Epidemiologists working for the government have estimated around 100 kilograms of illegally smuggled meat infected with Foot-and-Mouth Disease (FMD) enters Britain every year.
The finger of blame points ominously at this smuggled infected meat as the prime suspect for the catastrophic 2001 FMD outbreak. Heartbreakingly this outbreak led to the slaughter of over six million animals in Britain, and cost an estimated £8 billion.
In 2007 two outbreaks of FMD were confirmed in Britain, believed to have originated from a broken waste pipe leaking contaminated materials from the Pirbright Laboratory in Surrey, although the outbreaks were nowhere on the scale of the 2001 outbreak.
These outbreaks, and the fact this smuggling of infected meat continues suggests that another outbreak could be on the cards for the already beleaguered British countryside. But what is FMD? And why does a disease that is seldom fatal to animals and has been shown to seldom affect humans have such a devastating effect?
What is FMD?
FMD is a highly infectious disease affecting cloven hoofed animals in particular cattle, pigs, Sheep, Deer and Goats. Over 70 species of animals, species such as the Camelids (e.g. camels, llamas, alpacas) and Elephants can also be affected. This wide species host range makes control and containment of this disease very difficult.
The first written account of FMD is thought to have occurred in 1514, when the Italian scientist Hieronymus Fracastorius described a disease seen in cattle. It took almost another 400 years before; in 1897 the Prussian scientists Loeffler and Frosch demonstrated that a disease of animals was caused by a filterable agent, namely a virus, ushering in the era of virology. FMD is therefore considered the first animal disease identified as a virus.
Viruses are generally simple structures, consisting of nucleic acid (genetic materials) surrounded by a protective protein envelope or coat. They fall into two groups depending on their nucleic acid type: either DNA or RNA viruses. They are grouped in the same way as other organisms into different families due to their shape and structure. The FMD virus is a member of the family Picornaviridae meaning ‘small RNA viruses’ and there are seven known serotypes (variants) (O, A, C, SAT1, SAT2, SAT3 and Asia1) all with multiple subtypes of their own. The 2001 outbreak was caused by the highly virulent serotype O.
Viruses are essentially intracellular parasites, meaning they invade a ‘host’ cell and take over the machinery of the cell making it produce more virus particles.
What are the symptoms of FMD?
The interval between exposure to the disease and the appearance of symptoms varies between twenty four hours and ten days. Although different species react in different ways to the virus essentially the symptoms are characterised by lameness and fever followed by the development of vesicles (blisters), mainly in and around the mouth and feet.
Although FMD does not result in high mortality in adult animals the disease has many debilitating effects. These include a decrease in milk production and weight loss meaning a loss in production for a considerable amount of time. Mortality can however be high in younger animals where the disease can cause fatal myocardial (heart) lesions.
Animals can also become carriers, meaning they do not show symptoms but can transmit the disease to others. Cattle have been known to harbour the virus for as long as 3 years. In addition the condition can be difficult to distinguish from other diseases. In pigs, for example, swine vesicular disease cause symptoms so similar to FMD that diagnosis can be difficult. These factors make containment of the disease more difficult. Positive identification of FMD can be made by testing for antibodies for the disease in the blood of the animal in the laboratory.
How is the disease spread?
FMD is considered to be one of the most contagious animal diseases. Outbreaks have occurred in every livestock containing region of the world with the exception of New Zealand. FMD is endemic in parts of Asia, South America, Africa and the Middle East, with sporadic outbreaks occurring in other areas.
The disease can be transmitted from one animal to another in the fluid from the diseases blisters themselves, saliva, mucus, milk or faeces. It can also be spread by aerosols excreted from the lungs of infected animals. FMD can also be carried long distances on the wind, meaning control measures are difficult and costly. FMD can adhere and spread on many substances, wool, hair, straw, footwear, clothing, farming equipment or vehicle tyres, all helping to spread the disease further and act as a mechanism of infection. The infected animals secrete numerous virus particles before symptoms appear meaning containment of the disease is even harder.
Treatment and Control
There is, as yet, no known cure for FMD. The infection usually runs its course in a matter of weeks and the animals generally recover naturally. In the UK due to the welfare and economic problems associated with the after affects of the disease slaughter remains the basic control policy.
Vaccines for FMD do exist and in some countries are used. In fact, Loeffler and Frosch the same first discovers of the FMD virus agent were also the first to use an inactivated vaccine, in this case heat treated FMD virus material, to immunise animals against the disease. Despite this since 1992 though the European Union (EU) has banned the use of routine vaccination, this allows the EU states to have the highest FMD trade status ‘countries free from foot and mouth disease without vaccination’ making international trade easier.
Immunity offered by vaccination is also only temporary at present, lasting only months in some cases, as the virus mutates so rapidly. The different serotypes of the disease also require different vaccines, meaning that cross protection is not yet possible which can be problematic.
FMD is considered a notifiable disease in the UK (contact www.Defra.gov.uk for more information), meaning that anyone who has an animal suspected of having the disease must, as quickly as possible contact the authorities. The Animal Health Act 1981 provides the powers for the control of FMD in the UK. This Act allows the certain measures to help contain or control the transmission of the disease:
Power of entry to premises for the purpose of veterinary enquiry;
Slaughter of affected, suspected or exposed animals;
Seizure and control of affected carcasses;
Movement controls on people, animals and vehicles;
Cleansing and disinfection of premises, vehicles and people.
These measures essentially mean when the disease is reported and confined, notices are posted and movement of humans and animals controlled, restricted or banned. Disinfectant is used to ensure FMD is transmitted on vectors such as footwear, clothing or vehicles leaving the infected area. All animals with the disease, come into contact with or suspected of having the disease will be destroyed. So potent is the disease that even the disposal of the carcasses is controlled. In the future Defra have stated that the use of commercial incineration, rendering of licensed commercial landfill are the only acceptable methods.
Threat to Humans
FMD is considered a zoonosis, a disease transmissible to humans, but it crosses the species barrier with difficulty and human incidences are rare. The last recorded human case in Britain occurred in 1966, but the disease in people is only a short lived mild flu like illness.
The highly contagious nature of FMD makes an outbreak quick to spread if unchecked. This coupled with the long term debilitating symptoms of the disease make the impact to the economic ramifications of an outbreak easy to understand. Weight loss and reduction in milk production can be seen to be major problems for an industry already blighted by numerous others issues, for example from cheap foreign imports and by the cost of bearing other diseases such as Bovine Spongiform Encephalopathy (BSE).
The 2001 outbreak of FMD cost the British economy an estimated £8 billion. This coupled with the movement restrictions on British livestock impacting on international trade, and tourism in affected areas, not to mention damaging the reputation of British meat, impacting on sales long after the outbreak had been quashed.
It has been estimated that a large FMD outbreak in either the United States or northern Europe could cost over $100 million. Although economically perhaps it’s most devastating effects are the severe international trade restrictions imposed by the disease. In fact FMD has been recognised as the most important constraint to international trade in animal products by the World Organisation for Animal Health (OIE). This is due to the fact countries which are free of FMD ban importation of animal products from infected countries.
FMD was the first animal virus identified, but still in the 21st century it still threatens. FMD is not a threat because it causes wide spread death, in fact as discussed, it is infrequently fatal to adult animals and rarely infectious to humans, but it remains an international cause for concern due its high rate of infectivity and large host range which in turn means large costs to the farming industry and general economy through the loss of production, stock and harm to international trade through movement restrictions and bans. These financial problems to an infected country have drastic and long lasting effects on the economy. Until advances in science mean more efficient vaccines and antiviral agents against FMD are available, the effective control and limitations on the spread of FMD is, at present, the only suitable countermeasure to battle this long lasting and infectious old foe.