It is either not transmissible or poorly transmissible under natural conditions. Given this the scrapie eradication program focuses on classical scrapie.
Scrapie is a fatal, degenerative TSE disease affecting the central nervous system of sheep and goats. First recognized as a disease of sheep in Great Britain and other countries of Western Europe more than years ago, scrapie has been reported throughout the world. In the United States, scrapie has primarily been reported in the black-face meat breeds and their crosses. It also has been diagnosed in numerous other breeds and crossbreeds including wool and hair sheep, and in goats. At the end of FY , the percent of cull sheep found positive at slaughter and adjusted for face color was 0.
This measure of prevalence has decreased by 99 percent since slaughter surveillance started in FY Based on all goats sampled at slaughter through FY , the prevalence of scrapie in U. The agent responsible for scrapie and other TSEs is smaller than the smallest known virus and has not been completely characterized. There are a variety of theories regarding the nature of the agent.
The most widely accepted is that disease is caused by an infectious protein, or prion, that causes the normal cellular version of the protein to change shape such that it can no longer be degraded by the cell, causing the protein to accumulate and damage the cell.
The scrapie agent is extremely resistant to heat and to normal sterilization processes. It does not evoke any detectable immune response or inflammatory reaction in host animals. The scrapie agent is thought to be spread most commonly from the ewe to her offspring and to other lambs in contemporary lambing groups through contact with the placenta and placental fluids and through milk and colostrum.
Signs or effects of the disease usually appear 2 to 5 years after the animal is infected but may take longer to appear. Sheep usually live 1 to 6 months after the onset of clinical signs and in some cases longer, but death is inevitable. Signs of scrapie vary widely among individual animals and develop very slowly. As the result of nerve cell damage, affected animals usually show behavioral changes, tremor especially of the head and neck , pruritus, and locomotor incoordination, which progresses to recumbency and death.
Early signs include subtle changes in behavior or temperament. These changes may be followed by scratching and rubbing against fixed objects, apparently to relieve itching. Other signs are loss of coordination, weight loss despite retention of appetite, biting of feet and limbs, lip smacking, and gait abnormalities, including high-stepping of the forelegs, hopping like a rabbit, and swaying of the back end. The revised program requires the official identification of most sexually intact sheep and goats in commerce; additionally, it identifies scrapie-infected animals through surveillance of mature cull sheep and goats at slaughter as well as suspects reported by veterinarians and producers.
These records must be maintained for a minimum of five years. The success of the Scrapie Eradication Program is tied to producers keeping good records of animal sales and purchases. The National Scrapie Eradication Program provides free ear tags to sheep and goat producers. The SFCP identifies scrapie-free flocks by monitoring them over a year period.
The SFCP was revised on The program provides sheep and goat producers the opportunity to increase the marketability of their animals through demonstrating a negligible scrapie risk in their flock or herd.
The revised program additionally will enhance scrapie surveillance strategy, contributing to the final push to eradicate this disease from the United States. Official Identification official eartags, official tattoos, official electronic identification or official premises identification numbers are required when sheep and goats change ownership, except:.
In all cases where scrapie is suspected or confirmed or BSE cannot be excluded, APHA will gather details about the case which are used to study the disease. These may include a combination of the following controls for two years:.
APHA will also pay compensation for any other animals in the flock or herd which are compulsorily killed, or their products compulsorily destroyed, through the CSFS, following the confirmation of scrapie or where BSE cannot be excluded. Biosecurity is about being aware of the ways disease can spread and taking every practical measure to minimise the risk of disease spreading. The advice details practical things you can do on your farm to help prevent the introduction and spread of scrapie to and from your animals.
You should take precautions to reduce the risk of introducing scrapie into your flock or herd, as scrapie control measures will be applied to the whole flock or herd. However, where scrapie has been introduced we advise taking precautions to reduce the number of animals infected. This applies in particular to goat herds as goats appear to be more uniformly susceptible to classical scrapie. The genetic make-up of sheep affects their susceptibility to classical scrapie. You can discuss genotyping and breeding sheep for resistance with your private veterinary surgeon.
Classical scrapie is caused by an infectious agent. Most flocks or herds which contract scrapie have purchased an infected animal which is incubating the disease. You are advised to source either genetically resistant replacements or animals from flocks and herds which have been monitored for the past three years and in which scrapie has not been identified. Classical scrapie can also be spread through colostrum and milk.
If you purchase replacement colostrum or milk, you should only do so from flocks and herds which have been monitored for the past three years and in which scrapie has not been identified, particularly if you have genetically susceptible animals. In intensively managed flocks containing genetically susceptible animals, you can reduce the risk of spreading classical scrapie by avoiding using pooled colostrum and milk.
In both cases cow colostrum and artificial milk replacers should be considered as an alternative. Classical scrapie is spread from an infected dam to her offspring and other sheep or goats. Birth fluids and afterbirth from infected animals will contaminate pastures or buildings. Contact between sheep and goats and afterbirths should be kept to a minimum. Prompt removal of afterbirths and regular cleaning and disinfecting of buildings used for lambing or kidding may reduce the risk of exposure of animals to the scrapie agent.
This will help to control the disease but it is unlikely to remove all the contamination in the environment. It is possible that the scrapie agent is also spread in other ways e.
The scrapie agent is known to persist in the environment for several years. It is resistant to most commercial disinfectants although thorough cleaning and disinfection of buildings are likely to reduce the level of infection. You are advised to ensure that any disinfection is carried out in accordance with Environment Agency or Scottish Environmental Protection Agency requirements.
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