Malaria and tropical splenomegaly syndrome in the Anga of Morobe Province.

The Hamtai speaking Anga of the Upper Watut valley have long been considered to be unique in their response to recurrent malaria. Given sufficient exposure, the vast majority develop tropical splenomegaly syndrome concomitantly with their acquisition of effective immunity, whereas elsewhere this disease occurs sporadically. The present study indicates that the Menya of the Tauri valley, a related Angan group, respond similarly, in terms of frequency and degree of gross splenomegaly. On the other hand, the Kapau valley, the traditional homeland of the Hamtai, lying between the Watut and Tauri valleys, remains for the most part free of malaria. It is suggested that all Anga will respond to recurrent malarial infection in the same atypical manner; and that this response results from lack of appropriate genetically-determined mechanisms for mounting efficient immune responses to this infection, significant exposure to which is a relatively recent event for these people.