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Infectious diseases of birds of prey (Proceedings)

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Apr 01, 2008

This paper will provide an overview of selected infectious diseases that avian practitioners are likely to see in a clinical avian practice.

Pododermatitis—Pododermatitis (bumblefoot) is an inflammatory condition of the feet that most commonly involves the plantar surfaces. It is characterized by local abrasion to the foot pad, ulceration and swelling and erythema of one or more of the digital or metatarsal pads.1-3 Predisposing factors include trauma (self-inflicted talon puncture, bite wounds or fighting), inappropriate perch size or substrate, obesity, sedentary lifestyle, poor environmental hygiene and nutritional deficiencies.1,4 These factors then culminate in a destructive infectious/inflammatory disease process which may involve the skin, underlying soft tissues, and even bone. Staphylococcus aureus is commonly isolated from pododermatitis lesion; however, Escherichia coli, Klebsiella and Proteus sp have also been identified in foot lesions. 1,3,5 Swelling, inflammation and pain are the hallmark of pododermatitis. Clinically the raptor will favor one leg over the other or lay down in sternal recumbency if the pain associated with infectious severe. Pododermatitis is often classified as follows:. Type I—Serious, chronic infection with diffuse cellulitis of the metatarsal pads of one or more digits.1 Type 2—Similar to Type 1; appears as a localized lesions of the digital or metatarsal pads.1,2 Type 3—Demonstrates discrete lesion(s) with hyperkeratinization, localized swelling, and reddening, while Type 4—Marked enlargement of the distal digital pads as a sequelae to flexor tendon rupture. Effective treatment requires: reduction of swelling and inflammation, debridement of necrotic tissue, draining and removing abscesses if present, identifying and eliminating the underlying cause (pathogens and husbandry related etiologies), protecting the wound from further infection or trauma and promoting the development of healthy granulation tissue and further healing with bandaging and dressings.1,2 Antibiotic therapy is based upon bacterial culture and sensitivity. Remple (2006) suggest a four-pronged therapeutic regime consisting of (1) systemic antibiotic therapy, (2) direct intralesional antibiotic delivery, (3) surgical debridement, and (4) post-operative protective foot-casting has offered the most effective therapy for the treatment of bumblefoot (Remple).6

Viral Diseases

Poxvirus—Poxviruses are large DNA viruses that cause diseases in many different species of birds of prey.7,8 The hallmark of avian poxviruses are the large intracytoplasmic, lipophilic inclusion bodies (Bollinger bodies) that are found in epithelial cells of the integument, respiratory tract and oral cavity, resulting in hypoplasia of the affected cells.

Poxvirus infections cause several different clinical forms: (1) a cutaneous form which creates mild to severe proliferative lesions on unfeathered skin around the eyes, beak, nares, and legs, (2) a diphtheritic form which produces lesions on the mucosa, tongue, laryngeal mound as well as other areas of the oropharynx larynx, and (3) a septicemic form characterized by a lethargy, depression, cyanosis, anorexia, and wart-like lesions of the skin.7,8 Raptors most commonly demonstrate the cutaneous form of the disease. Transmission of avian pox requires viral contamination of broken skin.7 Since the virus is rather large transmission from bird to bird requires a vector (mosquitoes and other blood sucking arthropods) to get through the skin. Diagnosis of an infection with poxvirus is confirmed by signalment, history, clinical signs, histopathologic examination and demonstration of Bollinger bodies in affected tissues and electron microscopy.5,8 Culture may be necessary to confirm a diagnosis in septicemic infections.8 Therapy is non-specific and may involve antibiotic therapy to prevent or treat secondary bacterial infections.5,7,8 High frequency radio waves from radiosurgical units on low settings may speed healing of skin lesions. Vaccination is the best method of controlling poxvirus infections in gallinaceous birds; however, further evaluation of autogenous and heterologous vaccine efficacy in raptors is needed.7,8 Natural infections are thought to provide lengthy immunity. Infected birds should be isolated from uninfected birds if possible.