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AUTUMN 2015 ISSUE
EQUINE MATTERS
18
VET VIEWPOINT...
We view the opinions of our vets on the topic of West Nile Virus
Nathalie van Heesewijk BVSc(Hons) MRCVS,
Penbode Equine
Alistair Couper BVMS
MRCVS,
Capontree Veterinary Centre
Will Marshall BVMS MRCVS,
Clyde Veterinary Group
My first thought when asked for my
viewpoint about West Nile Virus and
whether or not we should be worried
about it was that since I couldn’t remember
anything about it other than the rather
obvious clues from the name that it is a
viral infection of horses which originates in
the West Nile area, my honest answer
was that I hadn’t got a clue whether I
should or should not be worried about it
and it was time for some research.
After conducting my research I discovered
that there was some good news and bad
news to take on board before making my
decision. The good news was that
although West Nile Virus causes an
encephalitis (brain inflammation), only
about 10% of infected horses show clinical
signs and the virus does not spread
directly between horses. The bad news
however was that there is no specific
treatment available in the UK with affected
animals requiring high levels of supportive
care and intensive hospitalisation and only
about 40-50% chance of survival. Since
mosquitoes are no longer completely
unheard of in Cumbria I was starting to
get a bit worried until I came to the final
bit of excellent news that no clinical cases
of infected horses have been seen in the
UK making it highly unlikely that I will
come across it on my rounds in rural
Cumbria so I stopped worrying.
With the introduction of bluetongue to the
UK in 2007 we should certainly be aware
of vector-borne viral diseases affecting our
horse population. Although there are no
reported cases of WNV in the UK to date,
the mosquito responsible for transmitting
the virus has been identified here earlier
this year; clinical cases have also been
reported in countries as close as France
and Italy.
Luckily horses with WNV are not
contagious to other horses and so the
risk to resident UK horses is believed to be
low. However, migrating birds from WNV
affected countries can affect susceptible
native birds. As such, I would not say we
should be worried about WNV in the UK
at this
point in time. However, it is important
that we follow the lead of other countries
with naïve populations and instigate our
own equine surveillance programme as a
method of disease prevention.
Should we be concerned about
West Nile Virus in the U.K.?
Although no cases of West Nile Virus
(WNV) have yet been recorded in the UK,
evidence of exposure to the virus has been
found in our migratory birds. Neighbouring
countries such as France have recently had
WNV outbreaks.
The main risk of introduction comes from
the migratory bird and mosquito
population. The
Culex modestus
mosquito
is the main WNV vector in Europe. It is
present in England, notably in the southeast
marshes, where susceptible migratory bird
species also flock.
Disease surveillance in host populations is
critical, as is increased awareness of the
disease to prevent silent spreading. All
horses, birds and humans presenting with
neurological symptoms compatible with
WNV should be tested accordingly.
Should the disease be introduced in the
UK, the Department of Environment, Food
and Rural Affairs (DEFRA) have developed
relevant contingency plans and a vaccine
is already available for horses travelling to
high risk areas.