equine assay data sheet

Equine encephalosis virus (EEV)

Test code: S0272 - Ultrasensitive qualitative detection of equine encephalosis virus (EEV) by reverse transcription real time PCR.

Equine Encephalosis Virus (EEV) is an insect-borne virus belonging to the genus Orbivirus within the family Sedoreoviridae. It is the causative agent of equine encephalosis (EE), a generally mild febrile disease affecting horses and other equids, including donkeys and zebras. Seven serotypes of EEV (EEV-1 to EEV-7) have been identified.

EEV is a non-enveloped virus with a segmented genome consisting of ten linear double-stranded RNA (dsRNA) segments. The total genome size is approximately 19–20 kilobase pairs (kb). These segments collectively encode seven structural proteins (VP1–VP7) and four non-structural proteins (NS1, NS2, and NS3/NS3A).

The virus is endemic in southern Africa, particularly South Africa, where a high seroprevalence indicates widespread prior exposure in equine populations. In recent years, EEV has spread beyond Africa, with outbreaks or serological evidence reported in Israel (2008–2009), Ethiopia, Ghana, Gambia, and other regions.

Clinical disease is often mild or subclinical. When clinical signs appear, they typically include a short-duration fluctuating fever (lasting 2–5 days), loss of appetite, elevated heart and respiratory rates, nasal congestion, and mild respiratory signs. Occasional cases may show facial swelling or conjunctival hemorrhages. Neurological signs are rare, and despite its name, equine encephalosis is not primarily a neurological disease. Mortality is low (generally ≤5%), and most horses recover fully. Pregnant mares may occasionally abort.

Diagnosis of EEV infection can be challenging. Virus isolation is difficult and time-consuming. Serological testing for antibodies is complicated by the high prevalence of past exposure in endemic areas, making it hard to differentiate recent from historical infections. Consequently, reverse transcription polymerase chain reaction (RT-PCR), is the preferred diagnostic approach, offering high sensitivity and specificity for the detection of viral RNA. (Maan et al., 2019; Rathogwa et al., 2014).

Utilities:

• Help confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of the presence of this virus
• Help ensure that horse populations are free of this virus
• Early prevention of spread of this virus
• Minimize human exposure to this virus
• Safety monitoring of biological products that derive from horses

References:
Maan S, Belaganahalli MN, Maan NS, Potgieter AC, Mertens PPC. Quantitative RT-PCR assays for identification and typing of the Equine encephalosis virus. Braz J Microbiol. 2019 Jan;50(1):287-296.

Rathogwa NM, Quan M, Smit JQ, Lourens C, Guthrie AJ, van Vuuren M. Development of a real time polymerase chain reaction assay for equine encephalosis virus. J Virol Methods. 2014 Jan;195:205-10.

Specimen requirements: 0.2 ml whole blood in EDTA (purple top) tube; or 0.2 ml fresh or frozen tissue; or 0.2 ml cell culture.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative reverse transcription real time PCR

Normal range: Nondetected