Immunization of cattle against Boophilus microplus using extracts derived from adult female ticks: Histopathology of ticks feeding on vaccinated cattle

Abstract

Immunization of cattle against Boophilus microplus using extracts derived from adult female ticks: histopathology of ticks feeding on vaccinated cattle. International Journal for Parasitology 16: 35–41. Histological examination of the tick Boophilus microplus fed on cattle vaccinated with tick extract showed that the gut was the primary site of damage. Within 24–48 h of attachment digest cells were either sloughed off into the lumen or were completely destroyed leaving only the basal lamina and muscle layer. Subsequent rupture of the gut allowed host leucocytes to enter the haemocoel and attack other tissues. After 6 days the surviving ticks showed a delay in development of digest cells and gut basophilic cells. Many host leucocytes had escaped into the haemolymph and these cells destroyed tick muscle and Malpighian tubules but not salivary glands. Females which survived to post-engorgement also had damaged gut cells. In males the histopathology of the gut was similar but the accessory gland of the reproductive organ was also damaged by host leucocytes. These effects on feeding ticks were not found on control cattle and have not been reported on animals with naturally acquired resistance to tick infestations. Vaccination apparently stimulated a different mechanism of resistance to ticks.