According to a ProMED report, Sweden has experienced yet another outbreak of Newcastle disease.  Following cases in 2023, the most recent infections have impacted a flock of 230,000 birds (unspecified, presumed egg production) together with a second flock of 60,000 birds.

Sweden is unique in that flocks in the nation are not routinely vaccinated against Newcastle disease, a standard procedure in most commercial poultry industries.

No details have been provided as to characterization of the isolate of paramyxovirus from the affected flocks, but the situation is reminiscent of the 1980s outbreaks of pigeon paramyxovirus in the U.K. during the 1980s.  Following extensive vaccination following the 1972 Essex outbreaks, authorities in the U.K. concluded ten years later that the infection had been eliminated from what is essentially an island nation.  The virus was reintroduced by racing pigeons from Europe with cohabitation with feral pigeons resident in Liverpool dockland. This resulting in contamination of imported feed ingredients in warehouses frequented by pigeons.  In the U.K outbreaks, the susceptible laying flocks were affected due to receiving contaminated ingredients in mash form.  Broilers, also susceptible were fed crumbled and pelleted feeds with heat having inactivated the pigeon paramyxovirus.

During the late 1980s, pigeon paramyxovirus was introduced into the U.S. but there was no extension to commercial flocks due to an acceptably high level of immunity stimulated by routine vaccination.  Infection among racing and show pigeons was controlled by a combination of live attenuated and inactivated oil emulsion Newcastle disease vaccines as approved by USDA.

Unless Sweden changes its policy regarding Newcastle vaccination, flocks will remain susceptible and additional outbreaks will inevitably occur.