Fungal diseases – do we need to be worried for our pets?

Does your pet like to dig in the soil, gleefully roll in the mud, or are they a garden sun worshipper? Then fungal diseases are something you should be aware of. Fungal diseases are usually picked up from the soil. They are parasitic organisms that feed off a host, like your frolicking pup, after being inhaled, eaten, or entering the body through a break in the skin. 

Can your pet breathe in fungus? 

Yes. Whether they’re snuffling in the dirt or having a good roll around, breathing in the pathogen/ fungus is indeed possible and a common route of infection; perhaps because our pets generally explore their surroundings with their noses and sense of smell. 

Fungal infections that attack the lungs commonly cause fever, coughing, and difficulty breathing. However, infections of the nose (Nasal aspergillosis) are more common and have less dramatic signs.

If your dog eats soil whilst playing, can they also ingest fungal spores that make them poorly?

Yes, our snuffling pups are also at risk of infection from fungal spores in the dirt. Fungal infections that attack the gastrointestinal system commonly cause abdominal pain, anorexia (loss of appetite) diarrhoea, and vomiting. 

If your dog has a wound, should you be more aware of cleaning the area after a play in the mud or in the garden?

Absolutely. Fungal elements can enter the body through a break in the skin or an injury and set up an infection. It is of course important to keep wounds clean to prevent any infection, fungal included. Particularly common are fungal infections related to nail injuries due to the proximity of the nails to the ground and how common it is to be in contact with soil/ dirt, so be sure to check your pups’ nails and give them a good wash-off after a play outside. 

What types of fungal diseases are there? 

There are a wide range , depending on the site of infection, the type of fungus, and the state of the pet’s immune system.

Those that are breathed in and therefore affect the respiratory tract – 

Nasal aspergillosis

Typically confined to the nasal passages and sinuses, although can spread to the nearby structures of the head. This type of infection is more common in long-nosed dogs. Caused by breathing in fungus and their spores from soil, symptoms include nasal pain, a chronic bloody nasal discharge, nosebleeds, and/or sneezing. 

Disseminated aspergillosis

Although very rare, a systemic (body-wide) type of infection can be seen in all species. The infection enters through the respiratory system and can travel to other parts of the body in the bloodstream. The focal part of the body seems to be species-dependent. So in cows, this can affect the womb and pregnancy. Whereas, in dogs, vertebrae (bones of the spine) and kidneys are attacked more frequently. And in cats, the sinuses, nasal passages, and lungs are most often infected. Symptoms can be quite general like loss of appetite, vomiting, muscle wasting, or weakness, but can be more localised, such as back pain or lameness in dogs. 

Cryptococcosis

Typically spread by birds, initially starts as a respiratory infection caught by breathing in the mould from the ground and then can spread to the rest of the body affecting the nervous system. Symptoms include lethargy, nasal discharge, and then potentially seizures, or other neurological complications. 

Blastomycosis

An infection with Blastomyces dermatitidis, that can be found in areas that are waterlogged such as lakes, marshes, ponds, and estuaries. The fungal spores are breathed in and initially affect the lungs before spreading out and affecting the rest of the body, such as the bone marrow and brain. Symptoms include a cough, fever, skin lesions, and unexplained lameness. 

This infection risk is low in the UK as it is not as commonly found here as it is in other countries but daily walks in wet areas could pose a risk.

Those that are eaten and therefore affect the gastrointestinal tract – 

Candidiasis

Affects the mucous membranes, the skin, and the gastrointestinal tract. Signs of infection are variable and nonspecific diarrhoea, weakness, and skin lesions. This type of infection is rare in dogs but more common in birds. In birds, candidiasis is a common infection of the crop leading to “sour crop”. 

Histoplasmosis

Generally transmitted in the faeces of birds/ wild animals, affects the gastrointestinal tract initially before potentially spreading and becoming a systemic infection affecting other body organs. 

Those that enter the body via broken skin and so are seen on the skin – 

Dermatophytosis (Ringworm)

Not in fact caused by a worm but by a fungus, ringworm presents as characteristic ring-like lesions on the skin. It is extremely contagious and spread by direct contact with fungal elements such as in bedding or on surfaces. Symptoms include flaky and itchy skin, brittle nails, and hair loss. It is one of the more common fungal diseases.

Fungal nail bed infections

Often species of Malassezia or Blastomyces dermatitidis (see above), enter the nail and nail bed through boggy conditions and broken nails, leading to development of brittle nails. More commonly seen in working dogs or active dogs working in wet conditions near waterways. 

Malassezia infection

Is by far the most common fungal infection in our pet dogs and cats. It is caused by an overgrowth of the natural yeast that lives on the skin, overpopulates, and overproduces. Symptoms include itchy flaky skin, red and irritated skin, and ear disease. More common in breeds with excessive skin folds or floppy ears. This fungus characteristically produces a strong musty smell. 

But you have a pet bird, they can’t get fungal diseases too, can they? 

All pets are able to catch and suffer from fungal diseases. Two of the most common fungal diseases of birds are Aspergillosis affecting the respiratory system and Candida infections affecting the gastrointestinal tract. Aspergillosis generally affects older birds who are immunocompromised. Symptoms are depression, anorexia, weight loss, increased respiratory rate, or dyspnoea. It is not infectious between birds but instead spread by aerosolised spores. Candidiasis is seen in young or immunocompromised birds, most commonly affecting unweaned chicks. Symptoms include weight loss, plaques in the oral cavity, anorexia, and regurgitation. Birds on antibiotics are at risk of developing this condition, it can also occur due to unclean living conditions and poor husbandry. Birds have been known to develop a Malassezia infection due to feather picking. 

What if your pet is already immunocompromised? 

Some fungal infections can cause illness in otherwise healthy animals. Many, however, fungal infections “prey” on those with weakened immune systems. Those with predisposing health conditions or those on medication that prevents the immune system from being as efficient, are much more likely to suffer from fungal infections. Health conditions such as diabetes, thyroid disease, FIV (feline immunodeficiency virus), some cancers, those with chronic skin disorders and those with Cushing’s disease are just a few disorders that could cause your pet to be prone to becoming infected with and developing illness from fungal diseases. 

Antibiotics or some types of medications like chronic steroid use can also lower the immune system; making it more likely your pet will develop an opportunistic infection of fungal origin. 

Treatment of fungal infections

Fungal infections can be treated with either topical creams, bathes, or oral medication. Sometimes a mixture of all types of treatment are given to control the infection; especially if the infection is over a larger area or widespread. 

Your vet may need to consider an underlying cause if infections are frequent, or the skin is visibly chronically thickened and discoloured (lichenified) and blood tests or further investigation may be warranted. Treatment to address the underlying cause could help prevent infections coming back or overwhelming your pet as frequently. 

Fungal infections, you, and your pet, should you be worried?

Some of the fungal infections discussed here can be passed between you and your pet. So it is prudent to make sure you seek medical advice if you notice any new symptoms in you or your pet. If you are worried about the possibility of your pup having a fungal infection, especially if they are taking medication regularly that could precipitate the infection growing or spreading, speak to your veterinarian and be vigilant in monitoring your pet’s health regularly. 

However, it’s important to remember that most fungal diseases are uncommon, and that viral and bacterial infections are much more common causes of illness.

References:

• Fungal Infections in Dogs – MSD Vet Manual
• How to spot and treat yeast infections in dogs
• Candida Infections in Birds – VCA Animal Hospitals
• Blastomycosis – UK DogOwner