Ireland - A deadly disease first takes finches’ songs – and then their lives
Event category
Biological origin - Epidemic (animal) Ireland
A devastating disease is spreading among
Irish songbirds. It is caused by a single-cell parasite that gums up the
throats of infected songbirds until they can no longer feed or drink.
Sick birds in gardens look puffed up and may not fly away when
approached.
Hardest hit has been the greenfinch, a species once
widespread in Ireland but now rarely seen or heard in parts of the
country. Its numbers halved since about 2006, when the parasite landed
in Ireland, likely from the UK. There are signs now that the disease is
spreading to other songsters such as goldfinches, bullfinches and
chaffinches.
In response, BirdWatch Ireland took the difficult
decision to ask people not to feed garden birds from May until October.
This is because of how the protozoan parasite spreads. Infected birds
have difficulty swallowing and breathing due to the presence of the
parasite. Eventually lesions in their mouth and throat make it
impossible for them to feed, and they regurgitate seeds that can infect
healthy birds.
Saliva from sick birds is contagious, and parent birds
can also infect their young when feeding them. Drooling and
regurgitation of food means they may have wetting of feathers around
their face.
“The birds look unwell and they are basically starving,”
says Niall Hatch at BirdWatch Ireland. “The poor birds try to feed up
until death, so people are finding them keeled over on their patio or
garden furniture or bird table, which is unusual.” He says the disease
was initially concentrated in a few places, like Dublin and Wexford, but
is everywhere now.
The parasite is a microscopic protozoa,
Trichomonas gallinae, that was known to infect pigeon species. It cannot
infect people. Some time in about 2005, it seems that a single strain
of the parasite jumped from pigeons to greenfinches, which are unrelated
types of bird.
“It started off in the West Midlands [of England] and
then spread to Wales and other parts of southern and central England.
It is now everywhere in the UK and has spread into mainland Europe,”
says Dr Will Peach, a conservation scientist at the Royal Society for
the Protection of Birds (RSPB).
This year the society – which has
more than 1 million members – also changed its advice about feeding
garden birds and says people should especially avoid putting out seeds
and peanuts, which attract finches.
Risks of transmitting the
parasite are heightened around popular bird feeders, where lots of birds
congregate. This stokes the risk of a sick bird joining the feeding
flock and spreading the parasite to others. When temperatures are mild,
the parasite can survive for up to five days outside a bird’s body.
“All
it takes is for an infected bird to go to a bird feeder and then there
is a ticking time bomb there for other birds,” says Hatch.
