The study has been published in the 'BMJ Global Health Journal'. Acute rheumatic fever is an important cause of serious heart disease, particularly for Maori and Pacific children and young people in Aotearoa, New Zealand and for many children and young people in low and middle-income countries.
Professor Michael Baker from the Department of Public Health at the University of Otago, Wellington, explained that it has long been recognized that rheumatic fever is a complication of group A streptococcus (GAS) pharyngitis, commonly known as "strep throat". However, new research indicated that streptococcus skin infections can also trigger the disease. "This study is a major breakthrough in understanding the causes of acute rheumatic fever," Professor Baker said.
"It is the world's first study to confirm that the risk of rheumatic fever rises after a GAS skin infection in a similar way to how it does after a GAS sore throat. Because acute rheumatic fever is an uncommon disease and few countries have comprehensive linked health data, no previous study has been able to quantify the rheumatic fever risk following a laboratory-confirmed infection," he added. New Zealand has one of the highest rates of rheumatic fever seen in a high-income country, with more than half of all rheumatic fever cases in the Auckland region.
This study used data on almost 1.9 million (1,866,981) throat and skin swabs processed in the Auckland region over an eight-year period, which was linked to hospitalization data to identify rheumatic fever cases, as well as prescribing data to identify if cases were dispensed antibiotics. The risk of rheumatic fever increased five-fold in the eight to 90 day period following collection of both a GAS positive strep throat swab and a GAS positive skin swab (compared with negative swabs). Maori and Pacific children had the highest risk of developing rheumatic fever following the collection of a GAS positive swab.
The focus of rheumatic fever prevention in New Zealand has been largely on diagnosing and treating GAS throat infections. This established thinking is behind the school-based sore throat management programme that has operated in several North Island DHBs for more than a decade. Professor Baker said that the study's findings have huge implications for the prevention of acute rheumatic fever. "While treating GAS sore throats should remain a key strategy in the prevention of rheumatic fever, a new focus should also be placed on addressing GAS skin infections to help reduce the risk of rheumatic fever in New Zealand and internationally," he said.
New Zealand has a high and increasing incidence of skin infections, with markedly higher rates in Maori and Pacific children compared with children of European and other ethnicities. "Health professionals caring for children at risk of rheumatic fever need to treat skin infections with the same level of intensity as throat infections. While a key message for the public is that skin infections matter and need to be treated promptly," he said. The study team is now planning research to build on these findings, said Dr Julie Bennett, who also worked on the research. "We are planning a trial of more intensive skin infection treatment to see if this can reduce the risk of developing rheumatic fever," she said.
The study also revealed that dispensing a course of oral antibiotics, which is the routine treatment for children following a strep throat diagnosis, was not associated with a reduced risk of developing rheumatic fever. "This is a worrying finding. It suggests that we need to find more effective ways of treating these infections than the course of oral antibiotics that is currently prescribed," Dr Bennett said.