What is Swine Dysentery?

Swine dysentery (SD) is a disease caused by Brachyspira hyodysenteriae, which recently reemerged in the North American swine industry. In addition, there are other forms of SD-like disease including the emergence or recognition of newly identified Brachyspira hampsonii.

The classical clinical sign of SD and SD-like disease is muco-haemorrhagic diarrhea (bloody diarrhoea).

Under current conditions, the epidemiology of the SD is not well described.

The disease is costly because of losses due to morbidity and mortality, impaired growth, cost of treatment for disease control and prevention, interference with the pig flow and its impact on animal welfare.

Objectives

• To examine risk factors associated with the use of antimicrobials as an indication of clinical disease progression
• To estimate the serial interval number using treatment rates of Denagard™
• To estimate the reproductive number as an indication of disease transmissibility

The Study

In this study, production data from a grower-finisher barn over a period of two years and 12 batches were used to analyse the risk factors (such as season and use of other antimicrobials) of injectible treatment rates of tiamulin (Denagard) as an indication of treatment due to clinical SD only.

Data were used to estimate the serial interval using the treatment rates for Denagard and to estimate transmissibility of disease in this early phase, using reproductive number (R₀) as the indication of transmissibility. R₀ is an important parameter for how the disease is transmitted within the herd.

In addition, the use of injectable treatment rates of lincomycin was also evaluated over seasons during this time since this antimicrobial was used for treatment of SD-like disease but also for the treatment of other infectious diseases.

Results and Conclusions

Results indicate that tiamulin treatment was used less in the winter season. This could indicate that clinical swine dysentery was not present during the winter time and it is possible that SD shows a seasonal pattern. Lincomycin, a different drug used, exhibited a different seasonal pattern than tiamulin. Using tiamulin treatment rates, a predictable pattern of SD peaked in 17 day-intervals. There is possible cyclic pattern of clinical disease every 17 days.

The R₀ ranged from 0.45 to 2.15, according to the treatment rates of tiamulin.

In this case, the current conditions did not show sustained within-herd transmission. A possible reason for this is that environment has a strong role in swine dysentery transmission. A combination of good biosecurity practices and treatment protocols could prevent signs of clinical disease.

Take-home Message

Good drug records can provide information about risk factors for disease and can be used in studying disease transmission patterns.

Acknowledgments: Funding was provided by the Ontario Ministry of Agriculture, Food and Rural Affairs. The authors acknowledge the swine producers and veterinarians for their contribution and participation for this project.

Reference

Walczak K., Z. Poljak and R. Friendship. 2015. Factors associated with the ue of antimicrobials commonly applied for treatment of sine dysentery in the grower-finisher phase of production. Proceedings of 34th Annual Centralia Swine Research Update. 28 January 2015. II13-II14.

Further Reading

You can view other papers from the Centralia 2015 Update by clicking here.
For more information on swine dysentery, click here.

April 2015