Scrapie
Scrapie is a chronic, progressive, and invariably fatal neurodegenerative disorder that affects sheep and goats. This disease has been present in parts of Europe since at least the 18th century and is currently identified in several countries worldwide. Scrapie belongs to a group of disorders known as prion protein disorders or transmissible spongiform encephalopathies (TSEs).
Symptoms and Diagnosis 🩺
Symptoms
Scrapie typically affects sheep between 2 to 5 years old. The symptoms can be quite varied and may include:
- Excitability, nervousness, or aggression
- Trembling
- Strange high-stepping gait
- Lack of coordination
- Intense itching leading to wool loss and skin lesions
- Severe weight loss
Other neurological signs may include teeth grinding, excessive salivation, and blindness.
Diagnosis
Diagnosing scrapie can be challenging due to the variability of symptoms. Early signs are often behavioral changes, which progress to more definite neurological symptoms. Post-mortem confirmation involves detecting characteristic vacuolation in the brain tissue and the accumulation of abnormal prion protein (PrP).
Treatment 💊
Unfortunately, there is no treatment for scrapie. Once a sheep shows symptoms, the disease is invariably fatal. Therefore, managing scrapie focuses on prevention and control rather than treatment.
Prevention 🛡️
Biosecurity Measures
Preventing scrapie involves strict biosecurity measures, such as:
- Buying replacement milk or colostrum from scrapie-free flocks
- Ensuring that bedding, buildings, equipment, and vehicles are free from contamination
- Implementing good husbandry practices to reduce the risk of transmission
Genetic Selection
Genetic selection for resistance to scrapie is another effective strategy. Certain genotypes, such as ARR/ARR, are known to provide full resistance to natural scrapie, while others, like VRQ/VRQ, are highly susceptible. Breeding programs can focus on selecting resistant genotypes to reduce the incidence of the disease.
Control Measures
In scrapie-affected flocks, control measures include identifying and eliminating infected animals, reducing the infectious load, and selecting for genetic resistance. Good husbandry practices, such as using multiple lambing areas and proper disposal of placentas, can also help reduce the spread of infection.
Notifiable Disease
Scrapie is a notifiable disease, meaning that any suspicion of the disease must be reported to the relevant authorities. This helps in monitoring and controlling the spread of the disease.