Dewormers are clinically proven to be safe but, when given after a horse has ingested plants from the toxic nightshade (Solanum) family they can experience invermectin poisoning. A horse experiencing invermectin poisoning will begin to show neurological signs. It is believed that the toxins in nightshade plants increase the invermectin absorption, and researches at Texas A&M believe it causes “accumulation of ivermectin in the brain.”
A study of six horse by the University of Texas A&M with invermectin poisoning presented these neurological signs.
- Lack of muscle coordination
- Facial nerve dysfunction, including drooping lips, dilated pupils, and weak tongue tone
- Muscle twitching and head tremors
- Mild fever
- Fecal and/or urinary retention
- Head/facial edema
Nightshade plants come in a wide variety of annual and perennial plants. Many are flowering plants and bear fruit. They grow as forbs, vines, sub shrubs, shrubs and some trees. To prevent invermectin poisoning it is important for owners to carefully inspect hay bales and pastures should be kept well mowed and weed free.
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