African Horse Sickness (AHS)

Test code: S0061

Test name: Ultrasensitive qualitative detection of African Horse Sickness virus by reverse transcription real time polymerase chain reaction

African horse sickness virus (AHSV) belongs to the genus Orbivirus in the family Reoviridae and is transmitted by Culicoides species midges, of which C. imicola is considered the most important. There are nine AHSV serotypes with significant genomic differences.

The AHSV genome is composed of ten double-stranded RNA segments which encode at least ten viral proteins. The genome segments are numbered 1–10 in order of their migration in PAGE. Seven of the viral proteins are structural and form the double-shelled virus particle.

African horse sickness (AHS) caused by this virus is associated with high morbidity and mortality in equine species. AHS is enzootic in southern, eastern, western and central Africa and probably in Yemen. Epizootics have occurred outside these regions on several occasions (Mellor, 1994; Mellor and Hamblin, 2004). For example, Spain experienced an outbreak of AHS in 1987–1989 following importation of zebras from Namibia (Rodriguez et al., 1993). The disease caused by AHSV serotype 4 (AHSV 4) also has been detected in Portugal (1989) and in Morocco (1989-1991).

Serological testing for AHSV is not practical because of the numerous serotypes of the virus. Molecular detection of AHSV is the best alternative for rapid diagnosis of AHSV. RT-PCR is a sensitive and rapid method for detecting AHSV nucleic acids during either the incubation period at the start of an African horse sickness (AHS) epizootic, or for epidemiological investigations in species where clinical signs may not be apparent.

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of AHSV infection.
• Ensure that horse populations are free of AHS
• Early prevention of spread of this virus
• Minimize personnel exposure to this virus
• Safety monitoring of biological products that derive from horses

References:
Mellor, P.S. (1994). Epizootiology and vectors of African horse sickness virus. Comparative Immunology, Microbiology and Infectious Diseases 17:287-296.
Mellor, P.S. and Hamblin, C. (2004). African horse sickness. Veterinary Research 35:445-466.
Rodriguez, M., Hooghuis, H. and Castano, M. (1993). Current status of the diagnosis and control of African horse sickness. Veterinary Research 24:189-197.

Specimen requirements: 1 ml whole blood in EDTA (purple top) or ACD (yellow top) tube, or plasma, serum or tissue, shipped overnight at room temperature; or 1 ml frozen plasma, serum or tissue, shipped frozen.

For specimen types other than those listed here, please call 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