Ringworm in Dogs (Dermatophytosis): A Comprehensive Guide

Ringworm is a common fungal infection that can affect your dog’s skin, hair, or nails. Despite its name, ringworm is not caused by a worm at all, but rather by various species of fungi. The medical term for this type of infection is dermatophytosis, and it’s a condition that requires proper veterinary attention to ensure effective treatment and prevent spread to other pets or humans.

What is Ringworm in Dogs?

Dermatophytosis, commonly known as ringworm, is a superficial fungal infection that affects the outer layers of the skin, hair, and occasionally the nails in dogs. Despite the misleading name, the condition has nothing to do with worms. Rather, it’s caused by a group of fungi called dermatophytes that feed on keratin – a protein found in the outer layers of skin, hair, and nails.

The infection typically creates circular lesions on a dog’s skin, which is where the name “ringworm” originated. These fungi thrive in warm, humid environments and can be highly contagious, spreading from animal to animal, from animal to human, and even through contaminated objects.

Causes of Ringworm in Dogs

Ringworm in dogs is primarily caused by three types of dermatophyte fungi:

• Microsporum canis – The most common cause of ringworm in dogs
• Trichophyton mentagrophytes – Affects both small and large animals
• Nannizzia gypsea (formerly Microsporum gypseum) – A soil organism that causes inflammatory lesions

Dogs typically contract ringworm through direct contact with an infected animal, person, or from contaminated objects like bedding, grooming tools, or surfaces. After contact occurs, the fungus attaches to the dog’s hair, skin, or nails, and signs of infection can develop within 1 to 3 weeks.

Risk Factors for Canine Ringworm

While any dog can develop ringworm, certain factors increase the risk:

• Young puppies (under one year old)
• Senior dogs
• Dogs with compromised immune systems
• Dogs living in crowded conditions (shelters, kennels)
• Dogs exposed to other infected animals
• Certain breeds may be more susceptible, such as Yorkshire Terriers
• Dogs living in warm, humid climates

Additionally, dogs that spend time in environments where they may come into contact with groups of other potentially infected dogs face a higher risk of exposure to ringworm. The condition occurs worldwide but is most prevalent in warm or humid climates where the fungi can thrive.

Symptoms of Ringworm in Dogs

Ringworm can manifest in various ways, and symptoms may differ from dog to dog. Some common signs to watch for include:

• Circular areas of hair loss, often with a red ring of inflamed skin
• Dry, brittle hair around the lesions
• Scaly, crusty, or flaky skin
• Redness and inflammation
• Darkened skin (hyperpigmentation)
• Itchiness (variable – some dogs may not itch at all)
• Small bumps or pustules on the skin
• Changes in nail appearance or structure (when nails are affected)

It’s important to note that ringworm can mimic many other skin conditions, making professional diagnosis crucial. The lesions most commonly appear on the head, ears, paws, and tail, but can develop anywhere on the body. Some dogs may be asymptomatic carriers, showing no visible signs while still being able to transmit the infection to others.

Diagnosing Ringworm in Dogs

Because many skin conditions can resemble ringworm, proper veterinary diagnosis is essential. Your veterinarian may use several methods to confirm the presence of dermatophytosis:

Wood’s Lamp Examination

This “bedside” examination involves using a special ultraviolet light (Wood’s lamp) to examine your dog’s fur and skin. Certain strains of Microsporum canis will fluoresce with a bright apple-green glow under this light. This examination is effective in about 72% of M. canis cases with active skin lesions. Fluorescence usually becomes visible about 5-18 days after an infection takes hold. While this test doesn’t catch all cases, it provides a quick, initial screening tool when ringworm is suspected.

Direct Microscopic Examination

Your veterinarian may examine hair samples and skin scrapings under a microscope after treating them with a special solution. This can reveal the presence of fungal spores and hyphae (fungal structures) on and within the hair shafts, confirming a ringworm diagnosis.

Fungal Culture

A fungal culture (sometimes called a DTM—dermatophyte test medium) is the most definitive diagnostic test. In this procedure, your veterinarian collects hair, scales, or scabs and places them on a culture medium that allows the fungus to grow. The medium contains ingredients that change color when dermatophytes grow, helping to identify the specific fungus causing the infection.

One significant advantage of fungal culture is that it doesn’t require an active skin lesion; any hair sample can be tested. While positive signs can show after 3-5 days, final results may take 10-21 days to confirm the presence and type of fungus.

Treatment Options for Canine Ringworm

Treatment for ringworm in dogs typically involves a multi-faceted approach, combining both topical and systemic therapies. The goal is to eliminate the fungal infection, prevent its spread, and restore skin and coat health. Treatment usually continues for 6-12 weeks, and follow-up testing may be necessary to confirm the infection has been completely eliminated.

Topical Treatments

Topical antifungal medications are applied directly to affected areas and sometimes to the entire body. These treatments help eliminate fungal spores on the hair coat, preventing further spread. Common topical treatments include:

• Antifungal shampoos containing miconazole, ketoconazole, or chlorhexidine
• Lime sulfur dips (highly effective but can have an unpleasant odor and may temporarily discolor light-colored fur)
• Antifungal creams or ointments for localized lesions
• Clipping hair in severe cases or for long-haired breeds to improve contact between medications and skin

Oral Medications

Systemic antifungal medications are often prescribed to target the infection from within. These medications work by eliminating the fungus inside hair follicles, where topical treatments cannot reach. Common oral antifungal medications include:

• Griseofulvin
• Itraconazole
• Terbinafine
• Fluconazole

Your veterinarian will determine the most appropriate medication based on your dog’s specific situation, including factors like age, overall health, and severity of infection.

Environmental Decontamination

Because ringworm spores can survive in the environment for up to 18 months, thorough cleaning of your home is essential to prevent reinfection. This includes:

• Regular vacuuming of carpets, furniture, and other surfaces
• Washing all bedding, toys, and grooming tools in hot water with bleach when possible
• Disinfecting hard surfaces with a solution effective against fungi
• Disposing of items that cannot be thoroughly disinfected
• Limiting the infected dog’s access to certain areas of the home during treatment

Prevention of Ringworm in Dogs

While it’s not always possible to prevent ringworm exposure completely, several measures can help reduce the risk:

• Keep your dog’s living area clean and dry
• Avoid contact with animals showing signs of skin disease
• Quarantine new pets until they can be checked for ringworm
• Maintain good overall health through proper nutrition and regular veterinary care
• Promptly treat any skin conditions to prevent secondary infections
• Practice good hygiene when handling multiple pets

Ringworm as a Zoonotic Disease

One important aspect of canine ringworm that pet owners must understand is that it’s a zoonotic disease, meaning it can be transmitted from animals to humans. People with compromised immune systems, the elderly, and young children are particularly susceptible.

If your dog has been diagnosed with ringworm, take these precautions:

• Wear gloves when applying topical treatments
• Wash hands thoroughly after handling your dog
• Keep the affected dog away from individuals with compromised immune systems
• Consult with your physician if you develop suspicious skin lesions
• Follow your veterinarian’s recommendations for environmental cleaning

With proper precautions, the risk of human infection can be significantly reduced while your dog undergoes treatment.

Recovery and Management

Most dogs with ringworm respond well to treatment and make a full recovery. However, the timeline for complete resolution varies based on several factors, including the severity of infection, the specific treatment protocol, and the dog’s overall health. Generally, treatment continues until all lesions have resolved and follow-up fungal cultures come back negative.

During treatment, it’s essential to:

• Complete the full course of medication as prescribed, even if symptoms improve
• Keep follow-up appointments for monitoring progress
• Continue environmental cleaning throughout the treatment period
• Monitor for any signs of recurrence after treatment has ended

When to Consult Your Veterinarian

You should seek veterinary attention if your dog shows any signs of skin problems, particularly if you notice:

• Circular areas of hair loss
• Red, inflamed skin
• Persistent scratching or licking of specific areas
• Crusty or scaly patches on the skin
• Any skin condition that doesn’t improve within a few days

Early diagnosis and treatment are key to resolving ringworm quickly and preventing its spread to other pets and family members.

Frequently Asked Questions About Ringworm in Dogs

Q: Can my dog get ringworm from my cat?

A: Yes, ringworm is highly contagious between different species of animals. If you have a cat with ringworm, your dog can contract it through direct contact or from contaminated environments.

Q: How long is a dog with ringworm contagious?

A: Dogs with ringworm remain contagious until the infection is completely eliminated, which typically takes 6-12 weeks of proper treatment. Your veterinarian may perform follow-up testing to confirm when your dog is no longer contagious.

Q: Can I get ringworm from my dog?

A: Yes, ringworm is a zoonotic disease that can spread from dogs to humans. Take precautions like wearing gloves when treating your dog and washing your hands thoroughly after handling them.

Q: Will ringworm go away on its own?

A: While some mild cases might resolve without treatment, most require medical intervention. Without proper treatment, the infection can persist for months, cause discomfort, and spread to other animals and humans.

Q: Can my dog get ringworm again after treatment?

A: Yes, dogs can be reinfected with ringworm if exposed to the fungus again. There is no long-term immunity after infection, so continued prevention measures are important, especially for dogs at higher risk.

Remember that any persistent skin condition in your dog deserves professional veterinary attention. While this information provides a comprehensive overview of ringworm in dogs, always consult with your veterinarian for diagnosis and treatment tailored to your pet’s specific needs.

Author

Shinta

 

Shinta is a biotechnologist turned writer. She holds a master's degree in Biotechnology from Karunya Institute of Technology and Sciences and a PG Diploma in cellular and molecular diagnostics from Manipal University. Shinta realised her love for content while working as an editor for a scientific journal.

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