MILAN – In a region where scabies is endemic, a , findings that may have implications for future treatment of scabies or other infestations in other regions, dermatologist Margot Whitfield, MD, said at the World Congress of Dermatology.
“Mass drug administration is highly effective and safe in the treatment of endemic scabies,” she said.
Using a strategy of directly observed treatment (DOT) with oral ivermectin or topical permethrin for all residents of two separate island groups in Fiji, Dr. Whitfield, together with epidemiologist Lucia Romani, PhD, both of the University of New South Wales, Sydney, and coinvestigators, demonstrated large and sustained decreases in the rates of scabies and impetigo (N Engl J Med. 2015 Dec 10;373[24]:2305-13).
Across study arms, which included a usual care arm, the baseline rate for scabies ranged from 30% to 40%. With usual care, the rate dropped from 36.6% to 18.8% at the end of 12 months, a relative reduction of 49%. However, the 15.8% prevalence rate 12 months after permethrin DOT (from 41.7%), and the 1.9% rate 12 months after ivermectin DOT (from 32.1%) – reductions of 62% and 94%, respectively – represented much larger decreases, “especially since these reductions were seen without any further interventions,” Dr. Whitfield said. “This was extremely exciting, and a game-changer as far as the management of endemic scabies is concerned.”
At baseline, impetigo rates hovered around 20%-25%, and usual care resulted in a 32% reduction at 12 months. With permethrin DOT, the impetigo rate dropped by 54%; with ivermectin DOT, the impetigo rate dropped by 67%. “The community level of impetigo went down, purely as a result of treating the scabies,” Dr. Whitfield said.
The outcomes of this study, she noted, “have contributed to the global discussion of the treatment of scabies.”
Two years after the mass drug administration (MDA) campaign, scabies prevalence remained much lower than at baseline, with clinical scabies diagnosed in 15.2% of the usual care group, 13.5% of the permethrin group, and just 3.6% of the ivermectin group. “The exciting thing for us was that these levels ... were able to be sustained at 2 years,” Dr. Whitfield noted.
The islands that had received ivermectin saw a continued decline in impetigo prevalence as well: By 24 months, impetigo was seen in 2.6% of participants in that arm.
Scabies is a neglected – but highly treatable – tropical disease, she noted. It is associated with intense pruritus, which results in reduced quality of life, and excoriations predispose those affected to bacterial superinfections, commonly impetigo in the young.
In Fiji, the scabies mite infests nearly 40% of those aged 5-9 years, and over one-third of those younger than 5 years. Rates drop steeply with increasing age and then climb again for the elderly; still, prevalence tops 10% for all Fijian age groups, Dr. Whitfield pointed out. Overall, scabies prevalence is 23% in Fiji, with resultant impetigo affecting 19% of the population.
Providing more details about the study, she said that she and her collaborators – working in conjunction with the Fijian Ministry of Health – took advantage of the geography of the island country, whose 850,000 residents live on 300 islands, to compare mass drug treatment with either ivermectin or permethrin with usual care. “We actually didn’t look for ‘infected scabies,’ ” she explained. “We looked for scabies as one outcome, and infection as another.”
The study was designed to take advantage of lessons from previous public health work addressing filariasis and soil-transmitted helminths, and addressed the following question: In Fiji, could a single round of MDA for scabies control lead to sustained reductions in scabies and impetigo prevalence 12 months later, compared with standard care?