Malaria and the tropical splenomegaly syndrome in New Guinea☆

The pattern of malarial parasitaemia and the incidence and degree of splenomegaly have been studied in the population of the Upper Watut Valley in New Guinea. Malaria is the only apparent cause of splenomegaly found in this area, and all cases of gross splenomegaly in adults conform to the descriptions of the tropical splenomegaly syndrome. Malaria is meso-endemic and moderately stable. The incidence of parasitaemia is similar in villages at 3300 feet and 5200 feet above sea level, although the incidence of splenomegaly in adults is lower at the higher altitude. Peak parasitaemia is recorded at 3 years of age and then declines slowly, and parasite rates are significantly lower in adult subjects with splenomegaly than in those without palpable spleens. No difference in distribution of species of plasmodia was found between individuals with different grades of splenomegaly or in different age groups or at different altitudes. P. vivax was the predominant species in all groups.