Despite the similar names, the foot and mouth disease of farm animals is not the foot and mouth disease that attacks children. All the information in the next article
Dror Bar-Nir
From time to time, a quarantine is imposed on an agricultural area, where foot-and-mouth disease breaks out in cattle and sheep herds or other farm animals. Humans also sometimes get sick with the disease that has the same name. In this article we will get to know the diseases and their causes, and we will prove that there is no connection between the disease in animals and the disease in humans - even though they once thought otherwise! To differentiate between the diseases we will call the disease in humans, for whom it is not acceptable to use the term "telepathy", by the relatively new name "mouth and limb disease".
Foot and mouth disease in animals
About a month ago, on August 2, 2007, the first reports were received of an outbreak of foot-and-mouth disease on a farm in Great Britain, in the county of Surrey (Surrey, see map). Two and three days later it was reported about two more farms in the area where the disease broke out. The affected animals were destroyed, and apparently all the cattle, sheep and pigs within a 3 km radius of the infected farms will also be destroyed. A strict lockdown was introduced in a radius of 10-3 km. The unique strain of the virus, O1-BFS, which caused the current outbreak, "escaped" from a nearby research laboratory - Pirbright, although at the time of writing it is not clear how - whether through the wind, whether through a flood that flooded a contaminated area of the laboratory, or through a person or object that He "carried" the virus with him and reached the first farm, 4.5 km away from it. This strain caused the foot-and-mouth disease in Britain in 1967, and is used to make vaccines.
Foot and mouth disease virus
The virus that causes the disease, known as FMDV - Foot and Mouth Disease Virus, belongs to the genus Apthovirus (in which there is one more virus, Equine Rhinitis virus) from the group of picornaviruses. The viruses that cause rhinitis (rhinoviruses) and the virus that causes hepatitis A also belong to this group.
FMDV is a single-stranded RNA virus, built from an icosahedral box - 20 strands, 30-22 nm in diameter. Its genome is 7,200-8,400 nucleotides long.
There are seven main strains (serotypes) of the virus, for each of which a separate vaccine must be developed. Serotypes O, A and C have been defined in Europe. Three of the serotypes are limited in their distribution to South Africa. The Asian serotype is found in Asia and also in our region (in the Middle East, which, as we know, is also part of Asia).
The current outbreak occurred after about six years "free from the disease" in Britain. The previous outbreak of the disease, which occurred in 2001 after 20 "clean" years, was severe in scope and economically traumatic. Millions of animals were killed and burned, and financial damages amounting to 20 billion dollars were caused. At the end of the process, Britain was declared free of the virus, and dairy and pork products were allowed to be marketed from it.
The commonality is a cloven horseshoe
Foot-and-mouth disease in farm animals is a highly contagious viral disease that causes enormous economic damage. The virus can infect and cause disease in many different species of plant-eating mammals from 10 different families. What they all have in common is that they are cloven hoofed - their hoof is cloven hoofed - therefore they belong to the Cloven hoofed sub-series (or cloven hoofed - Artiodactyla).
The virus that causes the disease is transmitted by direct contact between animals or by contact with contaminated objects. People and cars, veterinary and agricultural equipment can also transmit the disease. When the amount of virus secreted from the respiratory tracts of the sick animals is large, and absorbed into small droplets, then a low wind, but stable over time, can transport the virus-carrying droplets tens of kilometers away. In such a situation, even the quarantine does not prevent infection.
From right to left: Coxsackie virus and foot-and-mouth disease virus - the virus can penetrate through the respiratory system and the digestive system
Infected animals excrete the virus 4-5 days before the first signs of the disease appear. Vaccinating the animals does not prevent them from being infected with the virus, but they are symptomless or develop the disease in a relatively mild manner, so they can serve as carriers and infect non-vaccinated animals. There have also been documented cases where artificial insemination with infected sperm started an outbreak.
After incubation for two days to two weeks, vesicular lesions appear in cows on the tongue, gums, cheeks, lips, nostrils, snout, between the parts of the hoof, teats and nipples. Increased secretion of sticky and foamy mucus is the first prominent clinical sign. The body temperature rises, and after about a week or two the blisters burst, wear away, become inflamed and then heal. The general physical condition of the animals deteriorates, due to the decrease in eating due to the pain in the mouth. Pregnant females abort. Milk yield decreases. Calves have damage to the heart muscle, which causes death. The cows look bad and hardly move.
The signs in sheep and goats are less pronounced, so the disease is usually diagnosed later.
The clinical diagnosis of the disease in any animal is not sufficient, and laboratory identification is required. This detection is carried out by using appropriate antibodies or the PCR technology. That is, specific identification of the viral RNA.
There is no treatment for foot and mouth disease
In countries where it is not customary to vaccinate against the virus (e.g. Great Britain), all sick animals and all those who have been in contact with the sick animals are destroyed, as well as all farm animals that may become ill within a radius of 3 km from the place of the outbreak of the disease.
Coxsackie virus
The viruses that cause foot and mouth disease also belong to the group of picorena viruses, but to the subgroup of intestinal viruses (enteroviruses). In most cases, the virus known as coxsackievirus A16 is responsible. Sometimes other intestinal viruses cause the disease.
In countries where it is customary to vaccinate (for example in Israel), mortality is relatively low and most animals recover on their own over time, although there is a noticeable decrease in milk production and their general physical condition. The recovering animals can be carriers of the virus for a long period of time and be a source of renewed infection if they are transferred to a new herd. The virus itself can remain active for about a month - in food and on various objects in the environment. The virus can also infect wild animals and exist in them (in a carrier state) for extended periods. This is the main factor preventing the extinction of the disease.
Humans can also be infected with the disease, as Valentini had already hypothesized in 1695, and as Hertwig reported in 1834. Hartwig tells of three veterinarians who proved this: they drank 250 ml of milk from infected cows (then there was no pasteurization yet), every day for four days in a row. The doctors did get sick, but this disease is very rare, and is described as a mild flu accompanied by a few blisters in the mouth, legs and hands. In humans, this is a mild and rare disease, and has nothing to do with the disease with a similar name that will be described later.
In the second part of the article: the disease in history, and does pasteurized milk help?»
