Commentary: Equine Quarantine Increasingly Important

Epidemics of equine influenza in Japan and Australia during the summer of 2007 have raised questions regarding the failure of quarantine and influenza vaccination to control the spread of disease.

Expanding and increasingly mobile equine populations have changed the dynamics of equine infectious disease. For example, an increased number of Thoroughbred stallions are shuttling between the Northern and Southern hemispheres. Horses were traditionally shipped by sea, allowing time to recover during transit from diseases such as equine influenza. With widespread acceptance of air travel, horses arrive in the importing country 48 hours after departure, within the incubation period for influenza. Consequently, horses may have clinical signs on arrival, and more importantly, are shedding vast quantities of virus, infecting every horse with which they come in contact.

As a result, epidemics of influenza occurred among equine populations of South Africa in 1986 and 2003, Hong Kong in 1992, and Japan and Australia in 2007. These epidemics occurred despite imported animals being subjected to officially approved quarantine and vaccination against influenza.

Investigation of the outbreaks in Hong Kong and South Africa exposed flaws in quarantine that permitted animals to be released into the general population while still infectious. Contaminated personnel and equipment also inadvertently carried the virus outside the quarantine facility.

The outbreak in Australia has been calamitous, given its equine population had not been exposed to influenza and therefore was susceptible to infection. The social and economic disruption to the equine industry in Australia is significant. Federal and state authorities in that country continue to struggle to control the disease and provide massive financial support to sustain the industry.

The impact has prompted a major inquiry into circumstances surrounding the outbreak, particularly failure of the quarantine facility in Sydney to contain the outbreak among imported stallions shuttled from several countries in the Northern Hemisphere. The findings will be important in developing guidelines for more effective approaches to equine quarantine in all importing countries.

A procedure that could be applied immediately is to test horses in quarantine for influenza using polymerase chain reaction (PCR) or enzyme-linked immunosorbant assay (ELISA) rapid test kits. In the hands of trained laboratory personnel, the test kits are simple to use and inexpensive. They also provide good sensitivity and specificity, the requisite hallmarks of a reliable testing system. Such testing has successfully been used by the Hong Kong Jockey Club since 1992 to screen all imported horses, including those from Europe and North America, which are areas known to be endemic for equine influenza.

Veterinary regulatory authorities would do a considerable service to the equine industry by incorporating these modern technologies in their import certification protocols. The practical application of such a proposal during pre-export and/or post arrival will require very careful consideration prior to implementation. An agreed plan of action must also be in place if a positive result is reported.

Contact: Dr. David G. Powell, 859/257-4757, dgpowe2@uky.edu, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, Kentucky.

This is an excerpt from Equine Disease Quarterly, funded by underwriters at Lloyd's, London, brokers, and their Kentucky agents. More articles from Equine Disease Quarterly...

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