Immunization with tick salivary gland extracts.

Tick burdens cause direct damage to hosts and transmit several disease agents, the majority of which are secreted into feeding lesions through tick salivary glands. Reduced incidence of naturally transmitted tick-borne diseases was recently observed among cattle immunized with tick salivary gland extracts (TSGE). The aim of this work was to compare the ultrastructure of salivary glands from Rhipicephalus (Boophilus) microplus removed from cattle that were immunized with TSGE to those from control cattle injected with saline. Partially fed female ticks that infested these cattle were collected, and their salivary glands were removed and compared with light microscopy. More extensive salivary gland damage was observed in ticks collected from cattle immunized with TSGE than those from saline controls. Salivary glands from immunized cattle had extensive necrosis in agranular c and f cells; partial necrosis in granular b, c, and e cells; and slight necrosis in a and d cells. These results indicated that host immunization with TSGE causes detrimental effects to female tick salivary glands and correlated with the reduced incidence of naturally transmitted tick-borne diseases observed among these cattle.