With the emergence of 'Brachyspira hampsonii'-associated with clinical dysentery in North America, there is a need to identify effective treatments and interventions (1).

Tiamulin liquid concentrate is approved in the United States for the treatment of swine dysentery (SD) caused by Brachyspira hyodysenteriae at 0.006 per cent (60ppm) in the water. The effectiveness of tiamulin in the resolution of clinical disease and elimination of shedding of strongly Β-haemolytic spirochetes following infection with either 'B. hampsonii' (EB107) or B. hyodysenteriae (B204) was evaluated.

Material and Methods

Animals

A total of 78 seven-week-old crossbred pigs were ear-tagged for individual identification and randomly placed in one of nine groups as described in the table below.

Animal inoculation

Pigs received three doses of an agar slurry containing the appropriate inoculum for their group (100ml per dose) administered via gavage 24 hours apart with each administration preceded by a 12- to 18-hour fast.

Animal observations

Faecal scores were performed daily to assess development of diarrhoea with mucus and blood.

Bacteriology

Daily rectal swab samples were collected from each pig beginning four days post-inoculation through five days post-treatment to assess shedding of viable spirochaetes using standard selective anaerobic culture methods.

Treatment initiation

Once at least 30 per cent of pigs in a given main group (group 2 or 3) were culture-positive for viable spirochaetes and at least one pig within that main group had developed overt clinical dysentery, subgroups a and b of the same group were administered 0.018 per cent or 0.006 per cent tiamulin in the drinking water, respectively, for five days.

Ten days after the initiation of tiamulin treatment, all pigs in the main group were euthanised by barbiturate overdose and both rectal swab samples and mucosal scrapings were collected for culture.

Results

Both levels of tiamulin eliminated shedding of strongly haemolytic spirochaetes and resolved clinical disease within 48 hours of treatment initiation in pigs infected with either Brachyspira spp. and all treated pigs remained culture-negative for the remainder of the study as did all sham-inoculated controls.

Figure 1. Elimination of spirochaete shedding was significant when comparing medicated and non-medicated pigs infected with either 'B. hampsonii' (Group 2) or B. hyodysenteriae (Group 3; P=0.0077 and P<0.0001, respectively)

Discussion

These results are consistent with a previous report in which a five-day treatment of 0.006 per cent tiamulin in the water resulted in complete prevention of relapse and elimination of B. hyodysenteriae for 21 days following treatment (2).

Additionally, these results reveal that both of the Brachyspira spp. tested may be highly susceptible to intervention strategies incorporating tiamulin and support the use of this antimicrobial in the treatment and control of clinical dysentery associated with infection with either 'B. hampsonii' or B. hyodysenteriae.

Acknowledgements

^{This study was sponsored by Novartis Animal Health and the authors wish to thank Dr Mark Hammer and Dr Keith Erlandson for their support of this project.}

References

1. Burrough et al., 2013. 44th Annual AASV Meeting, Proc. 551-556.
2. Taylor, 1980. Vet Rec. 106: 526-528

The paper is by Wilberts B.L.¹, Arruda P.H.², Warneke H.L.² and Burrough E.R.² of the Departments of ¹Veterinary Pathology and ²Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, US.

It was presented at the 6th International Conference on Colonic Spirochaetes in Animals and Humans 2013, University of Surrey, UK. 5-6 September 2013.

Further Reading Find out more information on swine dysentery by clicking here.

October 2013