Hi...as you probably realize, most puppies are born with roundworms that they get from their mother. Most good breeders and veterinarians will recommend that puppies be de-wormed at 2,4,6,8,10, and 12 weeks. After that, your pet should be on a monthly heartworm preventive that will help to control roundworms and hookworms as well. Are you using a heartworm preventive?
Are you seeing the roundworms or has your veterinarian diagnosed them on a routine fecal exam? You might need to spend some time cleaning up the yard. Roundworm eggs are very hardy and can survive for long periods of time in the yard. Unlike hookworm eggs, roundworm eggs can also survive freezing. You should plan on "scooping the poop" daily and disposing of it in the garbage can.
Where do you live? Some areas of the country are worse for intestinal parasites than others.
Every pet in the household should be dewormed routinely, either by using a monthly heartworm preventive or routine dewormings quarterly at your veterinarian. If one pet is not being dewormed, that animal has the potential to spread these parasites to everyone else, including the human members of your family,especially young children.
Roundworms can produce about 200,000 eggs per day so the sooner you take care of this problem, the better off you will be. Make sure everyone washes their hands after playing with the pets and, as I mentioned, clean up the poop promptly.
I hope this helps! How many pets do you have and what kind are they?
Tomcat
Upon my vets recommendation I wormed all 10 of our dogs at one time and every six months after. Hope this helps.