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Wolbachia-based population control strategy targeting Culex quinquefasciatus mosquitoes proves efficient under semi-field conditions.

Atyame CM, Cattel J, Lebon C, Flores O, Dehecq JS, Weill M, Gouagna LC, Tortosa P - PLoS ONE (2015)

Bottom Line: This property can be used to reduce the density of mosquito field populations through inundative releases of incompatible males in order to sterilize females (Incompatible Insect Technique, or IIT, strategy).The results indicated that the LR[wPip(Is)] males successfully compete with field males in mating with field females, displaying even higher competitiveness than field males in April.Our results support the implementation of small-scale field tests in order to assess the feasibility of IIT against Cx. quinquefasciatus in the islands of southwestern Indian Ocean where this mosquito species is a proven competent vector for human pathogens.

View Article: PubMed Central - PubMed

Affiliation: CRVOI, Ste Clotilde, Réunion Island, France; University La Réunion, Réunion Island, France.

ABSTRACT
In mosquitoes, the maternally inherited bacterial Wolbachia induce a form of embryonic lethality called cytoplasmic incompatibility (CI). This property can be used to reduce the density of mosquito field populations through inundative releases of incompatible males in order to sterilize females (Incompatible Insect Technique, or IIT, strategy). We have previously constructed the LR[wPip(Is)] line representing a good candidate for controlling field populations of the Culex quinquefasciatus mosquito in the islands of the south-western Indian Ocean. The main purpose of the present study was to fill the gap between laboratory experiments and field implementation, i.e. assessing mating competitiveness of these incompatible males under semi-field conditions. In a first set of experiments, we analyzed crossing relationships between LR[wPip(Is)] males and La Réunion field females collected as larvae in 19 distinct localities throughout the island. This investigation revealed total embryonic mortality, confirming the strong sterilizing capacity of LR[wPip(Is)] males. Subsequently, mating competitiveness of LR[wPip(Is)] males was assessed under semi-field conditions in the presence of field males and females from La Réunion. Confrontations were carried out in April and December using different ratios of LR[wPip(Is)] to field males. The results indicated that the LR[wPip(Is)] males successfully compete with field males in mating with field females, displaying even higher competitiveness than field males in April. Our results support the implementation of small-scale field tests in order to assess the feasibility of IIT against Cx. quinquefasciatus in the islands of southwestern Indian Ocean where this mosquito species is a proven competent vector for human pathogens.

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Assessment of mating competitiveness of LR[wPip(Is)] males under semi-field conditions.In each confrontation, 200 field females were mixed with each of the four following field to LR[wPip(Is)] males ratios: 1:0 (200 field males), 1:1 (200 field males and 200 LR[wPip(Is)] males), 1:5 (200 field males and 1000 LR[wPip(Is)] males) and 0:1 (200 LR[wPip(Is)] males). The trials of the 1:0 and 0:1 ratios were performed in April; two trials for the 1:1 ratio were performed in April and four in December; whilst for the 1:5 ratio two trials were performed in April and three in December. Expected frequency of infertile egg rafts (in black) was calculated assuming equal competitiveness of LR[wPip(Is)] and field males. Total embryonic mortality (HR = 0%) was noted in all infertile egg rafts.
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pone.0119288.g002: Assessment of mating competitiveness of LR[wPip(Is)] males under semi-field conditions.In each confrontation, 200 field females were mixed with each of the four following field to LR[wPip(Is)] males ratios: 1:0 (200 field males), 1:1 (200 field males and 200 LR[wPip(Is)] males), 1:5 (200 field males and 1000 LR[wPip(Is)] males) and 0:1 (200 LR[wPip(Is)] males). The trials of the 1:0 and 0:1 ratios were performed in April; two trials for the 1:1 ratio were performed in April and four in December; whilst for the 1:5 ratio two trials were performed in April and three in December. Expected frequency of infertile egg rafts (in black) was calculated assuming equal competitiveness of LR[wPip(Is)] and field males. Total embryonic mortality (HR = 0%) was noted in all infertile egg rafts.

Mentions: As expected, all egg rafts from cages with only field males and females (1:0 ratio) were fertile (HR >90%) and full sterility (HR = 0%) occurred when only LR[wPip(Is)] males were present with field females (0:1 ratio) (Fig. 2 and S1 Table). Experimental cages with distinct ratios of field to LR[wPip(Is)] males (i.e. in 1:1 and 1:5 ratios) produced both fertile and infertile egg rafts. We never observed egg rafts with intermediate hatching rate, all egg rafts being either fully fertile or infertile.


Wolbachia-based population control strategy targeting Culex quinquefasciatus mosquitoes proves efficient under semi-field conditions.

Atyame CM, Cattel J, Lebon C, Flores O, Dehecq JS, Weill M, Gouagna LC, Tortosa P - PLoS ONE (2015)

Assessment of mating competitiveness of LR[wPip(Is)] males under semi-field conditions.In each confrontation, 200 field females were mixed with each of the four following field to LR[wPip(Is)] males ratios: 1:0 (200 field males), 1:1 (200 field males and 200 LR[wPip(Is)] males), 1:5 (200 field males and 1000 LR[wPip(Is)] males) and 0:1 (200 LR[wPip(Is)] males). The trials of the 1:0 and 0:1 ratios were performed in April; two trials for the 1:1 ratio were performed in April and four in December; whilst for the 1:5 ratio two trials were performed in April and three in December. Expected frequency of infertile egg rafts (in black) was calculated assuming equal competitiveness of LR[wPip(Is)] and field males. Total embryonic mortality (HR = 0%) was noted in all infertile egg rafts.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359102&req=5

pone.0119288.g002: Assessment of mating competitiveness of LR[wPip(Is)] males under semi-field conditions.In each confrontation, 200 field females were mixed with each of the four following field to LR[wPip(Is)] males ratios: 1:0 (200 field males), 1:1 (200 field males and 200 LR[wPip(Is)] males), 1:5 (200 field males and 1000 LR[wPip(Is)] males) and 0:1 (200 LR[wPip(Is)] males). The trials of the 1:0 and 0:1 ratios were performed in April; two trials for the 1:1 ratio were performed in April and four in December; whilst for the 1:5 ratio two trials were performed in April and three in December. Expected frequency of infertile egg rafts (in black) was calculated assuming equal competitiveness of LR[wPip(Is)] and field males. Total embryonic mortality (HR = 0%) was noted in all infertile egg rafts.
Mentions: As expected, all egg rafts from cages with only field males and females (1:0 ratio) were fertile (HR >90%) and full sterility (HR = 0%) occurred when only LR[wPip(Is)] males were present with field females (0:1 ratio) (Fig. 2 and S1 Table). Experimental cages with distinct ratios of field to LR[wPip(Is)] males (i.e. in 1:1 and 1:5 ratios) produced both fertile and infertile egg rafts. We never observed egg rafts with intermediate hatching rate, all egg rafts being either fully fertile or infertile.

Bottom Line: This property can be used to reduce the density of mosquito field populations through inundative releases of incompatible males in order to sterilize females (Incompatible Insect Technique, or IIT, strategy).The results indicated that the LR[wPip(Is)] males successfully compete with field males in mating with field females, displaying even higher competitiveness than field males in April.Our results support the implementation of small-scale field tests in order to assess the feasibility of IIT against Cx. quinquefasciatus in the islands of southwestern Indian Ocean where this mosquito species is a proven competent vector for human pathogens.

View Article: PubMed Central - PubMed

Affiliation: CRVOI, Ste Clotilde, Réunion Island, France; University La Réunion, Réunion Island, France.

ABSTRACT
In mosquitoes, the maternally inherited bacterial Wolbachia induce a form of embryonic lethality called cytoplasmic incompatibility (CI). This property can be used to reduce the density of mosquito field populations through inundative releases of incompatible males in order to sterilize females (Incompatible Insect Technique, or IIT, strategy). We have previously constructed the LR[wPip(Is)] line representing a good candidate for controlling field populations of the Culex quinquefasciatus mosquito in the islands of the south-western Indian Ocean. The main purpose of the present study was to fill the gap between laboratory experiments and field implementation, i.e. assessing mating competitiveness of these incompatible males under semi-field conditions. In a first set of experiments, we analyzed crossing relationships between LR[wPip(Is)] males and La Réunion field females collected as larvae in 19 distinct localities throughout the island. This investigation revealed total embryonic mortality, confirming the strong sterilizing capacity of LR[wPip(Is)] males. Subsequently, mating competitiveness of LR[wPip(Is)] males was assessed under semi-field conditions in the presence of field males and females from La Réunion. Confrontations were carried out in April and December using different ratios of LR[wPip(Is)] to field males. The results indicated that the LR[wPip(Is)] males successfully compete with field males in mating with field females, displaying even higher competitiveness than field males in April. Our results support the implementation of small-scale field tests in order to assess the feasibility of IIT against Cx. quinquefasciatus in the islands of southwestern Indian Ocean where this mosquito species is a proven competent vector for human pathogens.

Show MeSH
Related in: MedlinePlus