Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/1995
Publication Date: N/A
Interpretive Summary: Enteritis is of major economic importance to swine producers because of death from severe cases or lost feed efficiency during mild or moderately severe cases. The cause of 20 to 30% of the outbreaks investigated by diagnostic laboratories are never determined. The goal of the research was to determine whether two strains of chlamydia (R19 and R27) which were isolated from 6- to 8-weak-old pigs with enteritis and pneumonia would produce enteritis in gnotobiotic piglets. The isolates were inoculated into 3- to 4-day-old piglets by adding the chlamydia to the milk. Both isolates produced an extensive enteritis starting at 3-4 days after inoculation and lasting 7-8 days. High doses resulted in severe dehydration and recumbency of the pigs. The lesions were primarily in the distal jejunum and ileum and were characterized by atrophy and necrosis of the intestinal villi. The results indicated that the swine chlamydial isolates used in this study are intestinal pathogens and that they could produce a severe economic loss through decreased feed efficiency.
Technical Abstract: The objective of this study was to determine whether 2 distinct chlamydial isolates recovered from the intestines and feces of diarrheic nursery pigs could cause intestinal lesions in gnotobiotic pigs. Chlamydial isolates R27 and R19 were propagated in Vero cells or embryonated eggs. Each piglet was fed 1 ml of inoculum or sham inoculum at 3-4 days of age. Ten piglets were each fed 10**9 inclusion-forming-units (IFU) and 14 piglets were each fed 10**6 IFU of isolate R27. Twenty piglets were each fed 10**5 IFU R19. All infected piglets developed diarrhea 4-5 days postinfection (DPI). Most piglets fed 10**9 IFU R27 became anorexic, dehydrated, and weak and were necropsied 4-7 DPI. Diarrhea persisted in the piglets fed 10**6 IFU R27 or 10**5 IFU R19 through 12 DPI. At necropsy, all diarrheic piglets had watery colonic contents with flecks of undigested curd. Histologic lesions were seen most consistently in distal jejunum and ileum. Distal jejunum and ileum from piglet fed 10**9 IFU R27 and necropsied 4-5 DPI were characterized by villus atrophy and multifocal necrosis of villi. Mild to severe villus atrophy, lymphangitis, and perilymphangitis were seen in the distal jejunum and ileum from all infected piglets 7 and 10 DPI. Immunostaining done on sections of distal jejunum and ileum revealed chlamydial antigen in villus enterocytes. Ultrastructural examination of ileal villus enterocytes revealed chlamydiae in vacuoles or occasionally free in the cytoplasm. The results indicated that the swine chlamydial isolates used in this study are intestinal pathogens in gnotobiotic pigs.