Division of Geographic Medicine, Department of Medicine, Case Western Reserve University and University Hospitals, Immunoparasitology Unit, The Walter and Eliza Hall Institute of Medical Research, Papua New Guinea Institute of Medical Research, Cleveland, Ohio 44106, Australia
Bancroftian filariasis has been reported in several areas of Papua New Guinea. The epidemiologic features and natural history of Wuchereria bancrofti infection in this geographic region, however, have not been well-defined. The objective of this study was to assess the parasitological and clinical features of bancroftian filariasis in a community in East Sepik Province, Papua New Guinea. In a village of 99 individuals, the overall prevalence of microfilaremia was 68%. The microfilarial carrier rate was high in those ≤ 10 years (62%), remained elevated in the 11–20, 21–30, and 31–40 age groups (42–55%), and peaked in subjects ≥41 years old (90%). The geometric mean level of parasitemia in all subjects with patent infection was 3,198 microfilariae/ml blood. This value was 78 parasites/ml in the ≤10-year-old age group, increased to 1,753 in 21 to 30-year-olds and was markedly elevated in subjects ≥41 years old (6, 792 microfilariae/ml). Acute symptoms of filariasis (lymphadenitis and lymphangitis) were initially noted in individuals between the ages of 11 and 20 years (30%). Obstructive disease, manifested as elephantiasis and hydroceles, was present in 64 and 79% of 31–40 and ≥41-year-olds, respectively. These data suggest that intense transmission of W. bancrofti infection occurs at an early age in this area of East Sepik Province; patent infection remains high in older age groups. Irreversible lymphatic obstruction develops 20–30 years after initial infection and may be associated with either amicrofilaremia or microfilaremia.