EPIDEMIOLOGY OF PULMONARY EOSINOPHILIA IN RURAL SOUTH-INDIA - A PROSPECTIVE-STUDY, 1981-86

Study objective The study aimed to determine the prevalence and incide nce of pulmonary eosinophilia, with special reference to tropical pulm onary eosinophilia, in a rural community. Design-This was a five year prospective study from 1981-86. Setting-The study was conducted in fou r villages of Tamil Nadu in south India. Subjects-The study population consisted of 24 950 subjects. Measurements and main results-After bei ng questioned about pulmonary symptoms, the selected subjects had peri pheral blood examined for total leukocyte and eosinophil counts; stool s for ova, cysts, and parasites; sputum for acid-fast bacilli, and che st radiography. Subjects with blood eosinophilia of greater-than-or-eq ual-to 2000/mm3 were classified as having pulmonary eosinophilia. One of the 200 asymptomatic control subjects had blood eosinophilia >2000/ mm3. Twenty two (7-7%) of a further 286 subjects selected at random we re found to have microfilaraemia. Between 1981 and 1984 the annual inc idences of pulmonary eosinophilia were estimated at 4.1, 3.1, and 2.7/ 1000 while the prevalence rates were 6.4, 9.3, and 11.9/1000 respectiv ely. This rising prevalence over time occurring simultaneously with a falling incidence suggests that the final incidence rate (2.7/1000) wa s likely to be the most accurate of the three estimated. At resurvey i n 1986, 314 cases were classified as pulmonary eosinophilia giving a p revalence rate of 12.6/1000. Altogether 214 of them also had intestina l worm infestations, including 58 in whom eosinopenic remission was re corded after deworming alone. Eosinopenic remission was documented in 135 of 182 cooperative patients who were considered to have tropical p ulmonary eosinophilia and agreed to be treated with diethylcarbamazine . Conclusions-This study found that tropical pulmonary eosinophilia, e ither alone or with worm infestation, was a major cause or morbidity i n this rural population.