Scrapie, or staple the sheep , the scratching of sheep .
A slowly developing disease of small cattle, most often affecting sheep and goats, manifested by signs of central nervous system damage and exhaustion. [one]
Scrapie was first described in 1732 [2] , the most common disease in Europe , South Africa , India , Canada , USA . The disease is contagious, the incubation period averages from 1 to 4 years, but in some cases it can last up to 7 years. As a rule, several weeks pass from the manifestation of the first symptoms to the death of animals. During experimental infection of experimental animals, it was found that the minimum incubation period can be from six months to nine months.
The disease is ubiquitous, except in Australia and New Zealand .
History of the disease
Scrapie as a neurological disease of sheep was first described in England, France and Germany in 1732. Since wool was an important commercial product in England in the 18th century, the production of which was of significant importance for the country's economy, the detection of scrapie was recognized as a national threat, and in 1755 the government and parliament took a decision on this problem, and it took several years to develop measures to combat the spread of scrapie. The exact place and time of the first occurrence of scrapie has not been established, but there are suggestions that it was found in Europe before the 18th century.
In the 18th and early 19th centuries, the disease spread rapidly as a result of inbreeding, which was widely practiced to improve the quality of the coat. After the cessation of this practice, the wave of scrapie spread began to decline, but it was not possible to completely cope with the disease.
In the United States, the first case of scrapie was recorded in 1947 in a herd living in Michigan. As it turned out later, the owner of this herd imported sheep of British origin, which was strictly prohibited. Animals were imported semi-legally through Canada.
During the 1940s and 1950s, the active development of veterinary medicine made it possible to obtain more information about the behavior of the pathogen, including the determination that the infectious agent (prion) survived from a dose of ionizing radiation, which is incompatible with the biological integrity of the nucleic acid. As a result of this experiment, it was found that the disease causing agent may consist solely of protein. [3]
Symptoms and course of the disease
Symptoms of scrapie - increased irritability, severe chronic skin itching , trembling , paralysis , exhaustion . Animals as a result of infection, as a rule, die. Staple sheep and goats is an analogue of mad cow disease .
The manifestation of symptoms of scrapie increases slowly over several months. The first sign is the onset of unsteadiness of the gait in the animal, then in the region of the lower back and hind limbs scuffs on the hair and scratches appear, violations of the musculoskeletal system become noticeable, at the last stage of the development of the disease the animal suffers from constant itching. [one]
Also known under the names "trotting disease", "sheep shake", "sheep trembling."
The causative agent of this disease is the agent Scrapie agent, which is now referred to as prions. The disease is caused by degenerative changes in the central nervous system that occur in case of infection. Due to the pathological changes that cause itching, the animals rub against objects, trees, bite the affected areas of the skin in an attempt to relieve it. This leads to loss of hair and skin damage, injured areas of the skin are covered with festering erosion and scratches. At the last stages of the development of the disease, the symptoms are supplemented by tremors of the head, lips and limbs, involuntary grinding of teeth. Along with signs of arousal in some animals, depression, drowsiness, the appearance of increasing paralysis, ataxia and signs of exhaustion are noted, which is also a consequence of a malfunction of the central nervous system. At the last stage of the development of the disease, severe coordination disruptions, refusal of feed, stupor and paralysis occur, which leads to the death of the animal. [one]
It was noted that in goats, the signs of this disease are less pronounced than in sheep.
Prevention and treatment
Treatment of scrapie is possible only symptomatic, specific treatment methods have not yet been developed. [one]
Prevention is possible by preventing contact between infected and healthy animals. If there are cases of scrapie infection in the economy of any country, a strict culling is carried out with the subsequent slaughter of all patients and animals suspected of the disease. At the same time, the meat of such animals is forbidden to use for food.
In the USA, after a histological examination, during which the scrapie infection of at least one animal in the herd is confirmed, quarantine is imposed on agriculture in which a sick animal is found, and the slaughter of all animals in the herd where the infected animal was located. In Russia, herds where scrapie is found are also completely destroyed. [one]
Notes
- β 1 2 3 4 5 Staple sheep and goats - Infectious diseases - Infectious diseases - Prion infections, Diseases of sheep and goats - MRS . webvet.ru. Circulation date May 5, 2019.
- β Kazakov V.N., Shlopov V.G. Prion diseases: Monograph. - Donetsk: Donbass, 2009 .-- S. 10 .-- 444 p. - 1200 copies. - ISBN 978-966-1615-05-1 .
- β Scrapie . Fermer.Ru - Farmer.Ru - The main farming portal - all about the business in agriculture. Farmers Forum .. Accessed May 5, 2019.
Literature
- Kukhto A.F., The pruritus of sheep (scrapie), in the book: Diseases of the Sheep, M., 1963;