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The Virus Known As Bluetongue Virus
A notifiable disease is a disease that must be reported to a government authority such as DEFRA if a person responsible for animals suspects symptoms of a notifiable disease. Reporting the diseases gives an early warning of a potential outbreak and allows the disease to be monitored and controlled before it can become an epidemic or pandemic.
For this report, I have chosen to research the Bluetongue virus which is a notifiable disease that affects ruminants and camelids. Bluetongue is part of the Orbivirus genus in the Reoviridae family and there have been 26 different serotypes of the bluetongue virus identified. Bluetongue is an insect-borne virus passed on by midges (Culicoides imicola) (Culicoides variipennis) and 48 other culicoides which are known vectors for the disease. Bluetongue has the most severe effect on sheep, with cattle showing little to no symptoms at first but acting as reservoirs for the local midges to pick up the disease and infect more vulnerable animals like sheep. Sheep have higher infection rates and a mortality rate as high as 30%.
Bluetongue first originated in South Africa and since 1999 there have been outbreaks of the disease in Europe. The last outbreak to occur in the UK was in 2007 in Suffolk.
BTV is spread by Culicoides midges which are the main vectors for the disease. The midges carry the virus in their saliva and they firstly get the disease from biting a viraemic animal that has BTV. The primary route of transmission is through the skin when a midge bites an animal to feed. Other routes of transmission can occur iatrogenically because of poor hygiene practice for example: using contaminated surgical equipment or using the same needle on different animals. Bluetongue is able to pass transplacentally to a calf or lamb during pregnancy.
March through to September is generally the time of year to expect BTV as this is the midge season. There are many factors that affect the spread of BTV such as: temperature, wind directions, distance from other.
Impact on animal health and welfare
Animals with BTV will experience discomfort and pain due to the swelling and haemorrhaging. BTV causes a loss in appetite, pain when walking and difficulty breathing which makes the animal suffer greatly. The quality of life will be very low as they cannot carry out natural functions without experiencing pain. Because of the excessive salivation and lacrimation the animal will become dehydrated which will affect it cognitively which means the animal could put itself in dangerous situations that it wouldn’t normally.
Due to the lack of appetite the animal could become emaciated which will add to the suffering it experiences and leave the animal vulnerable to dying of exposure. The animal’s immune system will be weakened making the animal even more vulnerable to opportunistic diseases like Pneumonia, making the animal more likely to succumb to the BTV and dying.
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Immune system response
In cattle their immune system will usually fight off the disease after a few weeks if the cow is in good health and does not have a compromised immune system. When a cow’s immune system fight off the disease they are then immune to future infections because they have antibodies specific to the virus.
Treatment and prevention of the disease
There is not a treatment for BTV because it is a virus and viruses mutate too quickly for a cure to be effective instead the best method is prevention. There are vaccines available for serotypes 1, 2, 3, 4, 8 and 9 which can be used to prevent the spread of the disease depending on what serotype is most likely to infect the animal. What vaccine to use is determined by DEFRA as there will be examinations conducted to determine what serotype the virus is and what vaccine to use.
The last UK outbreak in 2007 was identified to be the BTV- 8 serotype which means the appropriate vaccine would be Bovilis BTV8 which is an inactivated vaccine that contains dead BTV bodies or particles. Bovilis is subcutaneously injected into the animal to get an immune response without the virus replicating or harming the animal. This gives the animal resistance for the next time it is exposed to BTV but it must have booster shots annually to maintain immunity.
Farmers all around the world (especially sheep farmers) live in fear of BTV. BTV has devastating effects on the farming community because it can render an entire flock of sheep economically useless due to the fact that if they are the 70% that manage to survive the virus they will still remain ill for many days. Infected pregnant ewes most of the time will have an abortion, fertility in flocks will plummet and farmers are unable to transport any of their livestock.
This greatly effects the livelihood of farmers and farming communities because they are not able to make any money out of their livestock if they are suspected of BTV infection. Some Farming communities can become financially crippled due to the fact they cannot make any money from their animals. In 2007 the BTV outbreak of Western Europe is estimated to cost the livestock industry $1.4 Billion – £989 Million.
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This article was written by a student studying medicine in Europe.