Performing Department
Veterinary Medicine
Non Technical Summary
"Brachyspira hampsonii" is a recently described, virulent spirochete capable of inducing clinical swine dysentery in growing pigs. The incidence of swine dysentery has increased in recent years and "B. hampsonii" has been recovered from pigs with clinical dysentery throughout the major pig-rearing areas of the United States as well as Canada. While clinical disease has been confirmed experimentally following oral inoculation with "B. hampsonii", there has yet to be significant work in determining effective intervention strategies in affected pigs. Tiamulin is an effective antibiotic for control of disease associated with the related spirochete B. hyodysenteriae; however, to our knowledge, the efficacy of this antibiotic against "B. hampsonii" has yet to be confirmed experimentally in clinically affected pigs. The results of this study will be of immediate benefit to swine producers and practitioners in North American as they develop intervention strategies for pigs with clinical dysentery associated with "B. hampsonii" infection.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The objective of this project is to compare the clinical response, gross pathology, and microscopic lesions of pigs infected with "Brachyspira hampsonii" or Brachyspira hyodysenteriae following treatment with tiamulin hydrogen fumarate water medication versus untreated controls.
Project Methods
Seventy-eight 7-week-old pigs will be purchased and acclimated for 7 days during which time they will be established on an antibiotic-free diet with protein content appropriate for growing pigs. Pigs will be randomly assigned to one of three inoculation groups, each receiving a unique inoculum, with three treatment subgroups as follows: non-treated, 60 ppm tiamulin, or 180 ppm tiamulin. Following acclimatization, groups of pigs will be inoculated orally once daily for 3 days with 100 ml of 1 x 108/ml of Brachyspira spp. or sham inoculum, specific for their group, administered via gavage. Prior to inoculation, pigs will be fasted for 12 hours, and feed will be returned 30 minutes after innoculation. Pigs will be monitored daily for development of clinical signs of dysentery (diarrhea with the presence of blood or mucus), dehydration (gaunt appearance, loss of skin turgor), and weight loss. All pigs will be swabbed rectally once daily beginning 48 hours after the last inoculation and throughout the duration of the study to assess shedding of viable spirochetes by microbial culture. Once at least fifty percent of pigs in a given inoculation group have shed viable spirochetes and at least one pig within that main group has developed overt clinical dysentery, the subgroups will be administered their respective tiamulin dose (0 ppm, 60 ppm, or 180 ppm) in the drinking water for 5 days. Ten days after the initiation of tiamulin treatment, all pigs in the main inoculation group will be euthanized by barbiturate overdose and necropsied for tissue collection and lesion comparison. In the event that no animals develop clinical disease in one of the groups by 21 days post-inoculation, the study will be terminated at that time. Statistical analysis will be used to assess differences in the following between treatment groups and between inoculation groups: fecal shedding of Brachyspira, development of clinical dysentery, degree of microscopic colitis, and average daily gain.