A Preliminary Study Of Screening Drugs Against Ticks And Its Compound Preparation

As a arthropods, tick has a complex life cycle and tenacious survival capability in adverse circumstances. It can spread many diseases to animals and people as a vector, which has posed seriously threat to animal husbandry and people’s health. Chemical acaricides are still the most popular measures to control ticks at the moment. With the long-term use of chemical acaricides, however, it results in resistance increasing in ticks and environment pollution, which is harmful to human and animal. To alleviate the resistance rapidly and reduce the use of acaricides and to obtain more effective and greener drug to against tick, the acaricides were screened and the effective compound preparations were manufactured. The main methods and results in this study are as follows:1. The efficacy determination and preliminary screening of anti-tick drugs from 30 different drugsHyalomma asiaticum and Rhipicephalus sanguineus of the engorged nymphs were used as experimental objects in the primary screening tests. The molting rate of engorged nymphs was determined and efficacies of the 30 drugs against ticks by immersion test in vitro in concentration of half of the recommended, recommended and double recommended concentration, respectively, were evaluated. The results showed that:(1) Nine kinds of drugs such as chlorpyrifos, pyridaben, etoxazole, diflubenzuron, lambda-cyhalothrin, emamectin benzoate, matrine, beta-cypermethrin, cypermethrin, spirotetramat have effects against ticks. Chlorpyrifos were 0, 0, 0; pyridaben were 33.33% and 0, 0; etoxazole were 40, 31.11 and 22.22%; diflubenzuron were 46.67, 22.22 and 11.11%; lambda-cyhalothrin were 51.11, 31.11 and 17.77%; emamectin benzoate were 51.11, 40 and 33.33%; matrine were 68.89, 48.8 and 28.89%; beta-cypermethrin 80, 55.56 and 37.78%; spirotetramat were 84.44, 62.22 and 37.78% to the molting rate of engorged nymphs of R. sanguineus, respectively. Other 21 kinds of drugs for R. sanguineus of the engorged nymphs haven’t the effect.(2) Eight kinds of drugs such as chlorpyrifos, spinetoram, etoxazole, diflubenzuron, lambda-cyhalothrin, matrine, beta-cypermethrin, spirotetramat have effects against ticks. Chlorpyrifos were 0, 0, 0;spinetoram 44.4 and 31.11%; etoxazole 46.67, 35.56 and 26.67%; diflubenzuron 80, 66.6 and 42.22%; lambda-cyhalothrin 57.78, matrine 60, 33.3 and 20%; beta-cypermethrin 80, 55.5 and 48.89%; spirotetramat 91.11, 51.11 and 44.44% to the molting rate of engorged nymphs of Hy. asiaticum, respectively. Other 22 kinds of drugs for Hy. asiaticum of the engorged nymphs haven’t the effect. Above three working concentration, chlorpyrifos has the highest efficiency to against R. sanguineus and Hy. asiaticum of the engorged nymphs, etoxazole came second; matrine, lambda-cyhalothrin, beta-cypermethrin, spirotetramat has effects on both engorged nymphs of ticks in these drugs concentration of double recommended concentration. while there were a disparity between R.sanguineus and Hy. asiaticum for pyridaben, diflubenzuron and emamectin benzoate against tick. They having poorly effect to kill on engorged nymphs of Hy. asiaticum, or none at all. Instead, spinetoram has good effects on engorged nymphs of Hy. asiaticum, and has no effect on engorged nymphs of R.sanguineus. Therefore, etoxazole, matrine, lambda-cyhalothrin, beta-cypermethrin, pyridaben, spinetoram 6 kinds of drugs were screened to prepare for the next test.2. The determination of killing activity of 6 drugs against tick and screening drugs with highly effective broad-spectrumEtoxazole, matrine, lambda-cyhalothrin, beta-cypermethrin, pyridaben, spinetoram 6 kinds of drugs were selected to against the life cycle of the different develops periods with Hy. asiaticum, R.sanguineus, Haemaphysalis longicornis. The results show that:(1) Etoxazole was effective only to engorged nymphs of Hy.asiaticum tick and R.sanguineus. Its’ LD50 values were 18.921 mg/L and 7.98 mg/L against the engorged Hy.asiaticum and R.sanguineus, respectively. Etoxazole had no effects on engorged female ticks of Hy. asiaticum and H.longicornis spawning. Unfed adult Hy.asiaticum treated with etoxazole does not die in 7 days, so it was effective only for the engorged nymphs.(2) Matrine was effective on engorged nymphs of Hy.asiaticum and R.sanguineus, it’s LD50 were 7.403 mg/L and 32.691 mg/L, respectively. Matrine also has killing effects to the unfed larva and unfed adults of Hy. asiaticum, its’ LD50 values were 9.227 mg/L and 221.204 mg/L, respectively. In addition, 50 mg/L of matrine could inhibit more than 85% egg laying for engorged females of Hy. asiaticum, R. sanguineus and H. longicornis.(3)The LD50 values of lambda-cyhalothrin were 22.045 mg/L and 11.696 mg/L against engorged nymphs of Hy.asiaticum and R.sanguineus, while it were 7.557 mg/L and 100.69 mg/L against unfed larva and unfed adult of Hy.asiaticum, it is good against unfed larva and unfed adults. In inhibiting laying eggs for the three ticks engorged females, the inhibition ratio is 100% when its concentration comes to 50 mg/L. So the efficacy of lambda-cyhalothrin is better than etoxazole and matrine with highly effective broad-spectrum.(4) The efficacy of beta-cypermethrin is low, that is inferior to etoxazole, matrine and lambda-cyhalothrin in killing the engorged nymphs; under the density of 50mg/L, the inhibition ratio of laying egg for the engorged females of Hy. asiaticum and H. longicornis are 78.83% and 65.02%, respectively, so it is not so good as matrine and lambda-cyhalothrin.(5) Although pyridaben has bad effect to against the engorged nymphs of Hy. asiaticum, it has high effect on H. longicornis, and the LD50 of pyridaben were 42.604 mg/L and 124.533 mg/L to unfed larva and unfed adults of H. longicornis, respectively. The inhibition ratio of laying egg for engorged females H. longicornis reaches to 99.6% at a concentration of 250 mg/L.(6) Spinetoram not only has a high efficiency on killing the engorged nymphs of Hy. asiaticum but also good at inhibiting engorged females of Hy. asiaticum laying eggs. Under the density of 75 mg/L, 83.50% were inhibited. Through above-mentioned experiment, matrine and lambda-cyhalothrin are the best broad spectrum drugs with high efficiency and low toxicity to be developed compound preparation.3. Preliminary development of compound preparations and evaluation of it’s efficacy against ticksMatrine and lambda-cyhalothrin were used as the main component, microemulsion which is a novel green water-based formulation was developed in the experiment. Solvents and their dosage are followed the principle of the lowest pollution to the environment. The new compound formula results was as follows: lambda-cyhalothrin 6.6%, matrine 4.4%, DMF 4.4%, butyl acetate 4.4%, compound emulsifier B 13.3%, compound emulsifier H 13.3%, ethylene glycol 4.4%, n-butyl alcohol 6.6% and deionized water 44%, respectively. The physical properties of this kind of compound preparation were confirmed through the stability test. The compound preparation was effective on engorged nymphs of Hy.asiaticum and R.sanguineus, it’s LD50 were 5.346 mg/L and 14.819 mg/L, respectively. its’ LD50 values were 3.324 mg/L and 47.832 mg/L against unfed larva and unfed adults of Hy. asiaticum, respectively. In addition, 5 mg/L of matrine could inhibit more than 90% egg laying for engorged females of Hy. asiaticum, R. sanguineus and H. longicornis. The lethal concentration of compound preparation to engorged nymphs of Hy. asiaticum and R. sanguineus, unfed larva and unfed adults of Hy. Asiaticum is lower than matrine and lambda-cyhalothrin; The concentration to inhibit egg laying was only about half of single drug’s. So the efficacy of compound preparations against ticks is better than single preparations.