28th September 2011
DIARRHOEAL DISEASE IN HORSES
RIRDC HORSE RESEARCH
by Thomas V Riley, Sara Thean and Briony Elliott
Report from RIRDC Publication No. 11/032 – April 2011
Clostridium difficile is a disease-causing pathogen in humans and horses. For the first time its presences has been confirmed in Australia on the report Diarrhoeal disease in horses in Australia – The possible role of Clostridium difficile.
Lead by Professor Thomas Riley at the University of Western Australia and funded by the Rural Industries Research and Development Corporation (RIRDC) Horse Program, this project represents the first survey of its kind in Australia. There is now no doubt that C.difficile can be found in Australian horses and can be associated with diarrhoeal disease. According to the report, the industry should be aware of this emerging threat to both animal and human health.
In the last 20 years, the anaerobic bacterium C.difficile has become accepted as an enteric pathogen in horses, particularly in Europe and North America. It has been associated with colitis in mature horses when they are undergoing treatment with antibiotics. It has also been associated with colitis in mares when their foals are being treated with antibiotics for Rhodococcus equi pneumonia. The role of it in relation to diarrhoea in foals remains controversial and foals under the age of two weeks can carry the pathogen with no apparent ill effects.
In humans, the pathogen is one of the most commonly diagnosed causes of infections hospital-acquired diarrhoea, causing serious infections in hospitals in Australia, the United States, Great Britain, Europe and Canada.
The Study
The objective of the study was to establish the prevalence of the pathogen in horses in Australia. 174 faecal samples were taken from adult horses and foals, predominantly in Western Australia. C.difficile was found in 26 per cent of diarrhoeal animals (including 11 foals), and none of the 112 healthy adult horses.
Implications For Vets And The Industry
There are significant implications for the horse industry as a result of this work. If C.difficile is truly will established in Australia then control measures need to be implemented. Anecdotally, expensive racehorses have dies as a result of C.difficile disease in the USA, The same is likely to be occurring in Australia. Most importantly, C.difficile infection in adult horses should be strongly suspected on cases of acute diarrhoea in association with antibiotic treatment.
The two major risk factors for getting C.difficile are exposure to the organism and exposure to some agent of process that alters the gut microflora. Therefore intervention will need to be targeted to these areas. It will be very difficult (but not impossible) to eradicate C.difficile from the equine environment as C.difficile forms spores that are hardy and remain viable for many months, so an easier way may be to look at antibiotic usage in the industry.
It may be possible to change antibiotic prescribing practices so that antibiotic s that have a major impact on the gut microflora of horses are replaced with less disruptive kinds. In particular, broad spectrum cephalosporins, such as ceftiofur, should be avoided as C.difficile is intrinsically resistant to this class of antimicrobials.
Further Research Is Need
The data presented in the study are preliminary and the study needs to be repeated with a larger sample size, better geographical representation and with a greater emphasis on collecting risk factor data. More research needs to be done evaluating various diagnostic methods in horses, because it cannot be assumed that what works for human infections, works for horse infections.
What role the organism plays, particularly in diarrhoea in foals, also requires further work. The evidence in adult horses, from the study and the literature, suggests this is an important cause of diarrhoea that the industry should not ignore.