Pododermatitis (Interdigital Dermatitis) in dogs

Overview of Canine Pododermatitis

The term pododermatitis is not a specific diagnosis. It simply means inflammation of the feet, and numerous diseases include involvement of the feet. Pododermatitis commonly occurs on the foot or between the toes in dogs.

As different diseases require different therapies, it is very important to establish a correct diagnosis. The history, age of onset, progression of the disease, presence of other skin problems in other parts of the body, presence of pruritus (itching) and existence of concurrent systemic disease, are all factors that should be considered to differentiate among diseases and establish a correct diagnosis. Other diseases that may include pododermatitis include:

Allergies can be present with itchy feet. Face and ears are also itchy and the dog tends to relapse with skin infections. Depending on the nature of the allergies, this could occur all year or only during certain times of the year. As a consequence of the itching, the feet tend to become swollen and infected. A rusty discoloration is present on feet that are chronically licked. This is called “salivary staining” and is caused by a substance present in the saliva of the animal. Allergies tend to worsen with age, so it is important to determine the exact cause in order to make your dog comfortable.
Auto-immune diseases like pemphigus and lupus can also manifest with a pododermatitis. Lesions are more severe than the those seen with allergies. The pads may become cracked, and the animal may be in pain when walking on hard surfaces. In most cases, other parts of the body are also affected, such as yellow crusts on face and ears, and the animal may feel depressed and have a poor appetite.
Internal diseases like pancreatic tumors or liver cirrhosis can also manifest with a pododermatitis. The pads become hard and cracked. Little sores may also be present around the mouth and on pressure points. Skin lesions may be evident months before other signs of systemic disease. This disease is diagnosed with a skin biopsy.
Fungal organisms are present in the soil of some areas, and animals may become infected by walking on contaminated areas. In those cases the nails may grow abnormally and become very friable. This is a mycosis that has the potential of being zoonotic, which means it can also infect humans, so early diagnosis is extremely important.
Mange can also manifest with pododermatitis. Two different types of mange occur. One is contagious to people and other animals (sarcoptic mange) while the second one is not contagious (demodicosis). Demodicosis commonly affects the feet, which may become very itchy and swollen. Secondary bacterial infections are also extremely common with this disease. Skin scrapings and biopsies may be necessary to diagnose the disease and determine the nature of the infection. When several feet are affected, prognosis is guarded. If your dog is less than 2 years of age, it is important that you consider neutering him, as this condition is hereditary. If your dog is older, an underlying disease may be present.

In rare cases, there may be sloughing of the nails, and the feet may become very painful. This could be due to auto-immune disease, drug reactions or a nail dystrophy. A biopsy is crucial to establish diagnosis.

Diagnosis of Pododermatitis (Interdigital Dermatitis) in Dogs

Early diagnosis is important, so that your dog can receive medical attention soon after the problem is identified. Your veterinarian may recommend the following:

A thorough history
In most cases, skin scrapings, cultures and biopsies to establish a diagnosis
Biopsies, usually taken under sedation. Stitches are placed to stop the bleeding and ensure proper healing.
In some cases, as when a nail dystrophy is suspected, it is necessary to remove the last part of the digit (P3) to make a diagnosis, as the characteristic changes are only visible in the nail bed.

Treatment of Pododermatitis (Interdigital Dermatitis)

In most cases, a secondary bacterial infection is present, and systemic antibiotics are required. Depending on the depth and severity of the infection, the length of antibiotic therapy may vary from 4 weeks with superficial infection to 8 to 12 weeks with deep infection.

If a fungal infection is diagnosed, antifungal therapy is necessary for a prolonged period of time due to slow growth of nails. The average animal requires at least six months of medications. Failures are possible and, in severe cases, removal of the affected nails may be the only option.

Home Care

You may need to shampoo your pet’s feet with medicated shampoos or soak the feet with special solutions. Hard surfaces should be avoided if easy bleeding or pain are present.

If a nail dystrophy is diagnosed, you may try medical therapy, like high doses of essential fatty acids and glucocorticoids. If medical therapy fails to make your pet comfortable, surgery to remove nails may be considered.

In-depth Information on Pododermatitis (Interdigital Dermatitis) in Dogs

Pododermatitis is not a specific diagnosis but more the description of a clinical presentation, namely inflammation of the feet. Specific terms are used to describe lesions involving the feet and nails. The most commonly used terms include onychomadesis (sloughing of claws), onychogryphosis (hypertrophy and abnormal curvature of claws), paronychia (inflammation of the nail fold) and onychodystrophy (abnormal claw formation).

Numerous diseases can involve pododermatitis and consequently the footpads and nails.

Diseases that can cause pododermatitis, usually without involvement of the footpads and nails, include atopy, food allergy, contact allergy, demodicosis, hookworm and Pelodera infestation, sarcoptic mange, dermatophytosis, Malassezia and bacterial infections.
Diseases that commonly affect the footpad causing crusting and ulcerations include: vasculitis; systemic lupus erythematosus; necrolytic migratory erythema (also called hepato-cutaneous syndrome); pemphigus complex (foliaceous and erythematosus); drug eruptions (e.g. erythema multiforme); zinc responsive dermatosis; generic dog food dermatosis, mycosis fungoides (also called cutaneous lymphoma); and primary diseases of keratinization.
Diseases that may cause brittle and deformed nails include: dermatophytosis, symmetric lupoid onychodystrophy, and idiopathic symmetric onychodystrophy of Siberian huskies and Rhodesian ridgebacks.

Symmetric lupoid onychodystrophy. It has been reported in Labradors, German shepherds, Rottweilers and boxers. Affected dogs are usually young and nail loss begins acutely and is associated with variable degree of pain and itchiness. Paronychia is generally absent.
Secondary bacterial infections are common and contribute to the pain and itchiness. The natural course of the disease involves partial nail re-growth of friable, abnormal nails that continue to be sloughed. Diagnosis is obtained with P3 amputation and histopathology.
Fungal infections of the nails are most commonly caused by mycrosporum gypseum or trychophyton. The affected claw is misshapen and friable. Paronychia is common. Diagnosis is made by culture of shavings or clipping taken from the nail.
Pelodera pododermatitis is caused by free living nematodes. The larvae invade the skin and may be found on skin scrapings. Infestation is self-limiting once the source of contamination has been removed. Destruction of bedding is mandatory and the patient should be washed with parasiticidal dip.
Hookworm infestation (Ancylostoma and Uncinaria) is a disease of kenneled dogs in poor sanitary conditions. Larvae penetrate the skin and cause an itchy, papular pododermatitis. The footpads become spongy and soft, especially at the margins. The chronic inflammation causes the nails to grow rapidly they may be deformed and break off easily. Diagnosis is based on a history of poor sanitation, clinical signs and positive fecal. Larvae are difficult to find on biopsies.
Idiopathic digital hyperkeratosis is a disorder of older dogs, sometimes seen in conjunction with hyperkeratosis of the planum nasale. Cocker spaniels are predisposed. Hyperkeratotic “feathers” are found at the margins of the pads. In some cases tissue may be so hard that fissures are the result. Diagnosis is based on clinical signs and biopsy.
Bacterial infections of the nails is usually secondary to trauma. Infections are associated with a significant paronychia, toe swelling and pain. Osteomyelitis may develop in some cases. Staphylococcus is usually isolated from these lesions.

Diagnosis In-depth of Canine Pododermatitis

Diagnosis in dogs is based on history, clinical signs and histopathology. A thorough physical and dermatological exam is important to evaluate concurrent systemic or skin disease.

Distribution of the lesions, nature of lesions and concurrent involvement of the pads and nails, are important to rank differential diagnoses and establish a diagnostic plan.
Deep skin scrapings are necessary in all cases of pododermatitis. Fungal cultures of the nails are recommended if nails appear to be deformed or friable.
If pads are involved, biopsies are necessary. Changes observed on histopathology are specific for each disease. Old, ulcerated lesions should be avoided. Biopsy should be done on fresh lesions. Several biopsies should be taken to increase the chances of finding characteristic lesions. It is not uncommon to repeat biopsies several times before obtaining a definitive diagnosis. Bacterial infections should be cleared before taking biopsies in order to limit secondary and non-specific changes on histopathology.
Fungal cultures of nails may be falsely negative. For this reason, it is important to combine histopathology with the culture. Special stains should be used to identify fungal hyphae in the nails.
If a dystrophy of nails is suspected, P3 amputation is necessary to obtain adequate biopsy sample.

Treatment In-depth of Pododermatitis in Dogs

Treatment options include:

Symmetric lupoid onychodystrophy. Therapy includes the use of high doses of essential fatty acids or anti-inflammatory doses of glucocorticoids. Secondary infections need to be addressed at the same time.
Fungal infections of the nails. Therapy includes systemic antifungal drugs and may take several months (average of 6 months). Itraconazole is preferred over griseofulvin and ketoconazole because of its affinity for nails and its residual activity after discontinuation of therapy. Terbinafine (Lamisil®) has also great affinity for nails and long residual activity. No study has been done to determine the appropriate dose in dogs.
Hookworm dermatitis. Treatment includes cleaning of the premises, frequent removal of feces and topical thiabendazole for the feet and routine antihelmintic treatment for all dogs in the kennel.
Idiopathic digital hyperkeratosis. Therapy is based on topical keratolytics (propylene glycole 1/1 with water, tar). Oral retinoids may be beneficial. Therapy should be continued for several weeks before improvement is evident.
Bacterial infections of the nails. Systemic antibiotics for 6 to 8 weeks is usually necessary. The presence of osteomyelitis may warrant P3 amputation.