Equine Viral Arteritis

Horse Virus Detection and Treatment
Equine viral arteritis (EVA) is defined by Timoney (2019) in the Merck Veterinary Manual as “an acute, contagious, viral disease of equids caused by equine arteritis virus (EAV).” EAV is also known as Epizootic cellulitis-pinkeye, Equine typhoid, and Rotlaufseuche (Timoney, 2019). The virus can cause symptoms of fever, conjunctivitis, depression, anorexia, nasal discharge, skin rash, subfertility in stallions, and death on young foals and abortion in mares (Price, Rentsch, Burn & Spector, 1998). 
The etiology of EVA starts with respiratory exposure: the virus invades the respiratory tract, where it then proceeds to duplicate itself in the tonsillar tissue and nasopharyngeal epithelium, as well as in bronchial macrophages (Timoney, 2019). Cells infected by EVA then transmit the virus to the lymph nodes, resulting in further multiplication of the virus and ultimate release into the carrier’s blood stream. Within one week, EVA will localize in small blood vessels and panvasculitis will result. The adrenals, thyroid and liver will also be infected. Vascular lesions, swelling and necrosis of infected vessels will occur, which sets off a chain reaction of negative effects, including edema and hemorrhaging. After a week and half, lesions will go into repair. After a month of infection, the virus is typically no longer detectable, though carrier stallions will carry the virus in their sex glands for years (Timoney, 2019). Currently no evidence exists that the disease can be contracted by humans, and it is hypothesized that it may also infect alpacas and llamas. Transmission between equines occurs via respiration, venereal contact or congenitally (Timoney, 2019). It is not a Foreign Animal Disease but does occur globally among equines throughout the world. EVA is a reportable disease in Virginia (Virginia Department of Health, 2016).
Clinical signs include fever, dependent edema on the hind limbs and mid-ventral edema on stallion’s scrotum and sheath (on mammary glands in the mare). Conjunctivitis may also be seen. Nasal discharge, lacrimination, hives, and depression have been found but these signs are rare (Timoney, Creekmore, Meade, Fly, Rogers and King, 2008). History questions that would be important to ask would be whether the horse has moved locations recently or come into contact with other horses, whether semen shipments were received and used, and what donors or recipients were recently at the farm (Timoney et al., 2008).
The disease is diagnosed by lab testing (Timoney et al., 2008). The clinical diagnosis is insufficient to accurately diagnose EVA. As Timoney et al. (2008) also point out, “presence of a neutralizing antibody titer (>1:4) to EAV in a single serum sample” is insufficient to confirm diagnosis (p. 5). Serological confirmation occurs with demonstration of seroconversion or a significant (4-fold or greater) increase in antibody titer. Tests include: virus neutralization, complement fixation, agar gel immunodiffusion, indirect fluorescent antibody, fluorescent microsphere immunoassay (MIA) and enzyme–linked immunosorbent assays (ELISA) (Center for Food Security and Public Health, 2009).
Collecting serum samples for shipment from lab should include taking nasopharyngeal swabs, conjunctival swabs or unclotted blood samples. If blood sampes are taken they must be anticoagulated using acid citrate dextrose or else with EDTA. Samples should be refrigerated and shipped cold. Semen samples should be taken from sperm-rich ejaculate fraction as the virus will not be found in pre-sperm (Center for Food Security and Public Health, 2009).
Post-mortem samples should collected from colon, spleen, lymph nodes and cecum, or adrenal cortex. For aborted or stillborn foals, the placenta and fetal fluids/tissues will yield a sufficient sample. Samples should be handled and shipped in the same way.
There are many labs that samples can be shipped to but Murray State University Breathitt Veterinary Center in Kentucky is one of the nearest. The form needed for filling out is attached in the appendix of this document via a URL link. The cost is minimal and can be completed for under $50.
There is no specific treatment of EVA and most healthy adult horses will recover naturally (Center for Food Security and Public Health, 2009). The virus can be inactivated by using detergents and disinfectants.
EVA can be controlled however by vaccination. Carrier stallions should not be used for breeding and should not be placed into contact with other mares or stallions. Sound management is the recommended policy for reducing the spread of the virus. Practices to follow include:
· Isolating all horses returning from farms and new arrivals for 3 to 4 weeks to see if symptoms appear before allowing them to mingle with the rest of the horses on the farm
· Pregnant mares should be segregated
· All breeding stallions should have blood tests done
· Semen should be tested
· Noncarrier stallions should be vaccinated annually
· Hygiene should be observed.
References
Center for Food Security and Public Health. (2009). Equine viral arteritis. Retrieved from http://www.cfsph.iastate.edu/Factsheets/pdfs/equine_viral_arteritis.pdf
Price, S. D., Rentsch, G., Burn, B., & Spector, D. A. (1998). The Whole Horse Catalog: The Complete Guide to Buying, Stabling and Stable Management, Equine Health, Tack, Rider Apparel, Equestrian Activities and Organizations... and Everything Else a Horse Owner and Rider Will Ever Need. Simon and Schuster.
Timoney, P. (2019). Overview of Equine Viral Arteritis. Retrieved from https://www.merckvetmanual.com/generalized-conditions/equine-viral-arteritis/overview-of-equine-viral-arteritis?query=Equine Viral Arteritis
Timoney, P. J., Creekmore, L., Meade, B., Fly, D., Rogers, E., & King, B. (2008). 2006 Multi-State Occurrence of EVA. https://www.animalagriculture.org/resources/Documents/Conf - Symp/Symposiums/2016 Equine/EDF Resources/EVA/USDA EVA_2006_Multistate_USAHA.pdf
Virginia Department of Health. (2016). One health notes, 1(1). Retrieved from
http://www.vdh.virginia.gov/content/uploads/sites/123/2016/12/OneHealthJan2016.pdf
Appendix
Link to Accession Form for MSU Vet Center https://breathitt.murraystate.edu/forms/Accession.pdf