My dog's bugs and me

 Diseases that are transmitted from animals to humans are called “zoonoses”. These can be serious, but the risks can be strongly reduced if the appropriate precautions are taken. To live safely with your dog, it is important to understand the potential risks and so carry out the necessary precautions.

This section considers zoonoses caused by worms and skin parasites. To find out more about other zoonises, follow the link to rabies and other diseases.

Common round worm (Toxocara sp)

In the dog, the eggs of the round worm are passed out in the faeces and infect other dogs when taken in by mouth. In humans, these worm eggs may be accidentally ingested, hatch and migrate through the body. The larvae may produce inflammatory reactions in a variety of organs including the brain and the retina of the eye.  The incidence in man is 2 cases per million population per year, and young children are particularly at risk.

No further development of the life cycle occurs in man and so there is no shedding of eggs. Control can be achieved by regular routine worming of dogs and by good personal hygiene. Commercially availably treatments vary in their safety and efficacy, and your veterinarian will be able to advise the appropriate treatment. For more information, follow the link.............


There are a number of tapeworm species that affect dogs, but the one that is a risk in terms of human disease is called Echinicoccus. The adult tapeworms are found in the gut of dogs. The eggs pass out in the faeces and enter the secondary host (usually sheep) by mouth. These hatch and invade the body where they form cysts within the body tissues. The life cycle is completed when a dog eats these cysts when feeding from a dead sheep carcase. In the UK the incidence is highest in areas where there are hill sheep (esp Wales).

Humans can become infected if they accidently ingest the eggs. Cysts may develop and the clinical signs shown depend on the site of the cyst. Approximately 30 – 40 human cases are reported in the UK annually.
To prevent this parasite entering the UK, dogs entering the country with a pet passport must be treated with an appropriate wormer between 24 – 48 hours of entry.

Flea bite reactions

Fleas feed by sucking blood from their hosts. During this process they inject some saliva into the skin. The host may show an allergic reaction when bitten. This is the reason a dog will scratch when infested with fleas – the amount of scratching being related to the hypersensitivity of the dog rather than the number of fleas. There are a large number of medications commercially available to control fleas, but these vary in safety and efficacy. Often a combination of products is necessary to ensure control on the pet as well as in the surrounding environment. For more information, follow the link to ...............................

Humans may also become hypersensitive to flea bites and show red itchy sores when bitten. The fleas cannot breed when sucking human blood alone. The problem can be controlled by appropriate treatment of any dogs and cats within the home as well as attention to destroying the eggs and larvae in the environment.

Sarcoptic mange

This is caused by a parasitic mite which burrows in the skin and is not visible to the naked eye. The canine strain is highly contagious and is usually transmitted by direct contact with an infected dog or fox. The dramatic increase in urban fox population in the UK has resulted in an increased incidence. The condition is very itchy and is usually quite distressing for the dog. Follow the link to ...................... to find out more about how best to control sarcoptic mange and other parasites.

The disease in man appears as a very itchy rash. it usually resolves if the animal is treated appropriately.


Cheyletiella is a larger mite than sarcoptes, but still not visible to the naked eye.
The mites can survive up to 10 days off the host and so transmission can also occur indirectly from inanimate objects.

The mite lives on the surface of the dogs’ skin. The dog becomes itchy and also produces excessive amounts of scurf. Indeed the condition is sometimes called “walking dandruff”.

Appropriate treatment is effective, but check with your veterinarian as some medications commonly used to treat parasites is not effective against Cheyletiella. In humans, the condition shows as multiple small red itchy sores. The condition is self limiting if the dog is treated appropriately.


This condition is not caused by a worm as the name suggests, but is due to a fungal infection.

Cats are probably a more common source than the dog, and many may be asymptomatic carriers.
The fungal spores may survive for long periods off the host so indirect spread by inanimate objects is important. In man the lesions may become worse if corticosteroid ointments are used.

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