Bacteria that are resistant to antibiotics have become a serious threat to humans and animals. Methicillin-resistant Staphylococcus aureus (MRSA) is an example of such a bacterium. MRSA infections in horses are difficult to treat, as there are so few effective antibiotics. By improving hygiene in hospital care for animals, the spread of resistant bacteria can be reduced.
Study of risk factors for MSRA
Horses that have been treated with antibiotics and that live on farms where MRSA is known to be present are more likely to be carrying MRSA when they are admitted to an equine hospital.
A dissertation by Karin Bergström, Swedish National Veterinary Institute provides insights into MRSA in horses and emphasizes the importance of measures to prevent infections in equine hospitals.
"The introduction of infection-prevention and control measures is a self-evident responsibility of horse hospitals, as MRSA involves both patient safety and the working environment," says Assistant State Veterinarian Karin Bergström.
In the summer of 2008, MRSA-infected horses were found at an equine hospital in Sweden. It was through the studies included in the dissertation that this outbreak could be established. A key observation was that infections of superficial wounds, which most of the horses were suffering from, healed without treatment with antibiotics. This event led to increased interest in preventing MRSA in equine healthcare.
The bacteria in the outbreak turned out to belong to a type of MRSA called CC398. This type is associated with foodstuffs-producing animals, but it has also been found in horses in Europe.
This was the first time this type of bacteria had caused infections in animals in Sweden. Of a total of nine horses that could be monitored after the infection, all but one evinced negative samples within two to seven months, and their nostrils proved to be the most reliable sampling site for revealing MRSA.
Collaboration between the hospital where the infection had spread, expertise healthcare hygiene in human medicine, and public authorities contributed to the development of a program for infection control.
The environment at a horse hospital presents challenges, and further studies are needed regarding how this environment can be adapted. For example, the development of surface materials that are suited to horses and at the same time easy to disinfect facilitated infection control in horse healthcare.
Environmental sampling showed that MRSA was prevalent in places accessible only to humans, which means that hand hygiene can be improved. Moreover, MRSA was found on furnishings that are difficult to clean. Therefore, mangers and water cups were replaced by buckets that could be disinfected.
Observations at three horse hospitals showed that routines regarding work clothing and the like were complied with in an exemplary manner. Compliance with routines for hand hygiene and disposable gloves was somewhat poorer. Reasons given for this were practical difficulties, insufficient knowledge, and high workloads.
- Staphylococcus aureus can also be found in the nose, intestinal tract or skin of a small percentage of normal, healthy horses, although the frequency with which it is found varies widely between studies.
- Studies in different areas of North America and Europe have identified MRSA in 0-10.9% of healthy horses, but on some farms over 50% of horses may carry MRSA.
- Most horses that are colonized with MRSA do not have an infection, and never develop an infection. However, they are at higher risk for developing an MRSA infection if they become sick, injured or stressed for another reason, such as when they are admitted to an equine hospital.
- Risk factors for MRSA colonization in horses in the general population have not been adequately studied. Horses that have been treated with antibiotics and that live on farms where MRSA is known to be present are more likely to be carrying MRSA when they are admitted to an equine hospital.
- As in human hospitals, MRSA can be spread between horses in equine hospitals. However, most MRSA infections in horses occur in animals that have never been in an equine hospital.