Bovine Spongiform Encephalopathy (BSE)

The objective of BSE surveillance is to detect occurrence of BSE within the bovine population.

I.  BSE is a progressive, fatal disease of the nervous system of bovines that usually has a harmful onset with no treatment. A range of clinical signs that vary in severity and between animals have been described for classical BSE:

1. 1. Progressive behavioural changes that are refractory to treatment such as increased excitability, depression, nervousness, excessive and asymmetrical ear and eye movements, apparent increased salivation, increased licking of the muzzle, teeth grinding, hypersensitivity to touch and/or sound (hyperaesthesia), tremors, excessive vocalization, panic-stricken response, and excessive alertness.
   2. Postural and locomotory changes such as abnormal posture (dog sitting), abnormal gait (particularly pelvic limb ataxia), low carriage of the head, head shyness, difficulty avoiding obstacles, inability to stand and recumbency.
   3. Generalized non-specific signs such as reduced milk yield, loss of body condition, weight loss and slow heart rate (bradycardia).

The clinical signs of BSE usually progress on a spectrum over a few weeks to several months, but on rare occasions cases can develop acutely and progress rapidly. The final stages of the disease are characterized by recumbency, coma and death.

II. Surveillance for BSE includes all bovines that show signs of the clinical spectrum of BSE.

The surveillance programme should consider that most cases of BSE arise as single, isolated events. The concurrence of multiple animals with behavioural or neurological signs, or non-ambulatory or fallen stock is most likely associated with other causes.

The animals that lie on the clinical spectrum of BSE should be targeted for BSE surveillance and the following animals should be reported and followed up with appropriate laboratory testing in accordance with the Terrestrial Manual to accurately confirm or rule out the presence of BSE agents, including discrimination between atypical and classical BSE strains.

1. those displaying progressive clinical signs suggestive of BSE mentioned in point 1 that are refractory to treatment, and where the clinical presentation cannot be attributed to other common causes of behavioural or neurological signs (e.g. infectious, metabolic, traumatic, neoplastic, or toxic causes).
2. those showing behavioural or neurological signs at ante-mortem inspection at slaughterhouse/abattoirs.
3. those unable to rise or walk without assistance, with an appropriate supporting clinical history (i.e. the clinical presentation cannot be attributed to other common causes of recumbency).
4. those found dead (fallen stock), with an appropriate supporting clinical history (i.e. the clinical presentation cannot be attributed to other common causes of death).

III. The credibility of the surveillance programme is supported by:

1. ongoing awareness and training programmes to ensure that all those stakeholders involved in the rearing and production of livestock, including bovine breeders, owners and keepers, veterinarians, transporters, and slaughterhouse/abattoir workers are familiar with the clinical signs suggestive of BSE as well as the statutory reporting requirements.
2. the fact that BSE is a notifiable disease throughout the whole territory.
3. appropriate laboratory testing in accordance with the Terrestrial Manual. 
4. robust, documented, evaluation procedures and protocols for:
   • the definition of the target population for BSE surveillance,
   • the reporting of bovines described in points II a) to 2 d),
   • the determination of animals to be subjected to laboratory testing,
   • the collection and submission of samples for laboratory testing,
   • the follow-up epidemiological investigations for BSE positive findings.