Don't be the one to miss these foreign animal diseases (Proceedings)

As a veterinarian working in the field, if you suspect that a foreign animal disease (FAD) is present, your obligation is to promptly report it to the appropriate authorities. The USDA-APHIS-VS Area Veterinarian in Charge (AVIC) for your State has primary responsibility for ensuring that all suspected FADs or emerging disease incidents are investigated. However, this is generally a cooperative effort between State animal health and Federal personnel. Consequently, you should have the contact information for both the office of your State Veterinarian or the AVIC for your State stored on your telephone or in some other readily accessible location if the need arises to report a suspected FAD.

In the aftermath of 9-11, it is also important for a veterinarian to keep in the back of his/her mind the consideration that an act of terrorism could be at work when a FAD is suspected. Remember, disease can occur from a spontaneous outbreak of a known endemic disease, a spontaneous outbreak of a new or re-emerging disease, a laboratory accident, or via intentional attack with a biological agent.

In general, the pattern of disease that is observed is an important factor in differentiating between a natural disease outbreak and an intentional attack. If the former is operating, typically, the number of cases gradually increases as a progressively larger number of animals come in contact with other animals or fomites or vectors that can spread disease. Eventually, the epidemic curve gradually decreases over time because most of population has been exposed to the disease agent and has become immune (or died). In contrast, an intentional attack may exhibit a steep epidemiologic curve typical of a point source exposure wherein it is compressed into a short period of time (hours or days). None of the following circumstances alone constitute proof of intentional use of a biological agent; however, together they can assist greatly in determining if further investigation of a FAD as a bioterrorist incident is warranted:

1. Large epidemic with higher number of cases than expected

2. Large number of cases of unexplained diseases or deaths

3. More severe disease than expected

a. unusual routes of exposure

b. unexplained increase in incidence of an endemic disease

c. higher morbidity and mortality in a common disease

4. Disease is unusual for geographic area, is observed outside of normal transmission season, or impossible to transmit naturally in absence of normal vector

5. Multiple simultaneous epidemics of different diseases

6. Zoonotic disease outbreak with human consequences

7. Unusual strains or variants of organisms or antimicrobial resistance patterns disparate from those circulating

8. Higher attack rates in those exposed in certain areas (e.g. indoors vs. outdoors)

9. Intelligence that an adversary has access to a particular agent or agents

10. Claims by a terrorist of the release of a biologic agent

11. Direct evidence of the release of an agent, with findings of equipment, munitions, or tampering

With respect to a FAD, it is always preferred to prevent a foreign pathogen from entering a premises because of having adequate biosecurity procedures in place than deal with biocontainment (preventing a pathogen from escaping a premises). Consequently, cattle producers should develop a biosecurity plan and commit to its implementation. Key components of any biosecurity plan involve isolation, traffic control, and sanitation. Basic isolation procedures involve minimizing movement and commingling of cattle and preventing contact between animals within a controlled environment. Traffic control involves management of vehicles, animals, and people that move on and off property as well as movement patterns within the premises. Sanitation should focus on disinfection of materials, equipment, and people entering the operation as well as the cleanliness of people and equipment on the operation.

Pursuant to the Bioterrorism Act of 2002, the USDA has identified Foot and Mouth Disease (FMD), Rift Valley fever, and Rinderpest as foreign animal diseases that pose the severest threat to the livelihood of the cattle industry. Contagious bovine pleuropneumonia, lumpyskin disease virus, and vesicular stomatitis virus (VSV) are also considered to have the potential to pose a severe threat. Through a series of photographs, this seminar will primarily focus on the salient clinical features of these diseases as well as heartwater and malignant catarrhal fever (MCF). For additional comments about the etiologic agent, host range, epidemiology, prevention, and control strategies for each of these diseases, visit the following web site: http://www.usaha.org/pubs/fad.pdf.

References

University of Nebraska Great Plains Veterinary Education Center Web site. Biosecurity basics for cattle operations and good management practices (GMP) for controlling infectious diseases. Available at: www.ianrpubs.unl.edu/epublic/live/g1411/build/g1411.pdf

Pavlin JA. Epidemiology of bioterrorism. Emerg Infect Dis 1999;5:528-530.

Ryan CP. Zoonoses likely to be used in bioterrorism. Pub Hlth Report 2008;123:276-281.

US Government Accountability Office Web site. Homeland security. much is being done to protect agriculture from a terrorist attack, but important challenges remain. Available at: www.gao.gov/new.items/d05214.pdf.