Bancroftian filariasis: the pattern of microfilaraemia and clinical manifestations in three endemic communities of Northeastern Tanzania.

Individuals from three villages in northeastern Tanzania, located 40 km inland from the Indian Ocean coast, were surveyed for parasitological and clinical evidence of bancroftian filariasis. Microfilarial (mf) prevalences ranged from 22.2 to 37.6%, and mf geometric mean intensities (GMI) ranged from 546 to 735 mf/ml blood, in the three villages. Microfilaraemia was rare in children below five years. The mf prevalences increased with age, reaching from 35.9 to 49.2% in individuals aged 45 years and above. No association between mf GMI and age was observed in any of the villages. Hydrocele was the most common chronic clinical manifestation, with prevalences ranging from 14.5 to 21.3% for all males, and from 52.9 to 62.1% for males aged 45 years and above. From 0.6 to 3.3% of the inhabitants in the three villages had elephantiasis, which most often affected the legs. Microfilaraemia was common in males with hydrocele, and in males of 45 years and above there was no significant difference in mf prevalence between males with (42.5%) and without (55.2%) hydrocele. In contrast, microfilariae were only detected in the blood from one of 18 individuals with elephantiasis. With respect to hydrocele, the present results do not support recently forwarded hypotheses assuming a general negative relationship between microfilaraemia and chronic clinical manifestations in bancroftian filariasis.