Dog Owner Must-Knows about Ringworm in Dogs

It can be difficult to see ringworm in dogs if you’re not aware of its distinct characteristics. After all, it doesn’t look the same as the classic ringworm in humans. Those inflamed red circular lesions in humans manifest in dogs differently. Hence, many dog owners may dismiss symptoms that are already definitive of ringworm in dogs.

Worried that your dog may be suffering from a pesky ringworm infestation? Here’s everything you need to know about ringworm in dogs. We’ll start by defining what ringworm is, then progress to what causes the condition, how it’s treated, susceptible dog breeds, and possible complications.

• Defining Ringworm in Dogs
• Causative Agents of Ringworm in Dogs
• Symptoms of Ringworm in Dogs
• Where Do Dogs Get Ringworm?
• Infection Course of Ringworm in Dogs
• Dogs Susceptible to Ringworm
• Diagnosing Ringworm in Dogs
• Treatment Plans for Ringworm in Dogs

Defining Ringworm in Dogs

Ringworm in dogs is a skin disease characterized by brittle hair follicles and claws. The illness also typically affects a dog’s skin and coat. 

Ringworm is formally known as dermatophytosis in dogs. It’s the most common fungal infection that dogs may catch and spread. The illness is contagious and spreads easily through infected skin and hair dropping from the infected dog’s coat.

The disease is mostly caused by the ringworm, a fungus scientifically known as Microsporum canis. It is named as ringworm because, in humans, the fungus creates reddish and itchy circular lesions visually similar to a ring. This is a misnomer for many since no parasite is involved for a dog to get infected with ringworm.

It is important to strongly emphasize that ringworm in dogs isn’t caused by a worm or parasite, but rather by a fungus.

Ringworm isn’t a life-threatening illness in most dogs. But it is seriously contagious and can be passed on to fellow dogs, other animals, and even to humans.

Some dog species and populations may be especially susceptible to ringworm. Such dogs may suffer more serious symptoms such as systemic body infections.

Causative Agents of Ringworm in Dogs

Certain fungal species may cause ringworm in dogs. These three species are collectively known as dermatophytes:

1. Microsporum Canis

Microsporum Canis is a spindle-shaped fungus belonging to the phylum Ascomycota. It can infect domesticated animals such as dogs and cats. It also infects humans occasionally. 

The fungus takes up residence in its host animal’s upper skin layers, which are mostly composed of dead skin. This explains why ringworm in dogs (and in other animals and humans) manifest with various kinds of skin symptoms.

1. Canis is responsible for almost 70% of ringworm in dogs. This makes it the most common fungal species infecting dogs and other domesticated animals with ringworm.

2. Microsporum Gypseum

Microsporum Gypseum is another type of fungal species that causes ringworm. This particular fungus is the causative agent for 20% of ringworm cases in dogs.

Microsporum Gypseum is abundantly found in soil. Dogs who contract ringworm with M. Gypseum as the culprit often get it from playing outdoors and soil-digging. However, infestation with M. Gypseum in dogs is rare.

3. Trichophyton Mentagrophytes

Trichophyton Mentagrophytes is another group of fungal species known to cause ringworm in dogs. But this group of fungi is often isolated in wild and domestic rodents such as mice rather than dogs. T. mentagrophytes in dogs is extremely rare, accounting for only 10% of ringworm cases in dogs.

A 2004 Croatian retrospective study on dermatophyte infections sought to delineate the clinical signs of dogs infected with T. Mentagrophytes. The study found out that most of the dogs with ringworm caused by T. Mentagrophytes had localized ringworm lesions on the head and legs.

Dogs can contract ringworm caused by T. Mentagrophytes upon direct contact with infected rodents. They can also catch the fungi from the environment.

Symptoms of Ringworm in Dogs

Ringworm symptoms may vary per individual dog and breed. But here are the general symptoms of ringworm found in most dogs:

• Hair loss (alopecia) in circular patches
• Scabby and inflamed skin
• Brittle and dry hair
• Brittle, rough, and broken claws
• Random hair loss in one area of the body

Most ringworm lesions are found on the head, ears, limbs, and paws. The lesions aren’t itchy but they are prone to inflammation. In most cases, the lesions gradually develop a scabby-looking covering accompanied by redness.

Some dogs may develop generalized lesions in the body. Such lesions are larger than typical ringworm lesions. Generalized body lesions are often a result of the immune response of the infected dog.

Hair shafts become weak and fragile as the fungus clings to them. This causes patchy hair loss in different body areas.

Ringworm can also affect the nails, a condition called onychomycosis in dogs. It causes the claws to become brittle, fragile, and weak. The fungus can also thicken a dog’s nails. Some cases of ringworm in dogs also present with misshapen nails and claws.

Some dogs with ringworm may appear asymptomatic. They have the fungus in their skin and hair but they do not show any visible signs and symptoms of the disease. Asymptomatic dogs may carry the disease and spread it unknowingly to fellow dogs and even to humans.

Where Do Dogs Get Ringworm?

Fungi spread through spores. Here are possible ways the ringworm fungi can spread from infected dogs:

• The most common way dogs contract ringworm is when they interact with another dog who carries the fungus. An infected dog with shedding and broken hair can spread the ringworm fungus to others during playtime or socialization activities, for instance. Ringworm can also quickly spread in areas such as kennels and dog shelters.

• Infected dogs can also leave fungal spores on couches, beddings, and carpets. These spores can then be picked up by other dogs using the same furniture, bedding, or carpet, transferring ringworm to them.

• Sharing contaminated objects among dogs such as toys, combs, grooming tools, and food bowls also helps spread ringworm. Groomer’s offices and dog boarding facilities are susceptible to having a ringworm outbreak.

• Dogs can also contract ringworm from other domesticated animals such as cats. They may also catch the illness from rodents. 

• There are also cases of humans transferring ringworm to their pet dogs, and vice versa. Ringworm fungi are zoonotic, which means animals and humans can swap the fungi and cause disease in both of them.

The fungus spores can live up to 18 months on infected dog hairs and other contaminated objects. The spores can spread ringworm within this period, making the illness highly contagious.

Note that exposure to an animal, human, or environment with ringworm fungal species doesn’t automatically mean your dog will contract ringworm instantly. Infection depends on your dog’s overall health, age, the condition of exposed skin, nutrition, and grooming. There’s a high risk of infection if the dog is generally weak or has lots of broken skin surfaces.

Infection Course of Ringworm in Dogs

Ringworm fungus attaches themselves to the host dog’s hair, skin, and nails. They begin to feed on keratin found in the skin, hair, and nails’ outer dead layers. The fungus proceeds to multiply and spread, forming lesions form on the areas where the fungus has congregated.

Ringworm fungi can also thrive on the hair follicles of dogs. They weaken the hair shaft and cause the round hair loss patches distinct to ringworm infection in dogs. After that, the fungi causing ringworm can move to the claws and cause nail thickening, brittleness, and breakage.

The circular lesions start to heal at the center with hair regrowth in this area. However, as lesions heal, they also flatten and enlarge. They may also appear scaly, scabby, and inflamed, although they aren’t necessarily itchy. Typical ringworm cases have several hair loss patches scattered across the dog’s body. Most lesions are concentrated on the head, ears, limbs, and paws.

Ringworm’s incubation period is 7-14 days. This is the time it takes for a dog to show signs of ringworm infection from the initial time he was exposed to the fungal causative agent. Other dogs may begin to show symptoms up to the 21st day following fungal exposure.

Dogs with a healthy immune system can get the fungi but do not exhibit outward signs and symptoms. They can become silent ringworm carriers, infecting other dogs, animals, and humans without knowing it.

Weaker dogs may get a severe case of ringworm infection. Their illness could progress and include a suppression in the overall immune system response and a problem in the endocrine system. 

Dogs Susceptible to Ringworm

Certain dog populations may be susceptible to getting ringworm infection. These include:

• Puppies
• Older dogs
• Immunocompromised dogs
• Dogs living with shelters and kennels together with other dogs
• Pet dogs in a home with other animals such as cats and rodents
• Dogs living with a human infected with ringworm
• Dogs who frequently play outside in the soil
• Breeds such as Yorkshire terriers, Boston terriers, and Jack Russell terriers

Diagnosing Ringworm in Dogs

Veterinarians use various diagnostic techniques to diagnose ringworm. They do so to rule out any skin infections that may look similar to ringworm infection.

Ringworm is quite noticeable due to its hallmark scabby, inflamed, lesions accompanied by hair loss. But to be sure, these tests are conducted to isolate the exact fungal causative agent and confirm a ringworm diagnosis:

1. Wood’s Lamp Examination

In Wood’s Lamp examination, the veterinarian uses an ultraviolet light source filtered with either nickel or cobalt. He shines it over the affected skin and hairs to look for the Microsporum Canis species of ringworm fungi. M. Canis fluoresces under ultraviolet light, enabling the vet to rapidly screen for ringworm infection.

A positive result may suggest the presence of M. Canis fungi. However, further tests are needed to completely confirm ringworm in dogs. Also, a negative Wood’s Lamp result doesn’t mean M. Canis isn’t present in the dog samples, as half of the M. Canis fungal strains do not fluoresce.

Nevertheless, Wood’s Lamp examination is useful for rapidly determining if a dog may be infected with ringworm or not.

2. Fungal Culture

Veterinarians take a sample of skin or hair cells from the infected dog and bring it to a laboratory for fungal culture. Special clean instruments or new toothbrushes are used to pluck hairs and skin cells around the dog’s lesions.

The cell samples are then spread over special dishes designed to nurture fungal cultures. If the growth of any of the three dermatophyte fungi species is present, the dog is diagnosed with ringworm.

A fungal culture may take 2-3 days to complete and yield results. Some fungal spores are slow-growing though and may take 2-4 weeks before showing up on fungal culture.

Generally, a fungal culture is among the most reliable ways to confirm a ringworm infection in dogs.

3. Microscope Examination

Veterinarians may also examine plucked hairs or skin cells directly under a microscope. They’ll look for fungal units growing in the hair shafts within these samples. 

Direct microscope examination may be time-consuming and does not completely indicate the presence of ringworm infection all the time.

4. Skin Biopsies

Skin biopsies are required for dogs with severe skin lesions that may be hard to obtain and culture. A skin biopsy often points out to a true fungal infection in the dog, as opposed to temporary fungal infections on the skin. Hence, this procedure is only reserved for dogs presenting with severe skin abnormalities.

3 Treatment Plans for Ringworm in Dogs

Dogs typically recover from ringworm on their own. But this process could take a long time. Hence, veterinarians prescribe medications and treatment plans to expedite the healing process of ringworm in dogs. Medications are also used to prevent further spread of the fungal spores causing illness in other animals and humans.

Combination therapy proved useful for combating ringworm infection in dogs. This is especially required for dogs experiencing persistent or severe ringworm infection.

A three-step approach consists of the following treatments:

1. Topical Ringworm Therapy

Ringworm can be treated by applying topical medications to the dog’s skin. Medicated shampoos, ointments, and creams can be used to calm inflammation and help hasten the lesions’ healing. Localized lesions benefit the most from topical ringworm therapy.

Effective antifungal agents used in topical ringworm therapy include miconazole and clotrimazole. Your dog’s veterinarian will prescribe the right dosage and frequency of using topical antifungal agents on your dog. It may take up to 6 weeks or more for the dog to be fully healed from ringworm through topical therapy.

Other possible dips and washes may be applied once or twice a week. These include:

• Accelerated hydrogen peroxide rinse in 1:20 ratio
• Enilconazole
• Climbazole mousse
• Lime-sulfur combination in 1:16 ratio

Veterinarians often advise dog owners to clip long hairs of dogs with ringworm. Shaving dog hair on the affected areas is also recommended to facilitate better treatment and faster healing.

2. Oral Ringworm Medications

Moderate to severe ringworm infections may require oral medications in conjunction with topical therapy. Medications your veterinarian may prescribe for your dog include:

• Itraconazole
• Fluconazole
• Ketoconazole
• Terbinafine
• Griseofulvin

Itraconazole and terbinafine are most effective for healing ringworm in dogs. Meanwhile, griseofulvin is also highly-effective especially when given with a high-fat meal. 

Always follow the recommended dosages your dog’s veterinarian will give you. Treatment consistency is key in beating ringworm in dogs, especially severe and systemic cases. Like topical treatments, allow 6 weeks up to 6 months for the oral medication course to fully work.

3. Decontaminating the Environment

Fungal spores can be aggressive and can live for long months in the environment. Hence, environmental decontamination is a crucial part of the treatment plan for ringworm in dogs. If decontamination isn’t done, other pets, as well as you and your family members, run the risk of contracting ringworm from your dog.

Decontaminating goals include:

• Removing as many stray hairs as possible
• Disinfecting the environment to kill fungal spores

It can be challenging to clean areas where your ringworm-infected dog stays inside the house. Hence, several veterinarians suggest moving your dog to a room with hard floors while he is infected with ringworm. 

Stray hairs are easily removed from hard floors by moping it with a veterinarian-recommended disinfectant or strong detergent. A good inexpensive yet effective option is to use a freshly prepared chlorine bleach solution in a 1:10, 1:32, or 1:100 ratio. Commercially-prepared disinfectants containing accelerated hydrogen peroxide or detergent-peroxide formulations are also advisable.

Some tips for environmental decontamination include:

• Vacuum, scrub, and wash all articles used by an infected dog using hot water, detergent, and bleach or disinfectant.

• If an item cannot be disinfected thoroughly, it’s sensible to throw them away.

• Floors, walls, and lamps should be disinfected with hot water, detergent, and bleach or disinfectant.

• Carpets are hard to completely decontaminate. The best option is to frequently vacuum the carpet and immediately dispose of the collection bag.

• If the carpet can be removed, consider washing it in hot water using strong detergents, bleaches, or disinfectants. Consider throwing a carpet away if it cannot be decontaminated effectively.

• Have your curtains dry cleaned by a professional cleaning provider.

• If a dog frequents a vehicle, clean the interiors with hot water, disinfectants, and bleach.

Completely clean and disinfect your environment once every 4 weeks at the very least. More frequent cleaning is better. Daily moping, cleaning, and vacuuming all areas accessible to your dog is recommended.

All those cleanings can potentially stress out your sick dog. Some sick dogs are potentially sensitive to the frequent use of vacuum cleaners around the house. Hence, it’s better if your dog has learned to conquer his fears through various types of training (1).

Wrapping It Up

Ringworm in dogs is a contagious skin illness caused by various kinds of fungi. It’s not life-threatening, but it can easily spread to fellow dogs, animals such as cats, and humans. Early detection, consistent and aggressive treatment, and effective environmental decontamination can help hasten dog recovery and help prevent the spread of harmful fungal spores in the environment.

References:

(1) Sundance, K. (2017). Dog training 101: Step-by-step instructions for raising a happy, well-behaved dog. Quarto Publishing Group USA Inc.