Equine Salmonella Infections (Salmonellosis): Background, Infections, Symptoms, and Treatments

The salmonella bacteria can be deadly to a wide array of mammals, and poses a life-threatening danger to humans and horses alike, as well as many other creatures in between. The protection of equine against the salmonella bacteria and the treatment of salmonella infections in horses when they do occur present unique challenges that require a comprehensive understanding of the infectious agent and the progression of the infection, as well as of course the treatment methods that can be used to combat salmonella infections. This paper attempts to provide this understanding in a brief overview of the salmonella bacteria itself, the methods of infection and symptoms of equine salmonellosis, and the methods for treating salmonella infections in horses when they occur.

Salmonella Background

Salmonella are common bacterial contaminant in the natural world, and thrive especially in decaying organic matter, including feces (EVSBC 2005). The organism ahs also evolved to many different host conditions, and the horse species is especially susceptible to many different stereotypes of the bacteria (Lane et al. 1992). All two thousand and two hundred forms of the gram-negative rods and non-spore forming bacteria are considered possible pathogens for adult horses (Reich & Langor 2005). Most horses carry at least one species of salmonella gastrointestinally, but overgrowth is prevented by competing bacteria (Johnson 2010).

Modes of Infection

Equine salmonella infections can occur in horses of any age, though foals are especially susceptible to infections during the birthing process, receiving the bacteria from the mare (EVSBC 2005). Adults will often not exhibit signs of illness, and death in these animals can be far more rapid because of the apparent lack of symptom presentation (EVSBC 2005). Manure is a common source for the spread of salmonella bacteria, especially as the bacteria resides in the gastrointestinal tract of most animals; manure can cause contamination in water, feeds, or pastures, leading most commonly to oral ingestion of the bacteria (EVSBC 2005; Lane et al. 1992). Because salmonella can survive for so long in the environment, outside of host animals, it can build up to levels more prone to causing infections if regular and through cleaning and management practices are not maintained (GPA 2010).

Though the salmonella bacteria exists in the gastrointestinal systems of nearly all animals, it is usually dormant and kept to levels that do not cause any adverse effects when horses have a healthy immune system (Johnson 2010). Stress can also be a major factor in the development of an equine salmonella infection; healthy horses that are free from other stressors can often ingest the bacteria without harm, whereas stress brought on by such things as extreme weather, prolonged transportation, or dehydration and hunger can increase the chance of an infection (Lane et al. 1992). When immune systems are otherwise weakened, either through stress, other disease factors, or simply youth, salmonella is most likely to strike.

Signs and Symptoms

Symptoms can range greatly in severity, and generally appear within one to three days of infection and persist for as little as a week, in mild cases, while killing horses within a matter of hours in others (EVSBC 2005). Heightened temperature (fever) is almost always apparent, and diarrhea is another nearly-universal symptom other possible symptoms of an equine salmonella infection include a loss of appetite, colic, depression, and in some instances certain ulcers and bloating (Johnson 2010; Lane et al. 1992). Most cases of salmonella present only some of these symptoms, rather than all of them, and most of the symptoms are located (as might be expected) along the gastrointestinal tract. Certain joint ailments and other disorders can occur form prolonged infection, however, and death is the likely result of many extreme cases of infection, or even untreated mild and moderate cases (GPA 2010).

Treatment

There are many different identified methods of treatment depending on the severity of the infection and how early it is caught. Isolation of infected horses and regular disinfecting of stalls with a variety of common cleansers while providing a stress free is environment is usually effective in early mild cases (Johnson 2010). In more severe cases, the replacement of fluids lost from diarrhea, often intravenously, and other symptoms can be treated to reduce stress, but resistance to antibiotics is common and the infections usually must be waited out rather than combated outright (Reich & Langor 2005; Lane et al. 1992).

The best treatment for salmonella infections, as for any disease, is to prevent infections from occurring in the first place inasmuch as is possible. This is accomplished largely through the isolation of infected horses; though infections generally run their course within seven to ten days, infected animals will continue shedding the bacteria for up to four months following an infection (Reich & Langor 2005). Preventative measures that can be taken to forestall an initial occurrence include covering horse food bins to prevent contamination of feed, ensuring adequate clean water supplies, general cleanliness including regular hand washing — especially when dealing with multiple horses, and the isolating of newly arrived horses for three weeks while monitoring their health (GPA 2010; Lane et al. 1992). With proper preventative measures, incidents of salmonella infections in adult horses are rare and easily treated, whereas improper facilities management can lead to epidemics that are more fatal and highly difficult to manage (Johnson 2010).

Conclusion

Salmonella infections in horses is a largely preventable occurrence, and given the potential for fatality when infections are allowed to become more prevalent and/or more virulent, it makes a great deal of practical and ethical sense to maintain cleanliness in order to avoid equine salmonellosis. Effective treatments for many types of the bacteria do exist, but the preventative measures that have been identified work for all strains, and help to promote general health as well.

References

Equine Veterinary Services and breeding Centre. (2005). “Salmonella infections and vaccinations.” Accessed 25 April 2010. http://www.equivetaustralia.com/vaccinations/salmonella.php

GPA. (2010). “Equine salmonellosis.” Accessed 25 April 2010. http://www.gopetsamerica.com/horse/diseases/salmonellosis.aspx

Johnson, P. (2010). “Salmonellosis in horses.” Accessed 25 April 2010. http://www.petplace.com/horses/salmonellosis-in-horses/page1.aspx

Lane, T.; Braun, R.; Madison, J.; Hawkins, D.; Brown, M. & Merritt, a. (1992). “Equine salmonella infection (Salmonellosis).” Accessed 25 April 2010. http://www.equivetaustralia.com/vaccinations/salmonella.php

Reich, B. & Langor, I. (2005). “Enteric Salmonellosis in Horses.” Accessed 25 April 2010. http://www.addl.purdue.edu/newsletters/2005/Winter/equine-es.htm