Limits...
Insecticide susceptibility of Phlebotomus argentipes in visceral leishmaniasis endemic districts in India and Nepal.

Dinesh DS, Das ML, Picado A, Roy L, Rijal S, Singh SP, Das P, Boelaert M, Coosemans M - PLoS Negl Trop Dis (2010)

Bottom Line: Resistance to DDT was confirmed in Bihar and in a border village of Nepal, but the sand flies were still susceptible in villages more inside Nepal where only synthetic pyrethroids are used for indoor spraying.The low effectiveness of indoor spraying with DDT in Bihar to control VL can be partially explained by this resistance hence other classes of insecticides should be tested.In both countries P. argentipes sand flies were susceptible to deltamethrin.

View Article: PubMed Central - PubMed

Affiliation: Rajendra Memorial Research Institute of Medical Sciences, Patna, India.

ABSTRACT

Objectives: To investigate the DDT and deltamethrin susceptibility of Phlebotomus argentipes, the vector of Leishmania donovani, responsible for visceral leishmaniasis (VL), in two countries (India and Nepal) with different histories of insecticide exposure.

Methods: Standard WHO testing procedures were applied using 4% DDT and 0.05% deltamethrin impregnated papers. The effect of the physiological status (fed and unfed) of females on the outcome of the bioassays was assessed and the optimal time of exposure for deltamethrin was evaluated on a colony population. Field populations from both countries were tested.

Results: Fed and unfed females responded in a similar way. For exposure time on field samples 60 min was adopted for both DDT and deltamethrin. In Bihar, knockdown and mortality with DDT was respectively 20 and 43%. In Nepal almost all sand flies were killed, except at the border with Bihar (mortality 62%). With 0.05% deltamethrin, between 96 and 100% of the sand flies were killed in both regions.

Conclusions: Based on literature and present data 4% DDT and 0.05% deltamethrin seem to be acceptable discriminating concentrations to separate resistant from susceptible populations. Resistance to DDT was confirmed in Bihar and in a border village of Nepal, but the sand flies were still susceptible in villages more inside Nepal where only synthetic pyrethroids are used for indoor spraying. The low effectiveness of indoor spraying with DDT in Bihar to control VL can be partially explained by this resistance hence other classes of insecticides should be tested. In both countries P. argentipes sand flies were susceptible to deltamethrin.

Show MeSH

Related in: MedlinePlus

Susceptibility tests using the WHO bioassays with the colony population P. argentipes (Patna).E: unfed; F: fed. For deltamethrin (Deltam) 3 exposure periods have been tested (15, 30, 60 min); for DDT 60 min was used. The total number of specimens tested and the number of replicates (R) are shown in brackets. Bars represent the standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2964302&req=5

pntd-0000859-g002: Susceptibility tests using the WHO bioassays with the colony population P. argentipes (Patna).E: unfed; F: fed. For deltamethrin (Deltam) 3 exposure periods have been tested (15, 30, 60 min); for DDT 60 min was used. The total number of specimens tested and the number of replicates (R) are shown in brackets. Bars represent the standard error of the mean.

Mentions: No significant differences were observed between unfed (E) and fed (F) sand flies for knockdown and mortality (Fig. 2) for DDT (Chi Square KD: p = 0.46; mortality: p = 0.99) and for deltamethrin (Chi Square: KD: p = 0.17; mortality: p = 0.12). For DDT only 38% mortality (N = 248; 11 replicates) was observed indicating DDT resistance in this colony population. For deltamethrin knockdown increased with time of exposure and mortality after 60 min exposure reached 99% (N = 193; 9 replicates). The exposure time of 60 min with a concentration of 0.05% was further adopted for testing the field populations.


Insecticide susceptibility of Phlebotomus argentipes in visceral leishmaniasis endemic districts in India and Nepal.

Dinesh DS, Das ML, Picado A, Roy L, Rijal S, Singh SP, Das P, Boelaert M, Coosemans M - PLoS Negl Trop Dis (2010)

Susceptibility tests using the WHO bioassays with the colony population P. argentipes (Patna).E: unfed; F: fed. For deltamethrin (Deltam) 3 exposure periods have been tested (15, 30, 60 min); for DDT 60 min was used. The total number of specimens tested and the number of replicates (R) are shown in brackets. Bars represent the standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2964302&req=5

pntd-0000859-g002: Susceptibility tests using the WHO bioassays with the colony population P. argentipes (Patna).E: unfed; F: fed. For deltamethrin (Deltam) 3 exposure periods have been tested (15, 30, 60 min); for DDT 60 min was used. The total number of specimens tested and the number of replicates (R) are shown in brackets. Bars represent the standard error of the mean.
Mentions: No significant differences were observed between unfed (E) and fed (F) sand flies for knockdown and mortality (Fig. 2) for DDT (Chi Square KD: p = 0.46; mortality: p = 0.99) and for deltamethrin (Chi Square: KD: p = 0.17; mortality: p = 0.12). For DDT only 38% mortality (N = 248; 11 replicates) was observed indicating DDT resistance in this colony population. For deltamethrin knockdown increased with time of exposure and mortality after 60 min exposure reached 99% (N = 193; 9 replicates). The exposure time of 60 min with a concentration of 0.05% was further adopted for testing the field populations.

Bottom Line: Resistance to DDT was confirmed in Bihar and in a border village of Nepal, but the sand flies were still susceptible in villages more inside Nepal where only synthetic pyrethroids are used for indoor spraying.The low effectiveness of indoor spraying with DDT in Bihar to control VL can be partially explained by this resistance hence other classes of insecticides should be tested.In both countries P. argentipes sand flies were susceptible to deltamethrin.

View Article: PubMed Central - PubMed

Affiliation: Rajendra Memorial Research Institute of Medical Sciences, Patna, India.

ABSTRACT

Objectives: To investigate the DDT and deltamethrin susceptibility of Phlebotomus argentipes, the vector of Leishmania donovani, responsible for visceral leishmaniasis (VL), in two countries (India and Nepal) with different histories of insecticide exposure.

Methods: Standard WHO testing procedures were applied using 4% DDT and 0.05% deltamethrin impregnated papers. The effect of the physiological status (fed and unfed) of females on the outcome of the bioassays was assessed and the optimal time of exposure for deltamethrin was evaluated on a colony population. Field populations from both countries were tested.

Results: Fed and unfed females responded in a similar way. For exposure time on field samples 60 min was adopted for both DDT and deltamethrin. In Bihar, knockdown and mortality with DDT was respectively 20 and 43%. In Nepal almost all sand flies were killed, except at the border with Bihar (mortality 62%). With 0.05% deltamethrin, between 96 and 100% of the sand flies were killed in both regions.

Conclusions: Based on literature and present data 4% DDT and 0.05% deltamethrin seem to be acceptable discriminating concentrations to separate resistant from susceptible populations. Resistance to DDT was confirmed in Bihar and in a border village of Nepal, but the sand flies were still susceptible in villages more inside Nepal where only synthetic pyrethroids are used for indoor spraying. The low effectiveness of indoor spraying with DDT in Bihar to control VL can be partially explained by this resistance hence other classes of insecticides should be tested. In both countries P. argentipes sand flies were susceptible to deltamethrin.

Show MeSH
Related in: MedlinePlus