Abstract:
To determine the geographical distribution and relative abundance of Culicoides species associated
with livestock, 220-V down-draught light-traps equipped with 8-W blacklight tubes were operated at 34
sites in different climatic regions in South Africa and Lesotho. From January 1984 to September 1986,
3 041 631 Culicoides, belonging to at least 50 species, were collected in a total of 959 collections. Of
these, 572 412 individuals were identified and sexed.
Culicoides species were found to be widespread in South Africa and were collected in varying numbers
at all the sites sampled. The average catch size, however, was larger in frost-free areas than in
areas with extreme winters. The more abundant and widespread species, which have the potential to
be vectors of stock-associated viruses such as bluetongue and African horsesickness, were C. imicola,
C. leucostictus, C. schultzei s.l., C. pycnostictus, C. nivosus, C. similis, C. zuluensis, C. magnus, C.
bedfordi, C. neavei, C. brucei, C. tropicalis, C. exspectator, C. gulbenkiani, C. bolitinos, C. ravus, C.
coarctatus and C. onderstepoortensis. Of these, C. imicola was the most abundant species, being
dominant at 17 of the 34 sites sampled and accounting for 71,4% of the specimens collected. As C.
imicola is relatively uncommon in hot and dry as well as cool and wet areas, this species cannot be
regarded as the only vector of stock-associated viruses in southern Africa. Future laboratory vector competence
studies, i.e. determination of viral-infection and -transmission rates, should first concentrate
on the above-mentioned Culicoides species, especially those known to feed on livestock.
