Zoonoses

Zoonoses

Zoonoses is not the word for the snout of a zoo animal, it means a disease that can be passed to you from your pet. We’re often asked about these diseases and there are a lot of myths out there that need to be explained.

I think my pet gave me…worms!

We’ll be starting the series with a discussion on worms and other parasites that can be passed to humans. It just shows - we don’t make you give your pet worming tablets purely for our own evil enjoyment!

Parasites

Intestinal worms and parasites can be passed to us from our pets. Worm and parasite eggs are passed in our pet’s faeces (poos) and it is through accidental ingestion of these eggs that people are infected. This can occur from patting your dog to playing outside in areas where he or she might go to the toilet.

· Hookworms and roundworms (Toxacara canis, Toxascaris cati, Ancylostoma spp.) can cause a syndrome in people called larval migrans, where the larvae of the worms migrate through the skin, internal organs, eyes or brain. This is a rare disease that is usually transmitted from puppies and kittens, which are infected when they are in the mother’s womb or from her milk when they are feeding.

· Tapeworm – Echinococcus granulosus can infect dogs when they eat the offal (intestines, stomachs, livers, lungs etc) of marsupials such as kangaroos or infected livestock (cattle and sheep). The eggs are passed in the dog’s faeces and can stick to the coat. People become infected when they accidentally eat these eggs and this causes the growth of hydatid cysts (you may have seen photos of enormous cysts in people’s abdomens!)

· Giardia is a small protozoan parasite that can cause diarrhoea in dogs and humans. Diagnosis is difficult in both of us and treatment usually involves supportive care.

How to prevent these diseases:

· Dogs and cats should be wormed regularly. Puppies and kittens should be wormed every 2 weeks until they are 12 weeks of age, then monthly until 6 months of age, then every 3 months after that. An all-wormer should be used to protect against tapeworm as well as the other intestinal worms.

· It is very important to worm the dam (mother) during pregnancy

· Don’t feed your dog offal from an unknown source

· Always make sure you wash your hands after playing with the dog or cat or handling its faeces. Getting children into the routine of hand washing is also very important, even after they’ve been playing in areas where the dog may defaecate.

I think my pet gave me … itchy skin

This article looks into two causes of skin disease in humans – ringworm and Sarcoptic mange (Scabies).

Ringworm

The biggest problem with ringworm is that it is named badly! Despite its name, ringworm is not a worm; it is actually a fungal skin infection which causes red, itchy rings on the skin of humans.

Ringworm can look very different on our pets. Sometimes they have small bald patches, which they may have been licking or scratching at and others can have a rash all over their bodies. Some cats and dogs can show no symptoms of ringworm at all and still be carriers of the fungi.

Ringworm tends to affect puppies and kittens, but our older patients and our patients that have a poor immune system (due to disease or medications) are also more at risk. In the same way, children and immunocompromised people (such as those with cancer or AIDS) are also more at risk than healthy adults. Ringworm is transmitted to humans by skin to skin contact with an infected person or pet, from contact with bedding, hair brushes or other items the infected person or pet have used, or less commonly, from the soil.

We can often diagnose ringworm in pets by running a UV light over the skin, however, this does not work in all cases and we may need to send some hair away to be cultured. Luckily, ringworm in ourselves and our pets can be easily treated with an antifungal medication or cream. If any family members find a red, itchy ring on their bodies, it is best to consult your doctor.

Sarcoptic Mange (Scabies)

“Mange” is a word that is often associated with stray or poorly looked after dogs; however, this is not always the case. Sarcoptic mange is caused by a microscopic mite (Sarcoptes scabiei) that lives in the top layer of the skin. Dogs can become infected by other dogs, foxes, wombats and other marsupials (e.g. kangaroos), and also by humans! They can pick up the mite even when they brush up against trees where affected wildlife have been scratching. People can also be infected by these animals.

In both dogs and people, the mite causes an intensely itchy rash. It can be very difficult to diagnose, and we often treat pets based on the suspicion that they have the disease. There is several different treatments available, including injections of a parasiticide, or topical application of Revolution or Advocate.

The risk of catching Scabies from your pet (or from wildlife) is slim; however, always consult your doctor if in doubt.

I Think My Cat Gave Me… Toxoplasmosis

For many years, cats have been accused of infecting women and causing miscarriages and congenital abnormalities through the transmission of Toxoplasmosis. However, cats are rarely the cause of these problems.

Toxoplasma gondii is a common intracellular parasite of animals, including humans. Cats are the primary host for this parasite and become infected when they eat infected meat (from wildlife or raw meat). The parasite replicates throughout the cat’s body, and eventually eggs are passed in the faeces. Other animals are then infected by ingesting these eggs, which grow into cysts inside the muscles of the body. When a cat eats these muscles, the cycle then starts again. Most cats that are infected with toxoplasmosis show no symptoms of the disease.

Humans can become infected by ingesting the eggs from cat’s faeces or more commonly, by eating undercooked or raw meat, or unwashed vegetables. Like cats, most people who become infected show no signs of the disease. However, this is not the case for pregnant women. If a pregnant woman becomes infected during pregnancy, there is a 40% chance that she can pass that infection on to the foetus, and 10% of these babies may be born with eye or neurological abnormalities. Interestingly, 30% of the adult population have already been infected and carry antibodies against the disease, so women that have been previously infected are not at risk.

Therefore, to prevent the infection from occurring, we recommend pregnant women take the following steps:

Cook all meat thoroughly
Wash hands, benches and cooking utensils thoroughly after handling raw meat
Wash all vegetables
Wear gloves when gardening (soil may be contaminated by cat faeces)
Have someone else empty and disinfect the litter trays daily.
Discourage pets from hunting

This page was last updated on: 31-Oct-02