Signalment:  

Juvenile mourning dove (Zenaida macroura), ColumboformeFound dead on Zoo grounds

Gross Description:  

A white, caseous, 5mm diameter mass is apparent within the oral cavity extending into the pharynx. Ventral to the mandible there are two bilateral, 5mm diameter caseous nodules on either side of the trachea. Within the esophagus on the mucosal surface there are multifocal, 3mm diameter plaques of white caseous material. 

Histopathologic Description:

ESOPHAGUS: In a focally extensive area, the esophageal epithelium is ulcerated and there is a transmural infiltration of inflammatory cells. Replacing the epithelium is a band of macrophages interspersed with 5 7 um diameter, ovoid to round protozoa, and a mat of bacteria at the luminal surface. Subjacent to this layer are many heterophils with few macrophages, necrotic debris and scattered protozoa. This inflammatory combination extends through the tunica muscularis to the serosa, which is expanded by heterophils and moderate amounts of mucinous material. The adjacent epithelium is moderately acanthotic with prominent intracellular edema. The serosa below the adjacent epithelium is expanded by a proliferation of capillaries with plump endothelial cells and diffusely the serosa is expanded by heterophils and mucinous material. Small clusters of macrophages, lymphocytes, and few plasma cells are present in the mucosal connective tissue of the remaining, intact esophageal mucosa.
Trachea: Essentially normal tissue for a juvenile bird with unmineralized tracheal rings.

Morphologic Diagnosis:  

Esophagus: esophagitis, histiocytic, heterophilic and necrotizing, acute, focally extensive and transmural, severe, with protozoa, mourning dove (Zenaitha macroura), columbiform, avian

Condition:  

Trichomonas gallinae

Contributor Comment:  

Trichomonas gallinae is carried subclinically by rock doves (Columba livia)⁵ but may become pathogenic in immunocompromised individuals and mourning doves. The characteristic canker, or caseous plaque of the dove oral cavity, esophagus, and crop, may also be seen in birds that prey upon or scavenge dead columbiformes, such as raptors and crows². Falconers that keep these birds call the condition frounce. Additionally, the protozoan may be passed to a chick from the parental crop milk⁵.

At necropsy, the flagellates may be seen on a wet mount from carcasses that are up to 24 hours old⁶. A cytologic flagellum stain or silver stains on histologic preps may also elucidate the organism.

JPC Diagnosis:  

Esophagus: Esophagitis, necrotizing, histiocytic and heterophilic, subacute, transmural, multifocal, severe with protozoa, mourning dove (Zenaitha macroura), avian.

Conference Comment:  

Trichomonas gallinae is a flagellated protozoan that contains four free anterior flagellae and one attached flagellum that trails along an undulating membrane, but does not extend beyond it.^3,8 In Columbiformes, transmission occurs directly through crop milk from infected adults to nestlings, through drinking water and food, as well as between adult birds during courtship behavior.^1,5 Transmission to raptors primarily occurs through ingestion of infected pigeons and doves.² Trichomonas gallinae has also been reported in Passeriformes (particularly canaries and zebra finches) and Psittaciformes (particularly budgerigars and cockatiels).⁴

Ultrastructural features of Trichomonads include piriform to spherical shapes, four anterior flagella of unequal size, well-developed undulating membrane, an axostyle, and a pelta surrounding the periflagellar canal.⁸ The anterior flagellae emerge from the periflagellar canal which is reinforced by the pelta.⁸

Gross differentials for Trichomonas gallinae within the esophagus and crop include avian poxvirus, oral capillariasis, and candidiasis. Fibrinonecrotic lesions of wetpox, caused by avian poxvirus, are characterized by small white nodules to coalescing raised plaques with a diphtheritic membrane within the mouth, esophagus, trachea, pharynx, and larynx. Oral capillariasis produces almost identical gross lesions to that of T. gallinae and requires further testing to differentiate.² Candida albicans causes gray-white pseudomembranous patches in the mouth, pharynx, esophagus, and, most frequently, the crop.⁷

References:

1. Bunbury N, Jones CG, Greenwood AG, Bell DJ: Trichomonas gallinae in Mauritian columbids: implications for an endangered endemic. J Wildl Dis 43:399-407, 2007
2. Heidenreich, M: Birds of Prey, Medicine and Management, pp. 131-132. Blackwell, Wissenschafts-Verlag GmbH, Berlin, 1995
3. Kocan RM, Herman CM: Trichomoniasis. In: Infectious and Parasitic Diseases of Wild Birds, eds. Davis JW, Anderson RC, Karstad L, Trainer DO, pp. 282-287. Iowa State University Press, Ames, IA, 1971
4. Lumeij JT: Gastroenterology, the esophagus and crop. In: Avian Medicine: Principles and Applications, eds. Ritchie BW, Harrison GJ, Harrison LR, pp. 491-497. Wingers Publishing Inc., Lake Worth, FL, 1994
5. Ostrand, WD, JA Bissonette, MR Conover: Trichomoniasis as a factor in mourning dove population decline in Fillmore, Utah. J Wildl Dis 31:87-89, 1995
6. Schulz, JH, AJ Bermudez, JJ Millspaugh: Monitoring presence and annual variation of trichomoniasis in mourning doves. Av Dis 49:387-389, 2005
7. Saif YM: Diseases of Poultry, 11th ed., pp. 896-898, 1006-1008, 1029-1030. Iowa State Press, Ames, Iowa, 2003
8. Tasca T, de Carli GA: Scanning electron microscopy study of Trichomonas gallinae. Vet Parasitol 118:37-42, 2003

A virtual slide is not available for this case.

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Fig. 2-1

Fig. 2-2

Fig. 2-3 Oropharnygeal region

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