What is your diagnosis?
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The bird was hospitalized, and supportive care was initiated, which consisted of warmed lactated Ringer's solution (60 mL SC) and buprenorphine (0.46 mg/kg SC). The egret was placed in an oxygen cage, where later that day it was found dead.
Differential diagnoses for the emaciation and weakness observed in this bird included fungal or bacterial infection and internal parasites. Disease considerations for the swollen and firm caudal coelomic cavity included overfeeding; visceral larval migrans, such as Eustrongyloides species (3,4); steatitis (5,6); foreign body ingestion; or neoplastic mass (eg, nephroblastoma). (7) From the list of differentials, steatitis was ruled out because no subcutaneous or coelomic fat was observed on physical examination. Traditional foreign body ingestion (eg, fishing tackle) was also ruled out because no metal density was observed in the radiographic images.
The radiographs (Figs 1 and 2) revealed no fractures but demonstrated a severely distended thoracic esophagus, proventriculus, and ventriculus. Moreover, apparent fish bones were observed in the esophagus, proventriculus, and ventriculus. When considering information provided by the history, the physical examination, and diagnostic test results, refeeding syndrome was suspected as the immediate cause of death. However, fungal, bacterial, or parasitic infection could not be ruled out. Unfortunately, the bird died before further diagnostic tests could be done. The body was submitted for necropsy.
Gross necropsy revealed a small, rounded liver, a distended gall bladder, and a distended thoracic esophagus, proventriculus, and ventriculus (Fig 3). When opened, the rostral portion of the thoracic esophagus contained 15 small, undigested bait fish. Two large Norway spruce (Picea abies) cones (141 mm x 30 mm and 145 mm x 23 mm) were found within the proventriculus and ventriculus, which caused severe distension (Fig 4). The cones completely obstructed the gastrointestinal tract, and no digested food material was found in the intestine. The cause of death was determined to be starvation caused by foreign body obstruction of the gastrointestinal tract. The spruce cones weighed a combined 168 g when wet and 50 g when air-dried.
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Great egrets usually nest in colonies that are located in areas where woody vegetation, shrubs, and trees grow. Typically, these nesting colonies contain mixed avian species, including other nesting herons and egrets. Great egrets may also nest over water or on islands. Although they primarily feed on fish, great egrets are opportunistic feeders and consume a variety of vertebrates and invertebrates, including amphibians, reptiles, small birds and mammals, crustaceans, and mollusks obtained from aquatic and upland habitats. (8)
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Based on the clinical and postmortem findings of this case, we speculate that the young egret misidentified floating spruce cones as easy prey near the surface of the water. As shown in Figure 5, a fresh, green spruce cone is fairly fusiform and fish-like in appearance. These cones also have a fish-like scale pattern and an iridescent green-purple coloration that would glint in sunlight, especially if wet.
Cases of foreign body obstructions or gizzard impactions are mainly reported in pet birds and poultry. (9) These obstructions are usually caused by 1 of 2 conditions: a mineral deficiency, which leads to high consumption of minerals and subsequent impaction, or foreign body ingestion, which in both instances leads to gastrointestinal tract obstruction.
As demonstrated in this case, a gastrointestinal tract obstruction is an emergency. An obstructed bird typically presents with a history of increased thirst, vomiting or regurgitation, anorexia, leaning forward while standing or perching, and droppings without the fecal component (ranging from clear and watery to white). Clinical signs associated with obstruction in birds are observed as early as 1 to 2 days after obstruction. The initial treatment for a minor gastrointestinal tract impaction includes gavaging mineral oil by a lubricated feeding tube as far distal into the esophagus as possible. (10,11) Other treatment recommendations for birds that present with minor gastrointestinal tract impaction are metoclopramide and additional fluids. (l1) However, the procedure of clearing the obstructed ventriculus with an injection of a lubricant may be stressful to critically ill birds and birds with a longstanding obstruction or large obstruction. Gavaged material possibly might be regurgitated and aspirated. Large foreign bodies, such as the spruce cones in this egret, require a more invasive approach (eg, gastroscopic removal or surgery) to resolve the problem. With such invasive approaches, the risk of death while the patient is under general anesthesia increases, especially in chronically affected patients. Critically emaciated patients also require immediate nutritional support. A high-energy feeding formula should be administered to address energy deficiencies caused by anorexia.
This case was submitted by: Jessica Martinez, BS (third-year veterinary student) and Mark A. Pokras, DVM, Wildlife Clinic, Tufts University, Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA 01536, USA.
Please evaluate the history, physical examination, radiographs, and blood test results before continuing. A t this time, based on your evaluation of the above information, please develop a differential diagnosis list as to the disease conditions that may have contributed to this bird's death.
(1.) Dunning JB. CRC Handbook of Avian Body Masses. Boca Raton, FL: CRC Press; 2007:672.
(2.) Sepulveda MS, Williams GE Jr, Frederick PC, Spalding MG. Effects of mercury on health and first-year survival of free-ranging great egrets (Ardea albus) from southern Florida. Arch Environ Contam Toxicol. 1999;37:369-376.
(3.) Roffe TJ. Eustrongylides sp. epizootic in young common egrets (Casmerodius albus). Avian Dis. 1988;32:143-147.
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(5.) Driscoll CP, Miller EA, McGowan PM. A case study: steatitis in great blue herons in Maryland. 76th Northeastern Conf Avian Dis, State College, PA. 2004:29.
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(7.) Schmidt RE. Types of renal disease in avian species. Vet Clin North Am Exotic Anim Pract. 2006;9:97-106.
(8.) McCrimmon DA Jr, Ogden JC, Bancroft GT. Great egret. In: Poole A, Gill F, eds. The Birds of North America. Philadelphia, PA: Cornell Laboratory of Ornithology and The Academy of Natural Sciences; 2001;570:1-31.
(9.) Mullin PM. Impaction and foreign bodies of gizzard. In: A Pocket Guide to Poultry Health and Disease. Available at: http://www.ThePoultrysite. com. Accessed January 26, 2010.
(10.) Heidenreich M. Birds of Prey, Medicine and Management. Malden, MA: Blackwell Science; 1997:191-192.
(11.) Lloyd C. Raptors: gastrointestinal tract diseases. In: Chitty J, Lierz M, eds. BSAVA Manual of Raptors, Pigeons and Passerine Birds. Quedgeley, Gloucester, UK: British Small Animal Veterinary Association; 2008:268.
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|Title Annotation:||obstructed bird|
|Author:||Martinez, Jessica; Pokras, Mark A.|
|Publication:||Journal of Avian Medicine and Surgery|
|Article Type:||Case study|
|Date:||Dec 1, 2010|
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