and it only takes one mosquito bite to transmit it. that's why you need to protect your dog with heartgard plus. just one real beef chew given once a month, every month, helps keep your dog safe all year long. test dogs for infection prior to use. in rare cases digestive and neurological side effects have been reported. for more information contact your vet. get your dog out of hiding. ask your vet about heartgard plus. the vet's # 1 choice