Chapter 25 – Preventive Medicine and Management of the Broodmare and the Foal

A 2 day old foal was presented with central nervous depression (coma) after moxidectin overdose. Moxidectin belongs to the milbemycin anthelmintics which elicit their working mechanism through a GABA (gamma-aminobutyric acid)-stimulatory mode of action. The foal developed profound hypothermia, bradycardia and hypoventilation. Absence of urine voiding and mild abdominal distension suggested a ruptured bladder, which was confirmed by transabdominal ultrasound and clinical-pathologic parameters. Repeat auscultation of the ventral lung parts and the occurrence of gastric reflux were suggestive of an aspiration pneumonia. The foal underwent surgical bladder repair, however, did succumb due to mixed acidosis and early signs of sepsis postoperatively. The findings in this foal are suggestive for moxidectin overdosing. The GABAergic working mechanism of moxidectin does explain the development of profound central nervous depression and its sequels hypothermia, bradycardia, hypoventilation and paralytic ileus. Dyssynergia was unexpected, however, has to be related to a central nervous problem, rather than a peripheral nervous problem.

M. M. Sleet Van Oldruitenborgh-Oosterbaan

Papers

Moxidectin poisoning in a foal