Imported

Belgium/Netherlands

Sheep Test Results

The U.S. Department of Agriculture’s Animal and

Plant Health Inspection Service (APHIS) announced

that 2 sheep from a flock of 125 which were 

confiscated in March of 2001 from a farm in Vermont

have tested positive for an atypical undifferentiated

transmissible spongiform encephalopathy (TSE).

TSEs are a class of degenerative neurological

diseases that are characterized by a very long 

incubation period and a 100-percent mortality rate.

Two of the better known varieties of TSEs are bovine

spongiform encephalopathy (BSE) in cattle and

scrapie in sheep.

Additional tests will be conducted to determine

exactly what TSE the animals have—BSE or scrapie.

These tests involve the use of bioassays that consist

of injecting mice with tissue from the infected animals

and waiting for them to develop disease. This testing

may take at least 2 to 3 years to complete.

This flock of 125 sheep was confiscated in March

2001 after 4 animals from an associated flock 

tested positive for an atypical TSE of foreign origin.

In all, APHIS acquired 380 sheep from a total of

three flocks. All of the animals were humanely euthanized, sampled, and disposed. The animals did not

enter the animal or human food supply.

The decision to confiscate the sheep was made

after four sheep from one the of the flocks tested 

positive for an atypical undifferentiated TSE of foreign

origin in July 2000. On July 14, 2000, USDA issued

a declaration of emergency and extraordinary

emergency to acquire the sheep.

The first flock of 21 sheep were voluntarily sold

to USDA on July 14, 2000. Those animals tested

negative for a TSE.

The owners of the other two flocks contested

USDA’s action. A federal district court judge ruled in

favor of USDA based on the merits of the case. The

flock owners appealed to the Second Circuit Court

requesting a stay, which was denied. After the

request for a stay was denied, the flocks were confiscated by USDA in March 2001.

The second flock of 234 animals was confiscated

on March 21, 2001. Testing for TSEs is ongoing for

this flock. The third flock of 125 sheep was confiscated

on March 23, 2001.

Background

APHIS’ mission is to “Protect American

Agriculture.” As part of that mission APHIS regulates

the importation of animals and works with U.S. producers to eradicate animal diseases. To improve the

genetic base of the domestic sheep population or to

gain access to breeds not commonly found in the

United States, there was a brief window of time in

1996 when USDA allowed the importation of sheep

from certain countries. In August and November

1996, two importations of sheep from Belgium

occurred. The sheep were primarily East Friesian

milk sheep which originated from both Belgium and

the Netherlands. A total of 65 sheep were imported.

These sheep were used for milk production; milk from

these sheep was used to produce cheese that was

sold locally and nationally.

This brief import window was shut in late 1996

after published research indicated that sheep that

were orally infected with BSE had a wider tissue 

distribution of the agent than cattle with BSE. This

raised the possibility that if sheep were naturally

infected with BSE the disease may spread from one

sheep to another.

In late 1997, both Belgium and the Netherlands

reported their first cases of BSE in native cattle. In

1998, the European Union’s Scientific Steering

Committee issued an opinion that stated it is highly

likely that European sheep were exposed to feed

contaminated with the BSE agent. Based on these

reports, the state of Vermont, in consultation with

APHIS, imposed a quarantine on these sheep in

October 1998. The two flocks of sheep and their

progeny were prohibited, by the State quarantine,

from entering either the human food or animal feed

chains or being sold for breeding purposes.

Subsequent to the quarantine, APHIS obtained 

information that the flocks of origin had been fed concentrates prepared at local mills. This practice has

been shown as the most likely route of BSE exposure

for the infected cattle in Belgium.

If any of the quarantined sheep were to be culled

or died, tissues from animals greater than 6 months

of age were collected for diagnostic purposes and the

carcasses were incinerated at APHIS’ expense.

Based on four animals from one flock testing positive

for an atypical undifferentiated TSE, USDA determined that an emergency and extraordinary 

emergency existed in Vermont. These declarations,

which were effective July 14, 2000, provided funds

and the authority to seize and dispose of these

sheep.

Factsheet

Veterinary Services April 2002

APHIS
The declaration of emergency provides authority

for USDA to seize and destroy the sheep and 

authorizes payment of fair market value for the sheep.

On October, 28, 2000, Congress provided the USDA

with additional authority and funding ($2.4 million) to

compensate the owners for economic losses incurred

due to seizure and destruction of the Vermont sheep.

This was in addition to fair market value funds that

would have been provided for the sheep. This additional funding, which was available only if the sheep

were destroyed on or before November 17, 2000, was

declined by the owners. The owners of the other two

flocks contested USDA’s action. A federal district

court judge ruled in favor of USDA based on the merits of the case. The flock owners appealed to the

Second Circuit Court requesting a stay, which was

denied.

TSE Testing 

Tissues from the sheep have been subjected to

three tests; histopathology, immuno-histochemistry,

and Western-blot.

Histopathology examines brain tissue for 

microscopic changes indicative of a TSE. Immunohistochemistry examines the brain tissue for the

abnormal prion protein, which is a marker for TSE 

disease. The Western-blot test also detects the

abnormal form of prion protein in the brain tissue. All

of these are recognized as official tests by APHIS.

The abnormal prion protein was detected by the

Western-blot test in all of the sheep that have tested

positive for a TSE in these groups of animals. The

method used for this test has been published in literature and is an accepted methodology. The tissue samples were from the obex, which is the best location in

the brain to find the abnormal form of the prion protein

(an indicator of TSE infection) if it is present.

The Western-blot test however cannot differentiate

between scrapie and BSE. The only known validated

method to differentiate between these two diseases

requires a series of mouse bioassay systems, which

take at least 2–3 years for completion.

The U.S. Department of Agriculture (USDA) prohibits discrimination

in all its programs and activities on the basis of race, color, national

origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to

all programs.) Persons with disabilities who require alternative

means for communication of program information (Braille, large

print, audiotape, etc.) should contact USDA’s TARGET Center at

(202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of

Civil Rights, Room 326–W, Whitten Building, 1400 Independence

Avenue, SW, Washington, DC 20250–9410 or call (202) 720–5964

(voice and TDD). USDA is an equal opportunity provider and

employer.

United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture