2008 has been a year of heavy mortality for Double-crested Cormorants. SEANET received reports a few months ago of substantial die-offs in the Canadian Maritimes. Our collaborators there asked us to keep an eye out for aberrant cormorant related events down here in the States. While we did not see anything out of the ordinary down here in Massachusetts, we did get word of unusually high numbers of sick and dead cormorants along the Maine coast this summer.
Our Canadian friends have since diagnosed their dead cormorants with Newcastle Disease, a paramyxovirus that is a common cause of cormorant die-offs. SEANET will be pursuing diagnostics in some of the birds found in Maine to determine if Newcastle Disease was at play there as well.
While all species of birds worldwide are potentially susceptible to Newcastle Disease, both cormorants and rock doves (piegons) appear to maintain the disease in their populations and can then suffer periodic severe mortality from it. Newcastle is also of major economic importance as it can decimate commercial poultry flocks. As a result, federal authorities are constantly vigilant in detecting and containing outbreaks of the disease.
Signs and symptoms of the disease are variable, but the most common ones are related to infection within the brain, spinal cord and nerves. Affected birds may be unable to fly or even walk and may lose balance and coordination before dying. Birds that survive the virus often suffer permanent paralysis, especially of a single wing. Seeing a number of birds with one paralyzed wing in a particular area is a good indication that an outbreak of Newcastle Disease recently ran through the population.
Newcastle Disease can also affect the lungs, intestine and kidneys of infected birds, and we will be submitting samples of those tissues to test for the virus in the Maine birds. Keep an eye on the blog for results of the cormorant necropsies and the viral testing to follow!