EN
Four experimental groups (litters) of suckling piglets were formed. Three-day-old piglets from groups I, II, and III were infected per os with I. suis oocysts (200,000, 50,000, and 50,000 oocysts per piglet, respectively) and piglets from group IV were the negative control. Faecal samples were collected from each piglet daily, from 2 to 23 d post infection, and examined with the use of the McMaster method. Additionally, the intensity of diarrhoea was estimated on the basis of consistency of faeces. The piglets from groups III and IV were weighed at the beginning of the experiment and then 1, 2, 3, 4, 6, and 7 weeks after the infection. Histological preparations were made from the intestines of piglets, which died due to the infection. Two or three phases of the intensifications of clinical signs and oocyst shedding were noted in the course of the infection. Moreover, the considerable differences in the intensity and time of oocyst excretion in individual piglets in the same litter were observed. The infected piglets had significantly lower body weight in 1, 2, 3, 6, and 7 weeks after the infection than the control piglets. The desquamation of intestinal epithelium and shortened intestinal villi were observed in histological sections of the small intestine. Moreover, the developmental stages of I. suis, i.e. meronts, merozoites, micro- and macrogamonts were observed in intestinal mucosa of the infected piglets.