Aberrant Hepatic Ascarid Migration in a Blue-fronted Amazon Parrot (Amazona aestiva)
Charles W. Brockus, Kenneth S. Latimer, Elizabeth W. Howerth, and G. Heather Wilson
Department of Pathology (Brockus, Latimer, Howerth) and Department of Small Animal Medicine (Wilson), College of Veterinary Medicine, The University of Georgia, Athens, Georgia 30602-7388 (USA)
Abstract. A 2-year-old, male, Blue-fronted Amazon parrot was presented to the veterinary medical teaching hospital for emaciation and abdominal enlargement. The bird was from an aviary with a history of severe ascarid infestation. Severe thoracoabdominal ascites and emaciation were noted on physical examination. The parrot died during hospitalization. Gross necropsy findings included an enlarged, tan colored liver with some mottling; diffuse intestinal hemorrhage, and severe nematodiasis. Numerous nematodes were observed in the proventriculus, duodenum, and common bile duct. Other gross lesions included cloudy air sacs, pulmonary hemorrhage, and a mottled pancreas. Histologically, adult nematodes, larvae, and ova were observed in the bile ducts and hepatic parenchyma. Associated necrotizing to pyogranulomatous hepatitis, bile duct hyperplasia, and hepatic fibrosis also were present.
Key Words: Avian, Aberrant ascarid migration, Amazona aestiva, Ascaridiasis, Bile duct hyperplasia, Blue-fronted Amazon parrot, Hepatobiliary ascarid migration, Hepatitis, Hepatic fibrosis
Case Report
A 2-year old Blue-fronted Amazon Parrot (Amazona aestiva) was presented to the veterinary medical teaching hospital because of progressive emaciation and abdominal enlargement. This bird was from a large aviary with a previous history of severe ascarid infestation in various species of psittacine birds. Physical examination disclosed ascites and confirmed emaciation. Approximately 30 ml of fluid was aspirated from the thoracoabdominal cavity. Despite supportive treatment, the parrot died during hospitalization and was necropsied.
Necropsy and Histologic Observations
Necropsy revealed additional fluid within the thoracoabdominal cavity. The air sacs were cloudy and the lungs were bright red. The liver was enlarged, tan, and had a mottled appearance. The pancreas also appeared mottled. Diffuse intestinal hemorrhage was present. When the alimentary tract was opened, numerous ascarids were observed in the proventriculus, duodenum, and common bile duct. Representative tissue sections were obtained, preserved in 10% neutral buffered formalin, and submitted for histologic examination.
Microscopically, major histologic lesions were present within the liver. Normal hepatic architecture was replaced by extensive fibrosis, bile duct hyperplasia, and inflammatory cell infiltrates (Fig. 1). Isolated clusters or individual hepatocytes were present within foci of fibrosis. Some hepatocytes were necrotic, while other hepatocytes exhibited anisocytosis and karyomegaly, suggesting hepatocellular regeneration. Intense bile duct hyperplasia also was observed. Individual biliary epithelial cells often contained a single, clear, cytoplasmic vacuole. Variably-sized foci of coagulative to caseous necrosis were present, involving both bile ducts and hepatic parenchyma. Foci of necrosis were surrounded peripherally by infiltrates of epitheloid macrophages, many multinucleated giant cells, and scattered heterophils. Occasional ascarid ova also were present. These ova had a thick smooth cell wall and a granular internal structure (Fig. 2).
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| Fig. 1. Parrot, liver, H&E stain. Bile duct hyperplasia, fibrosis, and inflammatory cell infiltrates are present. |
Fig. 2. Parrot, liver, H&E stain. Ascarid ovum has a thick, smooth cell wall and is surrounded by detritus. |
Ascarid larvae within the hepatic parenchyma were surrounded by epitheloid macrophages and fibroplasia (Fig. 3). Adult ascarids were present but rare. These adults were identified by the prominent muscle cells in the bulb of the esophagus
(Fig. 4).
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| Fig. 3. Parrot, liver, H&E stain. Ascarid larvae are present in the hepatic parenchyma surrounded by macrophages, giant cells, detritus, and fibroplasia. |
Fig. 4. Parasite, parrot liver, Modified acid-fast stain. Striations (center) identify the muscular layer of the bulb of the esophagus. |
Neither bacteria nor fungal organisms were identified with Giemsa, Lillie Twort, modified acid-fast, or PAS staining. Intestinal hemorrhage and pulmonary congestion also were observed. The remaining tissues were devoid of remarkable microscopic lesions.
Discussion
Gastrointestinal nematodes of psittaciform birds include Ascaridia sp. , Ascarops sp. , and Capillaria sp. These nematodes typically reside in the intestinal tract; however, aberrant migration may occur. Visceral or aberrant hepatic migration by larval ascarids has been reported in two parrots with severe intestinal ascariasis. 1 Hepatic trematodiasis has been reported in cockatoos and in other avian species in association with hepatic fibrosis, bile duct hyperplasia, cholestasis, and cystic dilatation of bile ducts. 2,3 The Amazon parrot described in this report also had hepatic fibrosis and bile duct hyperplasia. Some of foci of necrotizing to granulomatous inflammation involved bile ducts, suggesting ascending migration of nematodes. In summary, this case report illustrates an unusual presentation intestinal ascaridiasis with aberrant migration of ascarids into the hepatic parenchyma via the biliary tract. Speciation of the ascarids has not been completed.
References
1. Reece RL, Scott PC, Barr DA: Some unusual diseases in the birds of Victoria, Australia. Vet Rec 130:178-185, 1992.
2. Greiner EC, Ritchie BW: Parasites. In: Ritchie BW, Harrison GJ, Harrison LR (eds): Avian Medicine: Principles and Application. Wingers Publishing Inc. , Lake Worth, FL, 1994, p. 1021.
3. Minsky L, Petrak ML: Diseases of the digestive system. In: Petrak ML (ed): Diseases of Cage and Aviary Birds, 2nd ed. Philadelphia, Lea & Febinger, 1982, pp. 432-443. This Page Last Updated May 15, 1998 |