Wide area spray of bacterial larvicide, Bacillus thuringiensis israelensis strain AM65-52, integrated in the national vector control program impacts dengue transmission in an urban township in Sibu district, Sarawak, Malaysia

Abstract

Several sites, Z-7L, Z-5 and Z-14, in Sibu district, Sarawak, Malaysia, experienced intense dengue transmission in 2014 that continued into 2015. A pilot study with Bacillus thuringiensis israelensis (Bti) to control Aedes aegypti (L.) and Ae. albopictus (Skuse) was evaluated in Z-7L, a densely populated site of 12 ha. Bti treatments were conducted weekly from epidemiology week (EW) 24/2015 for 4 weeks, followed by fortnight treatments for 2 months, in addition to the routine control activities. Bti was directly introduced into potable containers and the outdoor artificial and natural containers were treated via a wide area spray application method using a backpack mister. Aedes indices significantly reduced during the treatment and post treatment phases, compared to the control site, Z-5 (p<0.05). A 51 fold reduction in the incidence rate per 100,000 population (IR) was observed, with one case in 25 weeks (EW 29-52). In Z-5 and Z-14, control sites, a 6 fold reduction in the IR was observed from EW 29-52. However, almost every week there were dengue cases in Z-14 and until EW 44 in Z-5. In 2016, dengue cases resurfaced in Z-7L from EW 4. Intensive routine control activities were conducted, but the IR continued to escalate. The wide area Bti spray misting of the outdoor containers was then included from EW 27 on fortnight intervals. A 6 fold reduction in IR was observed in the Bti treatment phase (EW 32-52) with no successive weekly cases after EW 37. However, in the control sites, there were dengue cases throughout the year from EW 1-52, particularly in Z-14. We feel that the wide area Bti spray application method is an integral component in the control program, in conjunction with other control measures carried out, to suppress the vector population in outdoor cryptic containers and to interrupt the disease transmission.

Insecticide resistance in dengue vectors from hotspots in Selangor, Malaysia

“…For temephos susceptibility status, previous reports of temephos susceptibility status [33] are consistent with our latest screening of Aedes population against temephos. In spite of the fact that temephos resistance at diagnostic dosage was widespread, it was noted that Aedes mosquito populations were still susceptible to temephos at operational dosage of 1.0mg/L; meaning, temephos usage in vector control program is still effective without control failure (Figs 1 and 2 and S1 Table ).…”

An evaluation of Bacillus thuringiensis israelensis (AM65‐52) treatment for the control of Aedes aegypti using vehicle‐mounted WALS® application in a densely populated urban area of Puerto Rico

“…In recent years, WALS® has increasingly become a recognized method of control for container‐breeding mosquitoes in a variety of geographical locations, using a range of equipment from aerial spraying 12 to ground treatment using backpacks 11 . In comparison with another study using vehicle‐mounted equipment where the net level of control reported was a 29% reduction of Ae.…”

“…WALS® is a biorational larvicide application strategy that uses wind‐distributed aqueous microdroplets of mosquito larvicide to target cryptic larval sources, such as containers, across complex landscapes. WALS® application of Bti AM65‐52 WDG has been successful for dengue vector and disease suppression in Malaysia 10, 11 and in Key West, Florida 12 . WALS® was also used successfully in Miami, Florida 13 and Brownsville, Texas 14 during the Zika crisis of 2016.…”

“…The inspiration for this study came as a result of the success of wide-area larvicide spraying in other locations. [10][11][12][13][14] Because Puerto Rico has a very different type of architecture from other parts of the USA reflecting more the Latin American style of small yards, properties located closely together, having flat roofs and high security often meaning access to back yards is limited, it was necessary to determine whether this type of larvicidal application was appropriate for control of Ae. aegypti in neighborhoods on the island.…”

Long-lasting microbial larvicides for controlling insecticide resistant and outdoor transmitting vectors: a cost-effective supplement for malaria interventions

“…The cost-effectiveness of LLML should also be evaluated in other places than African countries. So far, LLML has only been evaluated in Kenya, although the conventional formulation of the same microbial larvicides has been tested/used and cost has been evaluated in other African [ 22 – 29 , 35 – 40 , 46 ] as well as Asian countries [ 49 – 52 ]. The results have been shown to be promising across different ecological settings, which is especially relevant in low transmission areas that are targeting the goal of malaria elimination [ 53 ].…”