A survey of adverse effects associated with ivermectin use in Louisiana horses.

This article discusses a survey conducted on Louisiana horses which showed that ivermectin, a common medication given to equines, resulted in adverse reactions in about 11% of them, with one case leading to death.

Study Overview

• The main focus of this paper is to assess the adverse effects of ivermectin, a widely used horse medication, amongst horses in 13 Louisiana equine practices. Ivermectin is often used to treat various types of parasite infestations among animals. Over the course of the study, which took place from March to August 1983, a total of 3,316 horses were observed.

Study Findings

• The study discovered that 366 out of the 3,316 horses monitored showed adverse reactions after using ivermectin. This equates to an adverse reaction rate of approximately 11%. The report indicates that each of the 3 horses experienced more than one reaction. Despite this figure, most reactions were of minor to moderate concern.
• The most common reaction reported was ventral midline pruritus or swelling, occurring in 332 horses or about 91% of all adverse reactions. This indicates that about 10% of all doses resulted in this particular side effect.
• Other less frequent but notable adverse reactions included transient swelling and/or stiffness at the site of injection (15 horses), limb swelling (11 horses), and eyelid swelling (4 horses).
• Adverse effects that only occurred in two horses or fewer include an increased rate and depth of respiration, onset of fever, disorientation, and signs of colic.
• Most notably, one horse died shortly after receiving the injection and another became depressed. This represents just 0.03% of all horses evaluated, but emphasizes the significant risk tied to ivermectin use.

Conclusion

• The results of this study indicate that minor to moderate adverse reactions may be relatively common in horses following ivermectin administration. Although the percentage of severe reactions, including death, is quite small, it is still a notable concern for equine health and management practices.