African horse sickness in The Gambia: circulation of a live-attenuated vaccine-derived strain

• Published in: Epidemiology and infection Vol. 140; no. 3; pp. 462 - 465
• Main Authors: OURA, C. A. L., IVENS, P. A. S., BACHANEK-BANKOWSKA, K., BIN-TARIF, A., JALLOW, D. B., SAILLEAU, C., MAAN, S., MERTENS, P. C., BATTEN, C. A.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.03.2012
• Subjects: African Horse Sickness - epidemiology; African Horse Sickness Virus - classification; African Horse Sickness Virus - immunology; African Horse Sickness Virus - isolation & purification; Animals; Antibodies; Antibodies, Neutralizing - blood; Antibodies, Viral - blood; Biological and medical sciences; Epidemics; Equidae; Fundamental and applied biological sciences. Psychology; Gambia - epidemiology; Horses; Immunization; Infections; Microbiology; Other viruses; Reverse Transcriptase Polymerase Chain Reaction; RNA, Viral - genetics; RNA, Viral - isolation & purification; Sequence Analysis, DNA; Sequence Homology; Seroepidemiologic Studies; Serology; Serotyping; Vaccines; Vaccines, Attenuated; Viral Vaccines; Virulence; Viruses; Gambia; West Africa; Sub-Saharan Africa; Africa; Nigeria; Senegal; Spain; immunization (vaccination); veterinary epidemiology; Animal pathogens; asymptomatic viral infections; veterinary virology; Infection; African horse sickness; Vaccine strain; Viral disease; Tropical zone; Attenuated strain; Epidemiology
• ISSN: 0950-2688; 1469-4409
• DOI: 10.1017/S095026881100080X

African horse sickness virus serotype 9 (AHSV-9) has been known for some time to be circulating amongst equids in West Africa without causing any clinical disease in indigenous horse populations. Whether this is due to local breeds of horses being resistant to disease or whether the AHSV-9 strains circulating are avirulent is currently unknown. This study shows that the majority (96%) of horses and donkeys sampled across The Gambia were seropositive for AHS, despite most being unvaccinated and having no previous history of showing clinical signs of AHS. Most young horses (<3 years) were seropositive with neutralizing antibodies specific to AHSV-9. Eight young equids (<3 years) were positive for AHSV-9 by serotype-specific RT–PCR and live AHSV-9 was isolated from two of these horses. Sequence analysis revealed the presence of an AHSV-9 strain showing 100% identity to Seg-2 of the AHSV-9 reference strain, indicating that the virus circulating in The Gambia was highly likely to have been derived from a live-attenuated AHSV-9 vaccine strain.