Diseases which can pass between animals and people are called zoonoses and there are some which are transmissible from cats to man (and vice versa).
Although these hazards are few, you need to take precautions and be aware that there can be a problem.
Fortunately, most feline zoonotic diseases are rare, although many myths exist regarding disease risks, and misinformation is often spread through ignorance or fear. In reality many more people become sick each year from food-borne illnesses than ever fall ill from contact with cats. Practising common sense together with a good hygiene routine, including careful handling of litter trays and routine treatment of cats for fleas and other parasites, significantly reduces the possibility of disease transmission from cats to humans.
Some important zoonotic diseases:
Bacteria in the mouths of cats and, in particular, Pasteurella multocida, can cause infection of a bite wound and result in painful swelling and even abscessation. Bite wounds should be washed carefully and immediate advice sought if swelling, pain or obvious infection occurs. Routine protection against tetanus is also an important consideration and advice should be sought from your doctor.
Fleas are extremely common on cats and although most cat fleas cannot actually live on humans, they can bite humans and cause skin irritation. Fleas should be controlled by regular cleaning and spraying of the environment with a flea-control preparation in addition to regular treatment of all cats for fleas.
Ringworm (dermatophytosis) is one of the most common zoonotic diseases derived from cats. Cats should always be checked for suspicious lesions, and gloves worn if ringworm is suspected. Your veterinary surgeon can help in screening and identifying cats with suspected ringworm, and in treating any confirmed cases. It is important not to let children have direct contact with ringworm-infected cats, and careful hygiene precautions are necessary when handling such cats (disposable gloves and protective clothing). Attention must also be paid to environmental hygiene as ringworm spores are resistant and can be shed into the environment in high numbers. If any skin lesions occur after contact with cats, immediate medical advice should be sought.
See ringworm in cats
Toxoplasma is a parasite that infects cats and many other mammals, including humans. It is primarily a concern for pregnant women as, if infection occurs during pregnancy, damage can occur to the developing foetus. Most human infections come from poor meat hygiene (handling uncooked meat, eating undercooked meat). However, for a short period after they are first infected, cats may shed eggs (oocysts) in their faeces, and this is another potential source of infection for humans. Because of this, it is recommended that litter trays should always be emptied and disinfected on a daily basis (the eggs don't become infectious for humans until more than 24 hours after they are shed in the faeces) and that pregnant women are not involved in cleaning litter trays.
Very rarely, humans can become infected with a cat roundworm (Toxocara cati) or the tapeworm (Dipylidium caninum). These infections are very uncommon (canine roundworm infections are more common in people), but regular worming of cats for both roundworms and tapeworms is an important part of the health care of cats.
See worming your cat
Campylobacter and salmonella
These are two intestinal bacteria that can be a cause of severe gastrointestinal disturbances and can affect many animals, including humans. Infection in humans is usually through the food chain and infection from cats is rare, although they can be a potential source. Everyday hygiene precautions (eg, washing hands after handling a cat) should always be followed, but particular care should be paid to handling cats with diarrhoea. If the diarrhoea is prolonged, severe, or contains blood, veterinary attention should be sought to identify the underlying cause. If campylobacter or salmonella is identified, specific treatment and monitoring may be required.
Cat scratch disease
Cat scratch disease (CSD) is a rare condition characterised by swollen lymph nodes and sometimes other signs (eg, fatigue, muscle pain, sore throat) that can occur following contact (eg, being bitten or scratched) with a cat. CSD is an uncommon disease and serious illness is very rare. The main organism responsible for this disease (Bartonella henselae) appears to be quite common in cats, but transmission to humans is very inefficient. Transmission of this organism between cats appears to occur mainly via fleas.
Allergies to cats
People are allergic to many things - including cats - and these allergies can manifest themselves in different ways. Some people will be mildly affected, feeling itchy, snuffly or sneezing; others have severe skin reactions, and a few may experience a serious asthma attack.
These reactions occur because the person's immune system reacts to certain foreign substances (particular proteins derived from an animal or plant) to produce antibodies or chemical weapons to protect the body. One of the actions of the antibodies is to stimulate the body to release other chemicals to defend itself. Histamines are released in this way but in allergic people these can irritate the lungs, nose, skin and other tissues – hence the common reactions of sneezing, coughing, wheezing or itching.
The main trigger for the allergic reaction to cats is a protein which is secreted in saliva and in the skin of all cats (not in the fur or dander). It can be found on the coat because the cat grooms itself using saliva. It is also shed in urine or faeces.
The signs of reaction can occur if the allergen is inhaled or a person strokes a cat, cleans its litter tray or even sits where the cat has been sitting. All breeds of cat produce allergens, but some may produce more than others – it can be a case of trial and error to ascertain which cats you react to. Although there is no scientific reason for it, many people seem to react more to longhaired cats – perhaps because more allergen builds up on their fur or accumulates because of more hair around the house. Likewise, even cats with little hair such as Rexes or Sphynx cats may still cause a reaction – there is no easy answer to allergy-free cat keeping.
If you have a cat and are mildly allergic to it, then keep it out of your bedroom and off the bed and keep the house (carpets, curtains and cushions) well cleaned – a build-up of allergens is what can trigger reactions. Wooden or tiled floors with washable rugs are also much more cleanable than wall-to-wall carpets. Vacuuming is thought to be of limited help as it can stir up allergens and good ventilation is essential. Experts may suggest washing the cat regularly – they are probably not cat owners or they would realise the difficulty of doing this! There are products on sale which claim to reduce allergens if they are applied to the cat's coat regularly – at present there seems to be little information on how well these work.
There are drugs available from the doctor which can help ease the reactions but their efficacy is obviously dependent on that person's particular degree of reaction. A course of immunotherapy may also be suggested if the drugs are not working well enough. Immunotherapy is the process of injecting gradually increasing weekly doses of cat allergen into the skin. Many patients find their symptoms reduce significantly after six months, although relapses can occur – it will not suit everyone and needs discussion with your doctor or specialist. Researchers are working on other various means of tackling the problem but these will probably not be available for a few years yet. For some unlucky cat lovers it means living without a cat.