LYMPHOCYTE PROLIFERATIVE RESPONSES AND THE OCCURRENCE OF DERMATOPHILOSIS IN CATTLE NATURALLY INFESTED WITH AMBLYOMMA-VARIEGATUM

The proliferative response of lymphocytes from tick-infested Zebu type , N'Dama and Friesian cattle and acaricide-treated Zebu types and Frie sians in concanavalin A (Con A) stimulated cultures was monitored regu larly for periods ranging from 11 to 27 months. The numbers of ticks o n the animals and the presence of dermatophilosis were also noted. The Friesian cattle carried most and the N'Dama fewest Amblyomma variegat um ticks. The tick-infested Friesians all developed severe clinical de rmatophilosis within 5 months of becoming tick-infested. Dermatophilos is lesions on the tick-infested Zebu type and N'Dama cattle were less common and less severe especially in the N'Damas. The proliferative re sponse of lymphocytes from tick-infested Friesians in Con A stimulated cultures fell to almost half that of the acaricide-treated Friesians soon after the former became tick-infested. The tick-infested Zebu typ es also developed a depressed response compared with the tick-free Zeb u group over a 27 month study period. However, the responses of the N' Damas was similar to that of the tick-free Zebu types. The addition of autologous serum to Con A stimulated cultures of lymphocytes derived from the tick-infested Zebu types and N'Damas suppressed their prolife rative response compared with that of similar cultures for the tick-fr ee Zebu types.