AHSV9

AHSV-9 is one of the nine serotypes of African horse sickness virus (AHSV), a member of the genus Orbivirus in the family Reoviridae. AHSV is a non-enveloped, double-stranded RNA virus with a segmented genome, and it primarily infects horses and other equids. The serotypes are defined largely by the outer capsid protein VP2, and immunity to one serotype provides limited protection against others. As a result, AHSV-9 is distinguished from the other serotypes by its antigenic properties.

Transmission of AHSV, including AHSV-9, is mainly through Culicoides biting midges, which act as biological vectors. Horses and other equids are the principal hosts affected, while existing vector distributions limit the geographic range to regions where competent midges are present. Outbreaks have historically been concentrated in sub-Saharan Africa, with occasional incursions into other regions when suitable vectors are present or introduced.

Clinical disease caused by AHSV, including serotype 9, can present in several forms. The circulatory (cardiorespiratory) form and the pulmonary form are the most severe, often accompanied by high fever, edema around the head and neck, respiratory distress, and substantial mortality. Less severe febrile forms may also occur. Mortality rates vary with serotype, host factors, and management.

Diagnosis relies on molecular and serological methods, such as RT-PCR and virus isolation, with serotyping determined by neutralization tests or VP2-based assays. Vaccination strategies in endemic settings use multivalent, serotype-containing vaccines, complemented by vector control and movement restrictions to prevent spread. AHSV-9 remains a component of ongoing surveillance and research on AHSV diversity and vaccine efficacy.