PROBABLE EPIZOOTIC CHLAMYDIOSIS IN WILD CALIFORNIA (LARUS-CALIFORNICUS) AND RING-BILLED (LARUS-DELAWARENSIS) GULLS IN NORTH-DAKOTA

During the summer of 1986, more than 400 California gulls (Larus calif ornicus) and ring-billed gulls (Larus delawarensis), primarily fledgli ngs, died on an island in Lake Sakakawea near New Town, North Dakota ( USA). Mortality was attributed largely to chlamydiosis. Necropsy findi ngs in nine carcasses included splenomegaly (n = 9), hepatomegaly (n = 4), and pericarditis (n = 1). Livers from three California gulls and two ring-billed gulls, and spleens from the same five birds plus a thi rd ring-billed gull were positive for Chlamydia psittaci by the direct immunofluorescence test. Chlamydia psittaci was isolated from separat e pools of liver and spleen from one California gull and one ring-bill ed gull. This is believed to be the first record of epizootic chlamydi osis in gulls and the second report of epizootic chlamydial mortality in wild birds in North America.