Bumblefoot

Ulcerative Pododermatitis is commonly known as bumblefoot. This type of foot infection usually starts on the bottom (plantar) surface of the foot or digits and may affect any of the avian species. Bumblefoot is not commonly seen in the wild avian species, but most often a result of poor husbandry, improper surfaces on which the bird stands or inadequate perching material in captive avian species. Bacteria such as Staphylococcus sp., Escherichia coli (E. coli) and Pseudomonas sp. are most commonly found in bumblefoot lesions causing infection and inflammation. Bumblefoot may be classified into five stages, depending on the severity of the lesion. In the early stages or stage 1 there may be mild changes to the superficial layers of the skin with an area of redness on the plantar surface. Swelling may or may not be present. Stage two reveals deeper damage to the skin with swelling and evidence of infection. As the infection progresses, the foot becomes red, swollen and warm to the touch. Open sores may be present. This represents stage 3 and will painful to the raptor. Stage four involves the deeper structures of the foot, which may include the tendons, joint or bone. Stage fiveis the most severe form of bumblefoot with infection of the bone (osteomyleitis), the presence of granulation tissue, distortion of the foot and digits and possible loss of foot function. Permanent damage is always possible at this stage.

Causes

Not commonly seen in the wild avian population, bumblefoot occurs for a variety of reasons. Traumatic injuries to the foot or penetrating wounds may lead to a secondary infection. Certainly in the case of raptors, improperly maintained talons can cause self-inflicted wounds or bites from a prey species. Diets not balanced in proper protein, vitamin and mineral content will predispose a bird to nutritional deficiencies and affect skin health. This is especially true with hypovitaminosis A. Perching surfaces must be customized for the species of bird in captivity. The following are examples: Confining a heavily bodied raptor (falcon, some hawks, eagles etc.) to a flat surface will distribute all its weight onto the center of the foot. This constant pressure will predispose the raptor to pressure necrosis and bumblefoot lesions. Lightweight and small-bodied raptors (kites, merlins, kestrels etc) forced to perch on rough substrates will predispose them to bumblefoot. Raptors living in cold and dry climates may suffer from dry feet and cracks during the winter months causing concern for bumblefoot. Birds in captivity do best if a variety of perching surfaces are provided.

Advanced cases of bumblefoot require a complete medical evaluation. A secondary effect of bumblefoot is the development of vegetative endocarditis or amyloidosis in response to chronic infection. Cardiac lesions associated with prolonged bumblefoot may involve a focal necrotizing myocarditis or valvular (aortic and mitral) endocarditis. Serum amyloid is an insoluble acute phase protein produced in response to inflammation. This protein will be deposited abnormally in tissues especially the liver, kidney and heart. This is often a progressive fatal disease. A complete medical evaluation would include blood profiles, cultures of the affected feet, radiographs and even an echocardiogram if heart murmur or gallop rhythm is present. Aggressive supportive care and combination drug therapy is often necessary to stabilize the patient while a long-term therapy plan or surgery is considered.

The treatment of bumblefoot depends on many factors such as the stage of bumblefoot, bacterial and secondary fungal infections present and the chronicity of the infection. Treatment must be aggressive and complete for any stage of bumblefoot. Stage one with superficial lesions can be treated with antiseptics, creams, protective wraps to the foot and a change of the perching surface. More advanced stages may require surgical intervention. Often, the avian patient will require systemic antibiotics, surgical debridement of the affected area with administration of antibiotics into the lesion, and postoperative protective foot wraps/casting to keep the surgery site protected and limit the pressure placed on the surgery site.
Some patients may require more than one surgery to heal the foot. Intraoperative cultures are taken to identify what bacteria are present and to determine the correct antibiotic to use. Radiographs, to rule out osteomyelitis, are recommended for any bird with bumblefoot issues. The treatment for bumblefoot can be very long, taking several months to heal severe cases. Stage five carries a very guarded prognosis for complete recovery.

Providing the correct perch sizes, shapes and substrate to perch on is the key to prevention. During the falconry season, when raptors are confined to a block or bow perch, the covering needs to be appropriate for the size of the raptor. The smaller lightweight species may do better on the Astroturf resembling long leaf grass versus the stiff or course Astroturf suited for the heavily bodied raptors. Bow perches wrapped with rope are popular, but can be abrasive if the size and shape of the perch is inappropriate. Perch surfaces should be changed on a yearly basis. Captive raptors housed in a mew or chamber and considered “free lofted” should have a variety of perching surfaces. The feet should be inspected on a regular basis. The use of a stiff toothbrush to clean the plantar surface of the foot followed with the application of a lanolin based dressing such as Corona Hoof Dressing to prevent drying especially during the winter months is also recommended.