Strategies to help producers and dairy herds through an FMD outbreak

Estimated reading time: 6 minutes

Much has been said and written about preventing foot-and-mouth disease (FMD) and its impact on dairy herds and the broader value chain. However, far less guidance is available on managing an outbreak once FMD has entered your dairy herd.

The incubation period of the FMD virus ranges from four to 14 days. By the time clinical signs become apparent, the virus has often been circulating within the herd for at least four days or even longer. By this stage, it is safest to assume that all animals have been exposed, including those on satellite units such as heifer or dry-cow farms. Any movement of animals between farms should cease immediately.

Recognising the signs of FMD

Some of the earliest indicators of FMD are a drop in herd activity, reduced rumination, and a rise in somatic cell counts (SCCs) in milk. Initially, only a few cows salivate excessively, but within three days, the number of affected animals will increase dramatically. Painful mouth lesions can cause cows to reduce their feed intake or stop eating altogether.

Mastitis cases begin to emerge and increase over the next two to three weeks. Lesions develop on the teats and udders, and in severe cases, teats may even detach; holes may also form in the udder. Cows that refuse to be milked develop extremely high SCCs.

Lameness follows as lesions develop between the claws and around the hooves. Cracks may form and, in severe cases, claws or hooves may separate completely. These animals frequently refuse to walk to grazing, water or the milking parlour.

Animals with mild disease generally recover within two weeks. Severely affected cows, however, seldom regain their previous production levels, and many are eventually culled on welfare grounds.

Preparing before infection occurs

High-producing cows are generally more susceptible to FMD because of the stress associated with high milk production. Maintaining a balanced diet that supplies adequate vitamins and minerals is therefore essential to support immune function.

Teat and teat-end damage caused by FMD predisposes cows to secondary bacterial mastitis. A big part of the treatment regimen is therefore focussed on preventing bacteria from infecting animals. The herd’s vaccination programme should be up to date, particularly against organisms such as Staphylococcus aureus, coagulase-negative staphylococci (CNS) and Escherichia coli.

Although FMD vaccination does not guarantee protection against infection, it significantly reduces the severity of clinical signs and production losses. Most vaccines provide protective immunity to approximately 80% of a herd. In a herd of 1 000 cows, around 200 animals may therefore remain susceptible. This means infection is still possible if neighbouring farms experience an outbreak.

When FMD breaks out on a neighbour’s farm, consider the following measures:

• Administer a multivitamin and mineral supplement to all your animals.
• Some producers use Inforce 3®, an intranasal vaccine registered for respiratory disease prevention. Although it is not registered for FMD, the release of interferon into the nasal passages provides a natural antiviral effect for around ten to 14 days. However, it must not be administered once FMD is already circulating within the herd, as nose-to-nose transmission is already occurring.
• Consider slaughtering poor-producing cows, animals already identified for culling, and cows with chronic mastitis or lameness before infection reaches the herd. Once FMD is confirmed, quarantine restrictions will prevent animals from being sent to an abattoir for at least two weeks after day zero.
• At the first indication of FMD, dry off cows that are within two months of their planned dry-off date. This can reduce the severity of the subsequent mastitis storm.

Treatment of FMD

Because FMD is caused by a virus, there is no specific treatment. However, supportive care can help alleviate clinical signs, and prevent and manage secondary bacterial infections.

The following measures are recommended:

• Separate all animals exhibiting signs of disease from healthy animals.
• Start treating symptomatic animals immediately using anti-inflammatory medication. Always observe the prescribed milk withdrawal periods for any agents administered. Antibiotics should only be used when there is evidence of a secondary bacterial infection, such as open sores on the teats or feet.
• Mastitis may be treated with mastitis medication, although results are often limited because most cases are caused by the virus rather than a bacterial infection.
• Veterinarians use a local anaesthetic spray on affected teats before milking to relieve pain during the process. After milking, use an antiseptic or antibiotic ointment to treat teats with lesions.
• Treat sore feet with a copper sulphate footbath or an antibiotic spray. Lame cows that have difficulty walking should be housed as close as possible to the milking parlour.
• Cattle with painful mouth lesions may struggle to chew pellets or graze. Mixing meal or pellets with water and molasses to create a thick slurry can make feeding easier. Silage should also be provided to meet the animals’ fibre requirements.
• Milk healthy cows first, followed by cows showing mild clinical signs that are not receiving treatment. Milk from these animals is marketable, as FMD does not pose a risk to human health. Next, milk cows receiving treatment, followed by those with severe mastitis. Milk from treated cows and cows with severe mastitis should be discarded. Severely lame cows should be milked last, as they take longer to enter the parlour and can delay the milking process.

As soon as the first signs of FMD are detected in the herd, all calves should be separated from their mothers and isolated. Large quantities of the virus are shed in milk and can infect calves. Fresh milk should therefore not be fed to calves unless it has been boiled or pasteurised. A milk replacer is preferable. Reintroduce fresh milk only after at least two weeks have passed since the last affected cows showed clinical signs of disease.

The psychological impact

FMD can have a profound psychological impact on producers, their families, and farm employees. In addition to the financial implications, producers and their employees may face the emotional burden of monitoring the herd daily and making difficult decisions about culling or killing affected animals. Where possible, these responsibilities should be shared among several individuals to reduce the emotional strain on any one person.

Many people are also unprepared for the isolation that accompanies quarantine restrictions. Once a farm is placed under quarantine, no one – not even service providers – is permitted to enter your property. Even your veterinarian may be reluctant to provide on-site assistance when you need him or her most. Long working hours, combined with the ongoing demands of milking and treating animals, result in sleep deprivation and fatigue. This can make even routine decision-making more difficult.

The cumulative effect of these challenges can lead to anxiety and depression. For this reason, it is essential to establish a strong support network. Do not attempt to cope alone. Reach out to producer organisations, church groups, family, and friends. If neighbouring farms are affected by FMD, maintain regular contact with those producers to ensure they are not facing the crisis in isolation. – Dr Mark Chimes, veterinary advisor, Milk SA

Send an email to mark@milksa.co.za for more information.