Bumblefoot remains one of the commonest and most serious diseases of captive birds of prey.

Bumblefoot is an infected lesion affecting the ball of the foot, or one or more of the toes. Bumblefoot is a common disease of large species of raptors (especially longwings) maintained in captivity and tends to become chronic, progressive, invasive and eventually disabling. It is often either unresponsive or recurrent when treated with traditional methods. If the condition does occur in hawks or broadwings, it is usually responsive to simple therapy, whilst in longwings recovery rates are typically much worse. The condition is common in captive bird (wild caught or captive reared) but rare in wild birds.

The Cause

Raptor's feet are protected by a thick layer of dry hard skin. On the bottom surface is a covering of hard projections (tarsal pads), which help to spread the weight bearing function of the foot.

Bumblefoot arises for one of two reasons. Firstly following any penetration of the foot, caused by a talon, thorn, sharp

foreign body, rusty chain link fencing or any other sharp or abrasive object which may simultaneously introduce infection either into the skin or deeper structures of the foot. Secondly, (and far more commonly), captive birds, whether kept tethered on blocks or free in aviaries, may suffer from a pressure sore on the bottoms of their feet. This occurs because either they have been forced to use unsuitable perches, or simply because of periods of inactivity, during which time they are taking excessive weight on their feet. If weight is consistently taken by certain parts of the foot, the blood supply to these areas is compromised, leading to a reduction in the local skin defense system, such that bacteria which are living naturally on the skin, may penetrate these defences and enter the foot. Once the tissues are affected, they tend to swell, making this area of the foot even more prominent, and hence more likely to bear weight when the bird is standing, hence the blood supply to that area is further compromised. As bacteria enter the tissue of the foot, any attempt by the foot to effect a cure, is minimised by the lack of blood. In time bacteria pass deeper into the tissues of the foot causing infection of and damage to deeper structures resulting in severe and crippling bumblefoot.

Within 35 days of initial trauma, it has been shown that a scar tissue

barrier builds up around any area of infection or inflammation, thereby protecting the bacteria from the beneficial effects of the bodies defense mechanism (or antibiotics administered by a vet), which would normally be carried there by the blood supply. This mechanism explains the frequent failure to self heal, or respond following surgery and the reoccurrence rate of many cases.

Clinical Signs

If bumblefoot is to be successfully treated it is imperative that the condition is recognised at an early stage. Cases may be classified according to their stage of development.

Stage I (see figure I) is characterized by superficial changes only and carries a favourable prognosis, as there is no evidence of infection.

The changes generally respond to conservative husbandry changes, including changing perching surfaces and application of topical emollients eg. Preparation H (Whitehall Labs). Each further stage is characterised by more severe changes in the foot, in particular to the deeper structures. Stage II shows localised infection, which does not affect the deeper structures, whilst Stage III has more generalised infection, affecting deeper structures. Fig II shows a typical Stage III case, which inevitably will require

surgery, following bacterial sensitivity testing and antibiotics. If surgery has to be performed this should be done at an early stage, whilst the infective material can still be excised cleanly and before the infection has entered the tendons or bones.

In Stage IV, the deeper structures of the foot are affected, and the outlook has traditionally been serious, whilst in Stage V the bone is infected and previously such cases have been considered to be hopeless, with euthanasia being advised.

At the recent 3rd International Raptor Biomedicine Conference held in South Africa, David Remple from Dubai and Neil Forbes from England, presented their findings following a research project using a new technique in the treatment of persistent infections, which have so often previously been the problem with bumblefoot therapy. Remple and Forbes (1998) described the use of antibiotic impregnated bone cement beads in the treatment of bumblefoot. By this method increased local concentrations of antibiotic can be achieved than with injections or tablets administration without relying on blood supply, which is often impaired in such cases. Furthermore drugs which could not normally be used by injection or tablet, (in view of their potential toxic effects) may be safely administered in this local form.