Induction of Resistance to Rhipicephalus Appendiculatus Neumann in New Zealand White Rabbits through Immunisation with Commercial Moulting Hormons and Tick-Derived Haemolymph

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Samuel Kamau Mbogo
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Samuel Kamau Mbogo
This study was conducted to assess the possibility of immunising rabbits against Rhipicephalus appendicuatu Neumann, the vector for East Coast fever and Corridor disease, the most important tick-borne diseases in East and Central Africa. The antigens whose efficacy in the control of this vector were assessed included commercially available insect moulting hormone, beta-ecdysone and tick haemolymph components. However, since antibodies playa major role in the acquisition of tick resistance, it was imperative before any immunisation attempts were made to study the passage of antibodies (specifically immunoglobulin G (IgG) across the tick midgut membrane since potentially protective antigens could be of little value if the antibodies whose production they elicit do not cross the midgut barrier. These studies were undertaken, using the enzyme linked immunosorbent assay (ELISA) and the results obtained indicated that IgG can cross the midgut barrier and retain its biological activity. In addition the study also showed that the quantities of the IgG that cross this barrier are positively correlated to the antibody titres in the host blood. Of prime importance \vas the finding that destruction of the midgut barrier with anti-tick midgut antibodies could facilitate the passage of IgG across the midgut by an eight fold concentration factor and these antibodies maybe directed against antigens entirely different from those of midgut origin. Based on this findings, it was found feasible to immunise hosts against ticks using antigens that are found in the haemolymph.