Roundworms are intestinal parasites in many animals including dogs and humans. Eggs of roundworms are excreted through the feces of infected animals and contaminate grounds and objects. From these contaminated grounds and objects, eggs of roundworms are ingested by the dogs and these eggs develop in to adult roundworms.
All treatments available for roundworm infestation can anesthetize the adult worms, so, only adult worms are excreted. These medicines don't kill eggs and larvae of roundworms, that is why usually 3 treatment are recommended.
At the end of third treatment, dogs should be checked periodically for the roundworms. Your vet will make a schedule of this periodic checkup. So, as your dog has taken 3rd dose and now it is necessary to get schedule from you local vet for periodic checkup.
All treatments available for roundworm infestation can anesthetize the adult worms, so, only adult worms are excreted. These medicines don't kill eggs and larvae of roundworms, that is why usually 3 treatment are recommended.
At the end of third treatment, dogs should be checked periodically for the roundworms. Your vet will make a schedule of this periodic checkup. So, as your dog has taken 3rd dose and now it is necessary to get schedule from you local vet for periodic checkup.