- "Swedish veterinarians have found
a mink with an aggressive form of the H5 bird flu virus and had the mammal
put down, the National Veterinary Institute said on Monday.
- The animal was found in the Blekinge
region of south Sweden, an area where several bird flu cases have been
found. What is initially described as an aggressive form of H5 bird flu
is often later confirmed as the highly pathogenic H5N1 virus.
- The mink probably got the disease from
eating wild birds which were already infected, the Institute said in a
- The above comments provide additional
evidence that the Qinghai version of H5N1 is causing widespread infections
and death in carnivores that eat H5N1 infected birds. The H5N1 in
the mink is in addition to recent reports of H5N1 in a stone marten, dogs,
and cats who have eaten H5N1 infected birds.
- Linkage of H5N1 infections to carnivores
after eating infected birds has been noted previously in southeast Asia
and confirmed. The largest number of cases was recorded at a zoo
in Thailand in 2004. Bengal tigers were fed uncooked H5N1 infected
chickens, and although the number of tiger infections initially was small,
the H5N1 spread tiger to tiger and eventually 147 tigers died or were euthanized.
H5N1 was isolated from the tigers, and sequencing identified PB2 E627K.
This change had been previously reported in H5N1 from some patients in
outbreaks in 1997 and 2004 as well as in H7N7 from a fatal infection of
a veterinarian in the Netherlands in 2003.
- In the lab PB2 E627K was associated
with increased virulence in mice and had been isolated from mouse brain.
In the tigers from the Thai zoo, the H5N1 was also neurotropic and also
causes hind leg paralysis in lab infected ferrets.
- E627K is found in all human H1, H2,
H3 serotypes and is associated with the ability of the polymerase to efficiently
function at lower temperatures (33 C) compared to E627 (41 C). Prior
to last year, E627K had not been found in any bird H5N1 isolates.
However, at Qinghai Lake, all 16 bird isolates has E627K and all Qinghai
H5N1 strain isolates reported since last year have had E627K.
- The presence of E627K in all Qinghai
isolates may increase the likelihood of mammalian infections from eating
H5N1 infected birds. Therefore, the number of mammalian species infected
with H5N1 may be significantly higher than those reported above.
Transmission of H5N1 to other mammalian species increases the likelihood
of recombination and acquisition of mammalian polymorphisms, which can
lead to an expanded host range.
- The fixing of E627K in H5N1 in long
range migratory birds may have significant impact on H5N1 expansion of
both geographical and host ranges.
- © 2006 Recombinomics. All