Equine Arteritis Virus
The Disease | Viron Structure | Response to EAV Infection | Vaccine Information | Diagnosis
The Disease
- Systemic viral infection of horses and donkeys
- Monocytes, macrophages and endothelial cells of small blood vessels
- Symptoms are variable: from asymptomatic infections to severe illness
- Diagnosis by the laboratory: detection of serum antibody (VN, ELISA) or detection of virus or viral RNA
- Most important consequences
- Abortion in pregnant mare
- Persistent infection in stallions: long term virus shedders
Viron Structure
Response to EAV Infection
- Pyrexia: duration: 0 – 8 days, peak T (38.5°C - 41 °C) 2.
- Clinical signs: depression, anorexia, depression; lethargy; anorexia; weakness; congestion or petechiation of mucosal membranes; palpebral, periorbital or supraorbital edema; conjunctivitis; edema of mammary glands, prepuce, ventral abdomen and legs; urticarial skin rash; ataxia; respiratory distress; rhinitis with serous nasal discharge; diarrhoea and abortion in the pregnant mare OR none
- Virus nasal shedding: duration 0 – 11 days; virus tires (1– 105 TCID50/ml)
- Cell associated viraemia: day 2 - day 14 (may persist for several weeks)
- Serum VNAb: from day 7 post-infection – months or years
EAV Vaccine Information
- Live attenuated
- Good immunity
- Not safe in pregnant mares
- Inactivated
- formalin inactivated, no adjuvant (Japan)
- Inactivated, adjuvant (commercial)
- Serological discrimination between vaccinated and infected not possible
- Marker vaccines Allow vaccination and protection of a population without compromising serological detection of naturally infected animals.
EAV Diagnosis
Serology: It has been shown that horses develop long-lived circulating neutralising antibodies after infection. The Virus Neutralisation (VN) test is the internationally recognised standard serological test for EAV. However, it is not currently possible to differentiate between antibodies produced by natural infection and those produced by vaccination.
Virus Isolation: During the acute stage of the disease virus may be isolated from nasopharyngeal swabs, heparinised blood, semen, aborted foetuses and possibly urine. To optimise the chances of isolation of virus, specimens should be collected as soon as possible after the onset of fever in affected horses. Virus isolation from semen is also a means of identifying chronic ‘shedder’ stallions.
Nucleic Acid Detection: A reverse transcriptase polymerase chain reaction (RT-PCR) assay has been developed and is used for detection of EAV in clinical and post-mortem specimens. Results comparable with virus isolation have been obtained and the assay takes only 48 hours to carry out. However, PCR does not distinguish between infectious and non-infectious or incomplete virus and therefore cannot be used to determine the current infectivity status of the horse.
Equine Viral Arteritis is a notifiable disease in the UK, under the Equine Viral Arteritis Order 1995. It is a legal requirement to notify the Ministry of Agriculture, Fisheries and Food (MAFF) when it is suspected that a stallion has the disease or is carrying the virus. MAFF must also be notified if a mare which has been covered or inseminated within the last 14 day becomes infected.
