Epidemiology of acute filarial episodes caused by Wuchereria bancrofti infection in two rural villages in Tamil Nadu, south India

This year-long study investigated the epidemiology of acute filarial episodes due to Wuchereria bancrofti in 2 rural villages in south India. The annual incidence of 96.5 episodes/1000 population was significantly higher in males (1085) than females (841) and strongly age dependent. First occurrence of acute disease was observed in 0.86% of the population, and the average duration of each episode was 3.6+/-2.0 d. Although more than half(63.5%) of the affected individuals suffered only 1 episode, a few experienced as many as 8 over the one-year period. Individuals with chronic disease were more prone to acute attacks, with 82.9% of the total episodes occurring in this group. No seasonal pattern was observed in the frequency of episodes. Probit analysis showed that the number of episodes per affected person was dependent on sex and chronic condition. Swelling of lymph nodes in the inguinal region and fever were the most common symptoms of acute disease. The high incidence and resulting debility observed in this study suggest that acute episodes are a significant health problem associated with lymphatic filariasis. There is clearly a need for more studies on this acute form of filarial disease to aid in the understanding of the aetiology and epidemiology of acute episodes, in planning appropriate control interventions, and in evaluating the resulting health burden.