Actellic 300cs

Actellic^®300CS (Syngenta AG, Basel, Switzerland) was applied at a target dosage of 1 g of active ingredient (pirimiphos-methyl) per square meter (1g a.i./m²) in all houses of both villages in September 2017. We performed IRS using Hudson^® X-pert spray pumps (H.D. Hudson Manufacturing Co., Chicago, IL). The spray pumps (15 l) were fitted with a 1.5 bar control flow valve on the lance pressure and equipped with a ceramic 8002E nozzle according to the WHO guidelines [16 ]. The spraying was performed by volunteers from the local communities who were trained by the National Malaria Control Program (NMCP) staff on a previous IRS campaign in Diébougou in 2012. We re-trained the spray operators and supervisors prior to IRS operations in the villages.

The two formulations under evaluation were 50% wettable powder formulations containing broflanilide (tradename TENEBENAL^TM). Three application rates of the protype formulation (B2; batch no. 17I-3422) were used in the first experimental hut trial. The second trial included the improved formulation B3 (batch no 18I-3671) applied at two different rates and compared to formulation B2 (batch no 16I-3147) (Table 1).
Treatments were sprayed using manual compression sprayers, model CS-14 (Micron Sprayers Ltd, Bromyard, United Kingdom), with an 8002E nozzle spraying at an application rate of 30mL/m² using a 1.5 bar constant flow valve (CFV). Each treatment was sprayed on both concrete and mud substrates: the walls and ceiling of each hut were treated. For both trials the reference product was an IRS formulation of the organophosphate insecticide pirimiphos methyl (Actellic®300CS, Syngenta®, Basel, Switzerland) applied at the recommended label rate of 1000 mg/m², and the negative control was an untreated concrete-lined hut. Treatments were randomly allocated to the eight huts using the MS Excel RAND() function.

Three IRS products containing different active ingredients were sprayed in experimental huts: broflanilide (VECTRON^TM T500, Mitsui Chemical Agro Inc., Tokyo, Japan, batch no 18I-3671), pirimiphos-methyl (Actellic^® 300CS, Syngenta, Basel, Switzerland, batch no BSN9A2383), and a deltamethrin + clothianidin combination product (Fludora Fusion^®, Bayer AG, Leverkusen, Germany, batch no EQ13001804). Target application rates were 100 mg/m² for broflanilide (BRF), 1000 mg/m² for pirimiphos-methyl (PMM), 200 mg/m² for clothianidin (CTD), and 25 mg/m² for deltamethrin (DLT). A different spray tank (Micron CS14) was used for each insecticide product. For both application methods, the spray tanks were positioned stationary on the floor, which differs from the WHO guidelines for manual spraying where the tank is typically carried over one shoulder. For each insecticide, four panels were sprayed with the track sprayer and four panels were sprayed manually (Figure 1). Filter papers (9 cm diameter Whatman No. 1) were fixed inside Petri dish lids with sticky tack; the lids were pierced in the centre and attached to the panel using shoe tacks. Filter papers were positioned in a grid as shown in Figure 1, with three horizontal and five vertical positions per swath. Each panel with 15 filter papers constituted one replicate test, resulting in four replicates per insecticide product.

A soft-paint brush of 2 inch width was used to apply an aqueous suspension of micro-capsulated PM (Actellic® 300CS, Syngenta AG, Switzerland) onto mosquito-proof nettings screens after they had been installed. Following saturation calibration experiments to estimate how much aqueous suspension the PVC-coated fibreglass netting used to screen houses could hold (100 ml per m²), the working concentration of PM required to achieve a treatment dosage rate of 1 g per metre squared of netting was calculated as 10 g per l, prepared by diluting 33.3 ml of stock concentrate into each litre of water. Application was conducted using personal protective equipment (rubber gloves, face mask, plastic apron and rubber boots) to protect the operator. To prevent environmental contamination, plastic trays were used to collect falling insecticide droplets and plastic bottles were used for temporarily storing unused insecticide suspension. All such aqueous waste, including the triple washes of all plastic containers that were used to clean them, were disposed of in a charcoal-lined soak pit as per existing approved IRS protocols for Tanzania [42 ]. After they had been triple rinsed with water, all such containers were disposed of as routine plastic waste as per standard protocol [42 ].

Netting material used was 100-denier polyester netted fabric purchased from the local market. These were treated by dipping in either pirimiphos methyl CS (Actellic® 300CS, Syngenta, Basle, Switzerland) at 1 g/sq m or deltamethrin SC (K-Othrine 10SC, Bayer, Monnheim, Germany) at 55 mg/sq m. Treated NWH were left to dry in the shade for 24 hours before being hung onto the hut walls. In order to avoid contamination of the walls when rotating the treatments between the huts, an underlay of untreated plastic sheeting was used to separate the walls from the treated materials and these were rotated along with the respective treatments. Treated nettings were simply hung onto nails that had been fitted at the top edge of the hut walls. Areas of the treated NWH covering the windows were then cut out to allow exit of mosquitoes to window traps.

The WL was 50% shade cloth made of woven high-density polyethylene (Capatex Ltd, UK). The NWH was made of 100-denier nylon netting fabric. These materials were treated at 1 g/sq m with a micro-encapsulated formulation of pirimiphos methyl (Actellic® 300CS Syngenta, Switzerland). The WL was treated by spraying with a Hudson Xpert sprayer, while the netting fabric was treated by hand dipping. Pyrethroid-treated WL was factory-made, high-density polyethylene fibre sheeting impregnated with deltamethrin at 175 mg/sq m (Zerovector®, Vestergaard Frandsen, Switzerland). The LLIN (PermaNet® 2.0, Vestergaard Frandsen, Switzerland) was WHOPES-approved, made of 100-denier polyester, factory-coated with a wash-resistant formulation of deltamethrin at a target dosage of 55 mg/sq m. To simulate wear and tear, the nets were intentionally holed with six 4-sq cm diameter holes (two on each side and one on each end) according to WHOPES guidelines [18 ]. The WL was fixed to the walls with nails while the NWH were hung from the top edge of the walls.