Seroprevalence of African horse sickness virus and equine encephalosis virus in equids and abundance of Culicoides midges in Namaqualand, South Africa

Abstract

The purpose of this work was to determine the seroprevalence of African horse sickness virus (AHSV) and equine encephalosis virus (EEV) in Namaqualand, South Africa, as well as the abundance of potential vectors i.e. Culicoides midges in the area. Namaqualand is located in the arid north-west of South Africa. The area represent a unique biogeographical region. There are very phew studies on the seroprevalence of AHSV and EEV in the area. These diseases are unknown in the area and horse owners normally do not vaccinate their animals against these diseases. Information regarding the occurrence of Culicoides midges in this area are relative scares. Blood samples collected from equids throughout the region were analysed to establish the seroprevalence of the two viruses. ELISA results indicate that 4.4% and 30.9% of 874 equines assayed in Namaqualand have antibodies against AHSV and EEV respectively. Midges were collected weekly over one year with light traps at three sites in the area. The six most common Culicoides species to be collected were: Culicoides ravus (29.7%), Culicoides bedfordi (25.2%), Culicoides #89 (9.6%), Culicoides subschultzei (7.4%), Culicoides herero (7.1%) and Culicoides nivosus (6.8%). Culicoides imicola represented 0.9% and Culicoides bolitinos represented 1.5% of the total catches. Namaqualand is a relativeley low risk area for AHS and EEV. The known vectors for these two diseases are present in low numbers.