Study children received their monthly treatment from a VHW based in a PHC village. The VWH distributed the trial medication at a central point (usually a health post) during the first 10 days of the month during September, October and November. Mothers and carers were asked to bring their children to the central point during the morning when the VWH was available to distribute the drugs. When a child presented to the central point for medication, the VHW identified the study subject using the treatment card held by the mother and matched the information on the treatment card with that on his register. When he was satisfied that he had correctly identify the study subject, the correct dosage of the trial medication was given to the study subject. In non-PHC villages, mothers were asked to bring their children to their nearest PHC village to receive IPT during the transmission season.