Salinomycin toxicosis in horses.
METHODS
A 4-month-old American Paint filly was evaluated because of sudden onset of ataxia that progressed to recumbency. Five additional horses from the same and neighboring premises developed signs of poor performance, generalized weakness, ataxia, and recumbency; 2 of those horses were also evaluated. A new batch of a commercial feed supplement had been introduced to the horses' diet on each farm within the preceding 3 days.


RESULTS
Other than recumbency, findings of physical and neurologic examinations of the foal were unremarkable. The other 2 horses had generalized weakness and mild ataxia, and 1 horse also had persistent tachycardia. The foal had mild leukocytosis with neutrophilia, hyperglycemia, and mildly high serum creatine kinase activity. Results of cervical radiography, CSF analysis, and assessments of heavy metals and selenium concentrations in blood and vitamin E concentration in serum were within reference limits. Feed analysis revealed high concentrations of the ionophore antimicrobial salinomycin.


RESULTS
The 5 affected horses survived, but the foal was euthanized. At necropsy, a major histopathologic finding was severe vacuolation within neurons of the dorsal root ganglia, which was compatible with ionophore toxicosis. The surviving horses developed muscle atrophy, persistent weakness, and ataxia.


CONCLUSIONS
In horses, ionophore toxicosis should be considered as a differential diagnosis for acute weakness, ataxia, recumbency, or sudden death. Furthermore, ionophore toxicosis should be considered as a cause of poor performance, weakness, muscle wasting, and cardiac arrhythmias in horses. Surviving horses may have impaired athletic performance.
Aleman
Monica
M
Department of Medicine, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Magdesian
K Gary
KG
Peterson
Tracy S
TS
Galey
Francis D
FD
D000821:Animal Feed / Q000633:toxicity; D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D003937:Diagnosis, Differential; D017809:Fatal Outcome; D005260:Female; D005506:Food Contamination / Q000032:analysis*; D006734:Horse Diseases / Q000139:chemically induced* / Q000175:diagnosis / Q000473:pathology; D006736:Horses; D011714:Pyrans / Q000633:toxicity*; D000095662:Polyether Polyketides
D000900:Anti-Bacterial Agents; D011714:Pyrans; C010327:salinomycin; D000095662:Polyether Polyketides