Endemic incidence of infections caused by Mycobacterium kansasii in the Karviná district in 1968-1995 (analysis of epidemiological data--review).

The Karviná district (northwestern part of North Moravia and Silesia) is typical by its industrial character, above all mining of black coal which is coked and which led to the devastation of the countryside. The ratio of light industry is low. In a small area (347 km2) there is a population of 824 inhabitants per km2. The population is concentrated in particular in urban agglomerations of the flat block type. Up to 1990 almost 55% of the population was employed in heavy industry. Due to its industrial activities, incl. metallurgical plants and ironworks in nearby Ostrava and Trinec, the district is one of the areas with a heavily contaminated atmosphere in particular with solid aerosol containing toxic metals (the values of solid aerosol varied on average between 100 and 150 micrograms/ml), the elevated values of Nox due to contamination from traffic and polyaromatic hydrocarbons were not negligible either during the investigation period. Since 1968 an endemic incidence of mycobacteria has been recorded which is due to Mycobacterium kansasii. At first only an occasional incidence was involved, since 1973 there has been a more substantial increase with a maximum in 1983 (64 cases) and thus up to 1995 there are 961 cases on records, incl. 787 (81.8%) in men and 174 (18.2%) in women. From the total number of recorded M. kansasii in 937 instances (97.3%) the lungs were affected (777 men, 160 women). The mean annual incidence was 34.3 cases, i.e. 12.03 per 100,000 population (28.1, i.e. 20/100,000 in men, 6.2, i.e. 4.28/100,000 in women). As to age, 78.8% of cases are recorded in the age bracket from 25 to 64 years (in men 81%, in women 68.9%). The highest specific morbidity in men is in the age group from 45-54 years (on average 73.13 per 100,000 per year), in women in the age group from 75 to 84 years (on average 9.75 per 100,000 per year). As to occupation, the ratio of mine employees at the time of contraction of the disease (incl. retired miners) was 52.2%), other workers 14.6%--all stigmatized by an increased dust concentration in other workplaces in heavy industry. As far as the domicile is concerned, the incidence was by far highest in Havírov (more than 56%), followed by Karviná (26.7%). These towns are inhabited mostly by miners. As to the mode of assessment 68.8% cases were diagnosed on account of pulmonary complaints and during dispensarization (stigmatization by dust) and 24.6% cases during preventive radiodiagnostic examinations of miners lungs. It did not prove possible to reveal the source. Interhuman transmission was not proved in any of the patients. The causal agent of the infection is most probably transmitted through water (by the aerogenic route). M. kansasii was isolated from drinking water (560 samples, in 7% M. kansasii was found), as well as in industrial water. In 1971-1995 a total of 1231 samples of industrial water were examined (scrapings and untreated water). From these M. kansasii was isolated in 43.7% (538 specimens). In soil samples (93) and small mouse-like rodents (187) M. kansasii was not detected. The authors confirm that the development of disease depends in a decisive way on the susceptibility of the individual which in turn depends in particular on exposure to dust with possible lung damage and contamination of the atmosphere. In the district there is a high incidence of recurring acute diseases of the airways in children, incl. allergies affecting the airways. In the towns of Karviná, Havírov, Orlová, Bohumín and Ceský Tĕsín there is a high ratio of children with reduced immunity. In November 1981 to January 1982 987 first form pupils were examined for postvaccination TB allergy (standard tuberculin and avian tuberculin were used). The reactivity to avian tuberculin was higher than to standard tuberculin (see results). The highest ratio of intense reactions (30%) was recorded in children from Havírov where there is also the highest specific (and simple) incidence in adults.