Babesia bovis infection of secretory cells in the gut of the vector tick Boophilus microplus

Agbedh R. I. S., Kemp D. H. and Hoyte H. M. D. 1986. Babesia bovis infection of secretory cells in the gut of the vector tick Boophilus microplus. International Journal for Parasitology 16: 109–114. The gut epithelium of engorged Boophilus microplus females has only two cell types: digest cells and basophilic staining cells. A total of 12 Boophilus microplus females which had fed on Babesia bovis infected blood in vivo and in vitro were examined by light and electron microscopy. Some 84 gut cells were infected with B. bovis fission bodies and all were basophilic cells. This cell has secretory granules in the cytoplasm and lacks the pinocytotic vesicles and lysosomes of the digest cells. A basal labyrinth extends its contact with the haemolymph and the cell has many mitochondria. Ultrastructural studies confirmed that it is not a digest cell but has secretory activity, and may have other functions. Other authors have shown that a similar cell type in Rhipicephalus sanguineus synthesises and secretes most of the egg proteins (vitellogenins). As the Babesia fission bodies matured there was a loss of basophilia, hypertrophy of the nuclei and eventually degeneration of the basophilic cell. Kinetes (vermicules) were released into the haemolymph from these cells.