A new study has reported a strong link between scabies and rheumatic heart disease in Tongan schoolchildren, prompting researchers from Waipapa Taumata Rau (University of Auckland) to call for further investigation.

The research was funded by the Health Research Council and carried out with the Tongan Ministry of Health and Tonga National University.

Dr Gerhard Sundborn from Waipapa Taumata Rau said the work aligns with Tonga's existing school-based screening program.

"Tonga screens all primary school children every two years for rheumatic heart disease as part of its Mafu Sai (Good Heart) programme," he said.

"In 2023, some were also checked for scabies and skin infection."

Researchers trained nurses in visual scabies screening and supervised consistency across assessments.

They screened 400 children from four Tongatapu schools, recording scabies in 29.8 per cent, impetigo in 20 per cent, more severe bacterial skin infection in 15.5 per cent, and rheumatic heart disease in 4.5 per cent.

One scabies case was laboratory-confirmed in Auckland.

Researchers reported children with both scabies and a bacterial skin infection were almost five times more likely to have rheumatic heart disease than children with healthy skin.

They said the risk increased alongside the severity of skin problems, forming a statistically significant pattern.

They found that the combination of severe bacterial infection and scabies was closely linked to rheumatic heart disease, while scabies or impetigo alone were not.

Researchers estimate eliminating scabies and skin infections could potentially prevent about one-quarter of rheumatic heart disease cases.

Lead investigator Dr Simon Thornley said the association is strong and may guide prevention efforts.

"Mass drug administration using ivermectin has worked in the Pacific - studies in Fiji show scabies rates dropped by 80 to 90 percent within two years," he said.

The study does not establish causation but provides evidence that scabies control may reduce risk.

Rheumatic heart disease remains common in Tonga, affecting five in 100 children.

In New Zealand, rates are one in 1,000 overall, one in 100 Māori children, and two in 100 Pacific children.

Researchers are now planning a pilot project on a small island near Tongatapu with about 5,000 residents.

They intend to work with the Ministry of Health Tonga to deliver mass treatment for scabies and monitor new rheumatic fever and rheumatic heart disease cases over several years.

Tongan researcher Mele Tilema Cama said long-term screening has been essential and the new findings may offer a path toward prevention.

"For 20 years our Mafu Sai programme has screened about 5,000 primary school children annually," she said.

"It's resource-intensive but vital for early treatment. We are excited this research may offer a way to prevent rheumatic heart disease."

The findings are available via the Journal of Paediatrics and Child Health.