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DCC Generic Notifiable Animal Health Contingency Plan
Annex H
West Nile Virus
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
Contents
The contents of Annex H on West Nile Virus must be read in conjunction with the DCC Generic
Notifiable Animal Health Contingency Plan.
Annex H only contains information that is applicable during an outbreak of West Nile Virus. All
structures, stakeholders, roles and information that are relevant to all notifiable animal diseases
are contained within the main contingency plan.
Chapter
Subject
Page
1.
1.1
1.2
1.3
1.4
1.5
2.
2.1
2.2
2.3
2.4
2.5
3.
4.
5.
6.
Introduction
West Nile Virus
Risk of West Nile Virus Spreading to the UK
Human Health Concerns
Devon County Council Annex H on West Nile Virus
Overview of Devon County Council Role
Epidemiology
Definition
After-Effects of Disease
Transmission
Clinical Signs
Main Aspects of Disease Control
Legislation
Wider Stakeholders – West Nile Virus
Overview of Disease Stages and Controls
Plan Implementation – Devon County Council Functions and
Responsibilities
Animal Health and Trading Standards Officer Job Description –
West Nile Virus
West Nile Virus
Emergency Planning, Communications and Public Relations,
Environmental Health
Public Services – West Nile Virus
Stand Down and Recovery - West Nile Virus
Useful Information and Advice
Advice on Writing Public Information and Advice Leaflets/Letters
Frequently Asked Questions
3
3
3
3
4
4
5
5
5
5
5
5
7
8
9
10
6.1
6.2
6.3
6.4
7.
7.1
7.2
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
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11
14
14
15
15
15
1.
Introduction
1.1
West Nile Virus
West Nile Virus (WNV) is a viral infection of birds, horses and humans, that can cause
encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and
spinal cord). The disease is spread by the bite of infected vector, in this case a mosquito,
usually Culex species.
The horse seems the most susceptible to infection but most cases show no obvious signs of
disease. Mortality rates vary, but in the USA about 35% of the animals which show signs of
disease will die.
Whilst birds are the main carrier and most remain apparently unaffected, some species are
susceptible to disease - especially corvids (crow family). Mass die-offs can occur in these
species. Other animals that can be infected are cats, bats, chipmunks, skunks, squirrels,
rabbits and dogs (rarely). Poultry can be infected but do not usually develop disease. WNV is
primarily an infection of birds and although a range of other animal species, such as goats and
sheep can be infected, these species only develop low levels of virus. WNV is a flavivirus, one
of a member of a group of arthropod-borne viruses (arboviruses).
WNV is a zoonosis, that means the causative agent can be passed between animals and
humans.
1.2
Risk of West Nile Virus spreading to the UK
Recent research by Natural Environment Research Council (NERC) found antibodies against
the virus present in birds in Great Britain, suggesting past or present infection with WNV. WNV
infection has never been identified in horses or humans in Great Britain. Migrating birds are the
most likely mechanism of the infection being introduced into the UK. Humans, horses and other
animal species are believed to be dead-end hosts, i.e. there is no spread from them to other
people or animals. It is possible that a recently infected horse or person, incubating the
infection, could have the virus in their blood stream for a short time and during that time be
bitten by a mosquito, but the risk of this is thought to be remote.
The virus historically occurs in Africa, Europe, the Middle East, West and Central Asia, and
recent outbreaks have occurred in Morocco, Romania, Italy, Russia and France between 1996
and 2000. Since WNV was first recorded in the USA in 1999, it has spread throughout much of
the country where it is now considered to be endemic.
1.3
Human health concerns
Many infected people show no symptoms. When disease does occur, it is usually a flu-like
illness with fever. A small proportion of cases (less than 1%) develop meningo-encephalitis
which produces nervous signs and may be fatal. There is no evidence that the disease can be
passed directly from human to human, from horses to humans, or from humans to horses.
In the USA in 2002, 4,161 people were reported as infected with the disease, of which 277
died. In 2004, the Department of Health published a comprehensive contingency plan for West
Nile virus to protect the public's health.
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
1.4
DCC Annex H on West Nile Virus
The contents of Annex H on WNV must be read in conjunction with the DCC Generic Notifiable
Animal Health Contingency Plan.
Annex H only contains information that is applicable during an outbreak of WNV. All structures,
stakeholders, roles and information that are relevant to all notifiable animal diseases are
contained within the main contingency plan.
Further details are available in the Exotic Animal Disease Generic Contingency Plan produced
by Defra. This is available at:
http://www.defra.gov.uk/foodfarm/farmanimal/diseases/control/contingency-plan.htm
1.5
Overview of DCC role
DCC will perform a range of essential duties in the event of a WNV outbreak. Council Directive
90/426 makes Equine Encephalomyelitis, of all types, including West Nile Virus/Fever, a
notifiable disease. The Infectious Diseases of Horses Order 1987 provides clear obligations for
local authorities.
Devon County Council will have involvement on the Incident Control Team (ICT) established as
part of the Department of Health contingency plan.
Devon County Council will also play an essential role in ensuring that their communities are
accurately made aware of the current situation and any restrictions upon activities, without
causing any concern or panic. This role must be fulfilled through all feasible avenues, but
particularly the animal health and welfare, emergency planning and communications functions.
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
2.
Epidemiology
2.1
Definition
West Nile Virus (WNV) is an infection of birds which is spread by the bite of infected
mosquitoes. It can infect mammals and can cause disease in horses and people. The disease
has never been recorded in the UK, but there may be some evidence of infection in birds. Many
species of birds act as “maintenance” hosts and provide sources of infection, but horses and
people are regarded as “dead end” hosts from which no further spread occurs. The majority of
people who become infected do not suffer from any illness. Around 20 % of infected people
develop a ‘flu-like disease; a small number (less than 1% of infections) suffer serious disease
with potentially fatal meningitis, encephalitis or other neurological features.
The disease in horses (including donkeys, zebras etc) is notifiable. Clinical signs occur in
around 30% of those infected and include depression, fever, nervous signs and sudden death.
Infection in domestic poultry (chickens and turkeys) and other livestock does not usually cause
illness, but disease has been reported in goose flocks in Israel and Canada when many
affected birds died. In wild birds, serious disease with nervous signs and significant mortality
has been reported from the USA, particularly in the crow family. Elsewhere, disease in wild
birds is not usual. Human and horse cases have been reported from many parts of Europe,
including the South of France. However, the emergence of WNV in the USA with associated
human cases and deaths has raised public concern.
Also known as: West Nile Fever, West Nile Encephalitis and West Nile Encephalomyelitis.
2.2
After–Effects of the disease
In horses (and similar), mortality will result in around 30% of infected animals. The disease can
show some symptoms in birds (both wild and domestic), but death is unlikely, and seems to
depend on the species. Human health implications are also limited, given that most people
infected by the disease will not even show symptoms.
2.3
Transmission
WNV can only be transmitted by a vector. In this case, an infected bird is bitten by a mosquito,
which subsequently infects a mammal by biting it. The virus must multiply in the mosquito for at
least two weeks before it can be transmitted. It is extremely unlikely for the disease to be
spread directly between mammals, but is statistically possible in the case of blood transfusion,
organ transplant etc.
2.4
Clinical Signs
In humans, around 20% of those infected will exhibit 'flu-like symptoms. Infected birds will tend
not to show any signs of illness, but may die. Infected horses may display fever and
encephalitis with neurological symptoms, and will often die suddenly.
2.5
Main Aspects of Disease Control
In tackling an outbreak of WNV the Government’s objectives will be to eradicate the disease as
quickly as possible and maintain the UK’s disease-free status.
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
If WNV is confirmed, restrictions will be placed on infected premises until the situation is clear.
Local and national risk assessments will be undertaken by health, veterinary and environmental
agencies working in partnership. The Infectious Diseases of Horses Order 1987 allows
provisions for control of AHS, with a few additional measures allowed by the Animal Health Act
1981 (as amended). There is no statutory requirement to slaughter horses.
The Department of Health contingency plan will be followed and an ICT will be formed locally.
If there is an outbreak of WNV infection at a time when mosquitoes are active, measures to
control mosquito populations, by either targeting their breeding sites or, more rarely, killing
adult mosquitoes, will be considered. Enhanced surveillance for the disease might also be
appropriate. The action required will be determined by health risk assessments by the
Department of Health and Defra, locally and nationally.
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
3.
Legislation
The overarching requirements of the Civil Contingencies Act 2004, the Animal Health Act 1981
as amended by the Animal Health Act 2002 (but see below) and the European Communities
Act 1972, are detailed in the DCC Generic Notifiable Animal Health Contingency Plan. The
legislative information provided within this Annex relates specifically to WNV.
The Infectious Diseases of Horses Order 1987
This is the main legislation relating to controls specific to WNV. WNV is one of a range of
diseases termed ‘equine viral encephalo-myelitis’. The order includes powers and obligations
relating to;
 Notification of disease
 Declaration of infected place
 Veterinary enquiry
 Rules to be observed in an infected place, including movements and isolation
 Restrictions on premises exposed to infection
 Disposal of carcases
 Cleansing and disinfection
Animal Health Act 1981 (as amended)
This provides for the control of outbreaks of animal diseases. Article 2(b) of the Infectious
Diseases of Horses Order 1987 extends the definition of disease in the Animal Health Act to
include equine encephalo-myelitis (including WNV) for the purposes of the Act in its
application to the Order. The Order states the specific sections of the Animal Health Act
under which it exercises powers. Therefore only certain sections of the Animal Health Act
apply in relation to WNV. These are: 1, 7(1), 8(1), 15(4), 17(1), 17(2), 23, 28, 35(3), 72, 87(2)
and 88(2).
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
4.
Wider Stakeholders – West Nile Virus
Key stakeholders and wider stakeholders that are relevant to all notifiable animal health
diseases are listed within the DCC Generic Notifiable Animal Health Contingency Plan. . This
section only outlines wider stakeholders that may be of relevance during an outbreak of WNV.
Devon County Council should use this information as guidance to produce a list of relevant
local stakeholders, many of whom will already be known to authorities already. These will
generally be businesses and individuals who keep horses. Stakeholder lists should be
reviewed on an annual basis to ensure they are up to date.
There are a number of national associations that represent breeders and keepers of horses. It
is recommended that Devon County Council make contact with any local branches of the main
associations. It is also recommended that authorities make contact with any other hobbyists,
rare breed societies or specialist associations operating within their area.
Travellers often keep horses and special consideration should be given to liaison with any local
traveller population.
The majority of areas will have their own smallholders association. Details can frequently be
located on the internet, and authorities should also make contact with these.
Some relevant organisations include:
British Equine Veterinary Association
www.beva.org.uk
Promotes veterinary and allied sciences related to the welfare of the horse.
The Pony Club
www.pcuk.org
International voluntary youth organisation for those interested in ponies and riding.
The British Horse Society
www.bhs.org.uk
Focuses on horse welfare, horse and rider safety, access and rights of way, training and
approving livery yards and riding schools.
The Donkey Sanctuary
www.thedonkeysanctuary.org.uk
UK based charity working worldwide to improve conditions for donkeys and mules.
The Horse Trust
www.horsetrust.org.uk
The Horse Trust's Home of Rest for Horses caters for the retirement needs of over 100 horses,
donkeys and ponies.
World Horse Welfare (formerly International League for the Protection of Horses)
www.worldhorsewelfare.org
Leading equine welfare charity working towards a world where the horse is used but never
abused.
Horse Passports – Breed societies
http://www.horsepassportagency.co.uk/org/links.php?lid=1
DCC Contingency Plan Annex H – West Nile Virus – 09/2010
5.
Overview of Disease Stages and Controls
The following diagram details the various stages of a West Nile Virus outbreak, and the restrictions that
would be applied under The Infectious Diseases of Horses Order 1987, and the Animal Health Act 1981
(as amended). (Article numbers relate to Infectious Diseases of Horses Order 1987. AHA = Animal Health Act
1981 as amended).
Notification
Anyone who knows or suspects that a horse or carcass is
affected with AHS must notify the Divisional Veterinary Officer
(Article 4).
Suspicion
If an Inspector has reasonable grounds to suppose that AHS exists
or has existed within 56 days, he may serve a notice (Form A) on
the occupier of the premises, declaring an Infected Place (Article
5).
Veterinary Inquiry
A Veterinary Inspector shall take steps as may be necessary to
establish whether disease exists on a premises or has existed
within 56 days (Article 6), this includes tracing of contacts.
Confirmation of the disease shall be made by the Chief Veterinary
Officer
Controls
Control measures may include;
 Cleansing and disinfection of premises or vehicles (Article
11) in accordance with Schedule 2
 Prohibition or control of movement onto/out of any
premises (Article 13), in addition to controls relating to
suspect/infected premises (Articles 7 and 10)
 Controls on general movements of animals and issuing of
licences (Section 8 AHA)
 Prohibition or regulation of markets (Section 8 AHA)
 Orders relating to seizure of carcase, animal or any thing
else by which disease may be transmitted, may also
prescribe destruction, burial or disposal
Lifting Restrictions
Form A notice remains in force until a Form B (Schedule 1) notice is
served by a Veterinary Inspector withdrawing the declaration of
Infected Place (Article 5).
Form C notice remains in force until it expires or a Form D (Schedule
1) notice is served by an Inspector (Article10).
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Upon suspicion an Inspector will serve a
notice – Form A, as specified in Schedule 1.
Rules contained in Article 7, and any other
rules, will be set out in the notice, including:










Affected horses to be isolated, including
where specified, erection of fly-proof
screens
No horses to be moved into or out of the
infected premise without a license
No fodder, manure, bedding, vehicle,
equipment or thing to be moved off the
premise without a license
No person to enter or leave the premises
except with a licence and subject to biosecurity controls
Occupier to maintain a footbath at exits
Prevention of straying
Controls on cutting of carcasses
Notice of death or slaughter to be given to
the Divisional Veterinary Officer
Erection of notices at entrances
Veterinary Inspector may also require
disinfection or destruction of articles
(Article 8)
NB If disease is confirmed then the premises remain
under the Form A notice.
An Inspector may serve a notice (Form C – see
Schedule 1) on a premises exposed to infection
(Article 10). This will impose restrictions.
6.
Plan Implementation –DCC Functions / Responsibilities
There is a clear range of specific functions that must be performed by Devon County Council in
the event of a notifiable animal disease situation. The majority of these functions remain the
same for all types of notifiable animal disease, and therefore are comprehensively detailed
within the DCC Generic Notifiable Animal Health Contingency Plan. It contains a summary of
key actions to take within the first 24 hours of an animal disease outbreak and a template
agenda for initial meetings.
However, the role performed by the Animal Health and Welfare Enforcement Inspector will
change in consideration of legislative duties, and the operational requirements that are unique
to each disease. As a result each individual Annex includes further details of what is required
from that role in consideration of the unique requirements of each disease.
The details provided below must be utilised in conjunction with the DCC Generic
Notifiable Animal Health Contingency Plan. .
6.1
Animal Health and Welfare Enforcement Function – West Nile Virus
N.B Article numbers relate to Infectious Disease of Horses Order 1987, AHA = Animal Health Act 1981 (as
amended)
Key Responsibilities – Including Specific WNV Information
1.
Enforcement of Animal Health and Welfare Legislation
This specifically relates to the Infectious Disease of Horses Order 1987 and the relevant
sections of the Animal Health Act 1981 (as amended), Devon County Council, Trading
Standards Officers must always remain aware of all animal health and welfare legislation
2.
Enforcement of Movement Restrictions
There will be control on movements on and off of infected premises, including licence
provisions (Article 7). There may also be wider restrictions on movements (Articles 10
and 13, and Section 8 AHA). Government can make provision for wider licensing of
movements, and Devon County Council would be responsible for enforcing this.
The animal health and Trading Standards Officers would be responsible for completing
patrols, responding to intelligence and enforcing as appropriate. Officers therefore need
up to date information regarding new suspect/infected premises and changes to any
licensing regime.
3.
Devon County Council must work in partnership with the Local Disease Control Centre
(LDCC) to review priorities and resource requirements. Animal Health and the local
police force will be key partners in this work.
Contribution to the issuing of Notices and individual movement licences (if
required)
Devon County Council, Trading Standards Officers can issue Form A, C and D notices
(Infectious Diseases of Horses Order), however as Form A and C notices relate to
infected, and suspect infected premises it is unlikely that they will have widespread
involvement with these notices, but may be involved with the issuing of Form D notices –
notice withdrawing restrictions on premises exposed to infection.
If a wider movement licensing scheme is introduced then Devon County Council,
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4.
5.
6.
7.
6.2
Trading Standards Officers may be involved with the issuing of these.
Monitoring Cleansing and Disinfection Requirements
A veterinary inspector may require cleansing and disinfection to be carried out on
infected and suspect infected premises/vehicles (Article 11). Devon County Council
enforces these provisions, and may carry out works in default if not done satisfactorily.
Disposal of Carcases
The Divisional Veterinary Officer can require Devon County Council to dispose of
carcases affected or suspected of being affected with disease (Article 9). However, with
reference to the Animal By-Product Regulations 2005, responsibility for disposal of a
carcase of a farmed animal lies with the animal owner in the first instance, then the
landowner. There may be instances where a horse is not classified as a farmed animal.
Note: that as there is no statutory requirement for the slaughter of affected horses there
will be no issue in relation to disposal of carcases from slaughtered animals.
Identification of Premises
Premises with horses will not necessarily be known to Devon County Council. It will be
important to identify them in order to assist in the dissemination of information, and
monitoring movement restrictions. Some farms may have horses, therefore the list of
farm holdings will assist. Riding Schools are required to have a licence issued by the
district or unitary council, therefore district councils or the relevant licensing function of
unitary councils should be able to assist in the identification of these. In addition to this,
local intelligence and patrols should be used to help identify premises with horses.
Special consideration should be given to any traveller sites, as travellers often keep
horses. Many councils will have a specialist officer(s) dedicated to traveller liaison and
help could be sought from this person.
Dissemination of Guidance and Information
Animal health and welfare inspectors will need to ensure that accurate guidance and
information is provided to members of the community, including provision of leaflets or
letters during all intelligence and enforcement work. Section 7 of this Annex provides
some further information on this.
Other DCC Services – West Nile Virus
Other DCC services will be able to assist in the identification of premises with horses. Riding
establishments are required to have a licence from the district council. Therefore in County
areas assistance may be sought from the district councils. In unitary areas the relevant
licensing section can provide assistance.
Travellers often keep horses and this can provide unique challenges for identification and
liaison. Communities and Local Government (Gypsy and Traveller sites Unit) have a dedicated
traveller liaison officer and can provide valuable assistance.
WNV has the potential to have a considerable impact on local economies that rely on horse
industries, such as riding schools, trekking centres and horse racing. Liaison between all
services is vitally important to ensure that the approach to disease management is joined up
and promotes the need of the local community and economy.
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Given the human health implications it is likely that the environmental health function within a
council will have an important role to play. Therefore continued communication will be
important.
Communication with local residents is also of paramount importance. Emergency Planning and
Communications services must remain aware that accurate and timely communication with
residents will be a key function. A joined-up approach to communication with the public is
additionally important in consideration of the human health implications.
DEVON COUNTY COUNCIL DUTIES FOR THE PURPOSES OF WEST NILE VIRUS
CONTINGENCY PLAN
DEVON COUNTY COUNCIL
Trading Standard Service
Address:
Telephone Number:
Fax Number:
County Hall, Topsham Road, Exeter, EX2 4QH
01392 384772
01392 382732
Main Duties
1. A veterinary inspector may require cleansing and disinfection to be carried out on
infected and suspect infected premises/vehicles (Article 11). Trading Standard Officers
enforces these provisions, and may carry out works in default if not done satisfactorily.
2. The animal health and Trading Standards Officers would be responsible for completing
patrols, responding to intelligence and enforcing as appropriate.
3. Trading Standards Officers can issue Form A, C and D notices (Infectious Diseases of
Horses Order), however as Form A and C notices relate to infected, and suspect
infected premises it is unlikely that they will have widespread involvement with these
notices, but may be involved with the issuing of Form D notices – notice withdrawing
restrictions on premises exposed to infection.
4. If a wider movement licensing scheme is introduced then Trading Standard Officers
may be involved with the issuing of these.
5. A veterinary inspector may require cleansing and disinfection to be carried out on
infected and suspect infected premises/vehicles (Article 11). Officers will be required to
enforce these provisions, and may carry out works in default if not done satisfactorily.
6. Officers will be used to help identify premises with horses.
7. Trading Standards Officers will need to ensure that accurate guidance and information
is provided to members of the community, including provision of leaflets or letters
during all intelligence and enforcement work. Section 7 of this Annex provides some
further information on this.
8. To perform any other duties assigned by a Senior Officer of the Service.
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OFFICERS’ PROTECTIVE CLOTHING, EQUIPMENT
1
1
1
1
1
1
1
1
1
1
1
1
PAIR WELLINGTONS
WEATHERPROOF TROUSERS
WEATHERPROOF JACKET
CONTAINER OF DEFRA APPROVED DISINFECTANT
WATER CONTAINER
PRESSURE SPRAYER
BRUSH
BUCKET
HIGH VIS JACKET
GLOVES
EID READER
CAMERA
OTHER RESPONSIBLE ORGANISTATIONS
DEFRA- THE DEPARTMENT FOR THE ENVIRONMENT, FOOD AND RURAL AFFAIRS
Name:
Address:
Tel:
Fax:
Email:
DUTY VETAnimal Health, Clyst House, Winslade House, Clyst St Mary, Exeter, EX5 1DY
01392 266411 Out of Hours 01392 266373
01392 266374
[email protected]
DEVON & CORNWALL POLICE
Tel:
999 or 08452 777 444
Communications Desk for disease out breaks only
Tel:
01392 452023
Out of hours: 01392 223486
Police Liaison Officer: to be confirmed in the event of an out break
EXETER CITY COUNCIL (Riding School Approval List)
Licensing Authority Tel: 01392 265702
APPROVED RIDING SCHOOL IN DEVON
Web:
www.abrs-info.org/england/devon.htm
COMMUNITIES AND LOCAL GOVERNMENT (Gypsy and Traveller sites Unit)
]Email:
[email protected]
Tel:
0303 444 0000
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6.3
Other Local Public Services – West Nile Virus
As per the Department of Health contingency plan an ICT will be formed locally. This will
involve the Health Protection Agency, the Veterinary Laboratory Agency, the local Health
Authority, the Health and Safety Executive and the State Veterinary Service (SVS). Devon
County Council will also be involved in this ICT. Representation of the council on the ICT will
be decided locally and is likely to be dependent on local circumstances and the disease
situation.
6.4
Stand Down and Recovery - West Nile Virus
Services should follow the stand down and recovery procedures laid down in the DCC Generic
Notifiable Animal Health Contingency Plan. . In addition to this, continued liaison with the ICT
will be required.
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7.
Useful Information and Advice
7.1
Advice on Writing Public Information and Advice Leaflets/Letters
Information and advice leaflets could include:
 Information on any declared zones, including a link to Defra website showing the
extent of the zones.
 Clinical signs of WNV.
 Advice on contacting DVM if suspect horses are affected.
 Movement restrictions. This should include a link to information and any General
Licences on Defra website. It might be possible to include a list of General Licences
available; however it may not be possible to provide information on all types of
movement restrictions.
 Cleansing and disinfection / biosecurity requirements
 Practical advice on biosecurity
 Requirements to keep records
 Importance of preventing animals from straying
 Any controls on animal gatherings and gatherings of people
 Contact details for local authority, including specifically Animal Health and Welfare
Enforcement Team, Local Animal Health Divisional Office
 Details of DCC and Defra websites
 List of frequently asked questions, see below
7.2
Frequently Asked Questions
Information largely from Defra website, updated August 28 2008.
http://www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/westnilevirus/index.htm
The nature of the disease
What is it?
West Nile Virus (WNV) is a viral infection of birds, horses and humans, spread by the bite of
infected mosquitoes that can cause inflammation of the brain, its lining and the spinal cord. The
horse seems the most susceptible to infection but most cases show no obvious signs of
disease. In those that do, nervous behaviour and fever are typical, with death resulting in
around 30% of cases. Birds are the main carrier. Most remain apparently unaffected, but some
species are susceptible to disease - especially crows, for which the mortality rate can be high.
How is it spread?
The disease is spread by a vector (in this case, a mosquito). The mosquito bites an infected
bird and passes it among other birds. The mosquito may also spread the disease to a mammal
by biting it.
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Where does it occur?
The virus historically occurs in Africa, Europe, the Middle East, West and Central Asia, and
recent outbreaks have occurred in Morocco, Romania, Italy, Russia and France between 1996
and 2000. Since WNV was first recorded in the USA in 1999, it has spread throughout much of
the country where it is now considered to be endemic.
Can people contract the disease?
Yes, if a person is bitten by an infected mosquito, they could contract the disease. It is highly
unlikely to be transferred from one person to another, and would require a blood transfusion or
organ transplant to for this to occur.
What are the signs in horses?
If a person were to become infected, they probably would not show any signs or come to any
harm. Those who do will have flu-like symptoms. Around 1% develop meningo-encephalitis
which may result in death. The over-50s are particularly at risk of developing clinical signs, and
of these signs escalating.
What kinds of virus are there?
There are two genotypes (Lineage I and Lineage II), which all produce similar symptoms and
effects.
How is the virus destroyed?
It is easily destroyed with heat, detergent or solvents.
What are the effects of WNV?
WNV has serious implications. Uncontrolled disease could have a serious impact on the horse
industry and our ability to trade internationally, not to mention the human health implications.
Can WNV be cured?
A cure is not available, but treatments for human cases are available.
Disease control measures
How is the disease controlled?
In order to eradicate the virus and restore the UK's disease-free status as quickly as possible,
the Government will work to contain the disease by controlling the movement of horses. They
may also look to control the population of mosquitoes.
What happens when a suspect animal is found?
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The owner of a suspected animal or carcase must by law report the fact to the Defra Divisional
Veterinary Manager. The owner is not expected to diagnose the disease, but he ought to know
enough about the disease to suspect it. All owners and stockmen should make themselves
familiar with the symptoms, and call in a veterinary surgeon as early as possible; they should
never ask another stock-owner to look at the suspected animal.
Restrictions are imposed on the premises from the time of notification prohibiting any animal,
person or thing entering or leaving the premises without permission, and a Defra Veterinary
Officer (VO) makes an investigation. If signs suggest WNV is present, the VO, after consulting
Defra HQ, will sign a notice which prohibits the movement of animals and arrange for sample
material from the affected animal(s) to be sent to the Institute of Animal Health for testing. The
Chief Veterinary Officer will confirm the outbreak if the laboratory results confirm the presence
of WNV virus.
What happens if disease is confirmed?
The Government’s objectives will be to eradicate the disease as quickly as possible and
maintain the UK’s disease-free status.
If WNV is confirmed, restrictions will be placed on infected premises until the situation is clear.
Local and national risk assessments will be undertaken by health, veterinary and environmental
agencies working in partnership. There is no statutory requirement to slaughter horses.
The Department of Health contingency plan (for control of the disease in humans) will be
followed and an incident control team (ICT) will be formed locally.
The action required will be determined by health risk assessments by Department of Health
and Defra, locally and nationally. This may include control of the mosquito vectors, or
enhanced surveillance for the disease.
How are carcases disposed of?
Any carcases will usually be disposed of through rendering or incineration, though other
options are available. On-farm burial or burning will not be used as they are prohibited by the
Animal By-Product Regulations.
As there is no requirement for statutory slaughter of affected horses it is unlikely that there will
be an unmanageably high number of carcases.
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