Relationship between prevalence and intensity of Opisthorchis viverrini infection, and clinical symptoms and signs in a rural community in north-east Thailand

Abstract

In a large village in north-east Thailand, the overall prevalence of Opisthorchis viverrini infection (based on Stoll's quantitative egg count) was 89.5% in a total population of 1651 individuals. The prevalence was 32% in children under 5 years, 90% in those aged 5-9 years, and averaged 95.6% in age groups above 10 years. The mean faecal egg output (indicative of intensity of infection) was highest in the 40-49-year age group and remained relatively constant through older ages. In all age groups the prevalence and intensity of infection in both men and women were similar. A history of eating rawfresh water fish occurred more frequently in infected persons than in those uninfected. The following symptoms occurred significantly more frequently in groups with higher intensities of infections: weakness, flatulence or dyspepsia, and abdominal pain in the right upper quadrant. Nevertheless, infected persons did not report a reduced ability to work. Anorexia, nausea, vomiting, and diarrhoea were only weakly correlated with the intensity of infection. A palpable liver occurred more frequently in the infected groups and was correlated with intensity of infection. Icteric conjuctivae were observed in 2.2% of infected persons but not in the uninfected. Some 5-10% of the population had symptoms that were attributable to opisthorchiasis.