Most of us don’t regard our pets as mere companions or service providers – they are often seen as members of our family. We live in close physical contact with our cats, dogs and birds, with an estimated 50% to 60% of pets sharing their owners’ bedrooms, or even their beds. This close contact, though mutually beneficial, can also contribute to the spread of diseases from animal to human and vice versa.
The most dangerous of all infectious diseases that we humans can get from our pets is undoubtedly rabies. This is caused by a virus that contaminates the nervous system of the infected animal, causing it to behave strangely, eventually leading to seizures and death. The virus may be found in the saliva of the infected animal, and a bite from such an animal may result in infection of a person or another animal. Less commonly, the infected saliva may spread the disease by entering through scratches, abrasions or open wounds, or even into the eyes, nose or mouth of the victim. Luckily, highly effective vaccines are available and according to South African law, all dogs and cats must be vaccinated against rabies. This must be done twice in the animal’s first year and then every one to three years thereafter.
Beware during pregnancy
Toxoplasmosis is a condition that can cause serious abnormalities to a developing foetus if the mother is exposed to the organism during pregnancy. The organism is found in cat faeces, and contamination is by ingestion of the infective oocysts (egg-like structures). Unfortunately, because of the seriousness of this disease to the unborn child, many women will be advised to get rid of their cats without understanding the actual life cycle of the organism.
The cat is the intermediate hose of the organism, and if it is infected, it will shed these little egg-like oocysts in its faeces for the next two weeks. These oocysts must be left for at least 24 hours before they become infective to humans. Then, if a pregnant woman handles the faeces, contaminating her hands, and then ingests the infected oocysts, she will get toxoplasmosis; that is if she hasn’t already got antibodies to the disease, which more than half of our population do have. Actually, because of the short period of shedding infective oocysts, and the fact that once a cat is infected it will not shed ever again, the chances of getting toxoplasmosis are very small.
Pregnant women should not handle cat litter, and they should wear gloves when gardening and wash their hands carefully before eating.
Less fearsome, but way more common, are the various tummy bugs that we can catch from our pets. Usually the way these infections are spread is by contamination of our hands when touching food bowls, being licked or by handling an infected dog or cat or their body fluids. Prevention is therefore straightforward – wash hands after contact with animals and especially before handling food or eating. Because bacteria are sensitive to high temperatures, they will be destroyed by cooking. Therefore, pet food should be well cooked.
Although fairly uncommon, there are other infections we can get from our pets if we are scratched, bitten or even licked by them. Cats, in particular those with fleas, can carry bacteria under their nails that can cause cat scratch fever if they scratch us. This presents as a flu-like episode that usually resolves within a few days. All animals have a lot of bacteria in their mouths, so licking and biting can cause infection, especially where the human skin is broken. Abscesses, cellulitis and even septisaemia are all possible following a dog or cat bite or, less frequently, after being licked.
Some skin infestations are easily passed from animal to human and ringworm, more common in cats, is easily spread to other pets or people with whom they have contact. Cats may be carriers of ringworm. Even though they have the fungus and are shedding spores into the environment, they may have no visible lesions. Diagnosis and treatment of the pet are not difficult, but must be thorough, otherwise recurrence of the infection is likely. It is important to remember that ringworm is not actually a worm and deworming will not help in treating the ringworm lesions.
Another skin infection, which humans can catch, is scabies, a condition where tiny microscopic mites burrow into the dog’s skin, causing severe itching and hair loss at the site. Although canine scabies is self-limiting in humans (meaning that whether we treat it or not, it will go away by itself), the itching is severe and very uncomfortable, and scratching can cause a secondary infection. The more common demodectic mange that we see in dogs, is not catchy to humans or to other animals.
Plague of parasites
Any external parasites like ticks, fleas or lice can pass from dogs and cats to humans, and will cause varying degrees of discomfort and disease. Ticks brought in by our pets can carry tick-borne diseases. Fortunately, we don’t get Lyme’s disease in South Africa, but we can get the typical tick-bite fever that comes with generalised joint pain, severe headaches, fever and rash.
Fleas and lice will at the very least result in discomfort and itching but in severe cases infection of the flea bites as a result of scratching could occur.
Worms can also pass from dogs and cats to humans. They have adapted and evolved in order to efficiently pass from host to host. Worms can infect humans through the skin or the mouth. Having entered the body, the worms may travel to the liver, brain or even the eyes, resulting in associated symptoms such as swollen liver, meningitis and blindness. Once again, good hand washing practices can prevent oral spread, and avoiding contaminated sandy areas or not walking barefoot in such areas will prevent cutaneous spread. Regular deworming of pets is essential, and flea control must be attained, as fleas are part of the life cycle of a common tapeworm found in dogs and cats.
Although there are various diseases that we can catch from our pets, we mustn’t forget that we can similarly infect them. We can pass our lice, worms, fungi, bacteria and viruses to them. Good hygienic practices, in particular hand washing, should be emphasised and taught to our children from an early age.
We should also never lose sight of the enormous benefits we get from keeping these animals, which far outweigh the relatively rare risks they may pose to us.