WI - Cormorant Research Group News created on 23-10-2001

Newsletter Volume 5 Number 3
Winter 1998

Avian Cholera in Double-Crested Cormorants (Phalacrocorax auritius)

Avian cholera (infection with the bacterium Pasteurella multocida) occurred on four colonies of Double-Crested Cormorants in Alberta and Saskatchewan in the summer and fall of 1998. Very high mortality was documented at three of these colonies and is suspected at the fourth. The disease was first observed among hatch-year cormorants at a large breeding colony on Doré Lake, Saskatchewan (54º46'N, 107º17'W) and another on Lavallée Lake, in the northwest quadrant of Prince Albert National Park (54º19'N,106º33'W), on 30 July and 13 August 1998, respectively. Doré Lake was revisited on 18 August, and 1523 carcasses of full-grown hatch-year cormorants were counted. Multiple specimens of freshly-dead cormorants from both locations and a Common Raven (Corvus corax) found on the colony at Lavallée Lake were examined by the CCWHC and found to have avian cholera. Culture and histopathology found no evidence of Newcastle disease. In late September 1998, sick and dead cormorants were observed at a nesting colony on Lac La Biche, in east-central Alberta (54º52'N, 112º05'W). Subsequent investigation found 1000 dead birds on one colony on 2 October and 300 on a second colony on 7 October, at which time further mortality since the 2 October visit also was noted at the first colony. Dead immature gulls were also noted at both colonies. Freshly-dead cormorants were examined by Dr. D.K. Onderka, Alberta Agriculture, Food and Rural Development, Edmonton, and found to have died of avian cholera. Total mortality at Lac La Biche was estimated to be 1,500 cormorants.

This is the second recognized occurrence of avian cholera in Double-crested cormorants in Canada; the first was in 1988, also on a colony at Lac La Biche and also with mortality of about 1500 birds (Mutalib and Hanson, 1989.Canadian Veterinary Journal 30:350) Since 1990, cormorant colonies have been under scrutiny for mortality due to Newcastle disease. However, avian cholera was not noted among cormorants during this period until this year, when it occurred simultaneously at widely-separated locations. [M. Pybus, F. Kunnas, Alberta Natural Resources Service; D. Fransden, Prince Albert National Park; S. Lightfoot, H. Philibert, T. Leighton, CCWHC]