EPIDEMIC MYCOPLASMAL CONJUNCTIVITIS IN-HOUSE FINCHES FROM EASTERN NORTH-AMERICA

In the winter of 1993-94, house finches (Carpodacus mexicanus) with se vere conjunctivitis (later shown to be caused by Mycoplasma gallisepti cum) were first observed in suburban Washington D.C. (USA) and adjacen t states. Using a large network of volunteer observers in eastern Nort h America, we were able to track the monthly prevalence of the disease between November 1994 and March 1997. Using the information on 24,864 monthly data forms, we describe the very rapid spread of the conjunct ivitis epidemic through the eastern house finch population. The epidem ic first expanded mainly north, probably carried along by house finche s on their return migration, then mainly toward the southeast, and. la ter west. By March 1997, conjunctivitis had been reported from most of the eastern range of the house finch. The prevalence of the disease s eemed to fluctuate seasonally with increases in the fall, probably as a result of dispersing juveniles. House finch numbers decreased throug hout winter in areas with cold winters and high conjunctivitis prevale nce, suggesting significant mortality associated with the disease.