The conditions of malaria transmission in Katsina Province, Northern Nigeria, and a discussion of the effects of dichlorvos application.

A study has been made of the conditions of malaria transmission in the northern part of the Guinea savannah belt of West Central Africa. It was found that, in this holoendemic area, transmission occurs principally from August to December but continues on a much reduced scale throughout the rest of the year, even when anopheline densities are as low as 0.02 per hut. Longitudinal parasitological studies on infants, carried out on an area rather than an individual village basis, provide the most useful epidemiological technique during the minor transmission period. Examination of the spleens of children from areas that had been treated with dichlorvos suggested that the reduced hut anopheline densities resulting from the treatment were subsequently reflected in the reduced number of children showing markedly enlarged spleens.