Arteritis, Equine Viral

Arteritis, Equine Viral



Basic Information  image



Definition


Equine viral arteritis (EVA) is a contagious arterivirus disease of horses named for the characteristic vascular lesions that develop.



Epidemiology



Species, Age, Sex




• Disease of horses, but antibodies have been found in donkeys


• Disease depends on age and sex


• Inapparent infection, especially in mares


• Persistent infection only in stallions (testosterone dependent)



Genetics and Breed Predisposition




• Seroprevalence varies by country, breed, and age. EVA is endemic in Standardbreds (75%–80% seropositive) but has a low prevalence in Thoroughbreds, with a 1% to 5% seropositive rate. Many European Warmblood stallions are seropositive.


• Genetic differences conferring resistance to infection may be a factor but have not been proven.



Risk Factors




• Stallions may be inapparent carriers and can shed virus in the semen for years. Cooled or frozen serum can still retain infective virus.


• Infected mares and/or vaccinated mares bred to infected stallions can become infected and shed the virus.



Contagion and Zoonosis




• EVA is an arterivirus in the family of Arteriviridae. The first Bucyrus strain was isolated in 1953. Virulence is variable in terms of clinical disease and abortion of viral isolates, but all strains are neutralized by polyclonal antiserum from the highly virulent Bucyrus strain.


• There is no known zoonotic potential.



Geography and Seasonality


Worldwide except for Iceland and Japan



Clinical Presentation



History, Chief Complaint




• Anorexia, depression, edema (ventral limbs, preputial [male], mammary [mare]), abortion storms, urticaria.


• Most infections are subclinical or inapparent.



Physical Exam Findings




• Variable clinical signs (depend on age, condition of horse, viral strain, environmental conditions)


• Usually inapparent infection, particularly in mares


• Systemic disease: Fever (105°–106° F), anorexia, depression, edema (ventrum, periorbital, distal limbs, prepuce, mammary), urticaria, conjunctivitis, rhinitis, cough/dyspnea


• Less common: Icterus, photophobia, corneal opacity, abdominal pain, diarrhea, ataxia, petechiation, lymphadenopathy


• Abortion (3–10 months’ gestation) with no premonitory signs


• Neonates: Fulminant severe interstitial pneumonia or fibrinonecrotic enteritis


• Stallions: Temporary subfertility, decreased libido, decreased sperm motility, concentration, and morphology up to 7 weeks


• Stallions with persistent infection: No change in semen quality after acute recovery



Etiology and Pathophysiology




• Transmission is primarily by inhalation of aerosolized virus from respiratory secretions and contact with venereal secretions, urine, or exposure to aborted fetus or placenta. Indirect transmission of the virus with fomites is possible.


• Incubation is 3 to 14 days; the virus then spreads to the lungs and bronchial lymph nodes.


• The circulatory system spreads it through rest of body, with infection and replication of virus occurring in the endothelial cells.


• Increased vascular permeability, hemorrhage, and edema with degeneration and necrosis of the tunica media of small arteries (>1 mm).


• Mares remain infective for up to 2 weeks after infection, with shedding of the virus in nasal secretions.


• Transplacental infection of the fetus is possible if the mare is infected in late pregnancy.


• Virus is not isolated from horses after 28 days except for stallions.


• Persistent infection in stallions


• Unknown mechanism, testosterone dependent
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Arteritis, Equine Viral

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