Case 4 - 170519-4

Adult male house finch (Haemorhous mexicanus)

The wild bird was found down and apparently unable to fly. Physical examination identified corneal edema, conjunctival swelling, epiphora, and blepharospasm in both eyes, with some crusting around the eyes. No obvious musculoskeletal or neurologic abnormalities were identified.

The patient was euthanized based on the presumptive diagnosis and the concern for infectious disease transmission should rehabilitation and release be attempted.

There was moderate periocular swelling, and a small amount of clear fluid discharge from both eyes. The corneal surfaces were dull and slightly cloudy, and a small amount of brown, crusty material was on the skin surrounding the left eye. There were moderate intracoelomic fat stores. The spleen was 1 x 0.2 x 0.1 mm (subjectively enlarged). Each testis was approximately 7 mm in diameter.

Impression smears of liver, lung, kidney, and spleen demonstrated no evidence of infectious agents.

This slide has a parasagittal section through the head at the level of an eye, in which there are multifocal to coalescing inflammatory cell infiltrates within the bulbar and palpebral conjunctival mucosae. The conjunctival subepithelial stroma is moderately to severely expanded by a mixture of predominantly lymphocytes and plasma cells, with fewer heterophils. The inflammatory infiltrate forms cuffs around small vessels, as well as larger nodular aggregates, and the larger aggregates sometimes extend into the overlying epithelium. A moderate amount of submucosal lymphoid tissue is present, with variably prominent lymphoid follicles. Segments of columnar conjunctival epithelium are tattered and eroded with occasional individual cell necrosis and multifocal intraepithelial edema. There are rare small foci of necrosis in the submucosa, with some associated edema

The corneal stroma is infiltrated by moderate numbers of heterophils, with fewer lymphocytes and plasma cells, and there is a generalized reduction in stromal clefting (edema). Segments of epithelium along the eyelid margin are moderately thickened, and there are occasional, segmental foci of moderate hyperkeratosis. There is a regional aggregate of a superficial crust with embedded presumed plant or other debris as well as multifocal single to small aggregates of brown pigmented, circular, yeast-like structures.

No stains.

Conjunctiva: Moderate to severe, chronic, multifocal to coalescing, lymphoplasmacytic and heterophilic conjunctivitis Cornea: Moderate to severe, chronic, heterophilic and lymphoplasmacytic keratitis Eyelids: Moderate to severe, chronic, lymphoplasmacytic and heterophilic blepharitis with multifocal epithelial hyperplasia, hyperkeratosis, and serocellular crusts

Although a specific etiology for these lesions was not confirmed at the time of the conference, the lesions in this patient are typical of those seen in cases of Mycoplasma gallisepticum infection in finches.

An epornitic of Mycoplasma gallisepticum mycoplasmosis in finches began in the United States in 1994, with infections extending from the mid-Atlantic through much of the eastern United States within a matter of years. At present, the epiornitic has extended to the west coast, where it has been associated with significant declines in house finch populations. The conjunctivitis, blepharitis, and keratitis in these cases can be severe and debilitating. The same agent causes respiratory disease in commercial poultry species, and there is concern for transmission of mycoplasmosis from wild to farmed birds. Mycoplasmosis in this species is generally associated with lymphoplasmacytic inflammation, but the keratitis in this case is primarily heterophilic. This could be reflective of the stage of inflammation, or could be secondary to periocular disease, acanthosis, hyperkeratosis, and crusting, rather than directly attributable to mycoplasmosis. Conference participants discussed the testing options for confirmation of Mycoplasma gallisepticum infection. By immunohistochemistry, the distribution of organisms is generally characteristic in epithelial cells. PCR is also available for diagnosis, although there are some questions as to specificity. One conference participant suggested cryptosporidiosis as a possible differential diagnosis for the gross lesion in these cases. Another participant mentioned Mycoplasma sturni as another Mycoplasma species associated with similar lesions in passerines. However, an isolate from a house finch with conjunctivitis did not cause lesions in experimentally inoculated house finches. This case was contributed by Dr. Jim Maclachlan of the UC Davis, School of Veterinary Medicine.

Dhondt AA, Altizer S, Cooch EG, et al. 2005. Dynamics of a novel pathogen in an avian host: Mycoplasmal conjunctivitis in house finches. Acta Trop. 94(1):77-93.

Kollias GV, Sydenstricker KV, Kollias HW, et al. 2004. Experimental infection of house finches with Mycoplasma gallisepticum. J Wildl Dis. 40(1):79-86. Ley DH, Anderson N, Dhondt KV, Dhondt AA. 2010. Mycoplasma sturni from a California house finch with conjunctivitis did not cause disease in experimentally infected house finches. Journal of wildlife diseases. 46(3):994-9. Luttrell MP, Stallknecht DE, Kleven SH, et al. 2001. Mycoplasma gallisepticum in house finches (Carpodacus mexicanus) and other wild birds associated with poultry production facilities. Avian Dis. 45(2):321-9. Luttrell MP, Stallknecht DE, Fischer JR, Sewell CT, Kleven SH. 1998. Natural Mycoplasma gallisepticum infection in a captive flock of house finches. J Wildl Dis. 34(2):289-96.