DIRECT ASSESSMENT IN-VIVO OF THE EFFICACY OF COMBINED SINGLE-DOSE IVERMECTIN AND DIETHYLCARBAMAZINE AGAINST ADULT WUCHERERIA-BANCROFTI

When ivermectin and diethylcarbamazine (DEC) are given simultaneously in a single dose to persons with Wuchereria bancrofti infection, the r esulting suppression of microfilaraemia is more profound and sustained than when either drug is given alone. To assess whether this effect i s a result of enhanced macrofilaricidal efficacy, we used ultrasound t o monitor the adult worms in the scrotal area of men with W.bancrofti microfilaraemia. Twenty-one men were treated simultaneously with DEC ( 6 mg/kg) and either 200 mu g/kg or 400 mu g/kg of ivermectin (11 and 1 0 men, respectively). Ten other men received a single 200 mu g/kg dose of ivermectin followed 5 d later by a 6 mg/kg dose of DEC (sequential treatment). All men became amicrofilaraemic after treatment and all e xcept one remained so for one year. Cessation of adult worm movement, indicative of death of all the adult worms in a given 'nest', was obse rved in none of 30 nests in men who received simultaneous treatment an d in 3 of the 19 nests (16%) in the men who received sequential treatm ent (P=0.05). Scrotal nodules were detected in 5 of 21 men (24%) who r eceived simultaneous treatment and in 8 men (80%) who received sequent ial treatment (P <0.01). Thus, coadministration of ivermectin with DEC seems to interfere with the macrofilaricidal action of DEC. These fin dings have implications both for treatment of the individual patient a nd for community-based drug distribution programmes designed to interr upt transmission of W.bancrofti.