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- Title
Assessing insecticide susceptibility, diagnostic dose and time for the sand fly Phlebotomus argentipes, the vector of visceral leishmaniasis in India, using the CDC bottle bioassay.
- Authors
Chaubey, Rahul; Shukla, Ashish; Kushwaha, Anurag Kumar; Tiwary, Puja; Kumar Singh, Shakti; Hennings, Shawna; Singh, Om Praksh; Lawyer, Phillip; Rowton, Edgar; Petersen, Christine A.; Bernhardt, Scott A.; Sundar, Shyam
- Abstract
Visceral leishmaniasis (VL) is a vector-borne protozoan disease, which can be fatal if left untreated. Synthetic chemical insecticides are very effective tools for controlling of insect vectors, including the sand fly Phlebotomus argentipes, the vector of VL in the Indian subcontinent. However, repeated use of the same insecticide with increasing doses potentially can create high selection pressure and lead to tolerance and resistance development. The objective of this study was to determine the lethal concentrations and assess levels of susceptibility, diagnostic doses and times to death of laboratory-reared P. argentipes to five insecticides that are used worldwide to control vectors. Using the Center for Disease Control and Prevention (CDC) bottle bioassay, 20–30 sand flies were exposed in insecticide- coated 500-ml glass bottles. Flies were then observed for 24 hours and mortality was recorded. Dose-response survival curves were generated for each insecticide using QCal software and lethal concentrations causing 50%, 90% and 95% mortality were determined. A bioassay was also conducted to determine diagnostic doses and diagnostic times by exposing 20–30 flies in each bottle containing set concentrations of insecticide. Mortality was recorded at 10-minute intervals for 120 minutes to generate the survival curve. Phlebotomus argentipes are highly susceptible to alpha-cypermethrin, followed by deltamethrin, malathion, chlorpyrifos, and least susceptible to DDT. Also, the lowest diagnostic doses and diagnostic times were established for alpha-cypermethrin (3μg/ml for 40 minutes) to kill 100% of the flies. The susceptibility data, diagnostic doses and diagnostic times presented here will be useful as baseline reference points for future studies to assess insecticide susceptibility and resistance monitoring of field caught sand flies and to assist in surveillance as VL elimination is achieved in the region. Author summary: Synthetic chemical insecticides are mainly used for controlling sand flies via indoor residual spraying (IRS) and insecticide treated nets. Sand flies had developed resistance against DDT in endemic areas of Bihar, India, and was replaced by synthetic pyrethroids (alpha-cypermethrin) in the second phase of IRS in 2015. The substantial increase in the use of synthetic pyrethroids will potentially lead to increased resistance because DDT and pyrethroids both have the same target site. To monitor insecticide resistance in field caught sand flies, susceptibility status and diagnostic doses and times are warranted, as no diagnostic dose for resistance detection has been established for Indian sand flies. A laboratory reared P. argentipes was used to quantify insecticide susceptibility and determination of diagnostic doses and times. The CDC bottle bioassay was used with five insecticides viz., alpha-cypermethrin, deltamethrin, malathion, chlorpyrifos and DDT. Results indicate that the P. argentipes were highly susceptible to alpha-cypermethrin followed by deltamethrin, malathion, chlorpyrifos and least susceptible to DDT. This study provides critical base line reference data for further studies to assess insecticide susceptibility and resistance monitoring in field populations, as well as determining diagnostic doses and times for other insecticide susceptible sand fly populations undergoing surveillance to sustain VL elimination.
- Subjects
SOUTH Asia; BIHAR (India); INDIA; SAND flies; VISCERAL leishmaniasis; CENTERS for Disease Control &; Prevention (U.S.); PHLEBOTOMUS; INSECTICIDES; BIOLOGICAL assay
- Publication
PLoS Neglected Tropical Diseases, 2023, Vol 17, Issue 5, p1
- ISSN
1935-2727
- Publication type
Article
- DOI
10.1371/journal.pntd.0011276