An outbreak of Newcastle disease among cormorants, as was seen in the summer of 2018, can generate significant public interest when it occurs in an area also high in population of sympathetic humans.
But from the standpoint of human health and domestic poultry production, a much bigger risk would be present if the same infection took hold among pigeons.
Why it matters: Various strains of Newcastle disease can be present in both wild and domestic birds without any symptoms, but the viral infection can be highly contagious and cause devastating mortality if present in its most virulent strains.
“This is where it gets potentially a bit more dangerous because pigeons are everywhere,” said Dr. Brian Stevens, veterinary pathologist with the Canadian Wildlife Health Cooperative (CWHC) within the Pathobiology department at the University of Guelph.
Stevens spoke at the annual Poultry Industry Council Health Day on June 25 in Stratford.
Stevens says that despite having a lower media profile in recent years compared to avian influenza, Newcastle disease is more common in Ontario’s wild birds, according to reports and dead birds samples tested by the CWHC.
“We do see multiple strains (of Newcastle disease) out there, but it’s really the highly virulent strains we’re interested in.”
One of those showed up in 2018, in the form of a large die-off of juvenile cormorants. This became a high-profile event not because it was more severe than other recent outbreaks or presented more of a risk to human health or domestic poultry production, but because it happened in mid-town Toronto. Birds were seen in city parks, affected by what manifests itself as a neurological condition (teeter-tottering near the teeter-totters), and eventually dropped dead before the public’s eyes.
Newcastle disease outbreaks in pigeons, by contrast, should be a concern to poultry producers across the province. Stevens says pigeons can carry a multitude of diseases, but Newcastle disease is probably the one that poses the biggest threat to domestic flocks.
He encourages anyone who notices a cluster, even three in succession of dead pigeons to contact the agency, and they’ll send out a cooler to be filled with dead birds and returned to Guelph for analysis.
The same, he says, is true for any cluster of wild bird deaths on the farm.
Avian influenza is also a concern, but Stevens said, “we are not seeing a lot of avian influenza, but we are monitoring it and what we’re seeing now is not seen as a threat to human or domestic bird health.”
In the United Kingdom and British Columbia, there has been recent work on sampling of sediment from the locations where wild birds susceptible to avian influenza congregate. If that work is successful, it could turn into a much more effective way of monitoring wild bird populations.
Stevens also explained research undertaken recently by Amanda MacDonald into wild turkeys that have been hunted in Ontario. Testing of wild turkeys in the United States found Lymphoproliferative disease (LPDV) as well as multiple other diseases in two-thirds of hunted birds. The vast majority of these birds, the U.S. study noted, were not affected by symptoms.
MacDonald, in her PhD thesis completed in 2018, didn’t find anywhere near the same instances of infections in Ontario wild turkeys.
“Wild turkeys appear to be in good general health” in this province, Stevens said.