Zoonotic Diseases from Dogs and Cats

Zoonosis is any disease that can pass from animal to human. Some of these diseases are very serious whilst several can be fatal. Below are several zoonotic diseases that can be passed from dogs and cats, sometimes via other organisms that use the dog and cat as their host.

Toxocariasis

These are the roundworms of the dog and cat (and other species). They can be transferred to humans via their eggs which are left in soil after infected animals have defecated. Children are more predisposed to ingesting the eggs as they might play in the soil and not wash their hands. Adults can also ingest the eggs from eating raw vegetables that have not been washed properly.If the infection is heavy or repeated, it can cause the disease 'visceral larva migrans'. This is when the worm larvae move through the body and causing swelling to the major organs and affecting the central nervous system. High-temperature, coughing even pneumonia are various symptoms. The disease is also known to cause 'ocular larva migrans' when the worm larvae enter the eye causing inflammation and even blindness.Once this disease has been diagnosed it is easily treatable.

Dermatophytosis

More commonly known as ringworm, this highly infectious disease is normally carried by cats and is not a worm at all, but a fungal disease. It can be transferred from cats to humans by skin to skin contact. It can also be spread by contaminated clothing, brushes and other items that have come into contact with the animal.The disease is characterised in cats by circular, raised and dry lesions that are normally crusty and cause hair loss. The disease often starts on the head and feet areas, but can spread across the body if left untreated. In humans the infected areas are often red rings with scaly edges and are intensely itchy.Ringworm can be treated both in animals and humans with the correct medication, however full recovery can be prolonged.

Sarcoptic mange

This is caused by a mite known as sarcoptes scabei and is found predominately on dogs but also on cats (and other species). It is more commonly known as scabies and can infect humans by direct skin contact. In animals sarcoptic mange causes fur loss and intense itching, where in extreme cases animals can bleed by prolonged scratching. In humans it is also extremely itchy, however because the human is the wrong host, in most cases the mite will die off as they cannot complete their life cycle.

Leptospirosis

This is a bacterial disease that is carried through the body of the infected animal (in companion animals this is normally dogs) and excreted in the urine. Dogs can pick up the disease by wading through, sniffing or drinking contaminated water where rats have been. Humans can contract this disease with direct contact of the animals infected urine.In dogs the disease can cause vomiting, high-temperature, dehydration, shivering and muscle weakness. In advanced stages it can also cause chronic kidney failure, causing death.In humans common symptoms are like influenza, however severely infected people can get intense headaches, muscle weakness, high-temperature, vomiting and diarrhoea and meningitis. The infection can go on to produce jaundice and kidney failure. In humans the condition is known as Weil's disease and in up to 15% of people it can prove fatal.Although there is a vaccine for dogs, there is no vaccine for humans. Any person who has come into contact with leptospirosis could be put on large doses of antibiotics by their doctor.

Toxoplasmosis

This is a parasitic disease carried by cats. It can be transferred to humans by contaminated soil which carries the parasite after the cat has defecated in the area. The soil may be on poorly washed garden produce, much the same as Toxocariasis can be contracted. It can also be transferred to humans by poor hygiene after cleaning cat litter trays.In cats there are very non-specific symptoms of toxoplasmosis, they might display a lack of appetite, vomiting or diarrhoea, high-temperature, lethargy and weight loss. These symptoms can be attributed to many other cat illnesses. In humans the symptoms are usually mild but people may display a prolonged high-temperature. The main issue with toxoplasmosis is for pregnant women. Should women that are carrying unborn children contract the condition, it can result in an abortion or severe disease in the new-born child.

Rabies

Although this condition in the UK is very rare, it is not unknown. With the stringent guidelines of the pet passport scheme and quarantine, animals are highly unlikely to carry the disease in the UK.The disease itself is an acute viral infection that affects the central nervous system. Affected animals normally show behavioural changes, in further stages they can start drool, become excited then aggressive, attacking people and other animals. Convulsions and paralysis normally follow, before death.If a human contracts the disease through a dog or cat bite, it is invariably fatal. After the initial bite, a high-temperature followed by headache and nausea are common. Mood changes such as apprehension or excitability come before paralysis, fear of water and delirium. A respiratory paralysis is often the final cause of death.

Summary

Of course it is not just cats and dogs that carry diseases that can be passed to humans. Other species such as birds, goats and cattle can also carry diseases which can, if severe and left untreated, cause death. Reptiles and tropical fish are known to carry salmonella which can make humans very ill and even be fatal. Scientists are constantly monitoring infection and trying to develop treatments for new strains of zoonotic diseases for example avian bird flu, CJD and others. There are numerous zoonotic diseases in the UK (and there are more carried by cats and dogs that are listed above). Despite this by the use of proper vaccination (in the case of leptospirosis, regular boosters as well), parasitic treatments, stringent hygiene and common sense, risks to human health from animals can be minimised.