Ringworm isn’t either – Whole Dog Journal


Ringworm is not a worm. It’s not always ring-shaped either. This misnomer of a term stems from an early inaccurate assumption that the infection – which often causes a round, red, raised lesion on human skin – was caused by a worm. Unfortunately, this counterfactual name has remained and is still misleading today.

Ringworm, or dermatophytosis as it is scientifically called, is actually a fungal infection of the superficial layers of the skin, hair and / or nails. While a diagnosis of ringworm can give you the Heebie jeebies, it rarely causes serious problems and is both treatable and, to some extent, preventable. The early detection of ringworm infections can prevent transmission and limit contamination. Therefore, dog owners should be made familiar with the most common signs.


Although ringworm fungus is everywhere, there are conditions that predispose dogs to infection. Dogs at higher risk of developing the disease include puppies, older dogs, and dogs with weakened immune systems. Other risk factors include poor nutrition, high stress environments (e.g., animal shelters), housing high density animals, skin with pre-existing trauma, and living in close contact with affected dogs.

Certain dogs may have lifestyles that increase their risk of ringworm exposure, such as: B. Hunting and working dogs (including German Shorthaired Pointer, Fox Terrier, Labrador Retriever, Beagle, Jack Russell Terrier, German Shepherd), possibly due to increased contact with contaminated soil. Yorkshire Terriers also appear to be more susceptible and are often over-represented in ringworm research.

The good news is that ringworms are relatively rare in healthy dogs. Even if a dog has been exposed, it does not mean that it will develop the disease.


Dermatophytes invade keratinized structures that are on the skin, hair, and nails. In dogs, the head, ears, tail, and front paws are the most common sources of infection, although they can appear on any part of the body.

Ringworm infections usually manifest as small, non-itchy asymmetrical patches of alopecia (hair loss) that spread outward on the skin. However, any combination of hair loss, papules, scales, crusts, redness, follicular obstruction, hyperpigmentation, and changes in nail growth can be observed. The affected hair shafts are usually brittle and break near the surface of the skin, giving the lesion the appearance of a shave.

In the early stages, the center of the lesion often contains light-colored flakes of skin that give it a powdery appearance, and the edges are generally reddish in color. Blisters and pustules can also be seen. In later stages, the lesion may be covered with a crust and the edges of the lesion may become swollen.

When these circular lesions enlarge, the central area can sometimes heal, leaving a circular lesion with central crusts or even hair regrowth. In some cases there may only be one site of infection. In other cases there can be multiple patches. As the fungus grows, the lesions can shape and spread irregularly, and individual lesions can combine into large, irregular regional patches.

Severe infections can generalize (spread throughout the body); As a result, the appearance may be similar to demodectic mange. Generalized cases usually occur in dogs that are immunocompromised, especially dogs with adrenal disease or who have been treated with corticosteroids. Occasionally Ringworm infects a dog’s nails (since the nails are made of keratin), making them rough, brittle, and easy to break.

Knowing mushrooms

This culture plate contains a skin and hair sample from a dog suspected of having ringworm. Microsporum Canis grew in culture and confirms the diagnosis.

Fungi are found all over the world and play a crucial role in most ecosystems. While the early fossil record for mushrooms is not extensive (their inherent structure does nothing to preserve them), scientists recently reported a discovery in the Canadian Arctic of a fossilized mushroom believed to have lived nearly a billion years ago – before it existed of plants! Suffice it to say that mushrooms have been around for a very long time.

The early domestication of animals such as cats and dogs appears to have led to later development of host-specific fungi. The group of mushrooms referred to as keratinophylic Process keratin – a structural protein that forms hair, nails, feathers, horns, claws, hooves, calluses and the outer layer of skin in vertebrates. This group of mushrooms is quite large, but only three genera – Microsporum, Trichophyton, and Epidermophyton – are known to cause disease in animals and humans.

The microscopic organisms responsible for ringworm infections belong to this keratinophylic group and are known as dermatophytes (the MA = Skin, Phyton = Plants). That is why the infection caused by these active substances is called Dermatophytosis.

Some types of dermatophytes are species-specific, meaning that they only infect one species; others can be transmitted between different animal species, including humans. The three most common types of fungus that cause ringworm in dogs are Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes. Each of these is zoonotic (meaning the infection is transmitted between animals and humans), but the rate of transmission is unknown. M. canis is the etiological agent of about 70% of canine ringworm cases; The rest of the cases come from M. gypseum (20%) and T. mentagrophyte (10%).


Dogs that come in contact with the fungus spores can become infected if the dermatophytes infect growing hair or the keratin-rich outermost layer of skin. In most cases, dermatophytes live only in the dead cells of the skin and hair and do not affect living cells or inflamed tissue.

As a dog’s immunity to the disease develops, the infection usually stops spreading, but this process can take several weeks and infectious spores can still be spread. Therefore, treating cases of ringworm is a good idea so that the spread of the infection can be limited and the healing process and time improved.

While ringworm isn’t common in dogs, it is is contagious and most cases of ringworm spread through contact with infected animals or contaminated objects. Infected dogs shed spores into their surroundings, and spore-covered, broken hair is a major source of the disease’s spread. Grooming tools, dog beds, toys, bowls and furnishings are therefore the main items for picking up the contagious spores. All of these should be disinfected when the ringworm comes into the picture. Ringworm spores are very robust and can survive (i.e., infectious) for up to 12 to 20 months in suitable environments.

Ringworm fungi also live in the soil. Dogs that like to dig or roll around on the ground, or stick their heads in rodent holes, may be exposed to it on a regular basis. While these favorite pastimes may expose them to the ringworm fungus, the chance is from infection is not high; How an infection develops depends on the type of fungus and host factors in the dog. The susceptibility is increased if the dog has exposed skin surfaces (e.g. open wounds, cuts, scratches, burns) as well as in high temperatures and high humidity.

Note: some dogs can be asymptomatic carriers. They carry dermatophytes on their bodies but do not develop clinical signs of infection. These dogs are contagious and can contaminate the environment, which can be particularly problematic in multi-animal environments.

Ringworm lesions can be mistaken for other skin conditions. So do not delay a visit to the vet for a definitive diagnosis.

A dog infected with ringworms is considered contagious and can spread the disease to people or other pets, including cats, pets, cows, goats, pigs, and horses. Children (especially very young children), the elderly, and people with weakened immune systems or skin sensitivity may be more prone to infection.

Since ringworm can be transmitted to humans, appropriate measures should be taken to minimize exposure to the fungus while treating the dog. It is important to wear appropriate protection (especially gloves) and to wash hands thoroughly after handling an infected dog. Decontamination and control of the environment is critical in treatment.

Ringworm in humans generally responds well to treatment. If a person has not yet signed a contract with their dog at the time of diagnosis, it is likely that they have not.


There is not a single test to diagnose ringworm. To get an accurate diagnosis of ringworm, some complementary diagnostic tests need to be done to confirm the infection and rule out several other skin conditions that may appear similar in appearance.

* Woods lamp investigation. A Woods lamp is a small UV hand lamp that emits light in a specific wavelength range. When they bind to hair shafts, the M. canis Mushrooms produce a chemical reaction that fluoresces a striking, distinct apple green under the light of the forest in a darkened room. In many cases, the use of wooden light will reveal additional points of infection that were not visible to the eye.

That doesn’t mean either T. mentagrophytes Yet M. gypseum fluoresce under a Woods lamp. While the light is useful for making a preliminary diagnosis, it cannot be used to rule out ringworm infection.

* Microscopic examination. Since dermatophytes are visible under magnification, your veterinarian can take a sample of hair and skin abrasions to examine under a microscope to see if there are any fungal spores. About 85% of ringworm infections, regardless of the type of fungus present, can be confirmed this way.

* Mushroom culture. The most accurate test used to diagnose ringworm in dogs is to fungal culture from a sample of hair or skin cells. The sample is taken from the lesions and placed in a special culture medium where it is monitored for fungal growth. A positive culture can sometimes be confirmed within a few days, but in some cases the fungal spores can grow slowly; Culture results can take up to four weeks. Therefore, a suspected sample can only be classified as negative after four weeks.

* PCR test. The polymerase chain reaction test (PCR) is a newer diagnostic technique that can be performed on either tissue or hair samples. These samples are collected by your veterinarian and sent to a laboratory for processing. This test detects the DNA of fungi that cause ringworms and provides results in as little as one to three days. One caveat: the test is highly sensitive and cannot distinguish between real disease, surface contamination, and non-viable fungal spores (which cannot cause disease but can be detected in a DNA test). This means that PCR tests are beneficial for initial diagnosis, but not helpful in determining whether the infection has cleared up and treatment can be stopped.


In living hosts, dermatophytes usually reside in superficial tissues such as skin, hair, and nails and live on the dead top layer of the keratin protein. The lesions can be disfiguring and uncomfortable, especially if they are widespread.

However, in rare cases, dermatophytes can penetrate deeper into the body and invade subcutaneous tissues and other sites, especially in immunocompromised hosts.

Infections in healthy animals are usually self-limiting and can go away within a few months without therapy. Treatment is recommended anyway to speed recovery, reduce environmental impact, and reduce the risk of transmission.

There is no one-size-fits-all treatment plan for ringworm; Your veterinarian will develop a plan based on the severity of the infection, the number of pets affected, the number of children or other vulnerable and vulnerable people in the household, and the difficulty of disinfecting your pet Surroundings.

Effective therapy includes eliminating the infection from the dog through topical and / or systemic therapies, preventing further spread, and disinfecting and removing infectious material in the environment.

* Topical treatment. Topical therapy destroys the fungal spores on the lesion itself, thereby limiting pollution and preventing transmission. Topically treated hair is no longer infectious when it is dispersed in the environment. Topical therapy is especially important when infected dogs may or may not be restricted.

Whole body treatment twice a week is recommended for generalized dermatophytosis. Typical treatments include a lime-sulfur dip (calcium polysulfide) (leave-on rinse), an enilconazole leave-on rinse (a broad spectrum antifungal agent currently not available in the U.S.), or a miconazole-chlorhexidine rinse / Shampoo (this antifungal and disinfectant combination work together to fight the disease).

For localized treatment, clotrimazole, miconazole, and enilconazole have been shown to be effective. However, these are recommended as concurrent treatments and not as sole therapies. Topical treatment may be required for a period of several weeks to several months.

* Systemic therapy. The administration of an oral antifungal can be an important addition to topical therapy, especially in chronic or severe cases. Systemic antifungal therapy targets the active center of a fungal infection and spreads to the infected dog.

Effective systemic antifungals include itraconazole, terbinafine, fluconazole ketoconazole, and griseofulvin. While griseofulvin has been the traditional antifungal agent for decades, its use is no longer as widespread as it used to be; Newer drugs appear to be safer and have fewer side effects.

Ketoconazole can cause liver disease and is not recommended as a first line of attack, but rather reserved for resistant cases.

Studies have shown that Lufenuron (brand name program) has not been shown to be effective in either treating or preventing ringworm infections.

The disadvantages of systemic treatment are the relatively high cost of the drugs and the potential for toxic side effects, which should be considered when developing a treatment plan. Dogs receiving systemic antifungal drugs should be closely monitored and all drug administration instructions carefully followed.

Duncan, the dredger dog, gets ringworm

W.When my 10 year old Border Collie Duncan developed a lesion When I was 10 years old, I was surprised to learn that he had contracted ringworm. He hadn’t been around infected animals. I couldn’t figure out how he got infected with it – until my vet explained that the fungus was in the soil.

T.It was next to impossible to stop Duncan the Digger dog from digging.
nor did I want to spoil his fun. But at least there was a good theory about how he signed it. In hindsight, it was likely that in addition to being an older dog, he had a compromised immune system, as we learned later when he developed other health concerns.

W.The hat started when a small hairless patch soon turned into a shiny quarter-size lesion. When examined with the light of the forest, the affected area glowed like a glowing ball in the night sky. Since ringworm isn’t too common in dogs, my vet called everyone to see how my dog’s snout was fluorescing. To confirm the diagnosis of M. canis Infection, a sample of skin and hair was taken for culture.

W.While waiting for the results, we began topical treatment of 1% clotrimazole applied to the lesion two to three times a day and monitored the response to this therapy. The good news is that he responded well to localized topical treatment and neither I nor Daisy (my chemotherapy-compromised Border Collie) got the infection. In about three months the lesion was gone, the fur had grown back, and there was little to remind us of the fungal invasion.


Careful and thorough decontamination of the environment is an essential part of treatment. Without proper consideration of the environment, the infection may not go away, spread, or even cause re-infection.

If your pet has been diagnosed with ringworm, dermatophytes are likely to be everywhere your dog has been by now. Infected hair contains numerous microscopic fungal spores that can be released into the environment and can survive for almost two years.

Since infection of other animals and humans can occur either through direct contact with an infected dog or through contact with fungal spores, you must now clean and disinfect everything your pet has come into contact with – and continue to do so throughout the treatment period. Yeah, it’s a big bummer. However, this is an essential part of treatment as affected dogs will continue to re-infect their surroundings until the infection has completely resolved.

How often you need to clean and disinfect will depend on several factors, including the number of people infected, whether the treatment is topical, systemic, or both, and whether there are people in the household at risk. Your vet can recommend a tailored plan, but this is generally recommended The twice-weekly cleaning includes the mechanical removal of the hair as well as washing and disinfecting the target areas, followed by disinfection.

As soon as possible after diagnosing ringworm, do a thorough cleaning of your entire home, targeting your dog’s favorite spots. Mechanically remove hair, dander and skin particles from all surfaces. Note that vacuuming alone does not decontaminate surfaces, but it does remove infectious hair. So vacuum everywhere. After vacuuming outside the house, discard the vacuum bag or disinfect the canister immediately.

Vacuum or use tape or lint rollers to remove hair from upholstered furniture. Carpets can be decontaminated by washing twice with a carpet shampooer with detergent or by hot water extraction. For floors with a hard surface, use commercially available disposable cleaning cloths for dry wiping of floors (e.g. Swiffer). Avoid brooms and mops, as these are difficult to thoroughly clean and disinfect after use.

Dust with electrostatic cloths and dispose of immediately after use. Clean all washable surfaces with soap and water. Infectious material can easily be removed from the environment. If it can be washed, it can be decontaminated.

Any water temperature and detergent will be sufficient to decontaminate washable fabrics (don’t forget to wash your dog’s bedding and toys). Two washes on the longest cycle are recommended. Wash exposed items separately from non-exposed items and then disinfect the devices.

Every day It is recommended to remove hair from the area where your dog is caged.

Proper disinfection takes place in three steps:

1. Mechanically remove all visible residues (flakes of hair and skin). Disinfectants are not effective in the presence of organic residues.

2. Wash the target or surface with a detergent until the area is visibly clean, and then rinse to remove the detergent, as some detergents can inactivate disinfectants.

3. Apply a disinfectant to kill any remaining spores. Some of the readily available disinfectants include:

• • Sodium hypochlorite (household bleach). Effective at concentrations of 1:10 to 1: 100 even with short contact times.

• • Enilconazole. Available as a spray or ambient mist. Relative expensive. Availability is limited in some countries.

• • Accelerated hydrogen peroxide (AHP). A newer broad spectrum disinfectant that is widely used. Available in concentrates and ready-to-use formulations.

• • Rescue (acceleration). Another effective broad spectrum disinfectant. Available in ready-to-use formula, concentrate or wipes.

Should you lock him up?

It is often recommended that infected dogs be confined to an area of ​​the house that is easy to clean. This needs to be balanced with maintaining your dog’s mental and behavioral health, especially if he is young or newly adopted. The restriction should be applied with caution and for the shortest possible time. Ringworm is curable; Behavior problems can be lifelong.


Many dogs respond fairly quickly to treatment, and often show improvement within a week or two. Full treatment to clear the infection usually takes at least six to ten weeks, but it can take as long as three to four months.

Do not stop treatment as soon as your dog appears visually healed. Dogs can still carry infectious fungi even if the signs seem to have completely subsided. Recurrent or persistent infections are usually the result of treatment failure, either due to insufficient duration of therapy or insufficient environmental decontamination.

Your vet can monitor healing progress (using a forest’s light and / or mushroom cultures) and use these results to determine when your dog is cured. Following your veterinarian’s recommendations is very important to ensure a successful result and prevent recurrence.

The good news is that almost all dogs recover completely with no long-term effects (hair loss is not permanent unless the follicle has been destroyed). People, on the other hand, can develop a permanent aversion to house cleaning!

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