CONTAMINATION WITH HELMINTH EGGS OF VARIOUS PROCESSING STAGES OF THE SEWAGE TREATMENT PLANT

Abstract

Because of the establishment of a sewage treatment plant in the city of Isfahan in recent years, a study was undertaken to investigate the effect of this system in reducing the high prevalence of helminthiases. Samples obtained from various parts of the plant and at different stages of processing were examined and it was found that the eggs of Ascaris, Trichostrongylus spp. and Trichuris are found in very high numbers in the canal entering the plant, the majority of which were undeveloped. The average number of Ascaris ova found in one gram of fertilizer at the end of processing was 18, 100, the culture of which yielded a high proportion (up to 45 per cent) of eggs in larval stages. An examination of the inhabitants of two quarters of the city, one with and the other without .a sewage system, showed high prevalence of infection with helminthes among both groups. The difference between the prevalence of infection with each helminth was not significant in these, two groups. Similar infection rates were also found among the laborers working at the sewage plant. The contaminated fertilizer is used in vegetable farms and, because of the large consumption of vegetables by the inhabitants of the city, the important role of contaminated fertilizer in the transmission of Ascaris infection in the city of Isfahan is discussed.