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External and internal events of Rhipicephalus sanguineus larvae and nymphs infection by Metarhizium anisopliae

The adhesion, germination and colonization of Rhipicephalus sanguineus larvae and nymphs by Metarhizium anisopliae as well as the lesions caused by the fungus were studied. For this purpose, 11 groups of 250 larvae each and 11 groups of 75 nymphs each were bathed during 3 minutes under manual shaking in a 10(8) conidia/ml suspension. Corresponding control groups were bathed only in the suspension vehicle. Ticks were also submitted to both conventional microscopy and scanning eletronmicrocopy analyses at several post-infection periods (1 and 18 hours and 1, 2, 3, 4, 5, 6, 7, 9, and 11 days). Conidial germination occurred in less than 18 hours post-inoculation and the fungus penetration through the tegument into the larvae and nymphs in, respectively, two and three days post-infection. Following penetration, the fungus invaded the body of the ticks and colonized it diffusely without a noticeable predilection for tissue, but no apparent lesions were observed. Death of larvae and nymphs occurred on the 3rd and 4th post-infection days and pathogen sporulation over the dead tick began on the 6th post-infection day.

dog; tick; biological control; microbial control; entomopathogenic fungus

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