RANDOMIZED COMMUNITY-BASED TRIAL OF ANNUAL SINGLE-DOSE DIETHYLCARBAMAZINE WITH OR WITHOUT IVERMECTIN AGAINST WUCHERERIA-BANCROFTI INFECTIONIN HUMAN-BEINGS AND MOSQUITOS

Background WHO has targeted lymphatic filariasis for elimination. Stud ies of vector-parasite relations of Wuchereria bancrofti suggest that a reduction in the microfilarial reservoir by mass chemotherapy may in terrupt transmission and thereby eliminate infection. However, no fiel d data exist on the impact of chemotherapy alone on vector efficiency and transmission intensity of W bancrofti. We compared the impact of a n annual community-wide single-dose treatment with diethylcarbamazine alone or with ivermectin on rate and intensity of microfilaraemia, and transmission intensity in an area of Papua New Guinea endemic for int ense W bancrofti transmission. Methods We carried out clinical and par asitological surveys in 14 communities in matched pairs. People aged 5 years or older in seven communities received randomly assigned diethy lcarbamazine 6 mg/kg and people in the other seven communities receive d diethylcarbamazine 6 mg/kg plus ivermectin 400 mu g/kg. We made phys ical examinations for hydroceles and leg oedema and investigated micro filarial densities by membrane filtration before and after treatment. We selected five communities for monthly entomological surveys between September, 1993, and September, 1995. Mosquitoes were collected in th ese communities by the all-night landing catch method and were individ ually dissected to identify rates of infection and infectiveness. Find ings 2219 (87.6%) of 2534 eligible people received treatment. Microfil arial rate and density had decreased 1 year after treatment in all 14 communities; this decrease was significantly higher in communities giv en combined therapy than in those given diethylcarbamazine alone (mean decreases 57.5% and 30.6%, respectively; p=0.0013). Greater decreases were also seen in community-specific microfilarial intensity with com bined therapy (mean reductions 91.1% and 69.8%, respectively;p=0.0047) . The rate of leg oedema was not altered, but the frequency of advance d hydroceles decreased by 47% with combined therapy and 56% with dieth ylcarbamazine alone. 26641 Anopheles punctulatus mosquitoes were caugh t during 499 person-nights of landing catches. Exposure to infective t hird-stage larvae decreased in all monitored five communities. Annual transmission potential decreased by between 75.7% and 98.8% in combine d-therapy communities and between 75.6% and 79.4% in communities given diethylcarbamazine alone, Transmission was almost interrupted in two communities treated with combined therapy. Interpretation Annual singl e-dose community-wide treatment with diethylcarbamazine alone or with ivermectin is effective for the control of lymphatic filariasis in hig hly endemic areas, but combination therapy brings about greater decrea ses in rates and intensity of microfilaraemia.