Efficacy of rBm86 against Rhipicephalus (Boophilus) microplus (IVRI-I line) and Hyalomma anatolicum anatolicum (IVRI-II line) infestations on bovine calves

Abstract

With an aim to evaluate the protective potentiality of rBm86 against Rhipicephalus (Boophilus) microplus Indian Veterinary Research Institute (IVRI)-I line and Hyalomma anatolicum anatolicum IVRI-II line infestations on crossbred (Bos indicus × Bos taurus) calves, 20 animals of 3 months of age were randomly divided in to four equal groups and maintained in tick-proof conditions. Animals of groups 1 and 2 were immunized with 2 ml of rBm86 (100 μg)-based vaccine (procured from Revetmex S.A. de C.V, Mexico City, Mexico) thrice at 30 days interval. Animals of groups 3 and 4 were kept as negative control and inoculated with PBS only. Each animal of group 1 and 3 was challenged with 7-day-old 50 unfed adults of H. anatolicum anatolicum (1:1, male and female), and each animal of groups 2 and 4 was challenged with 6-8-day-old R. (B.) microplus larvae obtained from 50 mg of eggs, on 17th day of the last immunization. The efficacy of rBm86 against tick infestations was determined as percentage reduction in number of adults dropped (DT%), engorged body weight (DR%), egg masses (DO%), and immunogen efficacy (E%). The calculated data were 11.8, 10.8, 15.0, and 25.1 %, respectively, for DT, DR, DO, and E% against H. anatolicum anatolicum infestation, while in the case of R. (B.) microplus infestation, the corresponding data were 6.4, 11.24, 40.7, and 44.5 %, respectively. The results indicated partial effectiveness of rBm86 antigen(s) in imparting protection against homologous and heterologous challenge infestations of Indian ticks. The results indicated identification of more effective antigen(s) for the development of vaccine against economically important tick species in India.