The main health risk to humans from dog faeces is from roundworm and by far the best way to deal with this risk is prevention; removing the faeces safely before problems occur. The following explains in detail about how roundworm affects dogs and humans and also offers advice on how to prevent infection.
Roundworms have ’round’ bodies about 3 inches long and live in the dog’s intestines eating partially digested food. They move freely in their food, the contents of the small intestine. Roundworm lay large numbers of microscopic eggs which are passed in the dog’s faeces.
Bitches that have had roundworm at any time in the past can transmit them to their puppies before birth. The roundworm larvae are motivated by changes in the bitch’s hormonal status as a result of pregnancy and move across the placenta into the foetal tissues and eventually mature in the puppy’s bowel.
Another major source of roundworm infection for puppies is transfer via the mother’s milk when they are suckling. Both puppies and adult dogs may become infected by swallowing roundworm eggs which contain infective larvae. The larvae hatch out in the dog’s stomach and small intestine and move through muscle, liver and lungs over several weeks, before returning to the bowel to mature. When these worms begin to reproduce, new eggs will pass in the dog’s faeces, and the life cycle of the parasite is completed.
Roundworm eggs passed in one dog’s faeces are infectious to other dogs. Also a large number of other animal species have been found to harbour roundworms and represent potential sources of infection for dogs. These include cockroaches, earthworms, chickens and rodents. They are not highly harmful to adult dogs, but large numbers can cause weight loss and a pot-bellied appearance to puppies and weakness in adults. Decreased appetite, vomiting or diarrhoea will be observed on occasion. Large roundworm infestations can be serious in puppies as they can cause an obstruction of the bowel. This can cause death if the puppies are not promptly treated.
Treatment is usually quite straight forward; several very safe and effective drugs are available to kill roundworms in the intestine. None of these treatments will kill the immature forms of the worm or the migrating larvae, so it is important to repeat treatment in 3-4 week if the dog has a heavy infestation of worms.
The roundworms of both dogs and cats pose a health risk for humans. Children in particular are at risk should they become infected. A variety of organs may be affected as the larvae move through the body but the main danger is that the larvae migrate to the eye where they can cause blindness. In favourable environments, the eggs may remain infective to humans (and to dogs) for years.
Advice to Reduce Risk
Pregnant bitches should be wormed in late pregnancy when larva will be moving into the bowel, both of the bitch and the unborn puppies. This will help to reduce potential contamination of the environment for newborn puppies. All new puppies should be treated 2-3 weeks of age. To effectively break the roundworm life cycle, puppies should be wormed on the schedule recommended by your veterinary surgeon.
Prompt worming should be given when any parasites are detected; periodic worming may be appropriate for dogs at high risk for re-infection.
Adult dogs remain susceptible to re-infection with roundworms throughout their lives. Dogs with predatory habits should be wormed several times a year.
Prompt disposal of all dog faeces is important, especially in gardens, playgrounds and public parks.
Dogs should be discouraged from defaecating in areas normally used by children.
Strict hygiene is especially important for children.
Do not allow children to play in potentially contaminated environments.