Exposure to papain alters the integument morphology of female Rhipicephalus microplus ticks (Acari: Ixodidae)

Papain is a cysteine protease extracted from Carica papaya latex, with high proteolytic action and anthelmintic and nematicidal properties. However, its effects on the control of the cattle tick, Rhipicephalus microplus are still little known. This study aimed to evaluate the acaricidal activity of papain and its effects on the integument of R. microplus engorged female ticks. Six groups were established: five treatment groups, in which the animals were exposed to papain at concentrations of 10, 20, 30, 40 and 50% (w/v) diluted in distilled water, and one control group. The ticks were immersed in the solutions for 5 min each, dried and kept in a BOD incubator at 27 ± 1°C. After seven days, integument samples were collected from five randomly selected ticks per group for histopathological analysis. The histopathological evaluation showed significant changes in all treatments, with a dose-dependent effect: disorganization of the cuticular structure, alterations in the subcuticle, cytoplasmic vacuolization and the presence of pyknotic nuclei in the epithelial cells. This is, to the best of our knowledge, the first report of the effects of papain on the morphology of the integument of ticks. Our results indicate that papain can affect the integument morphology at high concentrations, suggesting its potential as an enhancer for more effective control of the cattle tick.