Rheumatic fever and streptococci: the Wairoa College study

The decline in incidence of rheumatic fever seen in many countries is not evident in New Zealand. Wairoa county has the highest hospital admission rate within New Zealand, 232 per 100 000 per year, five times the national average, 43 per 100 000. Studies in Wairoa included a cross-sectional survey of the local secondary school. Throat swabbing yielded 13.6% of subjects positive for beta-haemolytic streptococcus group A. Boys had a higher rate than girls, and girls aged 14 and over had a lower rate than younger girls. Discriminant analysis failed to identify ethnic, social or geographic factors as contributing to positivity. Sibling concordance was not significant. ASO titres were high in comparison with another New Zealand study (Rotorua Lakes). There was an association between high ASO titre and throat swab positive for group A and group C streptococci. The prevalence of definite rheumatic fever and rheumatic heart disease was established as 11/715 (1.5%). A wide range of residential geographic, climatic and socioeconomic factors failed to discriminate between cases and noncases. Ethnicity alone was a significant discriminator, the cases being more Maori than noncases.