conjunctivitis, and depression. Other clinical signs are swelling around the eyes and 

 ocular discharge, swollen limbs, swollen genitals in stallions, and swollen mammary 

 glands in mares. Abortion in pregnant mares is also a symptom of EVA. Abortion 

 rates in EVA-infected mares range from 10 percent to 70 percent. 



Diagnosis 



Horse owners should suspect EVA when respiratory symptoms accompany an 

 abortion in a mare. Because the clinical signs of EVA are similar to those of other 

 respiratory disease and no characteristic lesions are found in EVA-aborted fetuses, 

 only diagnostic tests can confirm the disease. Virus isolation can be attempted 

 from swabs of the nose, throat, or eyes; semen, placentas, or fetal tissue; and blood 

 samples. The most common method of diagnosis is testing blood for the neutralizing 

 antibodies of the virus. Although presence of these antibodies alone does not indicate 

 active infection, it does signify that EVA exposure has occurred. The signs of active 

 infection are very high levels of antibodies on a single sample or a rising antibody 

 titer from paired blood samples collected 14 to 28 days apart. 



Treatment 



Although there is no specific treatment for EVA, care should include rest and, 

 in selected cases, antibiotics, which may decrease the risk of secondary bacterial 

 infection. Adult horses recover completely from the clinical disease. However, the 

 virus commonly persists in the accessory glands of recovered stallions, and thus these 

 carrier stallions continue to shed the virus for years and remain a significant source 

 of infection. 



Prevention 



A safe, effective, and low-cost avirulent live-virus vaccine is now available. Combining 

 this vaccine with isolation of the vaccinated animal from noninfected horses can 

 prevent the spread of EVA. Because properly vaccinated EVA-negative stallions do not 

 become carriers, all EVA-negative colts less than 270 days old should be vaccinated. 

 The vaccine is not approved for use in pregnant mares. 



All vaccinated horses should receive yearly boosters to protect against infection and, 

 for the stallions, to prevent the development of a carrier state. 



The EVA Uniform Methods and Rules contain minimum standards for detecting, 

 controlling, and preventing EVA. These may be found at http://www.aphis.usda.gov/ 

 vs/nahps/equine/eva or obtained by contacting the local APHIS-VS Area Office. 



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