Comparison of the Epidemiological Features of Habu Bites among Amamioshima, Tokunoshima and Okinawa

Abstract

The present study was designed to compare the epidemiological features of habu bites among the three study areas ; Amamioshima, Tokunoshima and Okinawa. Results are as follows : 1) During the period of 8 years from 1977 to 1984, the annual incidence of habu bites showed a tendency to decrease on both Tokunoshima and Okinawa but not on Amamioshima. 2) The incidence rate of habu bite per 1000 of local population differed greatly among the study areas. However, the rate per 1000 farming population or per 100 ha farm land did not so widely differ among the areas. 3) Patterns for the monthly distribution of habu bite differed significantly among the study areas, the highest incidence was in June on Amamioshima and Tokunoshima but in October on Okinawa. 4) The incidence of habu bite increased with a rise in temperature and reached a peak at 24°C to 26°C, after which it tended to decrease. The incidence also increased steadily with an increase in humidity. 5) The distribution for the frequency of habu bite per day conformed to the negative binomial distribution on the yearly basis but to the poisson series on a monthly basis. 6) Assuming that the frequency of habu bite per head for those who have at least one bite was a truncated poisson distribution, the size of the population at risk was estimated by trial and error. The value obtained was 12, 757 or 15% of the total population for Amamioshima. Corresponding values for Tokunoshima and Okinawa were 15, 873 or 46% and 9, 877 or 1%, respectively.