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EIA - some facts



EIA is a viral disease first recognized in France in 1843.  It is closely related to Human Immunodeficiency Virus which causes AIDS.  EIA is, in fact, used for a model in many aspects of HIV research.  The virus only affects the equine family.  Since 1972 more than 15 million equine blood samples have been tested in the US for the presence of EIA virus .  Since testing was initiated, positive results have decreased from over 3% to less than 0.2%. 
 
92% of EIA test positive samples originated from horses in a 'hot zone'.  This includes Texas, Oklahoma, Mississippi River Valley and Southeast US.
 
Horses will die from the EIA virus and it's related complications.  Acute EIA will kill a horse in 2-3 weeks.  This condition is rarely seen in natural situations where blood feeding insects transmit only low doses of the virus.  Chronic EIA causes lethergy, loss of condition, anorexia, anemia and decreased platelets - the horse probably will not die.  But he will not be suitable for any useful purpose, he also will be a source of virus for biting insects to spread the disease to other horses.
 
The most common presentation of the disease is the Inapparent Carrier.  This horse may show no overt clinical abnormalities, but his blood consistantly contains EIA virus and thus he remains a long term reservoir of infection.  Due to low virus concentrations in the inapparent carrier, transmission is unlikely but possible.
 
The decision to treat all test positive horses the same was reached (quaranteen or euthanize) because it is known that each infected horse may develop clinical EIA upon treatment with immunosuppressive drugs and/or in response to natural stressors resulting in higher levels of virus in the blood and thus increased risk of transmission.
 
I have personally witnessed the natural transmission of EIA in a stable here in Western New York.  The virus, while rarely causing acute disease, does cause dibilitation, loss of use, and financial hardship.  Adherence to the laws regarding this disease have made this country much safer for your horse especially when you and your horse congregate in large groups from diverse areas.  When in such a gathering, you should be thankful that the horses that are surrounding yours have been tested negative.
 
Mark McConnnon, DVM
(husband of Laura Hayes #2741 NE)


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