Our understanding of colic has improved, but the cases keep coming

Survival rates from colic may have improved over the years, but our better understanding of this challenging condition has yet to see a reduction in cases, says equine surgeon Nathaniel White.

The professor emeritus of equine surgery at the Marion duPont Scott Equine Medical Center, part of the Virginia-Maryland College of Veterinary Medicine in Leesburg, Virginia, discusses colic in the latest issue of Equine Disease Quarterly.

He says there is a prophecy about equine colic: As long as there are horses, they will have colic.

“Based on reports in the literature over the last 50 years, the incidence of all colic cases has not changed over time and the incidence in a normal horse population ranges from 1 to 10 episodes of colic per 100 horses each year,” he notes.

“However, horses that have had one or more previous episodes of colic have an incidence rate up to 5 times higher.”

Survival varies with the severity of the disease, but the overall mortality rate for all types of colic in horses was approximately 7%-10%, second only to fatalities due to musculoskeletal injuries. Incidence varied from farm to farm based on management, with a higher frequency expected in specific populations of horses such as broodmares near term, horses with small strongyle infection, or those exposed to abrupt changes in management.

Horses being treated for eye disease and those hospitalized after general anesthesia for elective procedures also had an increased incidence of colic.

“The causes of these acute intestinal diseases remain elusive,” he says.

“Simple colic, commonly diagnosed as ‘gas colic,’ ‘spasmodic colic,’ or ‘ileus,’ makes up approximately 85% of all colic episodes, yet the cause or mechanism for these gastrointestinal abnormalities remains unknown.

“Similarly, the cause of diseases with a higher morbidity and mortality such as intestinal strangulations have no known cause.”

He said epidemiological research over the past three decades had identified risk factors that appeared to have a causal relationship, yet specific mechanisms such as why intestine twists and strangulates was unknown.

“Alteration in intestinal function is most likely multifactorial, with combined event and environmental factors increasing risk.

“Numerous factors are reported to increase colic risk including some basic husbandry and feeding practices. Some of these factors are non-specific, but still are significantly related to increased colic risk.”

White said survival had improved for the most life-threatening types of colic over the last four to five decades.

“During the 1960s to 70s, the survival rate for severe obstructions and strangulations was reported at less than 50%.

“Although improvements in surgical expertise, anesthesia, and postoperative medical care are associated with improved survival, rapid recognition of the need for surgery or critical care by veterinarians is a major reason for the improvement.

“With a rapid assessment and decision for specialty care, survival of 80%-90% can now be expected.”

White noted that multiple aspects of the pathophysiology of colic had been investigated.

“Research on intestinal motility, systemic inflammatory response syndrome (also known as endotoxic shock), intestinal injury and inflammation, parasite control, gastric ulcers, surgical techniques, and response to therapy have all improved the understanding of events that occur during colic.

“There is no question the additional information has changed the veterinarian’s ability to improve colic treatment and survival.

“Still, how intestinal dysfunction and systemic responses are initiated remain to be discovered. More research is needed if we are to change the colic prophecy.”

Factors predisposing to colic

  • Breed
  • Older age
  • Increased time in a stall
  • Cribbing/crib-biting
  • Recent transport
  • Inactivity following injury
  • Change in weather
  • Diet change
  • Round bale hay
  • High concentrate feeds
  • Decreased potable water
  • History of colic
  • Absence of deworming
  • Absence of dental exams
  • Tapeworm infection

– Source: Cohen ND, Epidemiology of risk factors, in The Equine Acute Abdomen, Wiley, 2017 in press.

Equine Disease Quarterly is funded by underwriters at Lloyd’s, London.

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