Foot and Mouth Disease (updated 7th March 2001)

About the disease

Foot and mouth disease (FMD) is an acute infectious viral disease causing fever, followed by the development of vesicles (blisters) – chiefly in the mouth and on the feet. It is probably more infectious than any other disease affecting animals and spreads rapidly if uncontrolled. Among farm stock, cattle, sheep, pigs, goats and deer are susceptible. Wild and domestic cloven-hooved animals and elephants, hedgehogs and rats are also susceptible.

Any practitioner or owner suspecting the presence of this highly infectious disease must inform their local Animal Health Office immediately.

Clinical signs

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.

Cattle

• Slobbering and smacking lips.
• Shivering.
• Tender and sore feet.
• Reduced milk yield.
• Sores and blisters on feet, mouth and teats
• Raised temperature
• Raised temperature

Pigs

• 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, tongue or teats.

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.

Sheep

See supporting information for images.

• Sudden, severe lameness. This is the commonest clinical sign associated with FMD in sheep. Increased heat in affected feet has also been reported, which may be a useful differentiating factor for shepherds if the visible lesions are small.
• Lies down frequently and is very unwilling to rise. This usually occurs on a flock basis basis but may also occur in small numbers of individuals.
• 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. Hair around the coronary band may have to be reflected to see the lesions. Vesicles may often also be seen on the bulbs of the heel.
• Sheep showing signs of lameness as a result of FMD may go sound after footbathing. It is therefore important that sheep in controlled areas are not footbathed in case this masks clinical signs associated with the onset of FMD.
• Blisters in the mouth are not always apparent but, when they do develop, form on the dental pad and sometimes the tongue. Instances of sheep standing smacking their lips have been recorded during the current outbreak. Blisters developing on teats have also been reported in some instances.
• The severity of the disease varies considerably with the breed of sheep, the virulence of the strain of virus and the environmental conditions. It should be remembered that clinical signs are often difficult to spot in sheep and looking at in contact cattle may be useful. Likewise, any goats on the same premises should also be examined.
• FMD does not usually cause mortality in adult sheep. However, as in the young of other susceptible species, the virus has a high affinity for the cardiac tissue of lambs, and may cause their death through heart failure. Cases of myocarditis have been observed in the current outbreak.
• Another significant feature of the current outbreak is the importance of sheep in disseminating the virus to other species, often as a result of animal purchase and movement. This may be compounded by delays in recognising, often apparently mild, clinical signs. Continued close vigilance by flock owners and vets is therefore of the utmost importance.
• Although most infections are detected on a flock basis, one incidence has been attributed to infection being identified in a single lamb. This should be borne in mind when examining cases of apparently individual clinical illness.

Signs and symptoms seen in the present outbreak

Differential Diagnoses of FMD:

 (from Kitching, R.P. & Mackay, D.K. (1995) Foot and Mouth Disease, State Veterinary Journal, Vol. 5, No. 3)

Spread

The spread of FMD virus can occur in a number of ways; by direct contact between infected and susceptible livestock, by contact with or feeding on infected meat products and milk, by infected semen or embryos, by the airborne route, by mechanical carriage on people, domesticated or wild animals, birds, vehicles and fomites. Sheep are more likely to be infected by direct contact, by the airborne route or through contact with contaminated people or carriage in contaminated vehicles. Sheep are infective for other susceptible animals by all routes both before lesions are apparent and in the early stages of lesion development. Virus production remains high until antibodies develop at approximately 4-5 days post infection. A proportion of recovered animals may become carriers although the proportion of virus recovered from these animals is much less than from acutely infected animals making this route of infection less important. Particular attention should be paid to stock bought in within the last 3 weeks.

For veterinary surgeons in infected areas, or in areas where animal movements are controlled, this raises the following important issues:

• Under no circumstances should sheep be transported to veterinary surgeries for treatments, assisted lambings etc., all procedures should be carried out on the farm.
• If you are a veterinary surgeon with a farm of your own or keep any livestock and you are called to what you suspect is a positive case of FMD, then do not return home until advised otherwise.
• Practices should consider the fact that members who visit suspect positive cases must not come into contact with people who work with livestock, eg. other vets, farm clients etc. This may mean that they could be restricted to LVI/FMD surveillance duties, small animal work or asked to take annual leave.

Disinfection

In the event of an outbreak, vets and people handling or coming into close contact with animals must disinfect themselves and their equipment before and after moving to other premises using those disinfectants approved by MAFF for inactivating the virus e.g. FAM.  An extensive list of MAFF approved disinfectants and their recommended working concentrations may be obtained from the MAFF website. Although very susceptible to acid and alkali pH, FMD virus can persist in the environment, particularly when associated with organic material.