The Effect Of Essential Oils And Acaricides On Toxicities And Enzyme Activities Of Two Ixodid Ticks

Ticks are haematophagous ectoparasitic arthropods that feed on mammals,birds,and reptiles;and many tick species are also vectors of bacteria,rickettsia,protozoa,and viruses.The emergence or re-emergence of tick-borne diseases is becoming an increasing problem for both humans and livestock.The tick Haemaphysalis longicornis is widespread in temperate regions,and can transmit a variety of pathogens resulting in diseases including babesiosis,theileriosis,rickettsiosis and anaplasmosis.These zoonotic diseases have been increasingly threatening the health of humans.The tick Hyalomma rufipes is the most widespread Hyalomma species in arid and semi-arid areas,especially in Africa and some provinces in China including Inner Mongolia,Shanxi,Ningxia and Xingjiang.It can transmit several zoonotic pathogens including Babesia occutans,Rickettsia spp.,and Congo-Crimean haemorrhagic fever virus,which can result in great economic losses.The present study investigated the possibility of plant-originated acaricides,including essential oils and acaricides,as alternatives for managing Ha.longicornis and Hy.rufipes.The toxicity of plant essential oils and acaricides was evaluated using direct-contact,fumigant and repellent bioassays.Meanwhile,the effect of essential oils and acaricides at median lethal concentration?LC50?on activities of Glutathione S-transferases?GST?,Carboxylesterase?CarE?,Mixed-function oxidase?MFO?and Acetylcholinesterase?AChE?of unfed adults of Ha.longicornis and Hy.rufipes was also explored.Additionally,the composition of the above used essential oils was also characterized using gas chromatography?GC?and gas chromatography-linked mass spectrometry?GC-MS?.The main results are as follows:1.Six essential oils including thyme oil,ceylon cinnamon oil,oregano oil,clove leaf oil,wintergreen oil and lemon oil,and two acaricides including?-cyhalothrin,and celangulin,resulted in various degrees of toxic effect toward different tick species and different development stages of ticks.Overall,clove leaf oil and oregano oil showed obvious acaricidal activity,whereas ceylon cinnamon oil and thyme oil displayed significant suffocating acaricidal property.2.For the enzymatic analysis of unfed adult Ha.longicornis against essential oils and acaricides under LC₅₀,the results were showed as follows:?1?After treated by essential oils and acaricides under LC₅₀,the activity of GST was significantly decreased?P<0.05?,except in thyme oil treatment group?P>0.05?.?2?After treated by essential oils and acaricides under LC₅₀,the activity of CarE was significantly decreased?P<0.05?,whereas in lemon oil treatment group,the activity of CarE were significantly increased?P<0.05?.?3?After treated by essential oils and acaricides under LC₅₀,the activity of MFO was significantly decreased?P<0.05?,except in lemon oil treatment group?P>0.05?.?4?After treated by celangulin,ceylon cinnamon oil and clove leaf oil under LC₅₀,the activity of AChE was significantly decreased?P<0.05?,whereas after treated by lemon oil,thyme oil,wintergreen oil and oregano oil,the activity of AChE was significantly increased?P<0.05?,and no significant change in the activity of AChE was observed at the given dose of?-cyhalothrin?P>0.05?.3.For the enzymatic analysis on unfed adults of Hy.rufipes against essential oils and acaricides under LC₅₀,results were displayed as follows:?1?After treated by essential oils and acaricides under LC₅₀,the activity of GST was significantly decreased?P<0.05?;whereas the lemon oil treatment group,the activity of GST was significantly elevated?P<0.05?.?2?After treatedby essential oils and acaricides under LC₅₀,the activity of CarE was significantly decreased?P<0.05?;whereas in the?-cyhalothrin,ceylon cinnamon oil and thyme oil treatment group,the activity of CarE was significantly elevated?P<0.05?.?3?After treated by?-cyhalothrin and clove leaf oil under LC₅₀,the activity of MFO was significantly decreased?P<0.05?;whereas in the ceylon cinnamon oil,oregano oil,wintergreen oil,lemon oil and celangulin treatment group,the activity of GST was significantly elevated?P<0.05?.No change was observed in the activity of MFO at the given dose of thyme oil?P>0.05?.?4?After treaed by thyme oil,wintergreen oil,lemon oil,celangulin and?-cyhalothrin under LC₅₀,the activity of AChE was significantly decreased?P<0.05?;whereas in the clove leaf oil and ceylon cinnamon oil treatment group,the activity of AChE was significantly elevated?P<0.05?.No change was observed in the activity of AChE at the given dose of oregano oil?P>0.05?.It is concluded that exposure to some of the essential oils and acaricides mentioned above could significantly change the activity of enzymes in ticks,and these changes are mainly dependent on the type of the tested essential oils or acaricides,and the effects area also different on different tick species.4.8 essential oils and 6 mosquito repellents were tested for repellent unfed nymphs of Ha.longicornis.Results indicated that essential oils show far stronger repellent effects than mosquito repellents.Oregano oil and ceylon cinnamon oil showed strongest repellent effects among them with EC₅₀?Median effective concentration?of0.13?l/m²and0.23?l/m²respectively.Meanwhile,N,N-Diphenylacetamide?DEPA?showed the strongest repellent effects among the mosquito repellents tested above with EC₅₀0 of 7.42?l/m².5.The results of the chemical analysis of EOs showed that phenolic substances may account for the certain effect on toxicities and enzyme activities of ticks,and may display inhibitory effect on enzymes activities.The above results provided theoretical basis for further application of new acaricides and repellent agents,as well as provided technological support in subsequent tick control.