US incursion of epizootic lymphangitis would be “impossible to eliminate” – expert

A horse suffering from epizootic lymphangitis.
A horse suffering from epizootic lymphangitis. © AAEP

Should the contagious disease epizootic lymphangitis make its way into the US, it would be “virtually impossible to eliminate”, a leading equine infectious disease expert says.

Epizootic lymphangitis is common in parts of Africa, the Middle East, Russia and Asia, where it causes chronic weight loss and progressive debility in affected animals.

It is a contagious, chronic granulomatous disease of the skin, lymphatic vessels and nodes of the limbs, neck and chest of horses and other equid species. As well as affecting the skin, there is also a respiratory form and an ocular form that is most common in donkeys. Cattle are also susceptible, but more resistant to the disease than equines.

Professor Peter Timoney has written guidelines published by the American Association of Equine Practitioners (AAEP) on epizootic lymphangitis to assist practitioners and regulatory agencies in the identification, diagnosis and control of the disease.

Caused by the soil fungus Histoplasma capsulatum var. farciminosum, epizootic lymphangitis has been eradicated from many countries, but remains a problem for equids, particularly in northern Africa, Asia, and the Middle East. Histoplasma capsulatum var. farciminosum can survive in dust and soil for extended periods of time, especially under warm moist conditions. It is highly resistant to the actions of physical and chemical agents.

Timoney said that while epizootic lymphangitis has not been recorded in the United States, its importance as a transboundary/foreign animal disease needs to be emphasized because of its similarity to several domestic diseases with which it can be clinically mistaken, including ulcerative lymphangitis, glanders and streptothricosis.

“Were it to be introduced, the causal agent can survive in dust and soil for an extended interval under conditions of heat and humidity, making it virtually impossible to eliminate,” said Timoney, the Frederick Van Lennep Chair in Equine Veterinary Science at the University of Kentucky’s Gluck Equine Research Center.

Epizootic lymphangitis is an OIE non-listed disease even though it is of significant socio-economic importance in countries in which it is endemic, some of which engage in the international trade of animals and animal products. It is notifiable in Britain. Any suspicion of the disease in the United States is immediately reportable to the US Department of Agriculture (USDA) and State Animal Health Officials in all 50 states and territories.

Timoney said that rare cases of human infection with H. capsulatum var farciminosum have been known to occur.

The Epizootic Lymphangitis Guidelines were edited and reviewed by Abby Sage, VMD, DACVIM, chair of the Infectious Disease Guidelines Subcommittee of the AAEP’s Infectious Disease Committee.

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