Insecticide resistance has become problematic in tropical and subtropical regions, where Aedes mosquitoes and Aedes-borne arboviral diseases thrive. With the recent occurrence of Chikungunya and the Zika virus in Jamaica, the Ministry of Health and Wellness, Jamaica, partnered with the United States Agency for International Development to implement multiple intervention activities to reduce the Aedes aegypti populations in seven parishes across the island and to assess the susceptibility of collected samples to various concentrations of temephos, Bacillus thuringiensis subsp. israelensis, (Bti), diflubenzuron and methoprene. Of the insecticides tested, only temephos has been used in routine larviciding activities in the island. The results showed that only temephos at concentrations 0.625 ppm and Bti at concentrations 6 – 8 ppm were effective at causing 98 – 100% mortality of local Aedes aegypti at 24 hours exposure. Surprisingly, the growth inhibitors diflubenzuron and methoprene had minimal effect at preventing adult emergence in Ae. aegypti larvae in the populations tested. The results demonstrate the need for insecticide resistance testing as a routine part of vector control monitoring activies in order to determine useful tools that may be incorporated to reduce the abundance of Ae. aegypti.

The larvicide susceptibility of wild Ae. aegypti populations was analysed from seven of the eastern parishes in Jamaica, namely, St. Catherine, Kingston and St Andrew (KSA), St Thomas, St Mary, and St Ann. Ovitraps were established around 100 homes in each of the parishes through the period of September 17^th, 2018 to December 7^th, 2018 (permission to establish ovitraps around homes were aquired prior to initiation of work). Egg papers from ovitraps were taken to the Mosquito Control Research Unit, Jamaica, where they were periodically set to hatch per parish for bioassays under insectary conditions. Six wild populations of Ae. aegypti were established under insectary conditions, with one population per parish, with Kingston and St Andrew represented as one single population of Ae. aegytpi, given their spatial proximity. The larvae were reared to their larval 3rd instar stage and used for Bioassays. WHO larvae test kits obtained from Universiti Sains Malaysia (USM), Vector Control Research Unit, Infotech (Pinang, Malaysia), the only agency approved by the World Health Organization (WHO) to supply insecticide kits and materials for regular surveillance in public health.

These kits were used as directed for Temephos, Methoprene and Diflubenzuron larvicide bioassays. 20 - 34 larvae were used per replicate per established population. 

Mortality was observed and recorded at 1 hour and again at 24 hour.

Each test was conducted with a control, which had 0.4% ethanol (supplied with the kits)

Bioassays using the biolarvicide Bacillus thuringiensis subsp. israelensis (Bti) (VectoBac WDG) was was also conducted. A 10,000 ppm (mg/litre) stock solution of Bti was prepared by vigorously stirring using a magnetic stirrer (C MAG HS 7; IKA) and aliquoted to give concentrations of 0, 2ppm, 4ppm, 6ppm and 8 ppm of Bti in 2,000 ml of distilled water. 250 ml of each concentration was poured into disposable paper cups containing 20 – 34 larvae; care was taken to agitate the mixture prior to each pour to ensure particulates remained in suspension.

Mortality was observed at 1 hour and again at 24 hour.

The laboratory Aedes aegypti strain, Rockefeller was used as a reference strain for the all assays. Rockefeller were originally donated from the CDC, Atlanta.

Samples from Portland were donated by the ministry of health and wellness, Jamaica.

larvae were then treated similarly to those reared in the insectary and also tested at their 3rd instar stage.

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