Pathogenesis on enteritis induced by Cryptosporidium parvum alone and combined with porcine rotavirus in piglets

Cryptosporidium parvum 단독 및 돼지 rotavirus와 혼합 감염시킨 자돈 장염의 병원성

The purpose of the present study was to understand the pathogenesis of infections in piglets inoculated with C parvum isolated from mice alone and combined with porcine rotavirus (S-80). Thirteen 10-day piglets were divided in four groups; Three, A group, were only given by C parvum. Four, B group, were orally administrated with firstly porcine rotavirus and then C patvum. Three, C group, were orally inoculated with porcine rotavirus alone. The rest, D group, were used as controls. During the experiment, there were daily recorded clinical signs including diarrhea to each pig. According to the periodic intervals for necropsy, all pigs were sacrificed from 4 to 12 days after the final inoculation of C parvum. Location and distribution of two pathogens, C parvum and rotavirus, in the intestinal mucosa of piglets tested were examined by pathological and immunohistological means. In addition, parasitological test using the feces of piglets was applied for the detection of cryptosporidial oocysts as well. A group showed diarrhea from 4 to 6 days post-inoculation(PI) and also discharged C parvum oocysts in feces during the day 4 to 7 PI. In tissue sections of jejunum and ileum, cryptosporidial oocysts were observed a few on the top of villi with slightly fusion. B group represented sign of diarrhea and discharge of oocysts from 2 to 11 days PI. There were some cryptosporidial oocysts both in the jejunal lumen and in the lumen of mucosal glands. As progressed, oocysts were most commonly distributed on the tip of villi of jejunum. Histopathologically there were also mild to moderately fused, attenuated focal desquamated, congested villi and mononuclear cell infiltration of varying degrees in the lamina propria of small intestine and colon at the day 4 and 7 PI. C group showed slightly to mildly attenuated and fused top of villi and mildly mucosal congestion. D group as controls was grossly and histopathologically normal in all parts of intestine. The present results indicate that the piglets inoculated with C parvum only are certainly milder in pathogenesis including duration of clinical course and severity of lesion than those in piglets concurrently infected with porcine rotavirus and C parvum. Also the strain (VRI-CN91) of C parvum used in the study has very low pathogenicity to occur enteritis of piglets.