Field investigation of Mycoplasma gallisepticum infections in house finch (Carpodacus mexicanus) eggs and nestlings

We conducted a field study to investigate the occurrence of Mycoplasma gall isepticum (MG) in eggs and nestlings from nests of house finches (Carpodacu s mexicanus). Forty-three nests were located between the months of April an d August 1998 and were followed with one to three sampling efforts. Vitelli ne membrane of fresh eggs, whole embryos, or swabs from the choanal cleft o r conjunctiva of nestlings were inoculated into mycoplasma broth for MG iso lation and polymerase chain reaction (PCR) testing. No isolation of MG was made from 39 eggs or 110 nestlings sampled during the study. Pooled choanal and conjunctival swab samples from two broods of nestlings, however, teste d positive for MG by PCR. None of the nestlings examined showed clinical si gns of conjunctivitis, and no nestling mortality could be linked to MG infe ction. Serologic tests from 37 older nestlings were negative for antibodies to MG. The results suggest transmission of MG is occurring between breedin g adults and their dependent offspring (pseudovertical transmission). Evide nce supporting transovarian transmission of MG was not found in these house finches.