Although they do not usually pose serious problems, worms in dogs always seem to be an issue, especially for puppies. This is because of the way their lifecycle works. Given that worms in dogs can cause health problems in both dogs and humans, owners have a responsibility to interrupt the cycle and try to keep it broken.

In the UK, the roundworm is the most common worm infestation seen in dogs, because most puppies are born with an infestation. This infestation often causes puppies’ abdomens to become distended and may delay their growth whilst in humans it has the potential to cause blindness.

Like other types of worms in dogs, the cycle can be broken with a little understanding. At the beginning of the cycle, a female puppy is infected by her mother, either before birth via the placenta or afterwards via her milk. Inside the infected puppy, some worm larvae will migrate via the bloodstream to the muscles where they will lie dormant in indestructible cysts. In the event of pregnancy in later life, the larvae will be reactivated and will move through the blood to infect the puppies.

Not all the larvae in the young puppy will form the cysts previously mentioned. Instead, some will remain in the intestine and grow into adults. After feeding on the part-digested contents of the intestine and reaching maturity, the adult worm releases eggs which are passed with the dog’s faeces. In the open air, the eggs are infectious to other dogs and even people. The risk of infection for people does not arise from handling puppies, but from touching soil which has been contaminated by puppies’ faeces.

That is how the cycle works and to break it, owners must treat adult dogs for worms every three months. As they are so prone to worm infection, puppies should be treated every two weeks from the ages of two to twelve weeks and once a month thereafter until they reach six months. However small and rare, worms in dogs can cause problems for human health, so dog owners must take responsibility for picking up after their dogs and encouraging good hand hygiene in the family, in order to break the cycle and reduce the risk.