Interdigital pyoderma in dogs is a common condition seen in veterinary practice and can be a frustrating and challenging condition to treat at times. The lesions may at times resolve spontaneously, wax and wane, or they may stay for good and persist indefinitely. Because there are several potential underlying conditions causing this skin issue, it's important to find the underlying cause so to treat it accordingly. A thorough evaluation is therefore a must. Following is information about interdigital pyoderma in dogs presented by veterinarian Dr. Eric Weiner.
Interdigital Pyoderma in Dogs
Let's start by breaking down the words. "Inter" means between, while "digital" refers to toes, so we know it is a problem between the toes. The prefix "pyo" refers to a bacterial infection and "derma" refers to dermis, or skin.
Therefore, we have a bacterial infection of the skin between the dogs’ toes. Furthermore, it is considered a deep pyoderma, as it often involves the hair follicles, known as a folliculitis.
In fact, another term for this disease is Interdigital Follicular Cysts, as they can appear as cysts, or fluid-filled lesions between toes, stemming from the cells lining the hair follicles.
What signs are seen in dogs with interdigital pyoderma? Clinical signs can range from red and raw thickened skin between the toes, to papules and fluid-filled cysts, with or without draining tracts. The feet may be swollen, but they are almost always very painful.
The dog may be limping on the affected foot. Owners often notice excessive licking of the feet and aversion to their feet being handled.
What causes interdigital pyoderma in dogs? Well to be honest we are not completely sure. However, we suspect there are multiple causes that may predispose certain dogs to getting interdigital pyoderma.
Causes of Interdigital Pyoderma in Dogs
One predisposing factor is short fur. Typically dogs with short fur, such as Bulldogs, Great Danes, and Boxers, are more likely to get these lesions. Their hair follicles are more likely to get clogged, causing fluid to accumulate and form cysts.
Another cause is abnormal biomechanical forces or friction. Toes rubbing against each other in abnormal ways are more likely to develop interdigital pyoderma. This can be caused by trauma, overgrown nails, obesity, or foreign material stuck to the paw or fur.
Another major predisposing factor is moisture. Moisture with friction can cause maceration, or softening and breakdown of skin. Anything that may cause the dog to lick at its feet excessively may predispose them to develop this condition.
Food and/or environmental allergies can make dogs more susceptible. Parasites such as fleas, mites, and even hookworms (which can enter the skin from an infected yard) all can be itchy, making dogs chew on their feet. Foreign bodies, such as plant material, bee stingers, glass, etc. can be irritating, leading dogs to pay more attention to their feet.
Sometimes dogs get bored and chew their feet simply because they are in front of them. The more they lick and chew, the more irritated they get. The more irritated their paws are, the more they want to gnaw on them. This is a vicious cycle, and can become an obsessive compulsive disorder.
There are also causes that are not directly associated with the skin or fur at all. Endocrine diseases, such as hypothyroidism, which is an underactive thyroid gland, indirectly weakens the skin and hair follicles, making recurrent skin infections more likely. Lastly, as is the case quite often in medicine, we are not always able to find any cause in some cases.
At the Vet's Office
A veterinarian will gather a history and perform a complete physical exam. Once the problem is localized, a thorough evaluation of the area will be carried out, looking for foreign objects, ectoparasites ( parasites, such as fleas, known for living on the outside of the host) or other reasons that may cause the dog to pay more attention to the toes.
Then a list of tests, or diagnostics, may be ordered to further assess the problem. The more information is gathered, the more targeted the treatment approach can be for the individual. These include skin scrapings to rule in mites, cytology (a sample of cells) to look for inflammatory response or rule out cancer, or a bacterial and/or fungal culture.
Although the infection is typically not the primary problem, secondary infections commonly occur once the body’s normal defenses are down and exacerbate the lesion. A culture and sensitivity will help isolate and identify the exact microorganism and the antibiotics that are most likely to work.
Another valuable piece of information, especially on rechecks or recurrent pyodermas, is the response to previous therapy.
Did the antibiotics and/or anti-inflammatories work? Did it get better and then come back as soon as the medications were discontinued? In some severe cases, biopsies are required to make a diagnosis. Biopsies are a collection of tissue, which will give a more accurate assessment of the lesion than just cells. Unfortunately this procedure is more invasive and almost always requires sedation.
Treatment of Interdigital Pyoderma in Dogs
The most important aspect of treatment is identifying and dealing with the underlying cause. Simply treating the symptoms is likely to result in recurrence. That means treating the allergies, the fleas, removing the foreign material, etc. Then we have the lesion itself to deal with. This can sometimes be achieved with medical therapy alone, but severe cases may require surgery.
Medical management focuses on decreasing inflammation and pain, and treating the secondary infection. Often a multimodal treatment approach is beneficial. Attacking the lesion with both systemic and topical medications may be more effective and successful.
Typically broad-spectrum antibiotics that have good penetration to the skin are chosen. Keep in mind that if cultures are not performed, which in first offense cases may be reasonable, empirical or first line defense antibiotics may not be effective.
Anti-inflammatories may include steroids or non-steroidal anti-inflammatories (NSAIDs) depending on the specific case, concurrent medications the patient is on, and doctor experience/preference. Topical treatments may include soothing antiseptic and anti-inflammatory solutions or ointments.
Surgery is sometimes indicated for the ones that do not respond to medical management. This may include removing the cyst lining where the fluid producing cells are located. Some hospitals may have a CO2 laser available that can be used with some success.
The bottom line is be patient. Because there are many causes that are not always immediately obvious, there is not one treatment approach that will work for every dog every time. Quite often treatments need to be repeated a number of times to gain control of the lesion and improve patient comfort.