Hematology and serum chemistry of captive juvenile double-crested cormorants (Phalacrocorax auritus).

Hematologic and serum chemical values were obtained for double-crested cormorants (Phalacrocorax auritus) to improve clinical diagnosis of disease in this species. Blood samples were collected from 20 captive double-crested cormorants at 4 to 6 weeks of age. Hematocrit and leukocyte concentrations were determined in heparinized blood. Concentrations of sodium, potassium, chloride, bicarbonate, calcium, phosphorus, creatinine, glucose, uric acid, total protein, and albumin, and the activity levels of alkaline phosphatase, creatinine kinase, and aspartate aminotransferase were determined in serum. Total leukocyte concentrations in these double-crested cormorants were higher than the limited ranges reported for cormorants of other species, possibly due to subclinical infection with the liver trematode Amphimerus elongatus, and to differences in species and age.

An epidemic of Newcastle disease in double-crested cormorants from Saskatchewan.

A Newcastle disease epidemic in double-crested cormorants (Phalacrocorax auritus) occurred in July and August 1995, during a 1994-96 study of a breeding colony of this species on Doré Lake (Saskatchewan, Canada). Clinical signs and mortality were observed from a tunnel-and-blind system, and moribund and freshly dead birds were examined virologically. Yolks from cormorant eggs and sera from cormorants and other birds were tested for hemagglutination inhibiting antibodies to Newcastle disease virus (NDV). Evidence of Newcastle disease was limited to juvenile double-crested cormorants, despite close contact with other birds, including American white pelicans (Pelecanus erythrorhynchos) and gulls (Larus spp.). Clinical signs included limb, head or neck paralysis, head or body tremors, ataxia, and blindness; pathogenic NDV was isolated from affected birds. The mortality rate of juvenile cormorants was 32 to 64%, which was high relative to overall first-year mortality in years without epidemics. Thirty-seven of 63 (59%) cormorant sera collected during the epidemic tested positive for antibodies to NDV. Antibody status of cormorant egg yolks depended on stage of incubation, likely due to changes in the amount of water in the yolks. The departure of juvenile cormorants from their nests at 4 wk of age, resulting in an increased contact rate among individuals, may have been important in triggering the epidemic.