Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to prevent botulism in horses [title] Get your horse vaccinated against a botulism infection. [step] Ask your vet to administer a type-b toxoid vaccine to protect your horse. Although it doesn't protect against all forms of botulism, it limits your horse's risk of contracting the illness.

Ending1: [substeps] Side effects of vaccine include headache, diarrhea, and weight gain, which are usually symptoms of botulism. This is especially problematic if your horse is already suffering from a blood clot. Ending2: [substeps] Keep in mind you can start vaccinating up to six months after it has been vaccinated, though it might take two to three months for the horse to become fully immune to the virus. [title] Give your horse medicines that also offer protection from botulism. Ending3: Unfortunately, it is a time-consuming time. In doing so, overly-vaccinated horses often develop varicella, which can be life-threatening. Ending4: The vaccine can be administered at any time after the horse is at least 2 weeks old. [substeps] Vaccination involves 3 initial dose vaccinations, followed by a single annual booster vaccination.

Answer format: ending1/ending2/ending3/ending4