Pet Health dog & cat

Published on January 11th, 2019 | by Debbie Martin


Zoonotic Diseases – A Guide

As we increasingly share our lives with various companion animals this can leave us exposed to the various diseases and health problems that they can get. Zoonotic is the term used to describe diseases that can be spread to humans from animals, or sometimes to animals from humans, whether through viruses, fungi, parasites or bacteria.

Diseases caused by worms

Anyone who shares their life with a dog, cat or horse will be familiar with the concept of intestinal worms. These are parasites which can be easily eradicated but if a worm infestation is left untreated the results can be horrendous for both animal and human. Here we will talk about some of the most common diseases caused by worms and parasites.

Hydatids Disease

Tapeworms can most commonly infect cats, dogs, sheep and humans among others. The resulting disease in humans arises when a person is in contact with a dog or cat infected with a tapeworm or echinococcus granulosus. This is the larval stage of the tapeworms’ lifecycle, where the tapeworm eggs are excreted in the animal’s faeces. If a person handles an infected animal or its faeces, or if the animal licks the person’s face after cleaning itself, that person can then become infected by Hydatids Disease. Luckily this is quite rare in humans with only around 10 reported cases annually however it can be unpleasant. Even though symptoms can take a long time to present themselves they can include fever, abdominal pain, skin problems and even allergic reactions. In the worst cases and if left untreated the disease could cause diarrhoea and vomiting, cysts on the liver or anaemia and could even be fatal. Hydatids Disease is not contagious between humans.


Although perceived wisdom has it that this can be contracted from dog faeces it is in fact more commonly caught from cats. The parasite which causes Toxoplasmosis is called toxoplasma gondii and can also be transferred to humans when eating undercooked and contaminated meat.

Cats can become infected with the parasite through eating birds or rodents and this will then be excreted out in the faeces. Infection in humans is especially worrying and dangerous for those who allow their cat to defecate in a litter tray in the home. It goes without saying that these should be kept well away from any small children in the house. Any place that an infected cat defecates will become infected including soil in the garden. If you grow vegetables in your garden soil it is vital that you thoroughly wash any that you harvest before eating them in order to avoid becoming infected with Toxoplasmosis.

This disease is not contagious between humans with one exception; it can affect unborn children in the womb and even though the mother may show no symptoms the child may unfortunately develop diseases of the eyes and the nervous system.

Dermatophytosis (Ringworm)

This is not actually caused by a worm but is a very common fungal infection. It is an infection of the skin, nails or hair and is caused by exposure to a dermatophyte and often from dogs, cats, guinea pigs or cattle. Although Ringworm – to give the name it is most commonly known by – is usually spread directly by human to human or animal to human contact it can also be caught indirectly from a contaminated environment.

Symptoms include some hair loss and an itchy, red rash which has a ‘bullseye’, or circular appearance, hence the name. The rash initially appears at the directly affected area but can than spread to other parts of the body including the scalp. Left untreated itchy patches can develop blisters which can then start to ooze.

Signs to look for in animals include hairless patches, broken hair, scaly or crusty patches on the skin and whitish areas around the claws.

In humans the symptoms appear around 4-14 days following exposure and, though Ringworm is very contagious it is treatable with anti-fungal creams from the GP.

Sarcoptic Mange

This is a highly contagious disease caused by the sarcoptes scabiei mite, hence the reason why this is called scabies in humans. Sarcoptic Mange is very common in dogs and causes intense itching as the mites burrow into the skin of the animal. The resulting scratching often causes the dog’s hair to fall out completely. The skin of the animal erupts with severe red bumps or blisters and the condition can be extremely distressing for any animal affected by it.

Scabies in humans is similarly caused by mites which can live on the skin for around 10-17 days. The condition is very contagious and if not treated properly can keep recurring. It is very treatable if it is carefully managed for instance by not sharing towels and bedding.


Rats are the main carriers of the bacteria which causes Leptospirosis, specifically in their urine. When the urine contaminates a water source the bacteria can spread to any other animals that drink from it. It can also be spread by the urine itself which infects food, soil and pasture. Dogs and cattle are particularly vulnerable to catching it but they can carry the disease for long periods of time and remain healthy but can still spread the disease to other animals and to humans.

Leptospirosis, also known as Weils Disease can cause a range of symptoms including flu-type symptoms, chills and headaches, diarrhoea and abdominal pain. In severe cases kidney disease, liver failure or inflammation of the brain and spinal cord can occur and, rarely, it can be fatal.

In rare cases, it can be caught through not wearing adequate protective clothing when handling aborted foetuses or afterbirth especially in the field of animal care. Leptospirosis can be treated with penicillin.

Precautions to take to avoid disease

All animals, domestic or otherwise should be wormed regularly using the correct worming product for the species, preferably one containing praziquantel. Because many infections originate from fleas, animals should be regularly treated with the correct flea treatment.

Faeces should always be promptly removed from gardens and litter trays and safely and correctly disposed of.

Never give undercooked or suspect meat to your dogs and cats.

Always wash your hands thoroughly after cleaning out litterboxes, clearing away faeces and handling pet food.

Avoid your dog or cat licking your face and hands but if they do, wash immediately.



About the Author

Debbie has worked for Beeston Animal Health for a number of years and although generally involved with the marketing these days she has a great deal of knowledge on many things to do with small animals.

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to Top ↑