Efficacy of rHaa86, an orthologue of Bm86, against challenge infestations of Hyalomma anatolicum anatolicum

Abstract

In an attempt to develop vaccine against Hyalomma anatolicum anatolicum, the protective efficacy of rHaa86 was evaluated against experimental challenge infestations of homologous tick species and lethal dose of Theileria annulata. Following challenge, a significant difference of 20.9% (P < 0.01) in the dropping per cent of ticks fed on immunized and control animals was recorded. A statistically significant reduction of 49.6 mg (P < 0.01) in the weight of ticks fed on immunized animals in comparison with control was noted. The ticks dropped from immunized animals laid fewer eggs and a reduction of 68.1 mg (P < 0.05) in comparison with the ticks fed on control animals was noted. The DT%, DO%, DR% and E% were calculated as 73.8, 31.3, 15.8 and 82.3% respectively. In all the calves fever (rectal temperature </=39.5 degrees C) was detected after a mean period of 7.2 days in immunized calves and on 5.8 days in control calves following lethal challenge with T. annulata. The mean Maximum Macroschizonts Index was 7.8% and 10.6% in the immunized and control calves respectively. Two calves (identification no. 351 and 354) died in the immunized group while all five calves died in the control group. The data demonstrated that rHaa86 antigen-based vaccine could serve as one of the effective components of the integrated control of H. a. anatolicum and T. annulata.