Could Mass Drug Administration Solve the Global Scabies Problem?

Scabies is a highly contagious skin condition caused by Sarcoptes scabiei, a female mite that burrows under the skin, defecates, and lays eggs, causing severe itching.¹

Spread through person-to-person contact, scabies is very common, affecting approximately 130 million people worldwide. Although scabies knows no borders, it is most prevalent in the tropics, where it disproportionately affects poor communities.¹

Scabies is responsible for substantial morbidity due to not only the debilitating itching, but also secondary bacterial skin infections (eg, impetigo), which are common and increase the risk of immune-mediated systemic complications involving the kidneys and heart. Effective treatments are available to treat scabies and include topical permethrin 5% cream and oral ivermectin.¹

How can we control and eventually eliminate scabies globally? A randomized controlled trial recently published in the New England Journal of Medicine sought to determine the most effective way mass drug administration could be used to do so.²

In this trial, 3 island communities were randomly assigned to one of 3 groups: standard care, topical permethrin, or oral ivermectin.

Standard care consisted of topical permethrin for those with active scabies and their contacts, while the topical permethrin and oral ivermectin groups consisted of a single dose of either drug for everyone, with a second dose for those with active scabies.

Among the participants excluded in the oral ivermectin group were pregnant or lactating women, as well as children weighing less than 15 kg, for whom drug safety is uncertain. Overall, 2051 children and adults participated in the study, consisting of 85% of the 3 communities’ populations.

At 12 months, the prevalence of scabies was reduced in all groups, from 32.1% to 1.9% in the ivermectin group, 41.7% to 15.8% in the permethrin group, and 36.6% to 18.8% in the standard care group. The difference in risk reduction was not statistically significant between the standard care and permethrin groups (P=0.09), but it was significant when comparing the ivermectin group with the other 2 groups (P<0.0001).

Similarly, the prevalence of impetigo was reduced in all groups, but the greatest reduction was seen in the ivermectin group. Although adverse events were more common in the ivermectin group, they were neither serious nor persisted for more than 7 days, and they mostly consisted of itching and headache.

This trial supports the theory that mass administration of ivermectin may be the most effective way to control scabies and reduce its global burden. Mass drug administration programs for antiparasitic drugs have been successful in controlling several parasitic diseases in endemic regions, including lymphatic filariasis.

As indicated in an accompanying editorial, the World Health Organization has not yet developed a formal program for scabies control and elimination,³ but this trial provides important evidence that should be integrated into existing health systems and public health programs in endemic populations.

References

1. Scabies. World Health Organization. http://www.who.int/lymphatic_filariasis/epidemiology/scabies/en/.Accessed December 10, 2015.

2. Romani L, Whitfeld MJ, Koroivueta J, et al. Mass drug administration for scabies control in a population with endemic disease. N Engl J Med. 2015;373:2305-2313.

3. Currie BJ. Scabies and global control of neglected tropical diseases. N Engl J Med. 2015;373:2371-2372.