"Monthly prevention" refers to taking regular measures or precautions on a monthly basis to avoid or minimize the occurrence of a specific problem or threat. Full definition
Despite monthly prevention, there are reported instances where pets are infected with heartworms. (shank-animal-hospital.com)
It is recommended that this test be done yearly, even for dogs on monthly prevention. (texassweetiesdogrescue.org)
All adoptions include all vaccines, spay or neuter, microchip, dogs are heartworm checked and are given monthly prevention for heartworms, cats are Felv / FIV tested, and all are on monthly flea control. (hailesangels.org)