Field investigation of Mycoplasma gallisepticum infections in house finches (Carpodacus mexicanus) from Maryland and Georgia

Abstract

A field study investigating the occurrence of Mycoplasma gallisepticum (MG) in house finches (Carpodacus mexicanus) was conducted in Maryland and Georgia. Eighty-eight finches were captured and examined grossly and microscopically for MG-related conjunctivitis. Serum samples were obtained for serum plate agglutination (SPA) and hemagglutination inhibition (HI) testing. Swabs from conjunctiva, sinus, and choanal cleft were inoculated into two mycoplasma broth media for culture and polymerase chain reaction (PCR) testing. From Maryland, 12 of 57 birds examined had gross conjunctival lesions. MG was isolated from 9 of the 12 affected birds and from three birds without gross lesions. Fourteen of 22 finches tested by PCR were positive for MG. Sixteen of 38 birds were positive for MG by SPA, and 9 of these had HI titers of 1:40 or 1:80. From Georgia, 3 of 31 finches examined had gross lesions; two of these were both culture and PCR positive for MG. Twelve birds were positive by SPA, and two of these had HI titers of 1:80. Histologic findings in birds with gross conjunctivitis from both locations were characterized by extensive epithelial and lymphoid hyperplasia as well as lymphoplasmacytic inflammation in conjunctival tissues; keratitis was rarely present. The source of MG infection in house finches is unknown, and further research is warranted to determine the prevalence and impact of this newly described disease.