Categories: Animal Health

Ringworm in Dogs

Do you want to know all the aspects of ringworm in dogs? In the following article, we explain the causes, symptoms, and treatments of this disease that can affect your dog.

What is ringworm in dogs?

The ringworm in dogs or dermatophytosis is a superficial mycosis whose etiological agents are varied. These invade our pets’ keratinized tissues (skin, hair, and nails), giving lesions known as ringworms.

Normally this infection is cutaneous without going through the stratum corneum, so it does not affect deep tissues or organs in animals with a good immune system. The genera of fungi involved in this process are:

  • The Genus Microsporum (skin and hair).
  • Genus Trichophyton (skin, hair, and nails).
  • Genus Epidermophyton (skin and nails).

These dermatophytes feed on keratin (a protein whose function is protection). They have keratinolytic activity; that is, they can use keratin as nutrients by means of enzymes (keratinases). The dermatophytes are classified as:

  • Zoophilic: these dermatophytes are mainly pathogenic in animals, being of more interest for this article. Microsporum canis is the most relevant in dogs and cats.
  • Anthropolitical:
  • Geophilic: the pH of the earth influences them. Microsporum gypseum and Microsporum racemosum belong to this group.

Regarding its epidemiology,  we can say that it is a disease with worldwide distribution. It affects more young animals, and its transmission mechanism is direct. In addition to age, other risk factors are overcrowding, poor diet, handling, and hygiene or not complying with the quarantine periods.

Is ringworm in dogs contagious?

Yes, ringworm in dogs is considered a zoonosis. According to the World Health Organization (WHO), a zoonosis is “that disease that is transmitted naturally from vertebrate animals to man and vice versa.” The contagion is carried out through direct contact with the fungus spores from the skin of dogs with the skin of humans.

In most people, these infections are mild and do not have many complications. The problem is when people have a depressed immune system, for example, people with AIDS. In these cases, the infections will be more persistent.

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Symptoms of ringworm in dogs

The severity of these symptoms depends on the virulence of the strain, the place where the disease will occur, or the individual himself. The clinical signs are highly variable and can be seen between 2 and 4 weeks. 

This period may decrease in animals with a suppressed immune system. The most characteristic symptom is alopecia (circular lesions), due to the affected hairs’ breakage. Sometimes there is inflammation, and the itching is variable.

Diagnosis of ringworm in dogs

If the diagnosis is made in the initial stages, it will be much more favorable for the treatment and in animals, as well as to avoid a public health problem and spread it to humans. So, do not hesitate to go to your vet whenever you see an anomaly in your pet.

The veterinarian must take an anamnesis, that is, the data of the animal’s medical history. A thorough physical examination is also performed in order to see the physical condition of the animal and the possible injuries that it may present. Once these steps have been completed, the assertive diagnosis is carried out using different tools:

  • Trichography: consists of the examination of the hairs under a microscope in order to find fungal elements. They appear as fine, greenish filaments. This test requires experience.
  • Wood’s lamp: it is a lamp that emits ultraviolet light. In dark rooms, these dermatophytes are fluorescent (yellowish-green). It is very common in veterinary clinics due to its easy use, but it has the disadvantage of giving false negatives (it only detects 30-40% of cases).
  • Culture: for culture, scrape the edge of the lesion with a scalpel blade, avoiding bleeding. The growth of these fungi is slow, and the culture media must be specific to avoid other microorganisms’ growth. The results can be obtained between 4 and 7 days at a temperature of 25-28 ºC.
  • Differential diagnosis is always important. Among the diseases with which a differential diagnosis can be made is acne in dogs.

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How to cure ringworm in dogs?

Dermatophytosis is a self-limiting infection; that is, the symptoms resolve on their own after a while, in this case, between 1 and 3 months. So just by improving the animal’s immune system, it ends up remitting on its own. In addition to this, the treatment will consist of symptom relief and isolation to avoid contagion to other animals and humans.

  • Topical treatment: the area must be shaved. With this, as much fungus as possible is eliminated through treatment, and reinfection is avoided. Shampoos are chlorhexidine or povidone-iodine are used to avoid secondary bacterial infections and their antifungal effect. Local treatments containing sulfur are among the most effective.
  • Systemic treatment: only used in severe cases. They are antifungal such as griseofulvin, ketoconazole, or itraconazole, at the doses prescribed by the veterinarian.

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Conclusions of ringworm in dogs

In dogs or dermatophytosis, ringworm is an infection caused by fungi that produce lesions in the keratinized tissues of both animals and humans, being a zoonotic disease. It is very important to be aware of the importance of going to the veterinarian to make the diagnosis and dictate the treatment guidelines for possible diseases. With this, we will improve our animals’ health;

we can avoid possible infections to other animals and a public health problem by avoiding contagion to people. For that, give your pet a good quality of life, a good diet, physical exercise, and comply with the vaccination guidelines and deworming. Also, keep your dog and the areas where it will live in good cleanliness and hygiene conditions.


Ringworm is the most common contagious skin infection in cats and dogs. It can not only be transferred…

Posted by Furry Friends Animal Rescue Qld Inc on Sunday, February 28, 2016