Zoonoses in dogs and cats
What is a zoonosis?
A zoonosis is a disease which can be passed between animals and humans.
The following information sheet is designed to give an overview of some common or important diseases which can be passed from cats and dogs to humans, however the list is not exhaustive. Conditions which can be passed to humans from other domestic or exotic species are not included. In general these diseases are of most significance to immuno-compromised people.
People who are immuno-compromised have immune systems which may not work very well. This group would include the very old and very young, people recovering from severe illness or surgery, people with AIDS/HIV and people on chemotherapy drugs.
Humans can be bitten by cat and dog fleas (See Ectoparasites in Dogs information sheet or Ectoparasites in Cats information sheet). The bites are seen as small, red, itchy lumps very often on the lower legs/ankles. It is important to keep cats and dogs regularly treated for fleas using a veterinary prescribed flea treatment. If humans are being bitten it is likely that the environment is infested, so the whole home should be treated as well. Make sure you follow any care and safety instructions when you spray your home.
Ringworm (dermatophytosis) is not a worm at all but a fungal infection of the skin. Many species of animals can carry this infection. It is often seen as patches of hair loss and scaling of the skin on cats and occasionally dogs. When humans pick up ringworm they develop red and often circular patches on their skin. This condition is treatable for both humans and pets.
Humans can also become irritated by mites that they acquire from their pets e.g. ‘fox mange’ (Sarcoptes scabei) and ‘walking dandruff’ (Cheyletiella). Infections on humans are usually self-limiting but it is advisable to visit the doctor. Cats and dogs can be treated under veterinary care after diagnosis in their owners.
We strongly recommend that pet cats and dogs are regularly wormed (See information sheets on Worming your dog and Worming your cat). Cat worms are currently not thought to cause problems for human health but we are not certain about this. Toxocara canis is a common round worm of dogs. If children are infected by this worm, the larva can occasionally ‘get lost’ on migration within the body and cause damage to the eyes, brain and elsewhere. Monthly worming of dogs with a good quality round wormer will prevent dogs becoming infected and spreading the worm.
Echinococcus granulosus is a dog tapeworm which also causes problems when larva ‘get lost’ on migration in the body, but this worm is thankfully only found in limited habitats (certain areas of Wales and the Hebrides). Hookworms (Ancyclostoma) which are passed occasionally in dog faeces can cause skin irritation when people have close contact with contaminated soil. Fortunately the condition is easily treated.
Hand washing and basic hygiene should always be used when clearing up after a pet, especially when they have vomiting or diarrhoea. Giardia, Campylobacter, Salmonella and E. coli are just some of the infections which may be passed on to humans. If these bugs are suspected we will test for them but sometimes infections are not obvious, so care should always be taken in clearing up pets’ faeces.
Toxoplasmosis is of particular concern for pregnant women. This is a common single-cell parasite which only causes mild flu-like symptoms in most affected people – however, it can be critical to the health of both mother and foetus if a pregnant woman is infected. Many species of animal can be affected by toxoplasmosis, but only cats, the primary host, can spread the disease. When the spores pass out of the cat in its faeces they are inactive. It takes about 24 hours of contact with air for the spores to become active or infective. This means that direct handling of an animal is not a great hazard, but pregnant women should not handle cat faeces or the litter tray. The greatest risk factors for Toxoplasmosis are gardening (i.e. handling soil), unwashed fruit and vegetables as well as undercooked meat. However, it is always recommended that pregnant women are especially careful to wash their hands after touching animals and before handling food. If you have any concerns about zoonoses during pregnancy you should discuss these with your midwife or doctor.
Weil’s disease is the severe human form of leptospirosis. This is an uncommon disease in humans and it is very rare for it to be passed from pet dogs. However, if a dog is affected its urine can be infective to humans. Both dogs and humans most commonly catch leptospirosis from stagnant or slow-moving water (specifically that which has been contaminated with rat urine). The disease causes sudden kidney and liver failure. We strongly recommend that dogs are vaccinated against leptospirosis annually (See Vaccination in dogs information sheet). Care should be taken when handling dogs’ urine and, if leptospirosis is suspected, handlers should wash their hands and ideally wear gloves.
Cat and dog bites can be very serious. Wash all bites liberally under running water and always seek medical advice from your doctor as antibiotics are often required. There may also be legal implications if a dog has bitten a person – please see the UK Government website - https://www.gov.uk/control-dog-public
Cat scratches can also be nasty. All scratches should be thoroughly washed. Any scratch which becomes inflamed or painful should prompt a visit to a doctor. There is a bacterium which some cats have in their saliva and on their claws called Bartonella henselae which causes ‘cat scratch disease’ in humans – symptoms include swelling at the site of infection, fever and swollen glands. Treatment may be required, especially in immuno-compromised patients.
If you have any queries concerns about your dog or cat and Zoonoses, please do not hesitate to contact us.
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