Pamela Wilkins, DVM, PhD, of the Graham French Neonatal Intensive Care Unit at the University of Pennsylvania's New Bolton Center, said that she has had a positive experience in treating botulism-affected foals. In her presentation "Botulism in Foals: A Survivable Disease," she said that botulism in foals less than six months of age is readily treated, with a survival rate of more than 95% in appropriately treated foals. Treatment can include nursing care, intravenous fluid support, nasogastric or nasoesophageal tube feeding, broad-spectrum antimicrobials, oxygen therapy, and the administration of botulism antitoxin. Approximately 33% of affected foals might require positive pressure mechanical ventilation, she said.

Wilkins and her colleagues did a retrospective study in which they examined data from 28 botulism-affected foals under the age of six months treated at the Graham French Neonatal Intensive Care Unit from 1989 to 2001. Of the 28 foals, 25 survived with no reported long-term or career-limiting problems. All surviving foals were treated with botulism antitoxin shortly after arrival at the clinic. One foal died from respiratory failure and cardiac arrest, while two foals were euthanized for economic reasons.

There are three primary ways that the botulism toxin can enter the horse–intestinal toxicoinfection, ingestion of preformed toxin, and absorption of toxin from wounds infected with Clostridium botulinum. The toxin then affects the neuromuscular (nerve-muscle) junction, resulting in weakness that progresses to flaccid paralysis (paralysis with a loss of muscle tone). In addition, foals can suffer from difficulty swallowing (dysphagia), muscle trembling, and recumbency (inability to rise). Some cases experience respiratory failure as a result of weakness of the respiratory muscles. Thirteen of the 28 foals in this study experienced respiratory failure.

Younger foals born to unvaccinated mares and those with failure of passive transfer are at an increased risk, as are older foals when maternal antibodies are decreasing. The good news is that vaccination in adults is usually protective, said Wilkins. Cost of treatment might be a determining factor for survival, and this depends on the length of hospitalization and treatments needed, which varies by clinic. (See complete article #4122