiversité, M’Zab, Algérie, Paludisme, Transmission.

The species diversity and seasonal abundance of biting midges of the genus Culicoides (Diptera: Ceratopogonidae) were studied in northwestern Argentina during the period 2003–2005. A total of 5437 Culicoides specimens were collected using CDC light traps in three areas of the mountainous rainforest area. The most common species were Culicoides paraensis (Goeldi) and C. insignis Lutz, Culicoides lahillei (Iches), C. venezuelensis Ortiz & Mirsa, C. debilipalpis Lutz and C. crescentis Wirth & Blanton were also collected. Culicoides paraensis was abundant during the summer, and C. insignis and C. lahillei during late summer and early fall. Accumulated rainfall was the climatic variable most related to fluctuation in abundance of C. paraensis.

Clinical bluetongue (BT) caused by BT virus serotype 9 (BTV-9) was observed in Kosova in 2001 and, although subsequently no further clinical cases was diagnosed, its continuing presence has been demonstrated by serological tests in cattle, sheep and goats. In this study, light traps were placed in stables near Prishtinë to identify possible vectors of BTV in Kosova. Samples were collected from October 2004 until the end of 2006. Culicoides were identified and speciated and results were plotted against temperature data. Samples contained Obsoletus and Pulicaris Complexes but not C. imicola. The first specimens of Culicoides were collected in April and they continued to be detected until November. Generally, Obsoletus Complex was present in the largest numbers, with the exception of the middle of the year when the Pulicaris Complex predominated. The number of Culicoides trapped was directly linked to temperature (p<0.05) and records indicated that Culicoides activity ceased when mi...

In 2012, six years after the previous epidemic, Bluetongue virus serotype 1 (BTV-1) re-emerged
in  Sardinia  causing  a  limited  number  of  outbreaks.  Due  to  impossibility  of  implementing  a 
vaccination  campaign,  the  BTV-1  then  spread  all  over  the  island  in  2013  with  about  7,000 
outbreaks  and,  in  September  2013,  the  virus  reached  Central  Italy,  with  a  limited  number 
of  outbreaks  located  along  the  Tyrrhenian  coast.  The  surveillance  system  in  place  in  Italy 
detected  viral  circulation  during  the  following  winter,  when  a  few  seroconversions  were 
notified.  Starting  from  mid  July  2014,  a  huge  number  of  outbreaks  were  reported  and  the 
disease  spread  toward  inland  territories,  affecting  Umbria,  Abruzzo  and  Marche.  In  2014, 
BTV-1  affected  areas  where 
Culicoides
  species  belonging  to  the  Obsoletus  and  Pulicaris 
complexes were identified as main vectors. The analysis of temperature and rainfall in Central
Italy revealed a significant warmer winter (2013-2014) and a cooler and rainy summer season
(2014). These climatic aspects might have certainly favored the overwintering of the virus in
local vector or host populations in the Tyrrhenian coast, and, then, the spread of the virus to
the  rest  of  Central  Italy.  However,  the  heavy  circulation  of  BTV-1  and  the  severity  of  clinical 
outbreaks recorded leave a number of ‘open questions’ that are currently under investigations.

The efficacy of sweep nets and a CDC white light-suction trap for the sampling of Culicoides
species (Diptera: Ceratopogonidae) were compared on a livestock farm in Northern Spain
during the Summer of 2013. A total of 6,082 specimens representing 26 species were
collected with sweep nets in 4 areas at different heights (ground level, 1.5 m, and 3 m),
and 8,463 specimens representing 28 species with a single white light trap. Eight species -
Culicoides brunnicans, Culicoides punctatus, Culicoides obsoletus/Culicoides scoticus, Culicoides
lupicaris, Culcoides picturatus, Culicoides achrayi, and Culicoides simulator - were dominant and
accounted for 97.4% and 97.2% of the total specimens collected with both methods, sweep
nets, and light traps, respectively. The sex ratios with sweep netting and light trapping were
strongly female biased (78.4% and 97.1%, respectively). Nulliparous and parous females were
predominantly captured with both methods. A high percentage (17%) of gravid females was,
however, captured on manure at ground level while sweeping. Searches for male swarms
revealed the presence of several C. punctatus swarms consisting of 26 to 196 males and 3
swarms of C. obsoletus that ranged from 1 to 12 males in size. This study suggested that both
methods are suitable and complementary tools for Culicoides sampling.

The Bluetongue and Schmallenberg virus outbreaks in Europe between 1999 and 2013 stimulated progress in Culicoides field ecology and control. In responding to these outbreaks, however, the deficit of broadly trained entomologists became evident. Culicoides research has been uneven, and critical gaps remain in our knowledge of vector ecology. Certain aspects of adult midge biology have gotten more attention (biting rates and relationship to trap collections, seasonal activity and survey, taxonomy of critical species complexes). Some aspects of adult midge biology (survival, resting site selection, or direct dispersal measurements) have been understudied. More work is needed on Culicoides immatures (taxonomy and details of ecology). Control research has centred on insecticide treatments applied to animals. However, our true goal is not vector control, but reducing disease agent transmission. We require field vector control targets (e.g. how far we might need to reduce biting rates) ne...

Clinical bluetongue (BT) caused by BT virus serotype 9 (BTV‑9) was observed in Kosova in 2001 and, although subsequently no further clinical cases was diagnosed, its continuing presence has been demonstrated by serological tests in cattle, sheep and goats. In this study, light traps were placed in stables near Prishtinë to identify possible vectors of BTV in Kosova. Samples were collected from October 2004 until the end of 2006. Culicoides were identified and speciated and results were plotted against temperature data. Samples contained Obsoletus and Pulicaris Complexes but not C. imicola. The first specimens of Culicoides were collected in April and they continued to be detected until November. Generally, Obsoletus Complex was present in the largest numbers, with the exception of the middle of the year when the Pulicaris Complex predominated. The number of Culicoides trapped was directly linked to temperature (p<0.05) and records indicated that Culicoides activity ceased when minimum temperatures fell below 0°C; activity recommenced when minimum temperatures rose to approximately 6°C. These results indicate that there was a lack of a vector for BTV during winter for a period lasting approximately five months.

Vector-borne diseases are exceptionally sensitive to climate change. Predicting vector occurrence in specific regions is a challenge that disease control programs must meet in order to plan and execute control interventions and climate change adaptation measures. Recently, an increasing number of scientific articles have applied ecological niche modelling (ENM) to study medically important insects and ticks. With a myriad of available methods, it is challenging to interpret their results.
Here we review the future projections of disease vectors produced by ENM, and assess their trends and limitations. Tropical regions are currently occupied by many vector species; but future projections indicate poleward expansions of suitable climates for their occurrence and, therefore, entomological surveillance must be continuously
done in areas projected to become suitable. The most commonly applied methods were the maximum entropy algorithm, generalized linear models, the genetic algorithm for rule set prediction, and discriminant analysis. Lack of consideration of the full-known current distribution of the target species on models with future projections has led to questionable predictions. We conclude that there is no ideal ‘gold standard’ method to model vector distributions; researchers are encouraged to test different methods for the same data. Such practice is becoming common in the field of ENM, but still lags behind in studies of disease vectors.

Beatrice Hill Farm (BHF) near Darwin, Australia was identified in the early 1970's as a site of high arbovirus activity. The first isolation of Bluetongue virus (BTV) in Australia was made on BHF in 1975. Since then, there has been continuous monitoring for BTV at BHF, the virus has been isolated on a yearly basis, with the only exception of 1990. All 10 serotypes known in Australia have been isolated at this site and an assessment of their biological behaviour made. Over the years, the methods and intensity of monitoring have been changed. In recent years molecular techniques have permitted more detailed examination of the origins of the viruses and their natural behaviour in field situations. Data collected at BHF have allowed modelling to detect likely origins of the BTVs that regularly enter Australia through wind borne infected Culicoides from South East Asia. Concurrent vector monitoring led to assess the Culicoides species more likely to be involved with transmission of these viruses.

Bluetongue (BT) was first recognized and described in Southern Africa, and only later elsewhere. It is now known that the causative agent of BT [BT virus (BTV)] occurs throughout temperate and tropical regions of the world. Previous OIE symposia in 1984, 1991 and 2003 clarified the global distribution of BTV and its epidemiology, pathogenesis, and diagnosis. Since the 3rd symposium in 2003, however, there have been significant developments. Notably, BT has emerged in Northern Europe and novel BTV serotypes have appeared in other endemic areas raising substantial questions regarding the environmental and anthropogenic drivers of emergence of BTV, including the invasion and spread of laboratory propagated viruses. Additional BTV serotypes with novel properties have recently been identified in Europe and the Middle East. Recent studies also confirm the importance of the Culicoides vector as the essential overwintering reservoir of BTV in temperate regions such as California and not ruminant livestock, proving wrong the prevailing thesis circulated prior to the 1st symposium in 1984. The challenge for participants of this 4th symposium is to predict collectively what the future might hold in terms of emergence of BTV globally, and what strategies are likely to be most feasible, justified, and effective for its control.

A real-time polymerase chain reaction (PCR) using a green fluorescence dye, followed by a comparison of derivative melting curves in the post-amplification phase, was developed to distinguish species of Culicoides within the Obsoletus Complex. The selected target sequence was internal transcribed spacer 2 (ITS 2) of the ribosomal DNA (rDNA). Using the newly developed method, 140 midges were morphologically classified in the Obsoletus Complex and were processed. The results were compared to those obtained by combining the morphological identification with the gel based reverse transcriptase (RT)-PCR. By analysing the species-specific pattern of the dissociation curves, it was possible to identify 52 midges as Culicoides scoticus, 82 midges as C. obsoletus sensu strictu and 6 as C. montanus. These results matched those obtained by the combination of gel-based PCR and morphological identification used on a routine basis. Given its diagnostic flexibility, rapid results, automation capability, high quality result performance and expression, the real-time ITS 2 rDNA PCR appears to be more functional and efficient than the gel-based PCR, especially when dealing with large-scale monitoring of midges belonging to the Obsoletus Complex.

In current sampling approaches, there exists a divergence between the surveillance of arthropod-borne and that of non-arthropod-borne viruses. It is commonly held that the collection of vector specimens applies only to arbovirus surveillance and that the surveillance of non-arboviruses must rely on traditional methods that involve the sampling of blood, faeces or saliva, or other examinations. The vector-based approach is a sampling method that has the ability to survey both arboviruses and non-arboviruses by distinguishing engorged vector specimens from entire vector samples. Accordingly, five arboviruses and three non-arboviruses were detected in a study using a vector-based approach conducted during 2012-2015. Hence, this report provides the first description of the Taiwanese vector species for the bovine arboviruses detected. The present investigations demonstrate that the vector-based approach applies not only to the surveillance of arboviruses, but also has potential as a possible tool for monitoring non-arboviruses on livestock farms in the future.

African horse sickness is a vector-transmitted viral disease that affects equidae. The authors report cases of disease that occurred in Namibia between 2006 and 2008. These were recorded by staff of the Istituto Zooprofilattico Sperimentale dell&#39;Abruzzo e del Molise &#39;G. Caporale&#39; and the Central Veterinary Laboratory in Windhoek. All cases described were confirmed by laboratory testing. This study received the support of Namibian state and private veterinarians and horse breeders.

African horse sickness (AHS) is a viral disease of equidae that is endemic in sub-Saharan Africa. Cases of the disease have been reported in North Africa where seroconversion still occurs in Morocco, in the Iberian Peninsula and areas of middle-eastern Asia. As is the case for ...

Bluetongue virus (BTV) and Epizootic haemorrhagic disease virus (EHDV) are double-stranded RNA orbiviruses of the Reoviridae family. Bluetongue virus and EHDV infect domestic and wild ruminants and they are transmitted by biting midges of the genus Culicoides (Diptera: Ceratopogonidae). Since 1999, BTV outbreaks have occurred in Tunisia and 4 serotypes, BTV2, BTV1, BTV4 and BTV3, were involved in 2000, 2006, 2009, and 2016, respectively. Epizootic haemorrhagic disease was detected for the rst time in Tunisia and in other Northern African countries in 2006. These incursions have caused considerable economic losses. Our study had the goal to describe diversity, distribution, and seasonal dynamics of Culicoides. Fourteen sampling sites were chosen throughout the country and 2-night trapping of midges was performed monthly from June 2006 to July 2008. A total of 11,582 Culicoides specimens were collected from 336 light traps, comprising 25 species, of which 7 were identi ed for the rst ...

The Bluetongue and Schmallenberg virus outbreaks in Europe between 1999 and 2013 stimulated progress in Culicoides field ecology and control. In responding to these outbreaks, however, the deficit of broadly trained entomologists became evident. Culicoides research has been uneven, and critical gaps remain in our knowledge of vector ecology. Certain aspects of adult midge biology have gotten more attention (biting rates and relationship to trap collections, seasonal activity and survey, taxonomy of critical species complexes). Some aspects of adult midge biology (survival, resting site selection, or direct dispersal measurements) have been understudied. More work is needed on Culicoides immatures (taxonomy and details of ecology). Control research has centred on insecticide treatments applied to animals. However, our true goal is not vector control, but reducing disease agent transmission. We require field vector control targets (e.g. how far we might need to reduce biting rates) needed to interrupt transmission. The most critical need is for studies incorporating vector control experimentally into epidemiological studies in active arbovirus transmission zones. Such field interdisciplinary studies are absolutely required to understand transmission dynamics. Through the power of experimental field studies, we should be able to develop both theoretical and operational guidelines for disease management.