Avian gastrointestinal anatomy and diseases (Proceedings)
Gastrointestinal diseases and disorders are common in avian patients.This presentation will give an overview of anatomy and clinical presentations of gastrointestinal (GI) disease in birds.
The avian gastrointestinal tract (GIT) consists of the oral cavity, esophagus, ingluvies (crop), proventriculus, ventriculus, small and large intestine, and cloaca.Diagnostic Techniques
Numerous diagnostic techniques are available for the diagnosis of GIT disease. The order of testing is based on signalment, physical exam findings and clinical signs. Consideration of species predilection for certain diseases can be helpful when developing a diagnostic plan. The history should include exposure to infectious diseases, diet, environment/housing, reproductive history, administration of medication and management practices. Critically ill birds should be stabilized prior to performing stressful diagnostic tests. Staging of diagnostic tests is often necessary for the patient. Anesthesia may be required for diagnostic testing such as radiography. Diagnostic tests useful for the evaluation of gastrointestinal disorders include a gram's stain of a crop swab or feces, parasite analysis, hematology, biochemistries, electrolytes, cytology, protein electrophoresis, microbiology, Chlamydophila testing, lead and zinc blood levels, viral testing, acid fast stain, radiography, endoscopy, biopsy, or necropsy.
The oropharynx is common site for variety of lesions. A thorough examination may not be entirely possible in the awake patient. A quick visual examination can be performed in most birds. Clinical signs of oropharyngeal disease include halitosis, anorexia, inappetence, dysphagia, rubbing of the beak or face, gaping, oral lesions such as plaques or granulomas. Differentials for oral plaques include bacterial infection, yeast/fungal infection, hypovitaminosis A, parasitic (trichomoniasis), or viral (pox). Cytology and/or culture of the lesion will help to determine the etiology. Cytological samples may be collected by rubbing a sterile cotton-tipped applicator along the lesion. This sample can then be placed on a clean glass slide. Samples for culture can be placed into proper culture media tubes for processing. Fresh preparations are good for looking for parasites (wet mount).
Bacterial Infections of Oropharynx
Pathogenic bacteria can cause granulomas or generalized stomatitis. Examples of bacterial organisms involved in infection include Staphylococcus sp., Klebsiella sp., gram-negative bacteria. Bacterial overgrowth may be caused by underlying immunosuppressive diseases or may be secondary to damage to the oral mucosa by irritants, rough food items, or accumulation of food caused by beak deformities. Treatment may include topical or systemic antibiotic therapy based on culture and sensitivity results. Topical treatment may be performed by placing an antiseptic solution such as chlorhexidine (1 ml in 30 ml of water) in the water supply or by gently flushing the oral cavity.
Granulomas can also be caused by Mycobacteria sp. Mycobacterium avium is the most commonly isolated species from oral lesions in birds. M. genovense and M. tuberculosis have also been identified. Mycobacteriosis more commonly affects the lower GIT.
Candida infection causes white plaques within the oral cavity. Candida albicans is most frequently cultured. Infection may be primary or secondary to other systemic or oropharyngeal disease or long term antibiotic usage. This disease is called "thrush" by falconers. Cytology of the lesion reveals darkly staining budding yeast cells. Treatment may be topical with chlorhexidine or nystatin (300,000 IU/kg PO BID) for mild infections (non-systemic). In order for topical treatment to be effective the medication much come into contact with the lesion. Severe or systemic infections may require systemic antifungal such as ketoconazole, itraconazole or fluconazole.
Vitamin A deficiency can result in squamous metaplasia of the epithelial lining of the oral cavity. Formation of plaques or granulomas can also occur. The choana may be wider than normal or papillae may be blunted. Cytology of lesions will often show only scant normal Gram positive bacteria. Granulomas can become secondarily infected. Biopsy of the lesion aids in diagnosis. Dietary history of diet deficient in Vitamin A can provide presumptive diagnosis.
Treatment involves dietary correction. Parenteral Vitamin A can be given for one or two doses which diet is being corrected. The choana and choanal papillae may remain abnormal even after treatment.