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Culicoides (Diptera: Ceratopogonidae) midges, the vectors of African horse sickness virus--a host/vector contact study in the Niayes area of Senegal.

Fall M, Diarra M, Fall AG, Balenghien T, Seck MT, Bouyer J, Garros C, Gimonneau G, Allène X, Mall I, Delécolle JC, Rakotoarivony I, Bakhoum MT, Dusom AM, Ndao M, Konaté L, Faye O, Baldet T - Parasit Vectors (2015)

Bottom Line: The monthly variation in host/vector contact was determined in the Niayes area, Senegal, an area which was severely affected by the 2007 outbreak of AHS.Nineteen of the 41 species collected were new distribution records for Senegal.This increased the number of described Culicoides species found in Senegal to 53.

View Article: PubMed Central - PubMed

Affiliation: ISRA, Laboratoire National de l'Elevage et de Recherches Vétérinaires, Route Front de Terre, Dakar, Senegal. moussafall08@yahoo.fr.

ABSTRACT

Background: African horse sickness (AHS) is an equine disease endemic to Senegal. The African horse sickness virus (AHSV) is transmitted to the mammalian hosts by midges of the Culicoides Latreille genus. During the last epizootic outbreak of AHS in Senegal in 2007, 1,169 horses died from this disease entailing an estimated cost of 1.4 million euros. In spite of the serious animal health and economic implications of AHS, very little is known about determinants involved in transmission such as contact between horses and the Culicoides species suspected of being its vectors.

Methods: The monthly variation in host/vector contact was determined in the Niayes area, Senegal, an area which was severely affected by the 2007 outbreak of AHS. A horse-baited trap and two suction light traps (OVI type) were set up at each of five sites for three consecutive nights every month for one year.

Results: Of 254,338 Culicoides midges collected 209,543 (82.4%) were female and 44,795 (17.6%) male. Nineteen of the 41 species collected were new distribution records for Senegal. This increased the number of described Culicoides species found in Senegal to 53. Only 19 species, of the 41 species found in light trap, were collected in the horse-baited trap (23,669 specimens) largely dominated by Culicoides oxystoma (22,300 specimens, i.e. 94.2%) followed by Culicoides imicola (482 specimens, i.e. 2.0%) and Culicoides kingi (446 specimens, i.e. 1.9%).

Conclusions: Culicoides oxystoma should be considered as a potential vector of AHSV in the Niayes area of Senegal due to its abundance on horses and its role in the transmission of other Culicoides-borne viruses.

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Diversity of the Culicoides captured by site (5 sites in the Niayes area of Senegal) and trap (light- and horse-baited trap) from July 2011 to October 2012. A: Centred principal component analysis (PCA) performed on the natural logs of the cumulative percentages of abundance by species, site and type of trap (axis 1/axis 2). B: PCA within-class analysis (axis 1/axis 2). C and D: PCA between-class analysis (axis 1/axis 2 and axis 2/axis 3).
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Fig4: Diversity of the Culicoides captured by site (5 sites in the Niayes area of Senegal) and trap (light- and horse-baited trap) from July 2011 to October 2012. A: Centred principal component analysis (PCA) performed on the natural logs of the cumulative percentages of abundance by species, site and type of trap (axis 1/axis 2). B: PCA within-class analysis (axis 1/axis 2). C and D: PCA between-class analysis (axis 1/axis 2 and axis 2/axis 3).

Mentions: In a first step, centred PCA was performed on the natural logs of the percentages of cumulative abundance by species, site and type of trap. The four first axes represented 89.8% of total variance (Figure 4A respectively 41.3%, 63.2% and 78.6% for each of the first three axes). Between-class (between sites) variance explained 74.0% (as against 44.9% predicted by a permutation test, p < 0.01) of the PCA variance, while within-class (between trap types) accounted for 26.0%, indicating that the site effect was much more predominant in Culicoides diversity than the trap effect. This result was illustrated by the resemblance of Figure 4A (PCA) and Figure 4C (PCA with a maximisation of the variance between sites) with the opposition on axis 1 between the Niague site characterised by C. kingi and the other sites characterised by C. oxystoma, and on axis 2 between Parc Hann and Mbao sites characterised by C. austeni and C. milnei and Pout and Thies sites characterised by C. imicola and C. bolitinos. Figure 4D illustrated the opposition between Mbao characterised by both C. oxystoma and C. kingi, and Parc Hann and Pout characterised by C. enderleini and C. nivosus on axis 3. Indeed, in Parc Hann, C. oxystoma was dominant (66.7% of light trap catches) and was associated with C. enderleini (12.6%), in Mbao C. oxystoma was predominant (69.9%) in association with C. kingi (12.5%) and C. imicola (11.4%), in Niague the prevalent species was C. kingi (78.6%) in association with C. imicola (10.3%), in Pout C. oxystoma was dominant (49.3%) alongside C. imicola (18.6%) and C. enderleini (10.9%) and in Thies C. oxystoma was predominant (38.9%) followed by C. imicola (30.0%). Hence there was a west-to-east gradient of increasing proportional representation of C. imicola (from 3.2 to 30.0%) and of decreasing proportional representation of C. oxystoma (from 66.7 to 38.9%, with the exception of Niague where C. oxystoma was less represented [3.1%]). Within-class (between trap types) analysis showed differences in catch diversity as between light and baited traps (Figure 4B). This structure was mainly attributable to the species C. kingi and C. enderleini, which were chiefly captured by light traps (total cumulative monthly abundance is respectively 39,308 and 3,942 for the light trap as against 258 and 50 for the baited trap).Figure 4


Culicoides (Diptera: Ceratopogonidae) midges, the vectors of African horse sickness virus--a host/vector contact study in the Niayes area of Senegal.

Fall M, Diarra M, Fall AG, Balenghien T, Seck MT, Bouyer J, Garros C, Gimonneau G, Allène X, Mall I, Delécolle JC, Rakotoarivony I, Bakhoum MT, Dusom AM, Ndao M, Konaté L, Faye O, Baldet T - Parasit Vectors (2015)

Diversity of the Culicoides captured by site (5 sites in the Niayes area of Senegal) and trap (light- and horse-baited trap) from July 2011 to October 2012. A: Centred principal component analysis (PCA) performed on the natural logs of the cumulative percentages of abundance by species, site and type of trap (axis 1/axis 2). B: PCA within-class analysis (axis 1/axis 2). C and D: PCA between-class analysis (axis 1/axis 2 and axis 2/axis 3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4307892&req=5

Fig4: Diversity of the Culicoides captured by site (5 sites in the Niayes area of Senegal) and trap (light- and horse-baited trap) from July 2011 to October 2012. A: Centred principal component analysis (PCA) performed on the natural logs of the cumulative percentages of abundance by species, site and type of trap (axis 1/axis 2). B: PCA within-class analysis (axis 1/axis 2). C and D: PCA between-class analysis (axis 1/axis 2 and axis 2/axis 3).
Mentions: In a first step, centred PCA was performed on the natural logs of the percentages of cumulative abundance by species, site and type of trap. The four first axes represented 89.8% of total variance (Figure 4A respectively 41.3%, 63.2% and 78.6% for each of the first three axes). Between-class (between sites) variance explained 74.0% (as against 44.9% predicted by a permutation test, p < 0.01) of the PCA variance, while within-class (between trap types) accounted for 26.0%, indicating that the site effect was much more predominant in Culicoides diversity than the trap effect. This result was illustrated by the resemblance of Figure 4A (PCA) and Figure 4C (PCA with a maximisation of the variance between sites) with the opposition on axis 1 between the Niague site characterised by C. kingi and the other sites characterised by C. oxystoma, and on axis 2 between Parc Hann and Mbao sites characterised by C. austeni and C. milnei and Pout and Thies sites characterised by C. imicola and C. bolitinos. Figure 4D illustrated the opposition between Mbao characterised by both C. oxystoma and C. kingi, and Parc Hann and Pout characterised by C. enderleini and C. nivosus on axis 3. Indeed, in Parc Hann, C. oxystoma was dominant (66.7% of light trap catches) and was associated with C. enderleini (12.6%), in Mbao C. oxystoma was predominant (69.9%) in association with C. kingi (12.5%) and C. imicola (11.4%), in Niague the prevalent species was C. kingi (78.6%) in association with C. imicola (10.3%), in Pout C. oxystoma was dominant (49.3%) alongside C. imicola (18.6%) and C. enderleini (10.9%) and in Thies C. oxystoma was predominant (38.9%) followed by C. imicola (30.0%). Hence there was a west-to-east gradient of increasing proportional representation of C. imicola (from 3.2 to 30.0%) and of decreasing proportional representation of C. oxystoma (from 66.7 to 38.9%, with the exception of Niague where C. oxystoma was less represented [3.1%]). Within-class (between trap types) analysis showed differences in catch diversity as between light and baited traps (Figure 4B). This structure was mainly attributable to the species C. kingi and C. enderleini, which were chiefly captured by light traps (total cumulative monthly abundance is respectively 39,308 and 3,942 for the light trap as against 258 and 50 for the baited trap).Figure 4

Bottom Line: The monthly variation in host/vector contact was determined in the Niayes area, Senegal, an area which was severely affected by the 2007 outbreak of AHS.Nineteen of the 41 species collected were new distribution records for Senegal.This increased the number of described Culicoides species found in Senegal to 53.

View Article: PubMed Central - PubMed

Affiliation: ISRA, Laboratoire National de l'Elevage et de Recherches Vétérinaires, Route Front de Terre, Dakar, Senegal. moussafall08@yahoo.fr.

ABSTRACT

Background: African horse sickness (AHS) is an equine disease endemic to Senegal. The African horse sickness virus (AHSV) is transmitted to the mammalian hosts by midges of the Culicoides Latreille genus. During the last epizootic outbreak of AHS in Senegal in 2007, 1,169 horses died from this disease entailing an estimated cost of 1.4 million euros. In spite of the serious animal health and economic implications of AHS, very little is known about determinants involved in transmission such as contact between horses and the Culicoides species suspected of being its vectors.

Methods: The monthly variation in host/vector contact was determined in the Niayes area, Senegal, an area which was severely affected by the 2007 outbreak of AHS. A horse-baited trap and two suction light traps (OVI type) were set up at each of five sites for three consecutive nights every month for one year.

Results: Of 254,338 Culicoides midges collected 209,543 (82.4%) were female and 44,795 (17.6%) male. Nineteen of the 41 species collected were new distribution records for Senegal. This increased the number of described Culicoides species found in Senegal to 53. Only 19 species, of the 41 species found in light trap, were collected in the horse-baited trap (23,669 specimens) largely dominated by Culicoides oxystoma (22,300 specimens, i.e. 94.2%) followed by Culicoides imicola (482 specimens, i.e. 2.0%) and Culicoides kingi (446 specimens, i.e. 1.9%).

Conclusions: Culicoides oxystoma should be considered as a potential vector of AHSV in the Niayes area of Senegal due to its abundance on horses and its role in the transmission of other Culicoides-borne viruses.

Show MeSH
Related in: MedlinePlus