The bird flu virus
that can kill humans has the potential to be spread by
cats, scientists have found.
It had been
thought that domestic cats were resistant to diseases
caused by influenza A viruses - one of which, H5N1, is
responsible for avian flu.
The disease killed at least
20 people in Asia earlier this year, and forced farmers
to cull almost 200m birds.The research, by Erasmus Medical
Center, Rotterdam, is published in the journal Science.The
researchers warn that their findings may mean that cats
are a potential source of infection for humans. It also
underlines the ability of the virus to evolve to infect
new species. H5N1 cannot currently pass from person to
person, but scientists fear that if the virus does acquire
this ability, it could pose a serious threat to millions.
The Dutch team focused on cats after some anecdotal reports
emerged during the recent outbreak linking the disease
to the animals.
They investigated whether
the virus could make cats sick when it was introduced
into the airways, or when the cats ate infected chickens.
The six cats developed severe lung disease and passed
the disease onto two additional cats kept in close quarters.The
authors also tested the effect of another type of influenza
virus, H3N2, that most commonly causes flu in humans.
Cats exposed in the same way to this virus did not develop
disease.Writing in Science, the researchers say: "The
implications are that, during H5N1 virus outbreaks, domestic
cats are at risk of disease or death from H5N1 virus infection,
either due to feeding on infected poultry or wild birds,
or due to contact with infected cats. "Second, the
role of cats in the spread of H5N1 virus between poultry
farms, and from poultry to humans needs to be re-assessed.
"Third, cats may form
an opportunity for this avian virus to adapt to mammals,
thereby increasing the risk of a human influenza pandemic."
Professor John Oxford, an expert in virology at Queen
Mary College, London, told BBC News Online the study was
"very significant and slightly alarming". He
said there was little evidence at present that cats could
be infected with other forms of human flu virus, and so
the possibility that H5N1 could mix with a human virus
inside a cat and produce a deadly new strain was probably
slim. However, he agreed that it was possible that cats
could be responsible for avian flu spreading from farm
to farm - a phenomenon which has baffled scientists.
Professor Oxford said there
was also work to suggest that pigs could be infected with
H5N1, and, unlike cats, they could also harbour human
versions of the virus. "H5N1 is getting more and
more worrisome," he said. "If any virus is going
to cause a great human pandemic in the near future, then
it is likely to be H5N1."
