Impact of Indoor Residual Spray (IRS) of synthetic pyrethroid (alphacypermethrin) on sand fly population in the Kala-azar endemic areas of Malda district, West Bengal, India

• Published in: International journal of tropical insect science 2022, Vol.42 (5), p.3293-3302
• Main Authors: Sardar, Ashif Ali, Saha, Pabitra, Maji, Dipankar, Guha, Ushnish, Maji, Ardhendu Kumar, Guha, Subhasish Kamal
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Cattle; Entomology; Insecticides; Life Sciences; Light traps; Original Research Article; Population density; Population growth; Population studies; Pyrethroids; Surveys; Villages
• ISSN: 1742-7592; 1742-7584; 1742-7592
• DOI: 10.1007/s42690-022-00830-6

Kala azar elimination programme in India is mainly depends on vector control measures and primary methods of application of insecticides is indoor residual spray (IRS). For vector control IRS should be carried out at regular intervals of six months. Presently, alphacypermethrin is used for IRS. This study was designed to study the impact of IRS with alphacypermethrin by analysing monthly population density following IRS-treatment. Twenty villages of Habibpur block, Malda district was selected for study which were grouped into study arm where IRS was done and control arm where IRS was not done. This study was conducted during April 2019 to June, 2020. In study villages, IRS was done during August, 2019 (1 st cycle) and January 2020 (2 nd cycle). Before and after IRS, entomological survey was carried out in cattle shades, human habitation and peri-domestic vegetations using mouth aspirators and light traps. Man hour density, per trap per night collection and % of reduction of sand fly abundance was calculated from survey result. In study arm after 14 days of 1 st cycle of IRS, sand fly population reduced at rate of 96.5% which continues upto 3 months (85.34%). About 90% sand fly reduced after 14 days but after 3 months of 2 nd cycle IRS density increased by 11.6%. Similar finding was recorded in the both cattle sheds and human habitations. Light trap collection from peri-domestic vegetation in both study and control villages were almost similar throughout the study period. Higher reduction rate of sand fly population following IRS showed that the used insecticide is effective against prevailing vector population of the study areas. The IRS has no effect on peri-domestic population. The presence of sand flies out side human habitation and cattle shades might play an important role in increasing population density following reduced residual activity of insecticide.