Equine Viral Arteritis
Equine Viral Arteritis (EVA)
In acute cases, transmission occurs mainly via aerosols and respiratory secretions. Furthermore, the aborted material in EAV-induced abortions is an important source of infection. During acute infection, mares excrete virus via vaginal fluid, whereas stallions can excrete virus via seminal fluid over a very long period of time. During pregnancy, virus transmission can occur from the mare to the foal.
Situation in Austria
Equine Viral Arteritis is a disease according to the European Animal Health Law, whose introduction and spread within the EU must be prevented and which must be monitored. Positive test results must therefore be reported to the official veterinarians. Currently, there is no special surveillance program in Austria.
Equine viral arteritis (EVA) is caused by equine arteritis virus, a single-stranded RNA virus of the arterivirus genus.
Most cases of EVA are subclinical, although clinical signs can vary significantly in type, duration, and severity. After primary pathogen replication in alveolar macrophages, the virus may further replicate in macrophages and endothelial cells of blood and lymphatic vessels after spreading through the circulation, resulting in characteristic panvasculitis and vascular necrosis. Symptoms range from flu-like symptoms with fever, anorexia, conjunctivitis, and nasal discharge to anemia, leukopenia, edema especially of the lower abdomen, hind limbs, scrotum, and prepuce, supra- or periorbital edema. Infection during pregnancy may result in miscarriage (from the 3rd month after infection until the end of gestation) and birth of weak foals. The lethality is very low, usually recovery occurs even after severe symptoms of the disease. However, increased mortality rates with symptoms of pneumonia, enteritis, or pneumo-enteritis are possible in young foals up to 3 months of age. Since the virus persists in the accessory gonads, stallions can become permanent or long-term excretors despite being cured and thus play a crucial role in the spread of the virus.
A diagnosis based on clinical symptoms is not possible because EAV is difficult to distinguish from other diseases. A suspected clinical diagnosis must therefore be confirmed by virus isolation and pathogen detection in PCR or specific AK detection. ELISA, virus neutralization, and RT-PCR are suitable for this purpose; CFT is less sensitive than ELISA and thus may be used more for the detection of recent infection.
There is no serological method that can reliably distinguish field titers from vaccine titers, thus in countries with approved vaccination, antibody testing is recommended before the start of basic immunization to avoid immunization of already diseased animals. However, in some countries the importation of horses with positive EAV antibody detection is prohibited.
Differential diagnosis: Equine herpesvirus 1 & 4, African horse sickness, Equine infectious anemia, Equine influenza, Equine rhinitis virus A & B, Equine adenovirus.
Last updated: 10.10.2023