204 research outputs found
Midichloria mitochondrii, an intracellular alphaproteobacteria considered as a symbiont of the tick Ixodes ricinus, found circulating in roe-deer (Capreolus capreolus) through molecular and serological evidences
No full textThe hard tick Ixodes ricinus, vector of pathogens important for both human and animal health (Parola and Raoult, 2001; Socolovschi et al., 2009) harbours Midichloria mitochondrii (order Rickettsiales; family Midichloriaceae), an endocytobiotic bacterium found in 100% of the females (Epis et al. 2008). Although its impact on the biology of its arthropod-host is still unknown, M. mitochondrii has first been detected in the reproductive apparatus of adult females where it is the most abundant and, more recently, also in the salivary glands of the parasite, suggesting the hypothesis of its transmission to the vertebrate host during the tick bite (Mariconti et al., 2012). To validate this hypothesis, the presence of M. mitochondrii DNA in the vertebrate hosts (dogs, sheep, horses and humans) was detected through the amplification of the 16S rDNA gene (Mariconti et al., 2012; Bazzocchi et al. 2013) and serological analysis on sera collected from humans and dogs exposed to the tick bite (Mariconti et al. 2012).
This experimental work aims to investigate the circulation of M. mitochondrii in roe deer (C. capreolus), which is the host of choice especially for the adult stage of I. ricinus in Europe and is therefore considered an efficient animal-sentinel for possible etiologic agents transmitted by this hard tick species. Briefly, we evaluate: 1) the presence of circulating M. mitochondrii DNA in blood of seven roe deer, different in age and sex, from a defined and controlled area (South-East Toulouse, France); 2) the immunological response of the roe deer individuals against a specific recombinant flagellar protein of M. mitochondrii (rFliD).
Molecular analysis were conducted using specific qualitative PCRs for 12S rDNA of C. capreolus (Fajardo et al. (2008) and 16S rDNA of M. mitochondrii ( Epis et al. 2008) after DNA extraction from blood samples. Immunological analysis were conducted using the recombinant protein rFLID as antigen in ELISA and Western blot testsAfter molecular analysis, only three of the seven analyzed blood samples were positive to M. mitochondrii DNA. On the base of the already set cut-off (designed on negative sera), six out of seven roe deer individuals resulted positive in ELISA. Western blot assay instead, showed the presence of a band, at the expected molecular weight, in all the examined samples, except for the negative control.
In conclusion, M. mitochondrii was detected in roe deer individuals through molecular and serological analyses, proving the circulation of M. mitochondrii in C. capreolus parasitized by I. ricinus. As already demonstrated in other studies, roe deer is a good subject to study the spread of tick-borne pathogens (or potentially pathogen). Further studies will allow the understanding of biological interactions of M. mitochondrii, the possible replication of this bacterium inside the host and its role in possible pathological alterations after its transmission
Docosahexaenoic acid-rich fish oil improves heart rate variability and heart rate responses to exercise in overweight adults
No full textDietary fish oil supplementation and regular physical activity can improve outcomes in patients with established CVD. Exercise has been shown to improve heart rate variability (HRV), a predictor of cardiac death, but whether fish oil benefits HRV is controversial. Obese adults at risk of future coronary disease have impaired HRV and may benefit from these interventions. We evaluated the effect of DHA-rich tuna fish oil supplementation with and without regular exercise on HRV in sedentary, overweight adults with risk factors for coronary disease. In a randomised, double-blind, parallel comparison, sixty-five volunteers consumed 6 g fish oil/d (DHA 1·56 g/d, EPA 0·36 g/d) or sunflower-seed oil (placebo) for 12 weeks. Half of each oil group also undertook regular moderate physical activity (3 d/week for 45 min, at 75% of age-predicted maximal heart rate (HR)). Resting HR and the HR response to submaximal exercise were measured at weeks 0, 6 and 12. In forty-six subjects, HRV was also assessed by power spectrum analysis of 20 min electrocardiogram recordings taken supine at baseline and 12 weeks. Fish oil supplementation improved HRV by increasing high-frequency power, representing parasympathetic activity, compared with placebo (P = 0·01; oil x time interaction). It also reduced HR at rest and during submaximal exercise (P = 0·008; oil x time interaction). There were no significant fish oil x exercise interactions. Dietary supplementation with DHA-rich fish oil reduced HR and modulated HRV in keeping with an improved parasympathetic–sympathetic balance in overweight adults with risk factors for future coronary disease.Daniel M. Ninio, Alison M. Hill, Peter R. Howe, Jonathan D. Buckley and David A. Sain
Experiments on phosphate-silicate liquid immiscibility with potential links to iron oxide apatite and nelsonite deposits
No full textThe formation of phosphorus-iron oxide (P-Fe) immiscible melts and their possible connection to the genesis of Kiruna-type and Nelsonite deposits was experimentally investigated by adding phosphoric acid (H3PO4), water, and sulfur, to andesite at 100-450 MPa, 500-900 degrees C, at the NiNiO and magnetite-hematite fO(2) buffers using internally heated gas vessels. The addition of up to 8.02 wt% of H3PO4 to the andesite causes crystallization of apatite. At higher concentrations of H3PO4 whitlockite crystallizes, and at concentrations above similar to 11.4% H3PO4 (at 800 degrees C, 385 MPa) an immiscible P-Fe melt forms. Adding sulfur at low fO(2) (NiNiO) causes an additional immiscible Fe-S melt to form. Increasing the fO(2) to the hematite-magnetite buffer causes the sulfur-rich melt to shift in composition to a Ca-S-O melt, and the coexisting P-Fe melt to incorporate large amounts of SO4. Immiscible P-Fe melts can form at temperatures above 1100 degrees C down to 600 degrees C (at 400 MPa). Mass balance calculations show that some experimentally produced P-Fe rich immiscible liquids may result in mineral assemblages similar to those found at some Kiruna-type deposits, such as actinolite-rich dikes, and apatite-rich veins. Depending on the geological conditions and the composition the fractionation of a P-Fe melt may result in the formation of nelsonites at high pressures, high temperatures, and low fO(2) or Kiruna-type deposits at lower temperatures and higher fO(2)
Bluetongue disease in the Ardennes : study of the biology of Culicoïdes and their epidemiological role
No full textLa Fièvre catarrhale ovine (FCO) est une arbovirose émergente en Europe depuis la fin desannées 90. Elle affecte principalement les ruminants par la piqûre de petits moucheronshématophages, les Culicoides (Diptera : Ceratopogonidae). Pendant l’été 2006, l’introductiondu sérotype 8 de la FCO, dans la région de Maastricht (Pays-Bas) a rapidement diffusé dansles Ardennes, générant de lourdes pertes pour les éleveurs de bovins et d’ovins. Cesévènements interrogent sur la capacité des Culicoides de la région paléarctique à transmettrela FCO. Ils révèlent la nécessité de mieux connaître la biologie de ces diptères.Nous avons développé successivement dans ce travail, trois axes de recherche qui se sontappuyés sur un travail de terrain réalisé principalement au sein de deux élevages situés dansles Ardennes françaises.Dans un premier temps, nous avons réalisé une expérimentation de gorgement de Culicoidesde captures et d’émergences, provenant des Ardennes, sur petits ruminants virémiques pour leBTV8. A l’issue des expérimentations, une femelle gorgée de l’espèce Culicoides obsoletus apondu et a été retrouvée faiblement positive lors de la recherche du génome du virus de laFCO. Les résultats obtenus ainsi que les difficultés rencontrées lors de la réalisation de cetype d’expérimentation sont discutés.Le deuxième travail exposé s’est intéressé au comportement trophique des Culicoides parl’étude de l’origine du repas sanguin de femelles de Culicoides piégées dans des biotopesvariés. A cette fin, nous avons utilisé des marqueurs moléculaires pour amplifier l’ADN devertébré présent dans les estomacs de femelles gorgées. Ces analyses ont permis de mettre enévidence que des espèces appartenant aux complexes Obsoletus, Pulicaris, ou encore,Culicoides dewulfi, avaient un spectre d’hôte large. Certaines d’entre elles peuvent se gorger àla fois sur les ruminants domestiques et sur la faune sauvage. De plus, ce type d’étuderenseigne sur l’écologie des différentes espèces de Culicoides.Enfin, nous présentons les résultats d’une étude faunistique fondée sur des captures avec despièges lumineux, mais aussi, des prélèvements de boue pour la recherche des gîtes larvaires.Les résultats de piégeages entre les deux exploitations ont été comparés, notamment en termesde biodiversité, et sont discutés en regard des différences de pratiques d’élevage entre lesdeux exploitations choisies d’une part, et la mise en évidence des gîtes larvaires d’autre part.De nombreuses espèces de Culicoides ont émergé au laboratoire à partir des prélèvements deboues, qui ont été caractérisés macroscopiquement. Les gîtes larvaires de C. obsoletus, peuconnus jusqu’alors, ont été mis en évidence dans les deux fermes. Ils ont fait l’objet d’un suivisur plusieurs mois.L’ensemble de ces études contribue à la meilleure connaissance des Culicoides présents dansles Ardennes et de leur biologie, elles permettent de rendre compte des espèces qui semblenttrès inféodées à l’élevage de bovins, et celles qui sont plus ubiquistes. Certains travauxprésentés pourraient être poursuivis pour mettre en évidence les espèces ou populations deCulicoides plutôt sylvatiques, et pour mettre en place de nouvelles expérimentations sur lacompétence et la capacité vectorielle des Culicoides.Since the late 90’s, Bluetongue disease (BT) can be considered as an emerging arbovirose inEurope. This disease is mainly transmitted to ruminants by the bites of minute size midges,the Culicoides (Diptera: Ceratopogonidae), also known as biting midges. An outbreak of BTserotype 8 occurred during summer 2006, in the region of Maastricht (Netherlands) andspread quickly to the Ardennes region. The epizooty lead to severe losses in cattle and sheepholdings. These events highlighted the lack of knowledge on the vectorial capacity ofpaleartic Culicoides species, and more generally on their biology.Three approaches are successively treated in this document. They are all based on field workconducted mainly in two holdings located in the Ardennes region.First, an experiment to assess oral susceptibility of Culicoides to Bluetongue virus (BTV) 8was undertaken. Field collected and emerging Culicoides coming from the Ardennes wereengorged on viremic small ruminants. At the end of the experiments, one Culicoides obsoletusfemale was found bloodfed and laid eggs. She was tested for BTV and was found weaklypositive for BTV genome. This result and the difficulties met during the experiment havebeen discussed.The second study focused on the bloodmeal origin of engorged females of Culicoides. Thesewere collected by light traps set in different kinds of environment. Molecular markers wereused in order to amplify the DNA of vertebrates present in the stomach of bloodfed females.Some of the species processed belonging to the Obsoletus or the Pulicaris complex, andCulicoides dewulfi fed on a wide variety of hosts, including domestic ruminants and wildanimals. Moreover, this kind of study brings information on the ecology of different speciesof Culicoides.Finally, a faunistic survey is presented. It was achieved through light trap collections ofmidges and also thanks to the sampling of potential breeding sites. Biodiversity in thecollection of midges captured by light traps between the two holdings were compared.Differences observed are discussed taking into account the differences in breeding practicesbetween the two holdings and the breeding sites investigations. Numerous species ofCulicoides emerged in the laboratory from soil samples which were macroscopicallydescribed. Breeding sites of C. obsoletus, which were not well documentated in the literature,were found in both farms. These were monitored over some months.This work contributes to a better knowledge of the Culicoides present in the Ardennes andtheir biology. It highlights the species which are closely related to the cattle holdingenvironment, and those which are ubiquist. Some of these studies could be continued in orderto highlight the species more related to the forested areas, and to set new experiments onvectorial competence and capacity
Resilience to large-scale disturbance in coral and fish assemblages on the Great Barrier Reef
No full textRecognition of the complex spatial and temporal variability of abundance and diversity found in many populations has led to a greater focus on the roles of heterogeneity, stochasticity, and disturbance in the structure and persistence of communities. This focus is directly relevant to coral reef communities that are characterized by very high species diversity in a spatially heterogeneous environment, display stochastic variability in community structure at small spatial and temporal scales, and are subject to major disturbances. We monitored coral and fish assemblages over 14 years on fixed sites spread over 80 km of the southern Great Barrier Reef (GBR), Australia, and found evidence of large-scale resilience and predictable recovery of these assemblages. Sometime between November 1987 and October 1989, live coral cover on the shallow northeast flanks of some reefs in the southern GBR decreased from >80% to <10%, probably as a result of storm damage. We compared the fish and benthic communities present in these areas prior to the disturbance (1983-1984) with those present in 1992 and the subsequent changes through to 1998. Hard coral cover increased slowly from 1992 to 1994, then accelerated to be indistinguishable from pre-impact levels by 1998. The response of the coral assemblages was largely due to the predominance of tabulate Acropora species and their characteristics of rapid growth and competitive dominance. Patterns of species richness of the fish families Acanthuridae, Chaetodontidae, Scaridae, and Pomacentridae mirrored that of hard coral, except the Pomacentridae had not recovered to pre-impact levels by 1998. Of the 26 fish species analyzed for changes in abundance, 88% decreased after the disturbance, then subsequently increased, with all but two recovering to pre-impact levels by 1998. Although processes such as settlement and immigration are ultimately responsible for replenishment of local populations, our data suggested that habitat plays a strong role in modifying fish assemblages. Thus, both coral and fish assemblages demonstrated resilience to large-scale natural disturbance and predictability in the structure of the assemblages, with most taxa approaching the asymptote of abundance and species richness that existed prior to the disturbance.PT: J; CR: ALLEN GR, 1998, GUIDE ANGELFISHES BU AULT TR, 1998, ECOL MONOGR, V68, P25 BAIRD AH, 2000, J EXP MAR BIOL ECOL, V251, P117 BELL JD, 1984, MAR ECOL-PROG SER, V15, P265 BOHNSACK JA, 1983, ENVIRON BIOL FISH, V9, P41 BORMANN FH, 1979, AM SCI, V67, P660 BROTHERS EB, 1983, MAR BIOL, V76, P319 BROWN BE, 1997, CORAL REEFS, V16, P129 BUDDEMEIER RW, 2002, CORAL REEFS, V21, P1 BYTHELL JC, 2000, MAR ECOL-PROG SER, V204, P93 CALEY MJ, 1996, J ANIM ECOL, V65, P414 CHABANET P, 1997, CORAL REEFS, V16, P93 CHEAL AJ, 2002, CORAL REEFS, V21, P131 CHESSON PL, 1986, COMMUNITY ECOLOGY, P229 CHOAT JH, 1996, MAR ECOL-PROG SER, V134, P15 CLEY MJ, 1997, P 8 INT COR REEF S, V1, P993 COLGAN MW, 1987, ECOLOGY, V68, P1592 CONNELL JH, 1978, SCIENCE, V199, P1302 CONNELL JH, 1983, AM NAT, V121, P789 CONNELL JH, 1997, CORAL REEFS S, V16, P101 CONNELL JH, 1997, ECOL MONOGR, V67, P461 CORNELL HV, 1996, J ANIM ECOL, V65, P233 DAVIES PJ, 1979, SEARCH, V10, P776 DAVIES PJ, 1980, NATURE, V287, P37 DOHERTY PJ, 1987, B MAR SCI, V41, P411 DOHERTY PJ, 1991, ECOLOGY FISHES CORAL, P261 DOHERTY PJ, 1997, P 8 INT COR REEF S P, V1, P1005 DONE TJ, 1992, CONT SHELF RES, V12, P859 FOWLER AJ, 1990, MAR ECOL-PROG SER, V64, P39 FOWLER AJ, 1992, MAR ECOL-PROG SER, V82, P131 FRIEDLANDER AM, 1998, J EXP MAR BIOL ECOL, V224, P1 GREEN AL, 1996, MAR ECOL-PROG SER, V133, P1 HANSKI I, 1998, NATURE, V396, P41 HART AM, 1996, MAR ECOL-PROG SER, V132, P11 HART AM, 1996, MAR ECOL-PROG SER, V132, P21 HEINSELMAN ML, 1981, P C FIR REG EC PROP, P7 HIXON MA, 1991, ECOLOGY FISHES CORAL, P475 HIXON MA, 1993, ECOL MONOGR, V63, P77 HOBBS RJ, 1994, PACIFIC CONSERVATION, V1, P170 HOLLING CS, 1973, ANNUAL REV ECOLOGY S, V4, P1 HUGHES TP, 1994, SCIENCE, V265, P1547 HUGHES TP, 1999, LIMNOL OCEANOGR 2, V44, P932 JONES GP, 1991, ECOLOGY FISHES CORAL, P294 JONES GP, 1998, AUST J ECOL, V23, P287 KARLSON RH, 1993, CORAL REEFS, V12, P117 LASSIG BR, 1983, ENVIRON BIOL FISH, V9, P55 LEWIS AR, 1997, MAR ECOL-PROG SER, V161, P37 LITTELL RC, 1996, SAS SYSTEM MIXED MOD LUCKHURST BE, 1978, MAR BIOL, V49, P317 MASSEL SR, 1993, CORAL REEFS, V12, P153 MCCULLAGH P, 1989, GENERALIZED LINEAR MEEKAN MG, 1999, B MAR SCI, V64, P383 NINIO R, 2000, MAR ECOL-PROG SER, V194, P65 NINIO R, 2002, CORAL REEFS, V21, P95 NOTT J, 2001, NATURE, V413, P508 ODUM EP, 1969, SCIENCE, V164, P262 OLIVER JK, 1995, LONG TERM MINITORING PAINE RT, 1981, ECOL MONOGR, V51, P145 PICKETT STA, 1986, ECOLOGY NATURAL DIST PIUMM SL, 1991, BALANCE NATURE ECOL RANDALL JE, 1990, FISHES GRET BARRIER ROBERTS CM, 1987, MAR ECOL-PROG SER, V41, P1 SALE PF, 1978, ENVIRON BIOL FISH, V3, P85 SALE PF, 1982, AM NAT, V120, P121 SANO M, 2000, MAR ECOL-PROG SER, V198, P121 STIMSON J, 1985, ECOLOGY, V66, P40 SWEATMAN H, 2000, 4 I MAR SCI SWEATMAN H, 2001, 5 AUSTR I MAR SCI SYMS C, 1998, J EXP MAR BIOL ECOL, V230, P151 SYMS C, 2000, ECOLOGY, V81, P2714 THOMPSON AA, 2002, MAR ECOL-PROG SER, V232, P247 VANWOESIK R, 1991, J COASTAL RES, V7, P551 WALSH WJ, 1983, CORAL REEFS, V2, P49 WELLINGTON GM, 1985, OECOLOGIA, V68, P15 WILKINSON CR, 1999, MAR FRESHWATER RES, V50, P867 WILLIAMS DM, 1982, CORAL REEFS, V1, P35 WILLIAMS DM, 1983, MAR ECOL-PROG SER, V10, P239 WILLIAMS DM, 1986, MAR ECOL-PROG SER, V28, P157 WILLIAMS DM, 1991, ECOLOGY FISHES CORAL, P437 WOODLEY JD, 1981, SCIENCE, V214, P749 WU JG, 1995, Q REV BIOL, V70, P439; NR: 81; TC: 9; J9: ECOLOGY; PG: 14; GA: 843VASource type: Electronic(1
A macroscopic kinetic model for DNA polymerase elongation and high-fidelity nucleotide election
No full textThe enzymatically catalyzed template-directed extension of ssDNA/primer complex is an impor-tant reaction of extraordinary complexity. The DNA polymerase does not merely facilitate the insertion of dNMP, but it also performs rapid screening of substrates to ensure a high degree of fidelity. Several kinetic studies have determined rate constants and equilibrium constants for the elementary steps that make up the overall pathway. The information is used to develop a macro-scopic kinetic model, using an approach described by Ninio [Ninio J., 1987. Alternative to the steady-state method: derivation of reaction rates from first-passage times and pathway probabili-ties. Proc. Natl. Acad. Sci. U.S.A. 84, 663–667]. The principle idea of the Ninio approach is to track a single template/primer complex over time and to identify the expected behavior. The average time to insert a single nucleotide is a weighted sum of several terms, in-cluding the actual time to insert a nucleotide plus delays due to polymerase detachment from ei-ther the ternary (template-primer-polymerase) or quaternary (+nucleotide) complexes and time delays associated with the identification and ultimate rejection of an incorrect nucleotide from the binding site. The passage times of all events and their probability of occurrence are ex-pressed in terms of the rate constants of the elementary steps of the reaction pathway. The model accounts for variations in the average insertion time with different nucleotides as well as the in-fluence of G+C content of the sequence in the vicinity of the insertion site. Furthermore the model provides estimates of error frequencies. If nucleotide extension is recognized as a compe-tition between successful insertions and time delaying events, it can be described as a binomial process with a probability distribution. The distribution gives the probability to extend a primer/template complex with a certain number of base pairs and in general it maps annealed complexes into extension products
Antibiotic treatment of the hard tick Ixodes ricinus: influence on Midichloria mitochondrii load following blood meal
No full textMidichloria mitochondrii is the most prevalent symbiont of the hard tick Ixodes ricinus, present in 100% of eggs and adult females of wild ticks. This bacterium is intracellular, and is the only known symbiont able to invade the mitochondria of the host cells. However, the role that M. mitochondrii plays in the host metabolism has yet to be elucidated. Multiple lines of evidence indicate the possibility of transmission of this bacterium to the vertebrate host during the tick blood meal. In order to investigate the role of M. mitochondrii in the biology of the tick host, we performed an antibiotic treatment on Ixodes ricinus individuals, with the aim of reducing/eliminating the symbiont, and to potentially observe the dynamic of bacterial infection in the tick host. We microinjected engorged adult females of I. ricinus with tetracycline, and we allowed the resulting larvae to feed on gerbils treated with the same antibiotic. The amount of M. mitochondrii was evaluated at different stages of the experiment using molecular techniques. In addition we evaluated the presence/absence of the symbiont DNA in the blood of gerbils used for the larval feeding. The performed treatments did not allow to eliminate the symbiont population from the host tick, however it allowed to reduce the multiplication that occurs after the larval blood meal. These results open the way for future experiments, using different antibiotic molecules, different administration methods and antibiotic administration on subsequent tick stages, to fulfill the goal of eliminating M. mitochondrii from the host I. ricinus, a major step in our understanding of the impact of this bacterium on ticks
Fièvre catarrhale ovine dans les Ardennes (étude de la biologie des Culicoïdes et de leur rôle épidémiologique)
No full textLa Fièvre catarrhale ovine (FCO) est une arbovirose émergente en Europe depuis la fin desannées 90. Elle affecte principalement les ruminants par la piqûre de petits moucheronshématophages, les Culicoides (Diptera : Ceratopogonidae). Pendant l été 2006, l introductiondu sérotype 8 de la FCO, dans la région de Maastricht (Pays-Bas) a rapidement diffusé dansles Ardennes, générant de lourdes pertes pour les éleveurs de bovins et d ovins. Cesévènements interrogent sur la capacité des Culicoides de la région paléarctique à transmettrela FCO. Ils révèlent la nécessité de mieux connaître la biologie de ces diptères.Nous avons développé successivement dans ce travail, trois axes de recherche qui se sontappuyés sur un travail de terrain réalisé principalement au sein de deux élevages situés dansles Ardennes françaises.Dans un premier temps, nous avons réalisé une expérimentation de gorgement de Culicoidesde captures et d émergences, provenant des Ardennes, sur petits ruminants virémiques pour leBTV8. A l issue des expérimentations, une femelle gorgée de l espèce Culicoides obsoletus apondu et a été retrouvée faiblement positive lors de la recherche du génome du virus de laFCO. Les résultats obtenus ainsi que les difficultés rencontrées lors de la réalisation de cetype d expérimentation sont discutés.Le deuxième travail exposé s est intéressé au comportement trophique des Culicoides parl étude de l origine du repas sanguin de femelles de Culicoides piégées dans des biotopesvariés. A cette fin, nous avons utilisé des marqueurs moléculaires pour amplifier l ADN devertébré présent dans les estomacs de femelles gorgées. Ces analyses ont permis de mettre enévidence que des espèces appartenant aux complexes Obsoletus, Pulicaris, ou encore,Culicoides dewulfi, avaient un spectre d hôte large. Certaines d entre elles peuvent se gorger àla fois sur les ruminants domestiques et sur la faune sauvage. De plus, ce type d étuderenseigne sur l écologie des différentes espèces de Culicoides.Enfin, nous présentons les résultats d une étude faunistique fondée sur des captures avec despièges lumineux, mais aussi, des prélèvements de boue pour la recherche des gîtes larvaires.Les résultats de piégeages entre les deux exploitations ont été comparés, notamment en termesde biodiversité, et sont discutés en regard des différences de pratiques d élevage entre lesdeux exploitations choisies d une part, et la mise en évidence des gîtes larvaires d autre part.De nombreuses espèces de Culicoides ont émergé au laboratoire à partir des prélèvements deboues, qui ont été caractérisés macroscopiquement. Les gîtes larvaires de C. obsoletus, peuconnus jusqu alors, ont été mis en évidence dans les deux fermes. Ils ont fait l objet d un suivisur plusieurs mois.L ensemble de ces études contribue à la meilleure connaissance des Culicoides présents dansles Ardennes et de leur biologie, elles permettent de rendre compte des espèces qui semblenttrès inféodées à l élevage de bovins, et celles qui sont plus ubiquistes. Certains travauxprésentés pourraient être poursuivis pour mettre en évidence les espèces ou populations deCulicoides plutôt sylvatiques, et pour mettre en place de nouvelles expérimentations sur lacompétence et la capacité vectorielle des Culicoides.Since the late 90 s, Bluetongue disease (BT) can be considered as an emerging arbovirose inEurope. This disease is mainly transmitted to ruminants by the bites of minute size midges,the Culicoides (Diptera: Ceratopogonidae), also known as biting midges. An outbreak of BTserotype 8 occurred during summer 2006, in the region of Maastricht (Netherlands) andspread quickly to the Ardennes region. The epizooty lead to severe losses in cattle and sheepholdings. These events highlighted the lack of knowledge on the vectorial capacity ofpaleartic Culicoides species, and more generally on their biology.Three approaches are successively treated in this document. They are all based on field workconducted mainly in two holdings located in the Ardennes region.First, an experiment to assess oral susceptibility of Culicoides to Bluetongue virus (BTV) 8was undertaken. Field collected and emerging Culicoides coming from the Ardennes wereengorged on viremic small ruminants. At the end of the experiments, one Culicoides obsoletusfemale was found bloodfed and laid eggs. She was tested for BTV and was found weaklypositive for BTV genome. This result and the difficulties met during the experiment havebeen discussed.The second study focused on the bloodmeal origin of engorged females of Culicoides. Thesewere collected by light traps set in different kinds of environment. Molecular markers wereused in order to amplify the DNA of vertebrates present in the stomach of bloodfed females.Some of the species processed belonging to the Obsoletus or the Pulicaris complex, andCulicoides dewulfi fed on a wide variety of hosts, including domestic ruminants and wildanimals. Moreover, this kind of study brings information on the ecology of different speciesof Culicoides.Finally, a faunistic survey is presented. It was achieved through light trap collections ofmidges and also thanks to the sampling of potential breeding sites. Biodiversity in thecollection of midges captured by light traps between the two holdings were compared.Differences observed are discussed taking into account the differences in breeding practicesbetween the two holdings and the breeding sites investigations. Numerous species ofCulicoides emerged in the laboratory from soil samples which were macroscopicallydescribed. Breeding sites of C. obsoletus, which were not well documentated in the literature,were found in both farms. These were monitored over some months.This work contributes to a better knowledge of the Culicoides present in the Ardennes andtheir biology. It highlights the species which are closely related to the cattle holdingenvironment, and those which are ubiquist. Some of these studies could be continued in orderto highlight the species more related to the forested areas, and to set new experiments onvectorial competence and capacity.REIMS-SCD-Bib. electronique (514549901) / SudocSudocFranceF
Substantial contribution of C16 : 0 PAF on the PAF-like bioactivity formed in oxidized LDL
No full textChemistry and Physics of Lipid
Wing geometry as a tool for discrimination of Obsoletus group (Diptera: Ceratopogonidae: Culicoides) in France.
No full textRemerciements ECOFECTInternational audienceIn Europe, Culicoides chiopterus, Culicoides dewulfi, Culicoides obsoletus and Culicoides scoticus, which belongs to the subgenus Avaritia and Obsoletus group are the most proficient Bluetongue and Schmallenberg vectors. Within this group, correct identification based on morphological traits is difficult but essential to assess disease transmission risk. The development of new tools has revolutionized taxonomy (i.e. geometric morphometrics and molecular biology). Wing morphology is of primary importance to entomologists interested in systematics. Here, we report phenotypic differentiation patterns among the species above mentioned using a landmark-based geometric morphometric approach that efficiently identified C. chiopterus and C. dewulfi. Wing shape of the C. scoticus sample exhibited large specific variability. Based on landmarks and phylogenetic analyses (Maximum Parsimony), we suggest that Obsoletus group in Europe includes only C. obsoletus and C. scoticus. C. dewulfi and C. chiopterus are clearly excluded. Their shape seems closer to C. obsoletus that is why we suggest that only these two species should be grouped in the Obsoletus group. In addition, the concordance between phenetic clusters and phylogenies inferred from molecular data based on a fragment of the mtDNA COI gene and rDNA 28S suggests the existence of a strong signal in wing shape. These findings encourage us to use this powerful tool in taxonomic studies
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