Foot and Mouth Diseasefaq’s

Foot and Mouth Diseasefaq’s

What is Foot and Mouth Disease (FMD)?

FMD is a highly contagious viral disease of cloven-hooved animals with significant economic impact, in cattle and swine as well as sheep and goats. In wildlife, all species of deer and antelope are susceptible to FMD with some of them such as the African buffalo, acting as carriers of the virus without showing clinical symptoms. In a susceptible non-vaccinated population, morbidity (the number of animals that will get the disease) could be as high as 100%. The disease is rarely fatal in adult animals but mortality can be high in young animals.

What causes Foot and Mouth Disease?

The virus which causes FMD is an aphthovirus of the family Picornaviridae. There are seven immunologically distinct types of FMD viruses, A, O, C, SAT1, SAT2, SAT3, and Asia1. There can be a variety of genotypes within each of these requiring a specific vaccine effective against the circulating viral field strain in the event of an outbreak, to ensure protection.

What are the clinical signs of FMD?

The severity of clinical signs will depend on the strain of virus, the age of the animals and the species and breed affected. The typical clinical sign is the occurrence of blisters (or vesicles) on the muzzle, tongue, lips, mouth, between the toes, above the hooves, teats and potential pressure points on the skin. Ruptured blisters in the inter-digital space can result in extreme lameness and reluctance to move or eat due to vesicles in the mouth. Secondary bacterial infection of open blisters can also occur. Other symptoms often seen are fever, depression, hypersalivation, loss of appetite and weight, and drop in milk production. The disease is rarely fatal in adult animals however, the disease can leave them weakened and debilitated and result in severe production losses. The health of young calves, lambs, kids, and piglets may be compromised by lack of milk from infected dams. When young animals are infected with the FMD virus, mortality can be high.

Where is the disease found?

FMD is endemic in several parts of Asia, a large part of Africa and the Middle East. In Latin America, the majority of countries applied zoning and are recognized free of FMD with or without vaccination, and the disease remains endemic in only a few countries or regions within certain countries. Australia, New Zealand and Indonesia, Central and North America and Western Europe are currently free of FMD. India is endemic to FMD.

How is FMD transmitted and spread?

FMD virus is found in all excretions and secretions from an infected animal. It can spread easily and rapidly by means of the following:

  • Introduction of new animals carrying the virus (saliva, milk, semen, etc.) to a herd
  • Use of contaminated pens, buildings or vehicles to house and transport susceptible animals
  • Use of contaminated materials such as hay, feed, water, milk or biologics
  • Wearing contaminated clothing or footwear, or using contaminated equipment
  • Feeding susceptible animals with animal products, raw or improperly cooked food, infected with the virus
  • Dissemination of virus by aerosols transported from an infected property via air currents
  • Accidental release of virus from a laboratory
  • Use of vaccines containing live virus due to production errors in manufacture.
What is the public health risk associated with this disease?

FMD is not readily transmissible to humans and is not a public health risk. Only a few benign cases of human infections have been documented, none requiring hospitalisation. These infections resulted from direct contact with infected animals. The infection in humans can be characterised by mild symptoms notably blisters on the hands and in the mouth.

Why is FMD such a serious problem?

In infected animals, the FMD blisters usually burst after a few days and the resultant sores generally clear up over a few weeks. During this time, animals have considerable difficulty in eating and walking. FMD therefore causes much suffering and loss in production. However, FMD is not usually fatal in healthy adult animals.

If an FMD outbreak were to occur, our major export markets for meat, dairy product and possibly even wool would be closed to us immediately. This could devastate our livestock industries, our processing industries and rural communities. As the 2001 FMD outbreak in the UK demonstrated, an outbreak of FMD here would also have a significant effect on our tourism industry. The Productivity Commission has estimated that a major outbreak of FMD could cost the Australian economy between $8 billion and $13 billion. It is also estimated that the rural communities most directly affected could take up to ten years to recover from the effects of a FMD outbreak.

If an outbreak of FMD were to occur on a property nearby, what immediate steps could people take to help contain the spread of the disease?

1. Move all livestock away from the boundaries of your property.

As soon as they are told of an FMD outbreak in their region, the first thing livestock owners should do is move their livestock away from their boundaries – ideally into a paddock with secure fencing in the middle of their property. If all livestock owners do this, it will create a network of buffer zones. This simple action is probably the most important thing that livestock owners can do to help contain the spread of the disease – providing, of course, it is done quickly and that there is a clean muster of all livestock from those boundary paddocks. If you have livestock on a property that is separate from your home block, the stock standstill will prevent you bringing your animals home. So you should move your animals away from the boundaries on each of your separate properties. In these first few hours of an FMD outbreak, we won’t know whether the disease has spread beyond the infected property and therefore we won’t yet have a clear picture of which other properties are at some risk of already having the disease. So, as a precaution, you should change your clothes and hose the mud off your vehicle as you leave each property. As an added precaution, you should also use a suitable disinfectant (one that is iodine-based is generally effective) on your footwear and vehicle tyres. You should reduce the number of times you visit each of the separate properties as much as possible.

2. Isolate any recent livestock arrivals and contact the concerned Veterinary/Animal Health authorities.

If you have bought any livestock through sale yards in the last three weeks and if any of these animals have come from the FMD infected property or any other property nearby, your property will be a “trace”. This means the concerned Vet shall help arrange for your animals to be checked for any signs of FMD. It will help our vets do their job more quickly if you can separate these new animals from the rest beforehand and have them handy to your stockyards for inspection.

If you have bought any livestock privately or if you have had any animals arrive on your property in the last three weeks for any other reason take the help of Vet. If the new animals have come from anywhere near the infected property, you should contact the concerned authorities and arrange for these animals to be inspected for any sign of the disease.

3. Make sure the Vet/Authorities knows about any pigs nearby.

With most species, it requires close contact between an infected animal and an uninfected animal for FMD to spread. That is why creating buffer zones around each property could be the most effective action we can take in the early hours of an outbreak. However, pigs present a much greater problem, in terms of containing the spread of FMD.

FMD can be spread over long distances simply by infected pig breathing. An infected pig’s breath contains about 1,000 times the concentration of FMD virus particles when compared with the breath of an infected cow or sheep. In other words, if a pig has FMD, it can spread the disease by viral plume even if the livestock owners in the region have created these livestock-free buffer zones around their properties. Because infected pigs are by far the most efficient spreaders of FMD. However, it is inevitable that some people who have a “backyard” pig or two should also be accounted, so it is important that these pig owners contact the authorities as soon as possible if an FMD outbreak were to occur.

4. Get the latest information on the outbreak and proper advice on what you can do to help contain the spread of the disease.

An outbreak of a highly contagious animal disease such as FMD is likely to cause great anxiety in the community – especially among livestock owners near the infected property or properties.

If you are a livestock owner or a resident of the region where an FMD outbreak has occurred, what you do – especially in the first few days of an outbreak – could have a major influence on how far the disease spreads. So, please make sure that, when you get advice on what to do, it is good advice based on sound science and the collective experiences of the vets and others who have actually worked in combating FMD outbreaks.

Please understand that our knowledge about the nature and spread of a particular FMD outbreak is likely to change rapidly in the first few days. If, for example, the owner of the infected livestock has sold animals through a saleyard in the preceding three weeks, this would create many “traces” that one have to follow up – in most cases by actually inspecting the animals on-farm. There is, therefore, some chance that further outbreaks may be diagnosed elsewhere around the region. If this happens, information about the restrictions on livestock movements and advice on human movements may change rapidly during the first few days of an outbreak.

5. Abide by all movement restrictions. (Please note that the following information about movement restrictions is a guide only)

  • A complete ban on the movement of all livestock. Any livestock in transit intended to be brought into the farm of village when the movement restrictions are applied would either have to be returned to the property they came from or keep in isolation for 3-4 weeks. The initial ban on livestock movements is likely to include sheep, goat and some times dogs.
  • People living on an infected property would be encouraged to remain on their property unless they have urgent business off the property, in which case they will have to undergo decontamination like washing soda bath each time they leave the infected property.
  • Farm workers and contractors (ie shearers, agricultural contractors) would be discouraged from going onto farms.
  • The farm where the animals are housed should be disinfected using 4% washing soda or 1% citric acid
  • Foot dip should be practiced at the entrance of the farm
  • All the vehicles coming in and going out should be disinfected using washing soda
  • Follow ring vaccination in surrounding farms which are more than 1KM away and in case of villages, all the surrounding villages if they are spread apart by 1km minimum from the infected village.
How to control FMD? Does an FMD vaccine exist and does it work?

Inactivated virus vaccines (where the virus has been subjected to a chemical treatment so it cannot reproduce in vaccinated animals) are highly recommended. Live virus FMD vaccines are not acceptable due to the danger of reversion to virulence and resultant difficulty in differentiating infected from vaccinated animals. The vaccines are formulated for the specific virus strains present in the country and the animal species it is to be used in. Many FMD vaccines are designed to provide cover against several different virus strains likely to be encountered in a given field situation, but no vaccine protects against all the virus strains circulating in the world. The current trend in vaccination strategies is to use highly purified vaccines which allow easy identification of naturally infected animals from vaccinated animals. Vaccination against FMD is used in many countries or zones that are now recognized as free from foot and mouth disease with vaccination.

What is the schedule to be followed for FMD vaccination?

The primary age of vaccination in cattle will be at 4 months age followed by a booster dose 1 month later and revaccination at every 6-12 months depending on local regulations and recommendations.

How safe are FMD vaccines?

In manufacturing FMD vaccines, virulent FMD virus will be used during the process. A key step in the process is the inactivation of the FMD virus. The commercial vaccine must be free from residual live virus. These vaccines will be controlled to ensure the safety of their use. Vaccines will also be field tested to demonstrate safety and efficacy under field conditions and to detect unexpected reactions. These tests are carried out before the vaccine is authorized for general use.

What are the factors influencing vaccination success/failure?
  • There should be high vaccination coverage (> 90%) in all susceptible animals for getting better herd immunity
  • Strict zoosanitory measures should be in place in the farm.
  • Cause of FMD outbreak in vaccinated area could be due to heavy virus load prevailing in the surrounding areas due to the infected animals. The other main source of infection could be the unrestricted movement of men and machinery between the affected and unaffected farms.
  • The non vaccinated animals just adjacent to farm could also be the source of virus (for infecting the farm animals)
  • Even within a vaccinated herd, the aerosol production of virus from a single infected animal can overcome the immunity of others in the herd resulting in a further increase in the level of challenge and the appearance of clinical disease. The several features involved in pathogenesis of FMD that render it very difficult disease against which to produce an effective and long lasting immunity.
  • The short incubation period of 48 h makes it very difficult to produce post exposure antibody response in primed animals (post vaccinal immunity).
  • Immunity to FMD depends on maintenance of critical antibody levels at the time of exposure and even though there is protective titre, presence of heavy challenge in the form of heavily infected animal will overcome the immunity of the herd.
  • The presence of large quantities of virus particles in the form of aerosol could result in penetration of lungs and subsequent viremia which could swamp normal protective levels of the antibody.
  • When a high incidence of infection present, there is a high probability that nonimmune animals to be exposed, sooner or later, to the virus and become infected.
  • Once a nonimmune animal has introduced the disease to a farm, there is a strong possibility that the immunity of vaccinated cattle which are in close contact will be swamped.
  • The animal to animal variation in the serum neutralizing antibody response following primary vaccination is very large in cattle of even same age and breed.
  • Nutritional and intercurrent disease will play a major role in influencing the magnitude of immune response after vaccination.
  • Parasitism and number of protozoan diseases will cause immunosupression in cattle. Do not administer immunosupressing agents like corticosteroids (like prednisolone, cortisol and other steroidal anti-inflammatory drugs) 2-3 weeks prior to and after vaccination. They may suppress the immune system with resultant poor immune response after vaccination. Always ensure the health status of the animal before vaccination. Perform deworming at least 1-2 weeks before vaccination and continue the same periodically.
What is the storage temperature of vaccine?

The vaccine must be stored between 2-80C

OIE recommend vaccine strains based up on vaccine matching studies and they vary from time to time. Currently OIE recommends O1 Manisa, A22 Iraq and Asia1 Shamir as the global strains. However, the local isolates are crucial in inducing protective immunity.

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