Animals that drink water contaminated with microcystins frequently show vomiting, diarrhea, weakness, lethargy, and pale mucous membranes within the first several hours after exposure. Death often occurs within 12 to 24 hours of exposure. Animals that drink water contaminated with anatoxins show weakness, lethargy, muscle tremors, rigidity, and seizures within 30 to 60 minutes of exposure. Excessive salivation may occur in some animals. Death from respiratory paralysis quickly follows the onset of signs. Treatment is limited and often unsuccessful due to the rapid onset of signs. Early and aggressive supportive care including intravenous fluids, electrolytes, and medications to control seizure should be used. Atropine may be helpful in those animals that are salivating excessively. Prevention of exposure is critical. Animals should be kept away from ponds and lakes with visible blue-green algae blooms. In small, backyard ponds, algae should be removed and discarded. Ponds and small lakes used as water sources for horses and farm animals should be fenced to prevent exposure, and alternate water sources should be provided.