There are four vesicular diseases of pigs which are difficult or impossible to differentiate clinically: FMD, swine vesicular disease (SVD), vesicular exanthema (VES), and vesicular stomatitis (VS). Of these, FMD is the most widespread and important with SVD being of secondary importance in some regions (e.g. the EU). The other two have very limited distribution and VES has disappeared.
Large unruptured vesicle on nose
Importance of FMD
FMD is the most important restraint to international trade in animals and animal products. Consequently, large sums of money have been invested in control and eradication programmes and also into research. As a result more is known about the FMD virus than about almost any other animal infection.
It generally produces severe disease in pigs and cattle.
FMD is so important because it is highly infectious, spreads rapidly throughout animal populations and over long distances on the wind and hence it is difficult and costly to control. Also because of its damaging and debilitating effect on cattle, a great deal of effort and tax-payers money has been spent keeping it out of large areas of the world. It would be highly irresponsible to let it back in.
If you live in an FMD-fringe area that is also free of swine vesicular disease (SVD) you should be aware of what early clinical signs would make you suspicious and what you should do if you suspected them in your herd. If you farm in an endemic area or a fringe area in which SVD is present then you should know a bit more, particularly about the clinical signs in pigs and vaccination regimes.
If you farm in an FMD-free country that takes sound precautions against its entry, the risk to your herd is negligible unless you farm in California where vesicular exanthema may pose a very small risk.
Among farm animals, pigs, cattle, sheep, goats and deer are susceptible. In addition, wild and domestic cloven hooved animals such as hedgehogs and rats are also susceptible as are elephants.
Early clinical signs
In cattle the early clinical signs are much more definitive or suggestive than in pigs. For example in a dairy herd several cows may suddenly show depressed milk yield, go off their feed, run a fever, have a dramatic drop in milk yield, and a little later start salivating profusely, the saliva running from their mouths (slavering). If you see such signs, jump into action, ring the vet. Veterinarians who have to deal with FMD say that if a farmer telephones to say that several cows are salivating profusely they think first “FMD?”.
If after cows have started salivating and smacking lips, vesicles are noticed on the lips, on the teats and around the coronets, the areas above hooves – your worst fears are probably true. The probability is that your pig herd has been infected too.
In pigs early signs are lameness a drop in food consumption and some pigs appear depressed and have fevers of about 40.5ºC,(105ºF). In piglets sudden death due to cardiac failure is common. What should make you strongly suspicious is the appearance a little later of vesicles up to 30mm. diameter, similar to those described above for cattle. They are most plentiful around the coronets but are less plentiful on the nose and lips although this is where you are likely to see them first. They often appear on the teats of recently farrowed sows. By then the sows and some of the other pigs may be dribbling saliva and chomping their jaws. If they are on bedding they may not appear lame but if they are on concrete they probably will be.
The early signs of swine vesicular disease (SVD) when it is severe, are indistinguishable from FMD so you should suspect it too.
If you farm near the coast of California where FMD and SVD are extremely unlikely, vesicular exanthema could be a possibility. If you farm in Georgia, the Carolinas or Central or South America and it is summer/autumn time perhaps you should think of vesicular stomatitis. The clinical signs of all four diseases are almost indistinguishable.
Within 24 hours many of the vesicles will have burst. On the lips and teats they may leave shallow erosions but on the coronets of the feet secondary infection and trauma may convert them into raw jagged-edged ulcers.
If the pigs are not killed some may lose their complete hooves (so-called “Thimbling”), sows may abort, as a result of fever, and in severe outbreaks some may die. Boars may go lame and stop serving sows, so there is an infertility side effect. There may also be an increase in mortality among suckled piglets. This is often the first sign.
In endemic areas where vaccination is carried out routinely the disease is not a serious economic problem in pig herds. In fringe areas, particularly where vaccination is not allowed (e.g. in the EU) it is a serious problem because the herd will almost certainly be slaughtered out and although compensation is likely to be paid, the farm cannot be restocked for at least six weeks, it is therefore out of production and in a negative cash flow for a long time.
Rapid accurate diagnosis is essential.
FMD cannot be distinguished from SVD on clinical grounds, or from VES in California, although SVD is often much milder. To differentiate these diseases and confirm the presumptive diagnosis, samples have to be sent to a laboratory capable of making a diagnosis.
There are not many of these. The main one is the World Reference Laboratory at Pirbright near London in England. There is also one on Plum Island off the coast of NY in the USA and one near Melbourne in Australia.
The samples sent are blood and pieces of the skin that overlay the blisters plus vesicular fluid if this is available. Once the samples have been received by the laboratory diagnosis is fairly rapid.
Tests called ELISAs are used for virus identification and if it is FMD they also indicate what serotype it is. The virus may also be grown in cell culture and the identification confirmed by other tests. A molecular genetic test called a PCR (polymerase chain reaction) may also be used to ‘fingerprint” the virus. The gene (genome or RNA) of FMD repeatedly undergoes minor changes as the virus spreads through animal populations so by identifying the precise sequence in the gene the laboratory staff are able to make an assumption where it may have come from by the most recent isolate with a similar sequence.
- There is no treatment. Animals should be destroyed.
Management control and prevention
Vaccination (where applicable)
- In endemic and high risk areas routine vaccination may be practised mainly to protect the breeding stock.
- Most FMD vaccines are produced in cell suspension cultures and inactivated by ethylenamine derivatives. An adjuvant is added to make them more potent. Oily adjuvants are used in swine.
- Vaccination in pigs is problematical. This is because protection is short-lived lasting only about six months. It is also partly because there are seven serotypes of FMD and protection against one leaves animals susceptible to the others. Vaccines must be multivalent (several serotypes) in most endemic regions. Since FMD is largely a winter disease, vaccination should be carried out in the autumn.
- Serotypes – There are 7 main serotypes: A, O, C, SAT 1, SAT 2, SAT 3 and Asia 1. There are also many strains within serotypes. Careful selection of the strains for incorporation in vaccines is essential to ensure they are effective.
- Countries in free and fringe areas apply strictly enforced national preventative measures against the introduction of infection. The main features of these measures are control over the importation of cloven-hoofed animals and of meat from such animals from counties in which FMD occurs.
- The virus does not survive rigor mortis but it can persist in bone marrow and lymph nodes of infected carcasses for several weeks.
- If the disease does enter a free or fringe area, a slaughter policy is implemented, all diseased and in-contact animals being slaughtered. A standstill on animal movement is imposed and tracings are carried out to check possible spread of the disease through previous contacts. Ring vaccination may be used around the affected region.
- If you farm in an FMD-risk region you should take strict precautions against the contamination of your herd. If you have a cattle or goat herd or a flock of sheep as well as a pig herd you should also adopt preventative measures for them and keep a wary eye for the appearance of typical clinical signs.
- Unfortunately, none of the measures described prevent the windborne spread of FMD. Infected pigs can produce huge quantities of infective virus as aerosols. They produce far more aerosol virus than cattle, goats or sheep. In dry weather when there are strong thermals the aerosol virus is rapidly inactivated so the wind does not carry infective aerosols very far. Strong winds, hills and objects such as high buildings and trees create turbulence and disperse the plume of airborne virus as they would a plume of smoke from a bonfire. In humid overcast weather with a steady light wind blowing over flat countryside infective virus may survive long enough to infect other herds up to 60km (36 miles) distant. Over water, given the same climatic conditions, infective virus has been shown to travel up to 300km (180 miles) so siting your pig herd on an island in a lake is not going to stop it. Windborne infection is impossible to guard against. Even if your pig herd is in closed buildings, the aerosol virus can get in through the ventilation system and you may carry it in from outside on your boots or clothes.
- If vaccination is permitted and the pig herd is in a high-risk area you should consider routine vaccination to reduce the susceptibility of your herd.
Basic biosecurity (also see “How to Protect your Farm” below )
Basic biosecurity measures are important in helping to minimise the spread of disease, and this becomes critical when there is a high risk of infection from a specific disease outbreak. These measures are important, unfortunately foot and mouth can spread on the wind and is therefore that much more difficult to keep out, however the following procedures could help to reduce the risk.
Below are a number of basic biosecurity measures and a checklist for clean down procedures.
- Standardise pig movements and keep to an absolute minimum.
- People and Vehicles are a potential source of potential contamination.
- Only allow essential visitors on to the farm and provide your own boots and clothing at the entrance.
- If visitors do not shower ensure hands are washed.
- Limit the movement of people between buildings as much as possible.
- Place foot dips at all entrances, service and feed delivery points. Use an approved disinfectant at the correct dilution.
- Review all cleaning and disinfection procedures. Only allow cleaned and disinfected vehicles to visit your farm.
- Adopt special precautions at loading ramps. Provide designated boots and overalls for use on the loading ramp only. Disinfect all loading areas before and after use. Check drainage is away from the farm.
- Clean all pens thoroughly. These should be disinfected and dried between pig groups.
Using the following protocol for cleaning swine facilities:
- Soften dirt and manure in heavily soiled areas using a low-pressure water spray. Leave to soak for a few hours.
- Once softened, use high-pressure sprays (750 psi to 2,000 psi preferred) to remove all the dirt and organic material.
- Start at the back of the pen or building and work toward the front.
- Spray the ceiling first, then the walls and finally the floor.
- Use sprayers and nozzles that allow you to wash hard-to-reach areas, including the undersides of troughs, feeders and flooring when possible.
- Once the pen is clean, rinse all surfaces to remove accumulated aerosol organic material.
- Spray on surfactant or emulsifying agent to remove any residual organic materials.
- Rinse all surfaces.
- Thoroughly Disinfect (NOTE: Disinfectants only work on clean surfaces).
- Disinfectants work best at temperatures above 65° F, but not above 110° F.
- Follow the manufacturer’s application instructions for the product.
- Apply the disinfectant with pressure (ideally through pressure washer) to force disinfectant into pores, cracks and crevices. Fog or aerosol application is a second alternative.
- Move from back to front and from top to bottom of the room.
- Allow the building time to dry.
- Leave rooms vacant for as long as the production system will allow before repopulating.
Read about How infectious agents are spread
Select the link, then select Chapter 2 – Understanding Disease and read the whole section onHow Infectious Agents are Spread (10 articles) – NOTE you will need to be a registered user to access this information. Registration is free, simply click the Register link on the login box and fill out the simple form.
Also Read about Biosecurity
Click the link and conduct a Search for “biosecurity”.
Links to other web pages
Below are some links to other web pages on Foot and Mouth Disease.
European Strategy for Emergency Vaccination against Foot and Mouth Disease
(PDF Document) Report of the Scientific Committee on Animal Health and Animal Welfare – Adopted 10 March 1999
European Biosecurity Procedures for FMD Outbreaks
A review of the different aspects of the European biosecurity procedures from The European Commission for the Control of Foot-and-Mouth Disease. The review includes the following aspects: personal, engineering control, operation and safety procedure inside of the high security area, waste management and emergency.
OFFICE INTERNATIONAL DES EPIZOOTIES – Foot and Mouth Disease
A thorough more technical description of the disease, but similar to above.
OIE – Experts and Reference Laboratories for FMD
List of Experts and Reference Laboratories for FMD
The following is information provided from MAFF
How to protect your farm
This leaflet provides information on preventative measures on how to protect your farm against foot and mouth disease. Further measures apply if your farm is in a declared infected area.
The following measures should be followed:
- You should ensure you maintain the highest standards of hygiene for all movements on and off your farm.
- Have only one combined entrance and exit. Display the name of the farm and the telephone number on the gate. Keep the gate locked.
- Provide a means of contact between farm entrance and house for essential callers, e.g. a bell or a gong. Supply a tub of disinfectant, a brush for scrubbing footwear and a spray pump. Keep the disinfectant solution clean and renew it daily.
- All vehicles entering and leaving the premises should have their wheels sprayed with approved disinfectant.
- Stop all non-essential vehicles and visitors from entering the farm and arrange whenever possible for collection and delivery of supplies to take place at farm boundary.
- Keep a record of all deliveries. In the event of disease being confirmed this may help in epidemiological investigations.
- Where possible, house all the animals or keep them away from the perimeter of your farm.
- Ensure you complete all records of stock movements as required by existing legislation.
- Each farm must be treated as a separate unit. Make separate arrangements for labour, management and feeding.
- Keep dogs, cats and poultry under control.
- Make every effort to destroy rats and other vermin. They may spread the disease.
- Keep your stock away from household waste, bones or swill.
- Limit contact with other peoples livestock and with other keepers of livestock.
- Should you have any contact with them, before you go near your own animals, disinfect your footwear, change your clothes and wash with hot water and soap, including your hair. Any item or object that may have had contact with disease must also be disinfected.
- Healthcare officials are aware of precautions necessary and you must not delay seeking medical assistance if needed.
Disenfection and approved disenfectants
A dirty surface must be cleaned before it can be satisfactorily disinfected. The dirt may make the disinfectant useless. It is therefore most important that anything which must be disinfected is first soaked with an approved disinfectant, then thoroughly washed and cleaned and finally washed down with an approved disinfectant.
You must use an APPROVED DISINFECTANT
A list of those approved for use against foot-and-mouth disease and the dilutions at which they must be used are available on the MAFF website.
An overview of the disease from MAFF
- Controlling the disease depends on the prompt reporting of all suspected cases. Delay allows the disease to get a start that is very difficult to overtake.
- Stock owners should therefore be constantly on the watch for any suspicious signs among their animals, even when the country is free from outbreaks of the disease.
- Special care is necessary with sheep and pigs where lameness is often the only sign. It must be remembered that animals can go lame for various reasons, of which foot and mouth disease could be one.
- Sheep lame apparently for another reason (for example foot rot) may also be affected by foot and mouth.
- Owners of livestock should always be suspicious when one or more animals become lame suddenly and the lameness becomes widespread in other animals on the premises.
- The owner of a suspected animal or carcase must by law notify the fact to the MAFF Divisional Veterinary Manager or to the police. 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 signs, and call in a veterinary surgeon as early as possible; they should never ask another stock-owner to look at the suspected animal.
- If the suspicion is strong it is better to notify as above without seeking other advice. If notification is via the police, they will at once get in touch with the Ministry’s Divisional Veterinary Manager for the area who will immediately arrange, without cost to the owner, for the examination of the suspected animal. The Ministry’s veterinary staff are available at all times, and if you suspect disease you are required to notify this suspicion immediately.
The interval between exposure to infection and the appearance of symptoms varies between twenty-four hours and ten days, or even longer. The average time is three to six days.
- Slobbering and smacking lips.
- Tender and sore feet.
- Reduced milk yield.
- Sores and blisters on feet.
- Raised temperature.
- Sudden, severe lameness.
- Lies down frequently and is very unwilling to rise.
- When made to rise stands in a half-crouching position, with hind legs brought well forward, reluctant to move.
- Blisters may be found on the hoof where the horn joins the skin which may extend all round the coronet and in the cleft of the foot. When they burst the horn is separated from the tissues underneath, and hair round the hoof may appear damp.
- Blisters in the mouth are not always apparent but, when they do develop, form on the dental pad and sometimes the tongue.
- Sudden lameness.
- Prefers to lie down.
- When made to move squeals loudly and hobbles painfully.
- Blisters form on the upper edge of the hoof, where the skin and horn meet, and on the heels and in the cleft.
- May extend right round the top of the hoof with the result that the horn becomes separated.
- Blisters may develop on the snout or on the tongue.
- It is important to remember that Swine Vesicular Disease has identical symptoms to foot-and-mouth disease. Therefore anyone who sees blisters in pigs must report the sighting as suspected foot-and-mouth disease until laboratory tests prove otherwise.
- Foot-and-mouth disease is extremely infectious. A very small quantity of the virus is capable of infecting an animal, and the disease could spread throughout the country if no attempt were made to control it.
- Airborne spread of the virus can take place and under favourable climatic conditions the disease may be spread considerable distances by this route.
- The virus is present in great quantity in the fluid from the blisters, and it can also occur in the saliva, exhaled air, milk and dung. Any of these can be a source of infection to other stock. At the height of the disease, virus is present in the blood and all parts of the body.
- Heat, sunlight and disinfectants will destroy the virus, whereas cold and darkness tend to keep it alive. Under favourable conditions it can survive for long periods.
- Animals pick up the virus either by direct or indirect (airborne) contact with an infected animal, or by contact with foodstuffs or other things which have been contaminated by such an animal, or by eating or coming into contact with some part of an infected carcase.
- Cattle trucks, lorries, market places, and loading ramps – where infected animals may have been present – are sources of infection until disinfected. Roads may also become contaminated, and virus may be picked up and carried on the wheels of passing vehicles such as delivery lorries, milk tankers etc.
- Any person who has attended diseased animals can spread the disease; and dogs, cats, poultry, wild game and vermin may also carry infected material.
- Previous outbreaks occurred in the eastern and south-eastern counties when the disease had been prevalent on the continent of Europe. In these cases infection was apparently brought to this country by airborne carriage of the virus under favourable climatic conditions. Imported meat, if found to be infected with the virus, may also be a source of infection.
- All affected stock and any others which have been exposed to a risk of infection such that it is reasonably certain that they would develop the disease if left alive, are slaughtered. Full compensation is paid for animals slaughtered.
- MAFF supervise disinfection of the infected premises takes place, and no fresh stock can introduced without MAFF approval. In addition to this, the SVS imposes restrictions on the movement of animals within and into an infected area which extends for a radius of not less than 10 kilometres around the infected place, and no movement of animals into or out of this area is permitted.