Relationships between dogs and humans can produce some health problems if some easy and basic rules are not followed. Toxocara-canis can be contracted by humans from dogs who are not regularly wormed and who are infected by the Toxocara roundworm. The Toxocara roundworm is a natural parasite of dogs and cats called Toxocara-canis and Toxocara-cati. Young animals who carry a large worm burden may fail to thrive and in extreme cases the gut can rupture. In the pregnant bitch the parasite is transmitted across the placenta to the pups and also during lactation. (In the case of cats the parasite does not cross the placental barrier but is passed on in the milk when the queen suckles her kittens).From the time of whelping until weaning, the untreated bitch will shed on average one million Toxocara eggs with each faecal deposit. The pups will be excreting eggs and possibly larvae by four weeks old, as they will be born already infected with the roundworm.

The adult roundworm measures from 7.5 to 12.5cm. looks like a grey earthworm and spirals like a corkscrew. It's lifecycle starts when
(1) the eggs are swallowed by the dog or received by unborn pups via the placenta. The eggs reach the intestine and become larvae.
(2) Larvae migrate to the tissues of the dog's body, travel to the lungs and trachea and are coughed up, - swallowed and become adult roundworm in the dog's stomach and intestine. An adult worm can lay 20,000 eggs a day.

T.canis eggs that are swallowed by older dogs tend to stay in the dog's tissues for longer periods, in a dormant state, however older dogs will pass adult roundworms in their faeces occasionally. The bitch that becomes pregnant is able to revitalise the dormant larvae in her tissues at and after day 42 of her pregnancy. She will then pass them to her pups. This highlights the importance of seeking veterinary advice about worming a bitch prior to and during a pregnancy.

When man swallows the eggs of T.canis and T.cati, the larvae emerge from the eggs in the intestine. They burrow through the intestinal wall and migrate into the bloodstream and the tissues and can reach such organs as the liver, lungs, kidneys and brain. The larvae can burrow for long periods, leaving a trail of inflammation before they die. In humans this is called Visceral Laval Migrans (VLM) and if the larvae reaches the eye, Ocular Larval Migrans (OLM). There are some 200 cases of toxocariasis a year. Those most at risk are children who eat soil, (the parasite can be found in soil and can live for up to 2-3 years. I t dies if it is dried out but can survive disinfectants and severe winters), or those who play with unwormed pups and dogs. The Toxocara eggs have a sticky coat and can attach themselves to a dog's tail, hind legs, muzzle and tongue.

Worming dogs with the appropriate preparation (and with possible veterinary supervision) will ensure that dogs are free from the Toxocara roundworm. The solution appears simple but reluctance exists amongst a small minority of owners to ignore the responsibility they have to keep their dog's parasite free. I repeat, a small minority of owners, however they are a large enough group to periodically come to the attention of the anti-dog lobby and give us all a bad name.

As humans we have controlled and eradicated many diseases and parasites that are a hazard to us as a species. It seems not unreasonable for us to attempt to do the same for the dog and by so doing protect our beloved canines from those who only see them with a negative viewpoint. We then truly place ourselves in the position of being 'the dog's best friend' as he is ours.