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Editor,—Rheumatic heart disease (RHD) is a major cause of morbidity and mortality in developing countries,1and its true importance may be much greater than is generally recognised. We conducted a prevalence survey of RHD in 8767 school children aged between 5 and 17 years in Samoa; the analysis was weighted to adjust for stratification by urban and rural populations and school level clustering. The prevalence of RHD in our survey was 77.8 per 1000 (95% confidence intervals (CI) 64.0 to 91.6).
The diagnosis of RHD was made on clinical rather than echocardiographic findings by a paediatrician with extensive experience in RHD, and a general physician with cardiology training. Echocardiography increases the specificity of diagnoses of RHD; previous studies suggest that we would have found a prevalence of RHD of about 30 per 1000 if we had used echocardiography. The prevalence of 77.8 cases of RHD per 1000 found in Samoa is the highest reported prevalence in the world to date. A World Health Organisation study estimated that the mean prevalence of RHD among children in developing countries is 2.2 per 1000.1
Three factors may explain the very high prevalence of RHD in Samoa. First, we found that the risk of RHD was significantly higher in rural areas in Samoa (odds ratio 1.86; 95% CI 1.37 to 2.53; p < 0.001) where access to medical services is poor. This is at odds with findings in other studies conducted in developing countries in Africa,2 where urban residence has been identified as an important risk factor in RHD.
Second, RHD and acute rheumatic fever appear to be particularly common in the Pacific region. The highest annual incidence of acute rheumatic fever in the world was found in Australian Aborigines (254 per 100 000)3 followed by Samoans in Hawaii (206 per 100 000).4 Whether this predominance in the Pacific region is due to environmental or genetic factors is not known.
Third, the Samoan children in our study had a high prevalence of pyoderma: the overall prevalence was 43.6% (95% CI 36.7 to 50.2%) and it was highest in the rural regions (57.2%). Unlike the situation in Australian Aboriginal populations,5 the high prevalence of pyoderma was not caused by secondary infection of scabies; the prevalence of scabies was only 4.9% (95% CI 3.0 to 7.0%) in our survey, perhaps because ivermectin has been widely used to eradicate filiariasis in Samoa.
In a subgroup of children, the carriage rate of group A streptococci was 2.4% in the pharynx and 51.3% in pyoderma lesions. This indicates that group A streptococci are more often found in the skin than in the pharynx of Samoan children, as observed in Australian Aborigines.5 The role of group A streptococci from pyoderma lesions in the pathogenesis of acute rheumatic fever and RHD is not clearly understood, although a possible mechanism has been suggested.5
RHD is a major cause of morbidity and mortality in Samoa. Further studies of the epidemiology of RHD are needed in the Pacific region, preferably with echocardiographic confirmation of the diagnosis.
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