Medicine and Treatments: Colic, Rabies, Pneumonia

Signs of Gastrointestinal Rupture

A study to determine the clinical signs of gastrointestinal rupture during colic was done by researchers at the University of California, Davis, and results were presented by Diana Hassel, DVM, of UC Davis. Results of the study could help veterinarians know what signs to look for to make a definitive diagnosis of intestinal rupture, thus allowing them to prevent prolonged suffering of the affected horse and additional expense to the horse owner, as euthanasia for a horse with a ruptured intestine is inevitable.

The medical records of 149 horses with gastrointestinal rupture admitted to the UC Davis veterinary teaching hospital from 1990 through 2002 were examined. Common clinical findings associated with acute intestinal rupture included depression, sweating, reluctance to walk, tachycardia (rapid heartbeat), fever, an increase in the concentration of red blood cells in the blood, an abnormally low number of white blood cells, abnormal mucous membranes, elevated peritoneal (abdominal cavity) fluid protein concentration, and abnormal peritoneal fluid color, said Hassel.

She said four signs were key in determining colic severity--heart rate, peritoneal protein concentration, blood lactate concentration, and mucous membrane appearance.

When horses underwent abdominocentesis (surgical puncture of the abdomen), the peritoneal fluid was found to be abnormal in color in 85.5% of cases. When the total protein concentration of the peritoneal fluid was analyzed, it was found to be elevated in 86.4% of cases with the presence of bacteria in 95.7% of cases.

"Abdominocentesis is an important diagnostic test in the assessment of colic cases and can be definitive in cases of rupture," said Hassel. (See article #4963 online.)

Managing a Rabid Horse

The horse with rabies is extremely dangerous to himself, other animals, and humans. Rabies is a fatal viral disease of mammals that can be spread to humans through bites, licks, or through contact with mucous membranes or an existing wound. Horse owners must use extreme caution if rabies is suspected, and a veterinarian should be called immediately. Tomas Gimenez, Dr.Med.Vet., a professor at Clemson University, discussed management of a potentially rabid horse.

Gimenez said clinical signs might not show up for two weeks or for as long as six months after infection is introduced. Signs include fever, lack of appetite, lameness, colic, facial nerve paralysis, weakness,
restlessness, a progressing lack of coordination, self-mutilation, aggressiveness, vocalization, drooling, and paralysis. If a veterinarian suspects rabies, then he must call the state veterinarian's office, county animal control, and the county health department immediately. Euthanasia is required, and anyone who has come in contact with the horse must undergo rabies treatment. Equine rabies is preventable with vaccination.

The rabid horse can show non-aggressive "dumb" behavior, or be aggressive and extremely dangerous, said Gimenez. Personnel should wear coveralls with long sleeves, boots, and double gloves. Clothing, equipment, and any objects that came in contact with the horse should be disinfected with bleach, and all facilities should be cleaned thoroughly. Avoid saliva and mucosal surfaces and secretions, but blood and urine do not contain the virus.

Confirmation of the disease must be made by examining the victim's brain tissue after death.

In addition to managing the rabid horse, all other animals on the property, such as dogs, cats, other horses, cattle, etc., should be isolated and quarantined whether they have been vaccinated or not. (See article #4962 online.)

Pneumonia in Foals

The Rhodococcus equi bacterium is the most common cause of severe pneumonia in foals. According to Noah D. Cohen, VMD, MPH, PhD, of Texas A&M University, there's often a push to identify the farm or region where the foals became infected. Cohen revealed that with the use of a DNA fingerprinting method, he and other researchers (from Japan, Argentina, and Ireland) discovered that it was not possible to clearly differentiate isolates from different countries, different regions within Texas, or even on the same farm. Therefore, it is nearly impossible to identify where R. equi came from based on the bacterium itself.

R. equi pneumonia can have a devastating impact because prevalence and case fatality rates are often high, and treatment can be prolonged, expensive, and not very successful. The disease also might diminish future performance in the affected animals.

Cohen and others summed up the research by saying, "Understanding epidemiologic characteristics of an organism is essential for developing methods to control and prevent disease caused by infection with that organism," adding that the "mechanisms of transmissions and spread of R. equi are poorly understood."

The researchers found that R. equi pneumonia occurs endemically on some farms, as expected. The variability of isolates was surprising. "We rarely found isolates from the same farm that were identical," he said.

Cohen said that it is clinically important to note:

  • Outbreaks at farms are not necessarily explained by having one particular strain;
  • Researchers didn't see evidence of specific R. equi endemic strains during outbreaks on farms; and
  • You need to consider the host and environmental factors in control of R. equi.

"There is considerable genetic variability among isolates of R. equi," said Cohen, adding that it's only rarely that DNA fingerprinting can help provide a strong genotypic link among isolates on the basis of source, time point, or location. (See article #4979 online.)

By Sarah L. Evers and Stephanie L. Church

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