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Worming of Puppies and Bitches

Regular worm treatment of dogs is a very important consideration, not only in maintaining the health of the dog, but also in the protection of human health, as a number of canine parasites pose a zoonotic risk. Most worms are transmitted through the passage of eggs or larvae in the faeces of infected animals. Environmental contamination thus occurs, and due to the fact that the eggs are extremely resistant to degradation, they can persist in soil for a long time (months or years). Dogs can be infected with worms at any age, so worm control right throughout life is necessary. In the case of puppies and bitches, there are specific recommendations that should be followed to assist in effective worm control.

The larvae of the roundworm, Toxocara canis, can remain dormant in the tissues of the dog's body. During pregnancy, these encysted larvae become activated and migrate to the uterus, causing infection of the puppies before birth. In addition to being born with a roundworm infestation, the pups will also pick up more larvae through consumption of their mother's milk due to larval migration to the bitch's mammary glands. The bitch is likely to develop a patent roundworm infection herself, as the activated Toxocara larvae will also make their way into her intestine, causing her to shed eggs in her faeces. Additionally, she will possibly also ingest eggs, larvae and adult worms when she cleans up the puppies' faeces.

After a puppy ingests Toxocara eggs, they hatch into larvae and burrow through the wall of the intestine. They then migrate to the lungs via the liver. The life cycle is completed when the larvae are coughed up and swallowed, thus returning to the small intestine where they mature into adult worms. Here, they will lay thousands of eggs, which then pass out in the faeces to contaminate the environment. The life cycle will then start all over again when another dog ingests them from the environment.

A heavy Toxocara burden can cause serious illness in puppies and may even be life threatening. When the larvae are migrating through the lungs, they can cause breathing problems and coughing. Puppies may have a distended abdomen, causing them to look pot-bellied, have poor thrive, a poor coat, abdominal pain and diarrhoea. If the worm burden is very heavy, with the stomach and intestine full of worms, it may cause a complete blockage of the digestive tract and may lead to intussusception.

It is thus important to heed the deworming regime recommendations for bitches and pups, not least due to the zoonotic potential of Toxocara canis, particularly in the case of children. In order to reduce the extent of transplacental transmission of larvae before birth and to lessen the transmammary infection via the milk, the bitch should be treated daily with a suitably licensed worming product from day 40 of pregnancy until two days post-whelping. However, although this regime has some efficacy, it does not guarantee completely that pre-natal and transmammary roundworm infection will be prevented. Further treatment of the bitch during lactation is thus recommended.

Puppies should receive their first worm dose at two weeks of age, using an appropriate anthelmintic product. The treatment should be repeated regularly until after the pups have been weaned, in order to target the transmammary transmission of larvae through the milk. The best treatment regime can be recommended by your vet. From two weeks post-weaning until six months of age, the frequency of worming treatments can be decreased to once monthly. The frequency of treatment after the age of six months is risk-based. The minimum frequency should be four treatments annually (i.e. at least every three months) throughout life. In circumstances of increased zoonotic risk (such as in kennels, or households where there are children), the frequency should be increased to monthly treatments.

As previously outlined, the development of a patent infection in the bitch means that she is likely to be shedding eggs while she is feeding the pups, so she should also be treated regularly along with the pups from two weeks after whelping until two weeks post-weaning.

Zoonotic risk of Toxocara canis

Toxocara canis eggs are not visible to the naked eye. They may be accidentally ingested when picked up from the grass or soil or from the coat or bedding of a dog. They do not develop into adult worms in the gut of a human, but will migrate as larvae throughout the body, settling in areas such as the liver, kidney or lung. This condition is known as Human Toxocariasis. A condition called Ocular Larva Migrans can occur if the migrating larvae settle in the eye, leading to impairment of vision or blindness. Children are most at risk. It is thus important that preventative measures are taken to reduce such zoonotic risks. These measures include:

  • Practising good personal hygiene, especially ensuring to wash hands after handling pets and before eating food. Do not allow dogs to lick children's faces or share food
  • Cleaning up pet faeces regularly and disposing of it responsibly. Do not dispose of it into compost bins
  • Controlling pet parasite infections through regular treatments
  • Minimising exposure of children to potentially contaminated environments. Keep children's nails short. Cover play sandpits