This news story was first published in print and online by The Medical Republic on 24th February 2016.
Scabies remains a scourge of remote Aboriginal communities although new strategies are promising.
Seven out of 10 children in such communities are thought to be affected with scabies, and infection with Group A streptococcus bacteria can lead to sepsis, rheumatic fever, acute kidney disease and rheumatic heart disease.
An intervention recently published in NEJM showed that treating all inhabitants of a Fijian island reduced prevalence of scabies by 95% at 12 month follow-up. This compared with a 62% reduction in a neighbouring island community randomly assigned to mass administration of topical permethrin.
The prevalence of impetigo also declined by more than half in the invermectin-treated community, and a 15 year follow-up of an ivermectin intervention in the Solomon Islands found only one case of scabies out of around 1500 people (PLoS Neglected Tropical Medicines).
By contrast, the findings from an invermectin mass-intervention in an island community 550km from Darwin were not encouraging. Although short-term results had matched the other trials, scabies prevalence bounced back up to 9% at 12 months follow-up.
The difference in outcomes can largely be explained by the arrival in the 2100 person aboriginal community of one or two individuals with crusted scabies, said Dr Thérèse Kearns who authored the report also in PLoS NTM. Where a person might ordinarily be infested no more than ten mites, in cases of crusted scabies there are thousands of mites.
In the light of recent research, crusted scabies was now managed not simply as an infectious disease, but as a chronic condition, said Dr Thérèse Kearns of the Menzies School of Health Research.
“So as for diabetes or kidney disease, if you have ever been diagnosed with crusted scabies you’ll now be followed up on a regular basis” Dr Kearns said. “You’d have your skin checked every month to prevent recurrence of infection of others.”
“But there will be some people that don’t show strong symptoms though they have a mite burrowing into the skin,” she explained. “In our ivermectin interventions, we went house to house and treat the entire household, whether they showed clinical signs or not.”
Australian public health practitioners reccommend this response when prevalence reaches 5% or higher, however, the World Health Organization has not yet issued guidelines for the management of scabies.
Dr Kearns said that screening for crusted scabies of visitors to remote communities was also essential, since a single individual could spark a widespread outbreak. Before ivermectin was introduced in the Northern Territory, around half of people with crusted scabies died within five years, she said.
In order to maximise participation in mass administration programs of people with very low health literacy, Dr Kearns and colleagues employed locals to tell illustrative stories with the permission of community elders. One of these stories described the poisonous cycad nut, which can however be eaten after proper cleaning process. “So the parallel is how you can cleanse your body and look after yourself to make it healthy,” said Dr Kearns.
Dr Kearns said the message was well received, as shown by the response of the community when her team flew back in after a period away for Christmas break. “People were lining up at the airport and asking could you please do my household first. They understood what needed to be done and were very willing participants.”
Further food for thought comes from recent Australian research on the genetics of scabies mites in indigenous communities, which found a patient was infected with mites more similar to those typically found on pigs.
“This suggests it may be possible for certain animal strains of mites to infect humans, which we did not previously know was possible. This could have major implications for disease control programs,” said author Dr Katja Fischer of the Queensland Institute of Medical Research.
NEJM 2015 Dec 10;373(24):2305-13
PLoS Negl Trop Dis. 2015 Dec 1;9(12):e0004246
PLoS Negl Trop Dis. 2015 Oct 30;9(10):e0004151