The clinical signs of Ivermectin poisoning are:

• excessive dilatation of the pupil of the eye (mydriasis)
• lethargy
• stupor
• coma
• tremors
• loss of coordination of the muscles, especially of the extremities (ataxia)
• vomiting (emesis)
• drooling
• death

Less visible symptoms:

• depression
• tachycardia (fast pulse)
• blood pressure fluctuation 

According to PIM 292, there is no evidence of increased birth defects in humans or mares subject to normal therapeutic Ivermectin treatment. But Ivermectin is teratogenic in rats, rabbit and mice at or near materno-toxic dose levels. The abnormalities are limited mainly to cleft palate.

Treatment is symptomatic and supportive in cases of overdose. Adverse effects are transient, but analgesics and antihistamines may be required. Since ivermectin is believed to enhance GABA activity in animals, it is probably wise to avoid drugs that enhance GABA activity (benzodiazepines, barbiturates, valproate, valproic acid) in patients with potentially toxic ivermectin exposure (MSD, 1988)

Animals with "White feet, don't treat".