Pathology Case of the Month - Ross's Goose
Case History: An adult male 1545-g Ross’s Goose (Chen rossii) was found dead on a refuge in Kansas, US. Collectively at this location, over 300 birds including Snow Geese (Chen caerulescens), Canada Geese (Branta canadensis) and Mallard Ducks (Anas platyrhynchos) were found dead with no reported clinical signs.
Gross Findings: There were no significant findings from the external examination. On internal examination, there was moderate subcutaneous, visceral and epicardial fat indicating good body condition. Petechial hemorrhages were present on the epicardium along the coronary groove and the liver was pale red brown and friable with miliary pinpoint tan foci which extended into the parenchyma. (Fig. 1A). Intestines contained abundant creamy stringy yellow mucoid material (Fig. 1B).
Histopathological Findings: Multifocally, hemorrhages often admixed with clusters of bacteria were present in the adipose tissue in the coronary groove of the heart (Fig. 2A). In the liver, there were multifocal random foci of necrosis with bacteria as observed in the heart (Fig. 2B).
Morphologic Diagnosis/es:
- Epicardial hemorrhage, multifocal, moderate, acute with intralesional bacteria
- Hepatic necrosis, multifocal, random, moderate, acute with intralesional bacteria
- Catarrhal enteritis, diffuse, severe, acute
Disease: Avian Cholera
Etiology: Pasteurella multocida, an encapsulated Gram-negative rod or coccobacillus-shaped bacterium. Many serotypes, often serotype 1 in wild waterfowl.
Distribution: Worldwide, but especially North America.
Seasonality: Any time of year, but epizootics in waterfowl often occur in winter or early spring. Summer epizootics in colonial nesting species.
Host range: Primarily waterfowl, but most avian species can be infected as can mammals.
Transmission: Bird-to-bird contact, ingestion or aerosol transmission in a contaminated environment. Predation or scavenging in avian predators.
Clinical signs: Usually found dead with no premonitory signs. With prolonged epizootics, may see lethargic birds with signs suggestive of neurologic involvement.
Pathology:
Peracute. No gross lesions.
Acute. Good body condition. Epicardial and serosal, petechial hemorrhages, hepatic necrosis, catarrhal enteritis, +/- hepatic petechial hemorrhages, splenic necrosis, splenomegaly, pulmonary congestion and edema.
Chronic. (E.g. Crows, gulls, raptors). Fibrinous pericarditis, airsacculitis, focal pneumonia.
Diagnosis: A history of acute death with few clinical signs with consistent gross and histologic findings is suggestive of avian cholera. Definitive diagnosis is based on isolation and identification of the organism and determination of serotype.
Public health concerns: Rare human infections through skin wounds.
Wildlife population impacts: Large, wide-scale epizootics can result in high mortality in susceptible avian species.
Management: 1) Reduce density by dispersing birds; 2) carcass removal to decrease environmental contamination.
References:
-
Samuel MD, Botzler RG, Wobeser GA. 2007. Avian Cholera. In: Infectious diseases of wild birds. Thomas NJ, Hunter DB, Atkinson CT, editors. Blackwell Publishing, Iowa, pp. 239–269.
U.S. Geological Survey. 1999. Field manual of wildlife diseases: general field procedures and diseases of birds, https://pubs.usgs.gov/itr/1999/field_manual_of_wildlife_diseases.pdf. Accessed July 2019.
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