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Zoonoses - Rabies, Toxoplasmosis, Ringworms and Roundworms |
By Dr Wendy Chee, JTVC, 2009
Zoonoses are defined by the World Health Organisation as 'diseases and infections which are transmitted naturally between vertebrate animals and man'. In many countries, food is the most common source of zoonotic diseases. It is perhaps worth noting that many of the zoonotic agents causing disease in humans cause little or no obvious clinical disease in their animal hosts.
Hygiene tips - Get into the habit of practising good pet hygiene to reduce your risk of infection.
- Wash your hands thoroughly for at least a minute. Always use an antibacterial soap after handling your pets (this is particularly essential before preparing food).
- Teach children to always wash their hands.
- Handle dog and cat faeces promptly and properly.
- Check that your pets are in good health. Vaccinations should be up-to-date. Regular check-ups at the vets can also spot any possible infections.
- Keep your pet clean. This may simply involve cleaning/washing their paws if they've dug up any soil or a thorough shampoo after swimming in possible contaminated areas.
RABIESRabies is an acute viral infection of the central nervous system that can affect any warm-blooded animal. Humans can get infected through the saliva or bites of a rabid animal. Although post-exposure treatment is available, once symptoms develop the condition is invariably fatal. Singapore has been rabies-free since 1953 and is very strict in measures to maintain this status. TOXOPLASMOSISToxoplasmosis is caused by the protozoan parasite Toxoplasma gondii. It is carried by cats and can affect virtually all warm blooded animals, including humans.
It is one of the most frequent parasitic infections of humans and is acquired most commonly through the ingestion of undercooked meat and also via hand-to-mouth contact with the faeces of infected cats, contaminated soil and poorly washed garden produce. Around a quarter to half of the world's population is thought to be infected. In most cases, the person affected doesn't have any symptoms.
In humans, the infection is usually asymptomatic or mild and self-limiting (persistent acute fever with enlarged lymph glands) but can be severe in immunocompromised individuals and unborn children.
If women become infected for the first time while they are pregnant, it may result in abortion or severe disease in the newborn. It can cause mental retardation and loss of vision in congenitally infected children and death in immunosuppressed patients, especially those with AIDS.
Toxoplasmosis does not require specific treatment when it occurs in healthy people. Control of this disease relies upon education and prevention of infection.
RINGWORMRingworm is a general term that is used to refer to a number of different fungal infections of the skin. The best-known type of ringworm is athlete's foot. It is known as ringworm because the skin develops ring-like, red patches. Typically the patches have scaly edges and vary from a few millimetres to several centimetres in diameter.
Inside the ring, the skin may be a bit scaly but looks normal in all other respects. The fungus spreads from the centre of the patch but the activity is confined to the outer edge. The infected areas are usually itchy. Ringworm can be passed from one person to the next by direct skin-to-skin contact or by contact with contaminated items such as combs or unwashed clothing.
Ringworm can also be caught from animals, cats being a common carrier. In animals, ringworm usually takes the form of a circular, dry, raised, crusty lesion with hair loss - often on the head or feet. It can also be carried by animals that show no clinical signs.
TOXOCARIASIS (ROUNDWORMS)Toxocariasis is a zoonotic disease caused by parasitic roundworms (Toxocara canis and Toxocara cati) found in the intestines and faeces of some dogs and cats. Toxocara worms produce a large number of eggs in the dog’s or cat's stomach, and the eggs then leave their body in their faeces, contaminating soil and other surfaces.
Humans can get infected by accidentally swallowing worm eggs, or by eating food that is contaminated with soil containing the eggs (such as unwashed raw vegetables). Toxocariasis cannot be spread from person to person. Once the eggs are in the human body they hatch and the worms begin to burrow through tissue.
The severity of a toxocariasis infection depends on the number of worm eggs swallowed and the severity of the reaction to them.
Children are most likely to develop toxocariasis, especially children between 2-7 years of age. This is because children are more likely to come into contact with soil or sand that contains dog or cat faeces, and are less likely to follow sensible hand-washing hygiene.
Parents and children should be aware of the dangers associated with puppies, kittens and older dogs and cats.
Many puppies are infested with Toxocara worms before birth and both puppies and kittens require de-worming with anti-worm medicine. Pregnant bitches should be treated with the same medicine. See your vet for specific advice on how to treat your pet.
Clean your pet's living area at least once a week. Faeces should be bagged and disposed of in the dustbin.
Toxocara eggs can survive for years in soil or sand, so it is important to be responsible and pick up faeces while walking your dog. Pets should also be kept away from children's sandpits. 
A pdf copy of this article can be found here.
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Pet Care Information