EN
Animals with diarrhoea caused by Balantidium coli were investigated. The results of estimation of pH in the caecum content show the marked concentration of H+ ions (pH 5.1-6.0). Changes in pH of the parasite environment can abate enzymes activity, which can initiate compensatory reactions of the parasite, among others - intensification of excretion, cytotoxic for the host's tissues.