Watch for foreign animal disease

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There’s good news and bad news about our nation’s vulnerability to agroterrorism. The good news is that state and federal government agencies have been creating action plans to guide our response in the event of a plant or animal disease introduction. The bad news is that we still have more to do.

The U.S. Government Accountability Office (GAO) just released (March 2005) their report to Congress on the current status of the nation’s readiness for an agroterrorist event. The 101-page document reviews the different agencies’ roles and responsibilities, new laws and regulations, and includes comments from state officials, researchers and veterinarians (www.gao.gov/new.items/d05214.pdf). In its report, the GAO defined agroterrorism from the “preharvest” side: “Agroterrorism refers to the deliberate introduction of animal and plant diseases at the farm level, prior to further processing or production.”

After September 11, 2001, the newly formed Department of Homeland Security (DHS) was given responsibility for coordinating the national efforts to protect against agroterrorism. They, along with USDA and other agencies, have worked on developing national response plans. DHS also provided funding for two Centers of Excellence, one for post-harvest food protection and one for foreign animal disease defense. In addition, government agencies undertook vulnerability assessments and performed exercises to test response plans. To help with state response plans, USDA established 16 Area and Regional Emergency Coordinator positions.

The very first challenge that the GAO noted was that many veterinarians lack training needed to recognize the signs of foreign animal diseases. Only about 26% of graduates have taken a course on foreign animal diseases, and foreign animal disease training is not required to be a USDA-accredited veterinarian.

Other challenges include the inability of government to use rapid diagnostic tests. Some rapid tests exist but have not yet been approved for field use in the United States. Another challenge reported by the GAO was that no specific decision-making process regarding vaccine use was yet in place. Since 9/11, for a variety of reasons, there has been a decline in agricultural inspections that could impact early detection. Finally, the report noted that there was a need for better coordination of laboratories and improved communications. But, it is the veterinary training issue that we, as practitioners, have control over.

The most important diseases that you, your associates, your clients and their employees need to be able to quickly recognize are the vesicular diseases, the most important of which is foot-and-mouth disease (FMD). Because the vesicular diseases look very similar, the recommendation is: “If it’s vesicular, it’s reportable.” If you see cattle with vesicular signs (see sidebar), you need to immediately report it to your state and/or federal veterinarian.

When a report is made
With a strong suspicion of a problem like foot-and-mouth disease, all movement of cattle and products will be stopped. The investigation will begin by state or federal veterinarians getting a definitive diagnosis from samples taken on the farm. Next, the investigators will try to identify the source of the problem through trace-back of animals, products and people coming onto the farm. They’ll also look for animals moved off the farm and for any potential for spread, such as from people traveling during the outbreak from the suspect farm to another
livestock operation.

The reaction to the problem will depend on what’s found. In some cases, there may be no action necessary. But in the worst case, the animals will be destroyed to prevent further spread of the disease. In addition, the farm will remain quarantined, and animals and milk will be withheld from market until the government veterinarians know that the disease has been stamped out and that it’s safe to resume business. There will be a fair-market indemnity paid for the products and animals that are destroyed.

There are many reasons why we should be looking out for foreign animal disease threats. There is the obvious threat to animal health and welfare during an outbreak. We know that it will seriously affect producer profits, not just of the farm first affected, but of the neighboring farms, as well. An FMD outbreak will affect our national and international trade. It will affect consumer confidence in cattle products because many do not understand that FMD is not a public-health concern. Consumers will lose the nutritious products our clients produce. Finally, the public will be emotionally involved in the destruction of animals and will feel the effects an outbreak will have on the environment and local, regional and national economies.

Your relationships with your clients, your knowledge and your expertise are vital for the early detection and response to a threat to our livelihoods and our local, state and national agricultural economies.

Dale Moore, DVM, MPVM, PhD, is the Livestock and Poultry Animal Health Disaster Management Extension Specialist with U.C. Davis and the National Center for Foreign Animal and Zoonotic Disease Defense. Marcia Merryman, DVM, is a staff researcher and writer for the National Center for Foreign Animal and Zoonotic Disease Defense.

Much of the information on the signs of FMD came from Iowa State’s Center for Food Safety and Public Health at www.cfsph.iastate.edu/Factsheets/pdfs/foot_and_mouth_disease.pdf and the U.S. Animal Health Association’s The Gray Book, 1998 (Pat Campbell & Associates and Carter Printing Company, Richmond, Va.) online at www.vet.uga.edu/vpp/gray_book/FAD/index.htm

FMD signs to look for

  • In cattle, FMD should be considered whenever salivation and lameness occur simultaneously, and a vesicular lesion is seen or suspected.
  • Often the first sign noticed by dairy producers is a drop in milk production.
  • Fever often precedes other clinical signs; therefore, febrile animals should be carefully examined. Early diagnostic lesions may be found before animals start to salivate, have a nasal discharge or become lame.
  • To avoid missing a diagnosis, examine the mouth of a lame animal and the feet of any animal with signs or lesions involving the mouth or nares. Good restraint is necessary.
  • Typically, FMD spreads rapidly, and there is a high clinical infection rate. This cannot be counted upon, however, because signs may be caused by a relatively avirulent strain or more resistant animals, such as sheep, could be affected.
  • In pigs, sheep and goats, FMD should be considered when animals have sore feet, a vesicular lesion is suspected, or both.

Who to contact

To find contact information for your state veterinarian or Area Veterinarian in Charge:

What FMD lesions look like

The diagnostic lesions are single or multiple vesicles ranging from 2 mm to 10 cm in diameter.

Vesicles

  • A small blanched whitish area develops in the epithelium.
  • Fluid fills the area, and a vesicle (blister) is formed.
  • Vesicle enlarges and may coalesce with adjacent ones.
  • Vesicle ruptures.
  • Vesicular covering sloughs leaving an eroded inflamed area.
  • Gray fibrinous coating forms over the eroded area.
  • Coating becomes yellow, brown or green.
  • Epithelium is restored.
  • Line of demarcation remains; then line gradually fades.
  • Occasionally “dry” FMD lesions develop on the tongue. (Lesions appear necrotic rather than vesicular.)
  • The oral lesions in FMD can appear similar to those caused by other vesicular diseases or infectious bovine rhinotracheitis, bovine viral diarrhea virus infection, malignant catarrhal fever or bluetongue.

Other lesions

  • In the feet of adult cattle, the vesicle in the interdigital space is usually large because of the stress on the epithelium caused by movement and weight. The lesion at the coronary band at first appears blanched; later, there is separation of the skin and horn. When healing occurs, new horn is formed, but a line resulting from coronitis is seen on the wall of the hoof.
  • In calves, the foot lesions (and resulting lameness) are not often observed because of their lighter body weight.
  • Vesicular lesions may also be seen on the rumen pillars.
  • Skeletal muscle lesions are rare.
  • “Tiger heart” is the grayish or yellowish streaking in the myocardium from degeneration and necrosis. The heart lesions may be the only FMD lesion seen in acutely dead calves less than 7 to 10 days of age.

 
  Myocardial necrosis

Course of an FMD infection

  • Day 1
    Exposure by inhalation or ingestion and subsequent infection.
  • Day 2
    Prepatent period; viral shedding up to four days prior to clinical signs.
  • Day 4
    Early clinical signs; pyrexia, anorexia, shivering, drop in milk production.
  • Day 5 to Day 9 
    Classical signs: Vesicles form on buccal, nasal and mucous
    membranes, mammary glands and/or between the claws and coronary band, causing smacking of the lips, grinding of the teeth, drooling, lameness, stamping or kicking of the feet. Vesicles rupture within 24 hours after formation leading to sloughing of tissues and epithelial erosions.
  • Day 10 to Day 15
    Healing of lesions and recovery.  


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