California Foal Survives Type A Botulism, Typically Fatal

by | 03.21.2016 | 8:00am

Type A botulism in horses is typically fatal. However, researchers from the University of California, Davis, treated a 10-day-old foal that beat the deadly disease.

A paralytic disorder produced by Clostridium botulinum, botulism in horses can take one of three forms: toxicoinfectious, food-borne and wound botulism. The toxicoinfectious form of botulism is typically seen in foals less than 6 months old. It occurs when botulism spores are swallowed and germinate in the intestinal tract.

Seen by Dr. Gary Magdesian and his colleagues, the Paint/pony cross was admitted because of a low head and neck carriage, which was originally suspected to be caused by a fractured vertebrae. No fractures were apparent in the X-rays taken before the foal was brought to the clinic.

The foal worsened to the extent that he could not stand unassisted, reports HorseTalk. There was no impediment to the cranial nerve and the filly demonstrated no neck pain when moving. She could walk, though her gait was short and stiff, and she tired easily. The veterinarians did note a decrease in tone that allowed for over-extension of the nuchal ligament, but the foal was able to suckle well (as long as she was supported) and she had normal tongue tone. Blood gas analysis revealed no abnormalities.

However, during her first three days at the hospital, her clinical signs worsened and she was no longer able to stand. Her tongue tone also worsened. Because of the progressive weakness and because she had no other clinical signs, the veterinarians began to suspect that toxicoinfectious botulism was at play. Botulism types A and C were considered most-likely since the foal was born on the West coast.

A fecal sample was tested by the National Botulism Reference Laboratory at the University of Pennsylvania. The results confirmed the presence of type A botulism spores, consistent with toxicoinfectious botulism.

The foal was given plasma containing antibodies to C. botulinum type B and C toxins. When it became available, plasma with antibodies to types A, B, and C2 were given.

The filly was helped to stand or turned every two hours. She was fed a mixture of mare's milk and a commercial milk replacer until she was transitioned completely onto a commercial milk replacer and the amount increased. The foal was also given enemas to combat constipation, which is a complication of botulism.

The filly had a very gradual return of strength and motor function that began on day four and lasted throughout her time at the clinic, which was 30 days. At discharge, the foal was still weak and tired easily, but was able to stand unassisted, walk with a shortened stride, drink from a pan and eat. Her head and neck position were normal.

Upon release, her owners were instructed to avoid repeated botulism exposure by removing the surface soil from the foal's stall and paddock, and disinfecting the area with a dilution of sodium hypochlorite. Four months after being discharged from the clinic, the foal had returned to normal strength with no persistent deficits or weakness.

The vet team reports that this is the first documented case of equine survival from Type A botulism. Timely therapeutic management appears critical for the successful treatment of Type A botulism, the treating veterinarians noted. They also noted that head and neck weakness can be an early indicator of botulism.

Read more at the Journal of Veterinary Internal Medicine.

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