Washing of nets by hand
The nets were hand washed and dried outdoor at KEMRI Centre for Global health research in Kisian village, western Kenya. Four field assistants from the local community were hired to do the washing. Hand washing was done by immersing the netting in a measured volume of water using a measured local detergent Omo. The field assistants were randomly assigned to wash the four brands of nets by hand rubbing in a 10-litre water bowl. Nets were washed for 10 minutes in 2 litres of cold rain water mixed with 5 g of detergent. After washing each net was rinsed twice for 5 minutes in same amount of clean water. Each net was washed twice a week. Washing was done mid-morning between 9 to 10 am.
Net drying procedures
The four different drying regimens were tested only on nets that were washed by hands. It is important to note that this is the most common washing method used in the local villages. After washing, the nets were air-dried as follows: one net from each treatment group was air-dried in the sun by hanging, while the second net was air-dried in direct sunlight spread on the ground. The third net from each group was air-dried under the shade spread on the ground and fourth net from each treatment group was dried under the shade hanging on a line. The nets were left in position to dry for a fixed period of 4 hrs. Initially before adopting a standard drying time, nets were inspected hourly to ascertain their drying status. It was established that 4 hours was the adequate period in the study area for nets to dry completely, whether in direct sunlight or under the shade. This period was adopted as the optimal time nets needed to dry and was used throughout the study
Washing of nets by machine
In this method, the net samples were washed using WHO protocol as follows: 1 gram of soap OMO powder was thoroughly dissolved in 500ml of rain water in 1 L Erlenmeyer conical flask. A single sample of netting 30 by 30cm was placed in the soap solution. The nets and soap solution were shaken for 10 min on an orbital shaker bath (C76 Water Bath Shaker; New Brunswick Scientific Co., Edison, NJ, USA) at 155 rotations per minute at room temperature. After washing with soap, the nets were rinsed twice by shaking for 10 min in 500 ml of rain water each. After the nets were rinsed a second time they were hung on a line indoors to dry for 4 hrs.