Horses 



Equine Infectious Anemia (EIA) 



EIA is an infectious and potentially fatal viral disease of members of the horse family. 

 The equine infectious anemia virus (EIAv) is categorized as a retrovirus: it contains 

 genetic RNA material, which it uses to produce DNA. The DNA is then incorporated 

 into the genetic makeup of infected cells. There is no vaccine or treatment for the 

 disease. It is often difficult to differentiate from other fever-producing diseases, 

 including anthrax, influenza, and equine encephalitis. 



Clinical Forms 



Acute — When horses are exposed to EIAv, they may develop severe, acute signs of 

 disease and die within 2 to 3 weeks. This form of the disease is the most damaging 

 and the most difficult to diagnose because the signs appear rapidly, and often only an 

 elevated body temperature is noted. One-fifth of a teaspoon of blood from a horse 

 with acute EIA contains enough virus to infect a million horses. 



Clinical signs of acute infectiousness are rather nonspecific; in mild cases the initial 

 fever may be short lived (often less than 24 hours). Horse owners and veterinarians 

 may not observe this initial response when a horse is infected with EIAv. Horses often 

 recover and continue to move freely in the population. The first indication that a 

 horse was exposed to, and infected with, EIAv may be a positive result on a routine 

 annual test. 



Chronic — If the horse survives the first acute bout, it may develop a recurring 

 clinical disease with most or all of the following signs: 



• Fever: An infected horse's temperature may rise suddenly to 40.5 °C (105 °F) 

 or, rarely, as high as 42.2 °C ( 108 °F) but may then drop back to normal for an 

 indeterminate period until the onset of another episode. 



• Petechial hemorrhages: Minute blood-colored spots appear on the 

 mucous membranes. 



• Depression: A horse appears more or less dejected (head hangs low) and 

 generally listless. 



• Weight loss: A horse may refuse feed or may eat an inordinate amount but still 

 continue an obvious decline from normal weight. 



• Dependent edema: A horse may develop swelling, which is evidence of 

 fluid collecting under the skin in the legs and under the chest and other 

 underbody surfaces. 



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