Long-term effect of mass diethylcarbamazine chemotherapy on bancroftian filariasis, results at four years after start of treatment.
The long-term effect of 4 strategies for control of bancroftian filariasis using mass diethylcarbamazine (DEC) chemotherapy was assessed and compared in 4 endemic communities in Tanzania over a period of 4 years. The strategies were the standard 12 d treatment (strategy I), semi-annual single dose treatment (strategy II), monthly low dose treatment (strategy III), and DEC-medicated salt treatment (strategy IV). Treatment was given only during the first year. All strategies resulted in considerable reductions in microfilaraemia, with maximum effects occurring 1-2 years after start of treatment. At 2 years, the greatest reductions were seen for strategies III and IV, followed by strategy II and finally strategy I. The overall performance of the 4 strategies evaluated over the 4 years period followed the same sequence. Between the 2 years and 4 years follow-up surveys, a significant increase in microfilarial (mf) burden occurred in all 4 communities, but the mf geometric mean intensities (GMI) remained low. Thus, in individuals who were microfilaraemic before treatment, the rates of microfilaraemia were 66%, 44%, 34% and 43%, and the mf GMIs were 6.8%, 3.3%, 0.5% and 0.7%, of pre-treatment level, 4 years after start of treatment with strategies I, II, III and IV, respectively. Most individuals who developed microfilaraemia between the 2 years and 4 years follow-up surveys had been microfilaraemic before the start of treatment. Hence, the rate of development of microfilaraemia was much higher (18 times on average in the 4 communities) among those who were microfilaraemic before treatment than among those who were amicrofilaraemic. The long-lasting effect of treatment adds a promising potential to the use of mass DEC chemotherapy for the control of bancroftian filariasis.
Danish Bilharziasis Laboratory, Charlottenlund, Denmark. dm@bilharziasis.dk
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DW
Meyrowitsch
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PE
Simonsen
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D004049:Diethylcarbamazine / Q000627:therapeutic use*; D004334:Drug Administration Schedule; D004605:Elephantiasis, Filarial / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008842:Microfilariae / Q000302:isolation & purification; D008875:Middle Aged
D000871:Anthelmintics; D004049:Diethylcarbamazine