How to Eradicate the Remaining Cases of Scrapie

(Nov. 1, 2012) “In the past, when I was asked the question about what the top sheep diseases in the United States are, scrapie would have been at the top of the list,” says Larry Goelz, DVM, Pipestone Veterinary Clinic, Pipestone, Minn., to the attendees of the South Dakota Sheep Growers Association during its annual meeting. “So much progress has been made in the last 10 years on eradicating this disease that, for me, it is no longer on that list. Foot rot, contagious abortion, parasites and Ovine Progressive Pneumonia would round out my top four.”

This matches the statistics obtained from Diane Sutton, DVM, national scrapie program coordinator with the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) who states, “There has been a 96-percent decrease in the percentage of positive sheep sampled at slaughter, adjusted for face color, since the start of Regulatory Scrapie Slaughter Surveillance (RSSS) in fiscal year 2003.

“There were only eight newly identified infected and source flocks in fiscal year 2012. A 47-percent decrease from fiscal year 2011,” continues Sutton. (The below table shows the history of infected and source flocks from 1997 to current.)

The completion of any disease eradication effort can be the most difficult since the frequency of discovering the disease has been decreased to the point that finding it can be very difficult. Scrapie is no exception. As infected flocks have been cleaned up and disease prevalence decreased, finding the last vestiges or pockets of infection is challenging. Additionally, without robust surveillance in mature sheep and goats that die on the farm and in live sheep and goats, the effort becomes even more difficult. Slaughter surveillance has gotten the industry where it currently is in the eradication effort. Now it is going to be necessary to ramp up the surveillance of mature animals found dead on the farm and live animals to finish the job. The biggest challenges will be the willingness of the industry, particularly producers, to actively participate in this effort and the availability of resources for sample collection and testing. 

“We are having discussions with APHIS regarding some regionalized pilot projects involving a coalition of states where a state certification of scrapie freedom might get the ball rolling,” says Jim Logan, DVM, Wyoming state veterinarian. “This must be industry and market driven and it will require a great deal of education at the producer and state levels in order to be successful. My hope is to be able to report, in the next several months, that there have been some state and industry participants prepared to keep the eradication effort moving forward and prove that this effort we have been working on in this country for years can be finished.”

Even with this range of positive statistics and comments, there is still work to be done. Producers can contribute significantly to finding and eliminating the remaining cases by:

  • officially identifying their sheep and goats per the federal regulations and the regulations of their state;
  • reporting suspect sheep and goats to a state, federal or accredited veterinarian; and
  • submitting animals for scrapie testing that die when they are over 18 months of age from causes other than normal slaughter.

 

Identification
“Identifying sheep and goats that leave a premises or change ownership is required by USDA as well as by state rules,” states Logan. 

“It is also important to identify these animals for traceability purposes,” he continues. “If an animal is found to have scrapie after it has left a flock, the sooner regulatory officials can trace the disease back to the infected flock, the less likely the disease is to spread in your flock. In many cases, good identification and good records have resulted in ruling out a producer in a trace.”

Reporting Suspect Animals
If an owner suspects scrapie in a flock, it is prudent and good management to report the situation and have laboratory diagnostics done to determine if the disease is present. In fact, in most states, it is a legal requirement for veterinarians and animal owners to report suspected cases of scrapie. Rapid reporting and diagnosis will help a producer with an infected flock avoid the spread of the disease. 

“Yes, if scrapie is found, there will be a quarantine and some inconvenience,” expresses Logan. “However, the inconvenience of a quarantine is small compared to the depopulation of an entire flock because of failure to report. It is also good bio-security and disease control to get a veterinarian involved early if scrapie is suspected.”

Submitting Animals
USDA initiated an accelerated scrapie eradication program that includes slaughter surveillance. The objective of slaughter surveillance is to find and eliminate infection and to estimate the national prevalence of scrapie in mature sheep by testing them for scrapie. As more of the U.S. sheep inventory gets marketed through non-traditional channels, these animals are also bypassing the traditional USDA inspected plants and, thus, scrapie testing.

Producers, particularly those that market through non-traditional channels, are asked to submit for scrapie testing the heads of mature animals (18 months or greater) that die from causes other than normal slaughter. The side-bar provides the details of how to participate in this program.

This is important for a couple reasons: 

1. In order for a state to maintain its Scrapie Consistent State Status with USDA, it is required to submit and test a certain percentage of ‘deads’ for tissue sampling. This percentage is calculated by APHIS based on the sheep population in that state. Consistent status is important to a state’s sheep industry as it allows for interstate marketing without additional regulatory requirements.

2. “Producers should want to know why an animal has died so that preventive measures can be taken,” said Logan. “When any disease, especially scrapie, is in a flock, the sooner it is discovered, the sooner it can be cleaned up, reducing its spread within the flock. Nobody wants to find scrapie in their flock but, if it is there, the sooner it becomes a priority, the sooner it can be eradicated.” 

“Statistically, it is extremely important to have a representative sample of sheep tested to show that scrapie is being eliminated in the United States,” said Michael L. Thonney, professor of animal science at Cornell University. “The presence of scrapie prevents the export of breeding stock, semen and embryos to many other countries.”

Conclusion
Scrapie was first found in the United States in 1947. In order to eradicate it, everyone in the sheep industry has a responsibility to this cause.

“My first scrapie experience was not very positive,” remarks Nick Forrest, producer from Ohio. “I purchased a ewe and a ram from a very credible breeder yet received a letter stating that I needed to get rid of these animals due to scrapie.

“At that time, I made the decision to get involved with the sheep industry at the state and national level to learn more about this disease. After 20 years, scrapie is much better controlled but there are still people out there who do not know its details. If an animal dies, they bury it and move forward.

“I would encourage all producers to become proactive in the eradication of scrapie in the United States,” resumes Forrest. “In my travels throughout the East, I found that there were many farmers with smaller flocks who have not been fully educated about the programs to eradicate scrapie. I believe they would be interested to know if their animals have scrapie or are susceptible to the disease but they don’t know what to look for or how to get them tested.”

Information on the scrapie programs is available on the APHIS website atwww.aphis.usda.gov/animal_health/animal_diseases/scrapie. Questions can also be directed to the American Sheep Industry Association at 303-771-3500.

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