THE POSSIBLE ROLE OF 2 COMMON 3-HOST TICKS, RHIPICEPHALUS-APPENDICULATUS AND AMBLYOMMA-HEBRAEUM, IN THE TRANSMISSION OF BOVINE LEUKOSIS VIRUS

The possible role of Rhipicephalus appendiculatus and Amblyomma hebrae um in the mechanical and transstadial transmission of bovine leukosis virus (BLV) was investigated. BLV-free laboratory strains of X. append iculatus and Al hebraeum nymphal ticks (n = 400) were led on a BLV-inf ected and a negative control bovine. At various intervals after engorg ement the ticks were homogenised and injected subcutaneously into BLV- negative sheep. Adult R, appendiculatus and A, hebraeum, which had fed as nymphs on the BLV-infected bovine, were then allowed to feed on BL V-negative sheep. A control sheep was also injected intravenously with blood from the infected bovine. Only the control sheer that received blood from the BLV-positive bovine seroconverted 9 months later. All t he other surviving sheep remained serologically negative during the 13 months observation period. It is suggested that the nymphal stages of these tides probably do not play a role in the transstadial transmiss ion of BLV in southern Africa. The significance of these results is di scussed.