The three major Soil-Transmitted Helminths (STH), Ascaris lumbricoides, Necator americanus/Ancylostoma duodenal and Trichuris trichiura are among the most prevalent parasites worldwide. The objective of this multicentre international study is to define the efficacy of a single 400 milligram dose of albendazole (ALB) against these three STHs using a standardised protocol. The trial will be undertaken among school age children in seven countries - Brazil, Cameroon, Cambodia, Ethiopia, India, Tanzania (Zanzibar) and Vietnam - each with a different epidemiologic pattern of infection. A trial of this nature is urgently required because in spite of the wide usage of albendazole over the last 3 decades, there is still no key publication reporting the efficacy of the anthelmintic accurately, and to modern conventional standards, that can act as a central reference for the baseline efficacy. The latter is critically important because albendazole is now being used even more widely, as large scale mass treatment campaigns are being implemented in Africa and elsewhere, with the intention of reducing morbidity in children. Such large scale usage of a drug risks resistance developing, but resistance cannot be detected unless benchmark values for baseline efficacy are widely known.

Inclusion Criteria:

• Children should be infected with a minimum of 150 eggs/gram of any of the three species of STH (i.e. Ascaris or hookworms or Trichuris).

Exclusion Criteria:

• Not willing to participate
• Unable to give samples for follow up
• Severe intercurrent medical condition
• Diarrhoea at first sampling