author(s)
Shimaa S Ahmed, Ola H Zyaan, Shaimaa A Moamen and Shireen AM Maamoun

abstract
The present study aimed to demonstrate the effects of eucalyptus oil nanoemulsion on the Ornithodoros savignyi semi engorged females. For this purpose, the semi engorged females of O. savignyi were exposed to eight serial dilutions of oil nanoemulsion (5, 10, 15, 20, 25, 30, 35, and 40%) using a ‘‘dipping method’’ in vitro. The semi engorged ticks were immersed in different dilutions (5 replicates per dilution) for 2 min then each replicate was incubated in separate vial at 27°C±1, 75% relative humidity. The mortality percentage for adult ticks exposed to different dilutions of eucalyptus oil nanoemulsion showed a concentration-dependent effect. It was however not significant only for the 5% when compared to the non-treated ticks (P < 0.05). While, it was significant for other dilutions (P < 0.05). The highest mortality was reported for ticks treated with 40%. The LC₅₀ obtained from bioassay test was 25%. Salivary glands were dissected and evaluated through morphological techniques using light and scanning microscopy. Results showed that eucalyptus oil nanoemulsion is an effective substance that acts morpho-physiologically on the tick glandular tissue, causing changes in the acini shape, vacuolation in acinar cells, and disruption of the tissue by cell death process with subsequent formation of apoptotic bodies, thus preventing the accurate identification of different types of acini. These results confirmed the potential of eucalyptus oil nanoemulsion as an alternative method for controlling Ornithodoros savignyi ticks, instead of synthetic acaricides.