KO-Tab 123 (Longer lasting Net Retreatment): Uganda
Situation:
Insecticide treated nets are an important method of preventing malaria, however to remain effective they need to be retreated with a pyrethroid insecticide every 6 months to a year. Systems for retreating nets in malaria endemic areas are generally limited, and the majority of nets in use have only been treated once at the most. Bayer Environmental Science has developed a longer lasting formulation, KO-tab 123, which is an easy to use unit-dose tablet formulation of the pyrethroid, deltamethrin. It is easy to transport and use under field conditions, and renders the insecticide more wash-resistant than conventional treatments.
Response: 
The Malaria Consortium is carrying out research in Uganda using the new long term insecticide formulation, KO-tab 123, to look at duration of insecticidal effects under field conditions and assess the feasibility and cost of net treatment in mass campaigns with this product. Two studies are carried out each with a different approach.
In the district of Kayunga a mass net treatment campaign was carried out using KO-tab 123 in October 2005 treating more than 11,000 nets. After the campaign perception of dippers and net users on the new treatment and its ease of use as well as cost were recorded. One week after the campaign a survey was carried out in one administrative area and a total of 224 nets of various ages, materials and colours were recruited for the study. At baseline and every 6 months a sample was taken from these nets up to 18 months of follow-up. These samples were tested for chemical residue of deltamethrin. In addition, information on the washing, use and physical condition of the nets were collected every 3 months. Results from this study are expected in October 2007.
The second study is carried out in Kyenjojo District, Western Uganda and is designed as a phase III WHOPES trial where new nets are given to families to use and a random sample of 40 nets collected for chemical analysis as well as bio-assays after 6, 12, 24 and 36 months. Here we compare a single dose of KO-tab 123 with a double dose (2 tablets) which is closer to the starting dose used in factory treated long-lasting insecticidal nets. This study is now in the second year.
Points to note: 
KO-tab123 has now been given recommendation by the WHO Pesticide Evaluation Scheme as an appropriate treatment for ITNs. The WHOPES statement confirms that KO-tab 123 provides wash resistance up to 15 washes. These WHOPES tests involved the first two phases of a three phase testing programme. The third phase looks at insecticidal life in real life conditions rather than in laboratory wash tests. Our studies and a similar study we are carrying out in Mozambique will provide valuable information about the true insecticidal life in the field. KO-tab123 insecticide treatment has not been shown to last as long as pre-treated LLIN such as PermaNet or Olyset in the phase I and II wash tests and hut studies but is an extremely useful tool to extend the life of field treated nets.
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Photo: Malaria Consortium