What causes roundworms in dogs?
1. From their mother.
Roundworms are quite prevalent in puppies, as the larvae are commonly transmitted from the mother right before birth or through nursing.
This is how it works: Unfortunately, the canine roundworm has developed a highly efficient method of reproduction. Even after a dog has been treated for roundworms and the adult worms have been removed, a number of dormant (“encysted”) larvae can remain in bodily tissues. These encysted roundworm larvae can lay dormant for the rest of a dog’s life, unless the dog is a female and becomes pregnant, in which case the larvae reactivate and are passed on to her puppies. Puppies can be infected while still inside their mother’s body or after birth through her milk. Even if the mother dog and puppies are exceptionally healthy and well-cared for, the puppies should be treated for roundworms (see below) from a young age. Pregnant dog owners should see their veterinarian about safe deworming therapy for the dam during pregnancy, which may limit transmission to the puppies.
During a dog’s pregnancy, reactivated larvae can linger in her body and make her unwell.
In adult male and female dogs with certain underlying health issues, encysted roundworms can develop to the adult form and cause illness.