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Two groups of Wuchereria bancrofti-infected Haitians who had undergone treatment with diethylcarbamazine (DEC) were followed for up to five years after treatment to document the long-term effects of treatment on adult worms and microfilariae and on the recurrence of infection. One group of 69 persons who had received 12 daily treatments had a significant decrease in microfilaria levels until year 4, when a small number of individuals experienced a resurgence of this parasite stage in the peripheral blood. In a second group of 57 persons who had been treated weekly for 12 consecutive weeks, there was a greater reduction in the microfilaria levels following treatment, and for the full four years of followup, these levels remained more depressed than those of the group that received daily treatment. Our results indicate that DEC kills or permanently sterilizes adult W. bancrofti. Furthermore, these results demonstrate conclusively that in Haiti, the use of DEC provides long-term benefits to treated persons, even though they continue to reside in an area with endemic filariasis.

Reported are results for 23 Haitian patients with capillary Wuchereria bancrofti microfilaremias greater than 30 mf/20 cmm blood. In capillary blood, the number of microfilariae was 0.9 to 7.8 times greater than expected when compared with that in venous blood. When the values for venous blood and capillary blood from these high count patients were plotted, the simple linear regression y = a + bx (r2 = .36) and the exponential function y = aebx (r2 = .34) both represented the relationship. However, when values for high and low count patients were plotted, the power function y = axb (r2 = 0.82) best described the relationship between the number of microfilariae in venous and capillary blood.