A new approach to the measurement of residual transmission in a malaria control scheme in East Africa

Abstract
In the 4th year of protection in a malaria control scheme, despite the absence of infected anophelines and a very low infant parasite rate, infections with P. falciparum were still fairly common in children and adolescents. After a preliminary trial, which encouraged belief in the adequacy of the doses used, a group of people were treated with drugs to clear them of infections with P. falciparum. When examined 4 months later all those found infected on the first examination were clear of parasites while, conversely, a number who were uninfected earlier had a parasitaemia. These results were interpreted as evidence of recent transmission, although certainty must await more complete knowledge of the biology of P. falciparum infections in partially immune Africans, and the reaction of such infections to small doses of drugs. Doubt is thrown on the infant parasite rate as the most satisfactory index of malaria transmission in eradication schemes and an alternative method suggested.