Recent trends of paragonimiasis westermani in Miyazaki Prefecture, Japan

Miyazaki Prefecture has long been known as one of the endemic areas of paragonimiasis westermani. The prevalence of this disease peaked around 1956 and then drastically decreased. A few sporadic cases are still occasionally found in Miyazaki Prefecture; however, the number of new cases has gradually increased during the last 5 years. One important point to be noted is the change of clinical manifestations in the patients. A classically known form of paragonimiasis westermani is characterized by persisting cough, bloody sputum, and nodular or ring shadows in the lung field by chest x-ray. However, the patients recently found in Miyazaki Prefecture rarely showed such typical symptoms. Only four of 13 cases were found to have pulmonary infiltration and nine cases showed massive pleural effusion without pulmonary infiltration. Such atypical cases may be caused by low intensity of infection or, alternatively, be due to the earlier diagnosis.