Parasite Control Laboratory, Federal University of Maranhão - UFMA, São Luís, MA, Brazil; Fuel, Catalysis and Environmental Center, Federal University of Maranhão - UFMA, São Luís, MA, Brazil.
Parasite Control Laboratory, Federal University of Maranhão - UFMA, São Luís, MA, Brazil.
Vet Parasitol. 2024 Apr;327:110149. doi: 10.1016/j.vetpar.2024.110149. Epub 2024 Feb 20.
The tick Rhipicephalus microplus is a parasite of great importance in cattle breeding. It is responsible for huge economic losses. The application of synthetic acaricides is used as a form of control. However, resistant strains have been selected over the years, making it necessary to search for new alternative formulations. The present study aimed to formulate biodegradable films impregnated with the terpenes carvacrol and thymol and evaluate their efficacy on larvae and adults of R. microplus through in vitro tests. The following formulations were prepared: Film 1 (starch based); Film 2 (based on starch and glycerol); Film 1 + Carvarcol or Thymol; Film 2 + Carvarcol or Thymol. Terpenes had a final concentration of 5.0 mg/mL. To evaluate the formulations on larvae, the immersion test was performed by dividing into six groups according to the concentration of terpenes: 5.0, 2.5, 1.25, 0.625, 0.313, 0.156 mg/mL and the control groups: 1% ethanol solution; 10% ethanol solution; Film 1; and Film 2. For the evaluations on adult ticks, ten experimental groups (n = 10) were used: 1) Carvacrol; 2) Film 1 + Carvacrol; 3) Film 2 + Carvacrol; 4) Thymol; 5) Film 1 + Thymol; 6) Film 2 + Thymol; 7) Distilled water; 8) 10% ethanol solution; 9) Film 1; and 10) Film 2. In experimental groups 1-6, carvacrol and thymol (free or incorporated in two different biodegradable film formulations) were evaluated at the same concentration (5.0 mg/mL). Each group of ticks was immersed in their respective solutions for five minutes. The results of the tests on larvae showed that the Film 1 + thymol and Film 2 + carvacrol formulations had the lowest lethal concentrations (0.076 and 0.255 mg/mL, respectively), values up to 9.0-fold lower than the monoterpenes tested outside the formulation. Carvacrol and thymol at the concentrations tested were effective in controlling engorged females with a percentage of 32.2% and 63.8%, respectively. When incorporated into biodegradable film formulations, these monoterpenes showed much greater efficacy. Film 1 + carvacrol and Film 2 + carvacrol with control percentages of 71.6% and 97.2%, respectively, while the formulations Film 1 + thymol and Film 2 + thymol showed values of 96.9% and 100.0%. The tick control activity of the biopolymer formulations with thymol and carvacrol was demonstrated through the high mortality rates of larvae and engorged females of the tick R. microplus. Therefore, the results obtained indicate that these formulations have great potential for tick control mainly because of the percentage of control up to 100% in engorged females in in vitro tests.
壁虱 Rhipicephalus microplus 是养牛业中一种非常重要的寄生虫。它导致了巨大的经济损失。应用合成杀螨剂是一种控制手段。然而，多年来已经选择了耐药菌株，因此有必要寻找新的替代制剂。本研究旨在配制可生物降解的薄膜，浸渍有萜品烯-蒈烯和百里酚，并通过体外试验评估其对 R. microplus 幼虫和成虫的功效。制备了以下配方：薄膜 1（基于淀粉）；薄膜 2（基于淀粉和甘油）；薄膜 1+蒈烯或百里酚；薄膜 2+蒈烯或百里酚。萜烯的终浓度为 5.0mg/mL。为了评估幼虫的配方，通过根据萜烯的浓度分为六个组进行浸浴试验：5.0、2.5、1.25、0.625、0.313 和 0.156mg/mL，以及对照组：1%乙醇溶液；10%乙醇溶液；薄膜 1；和薄膜 2。对于成蜱的评估，使用了十个实验组（n=10）：1）蒈烯；2）薄膜 1+蒈烯；3）薄膜 2+蒈烯；4）百里酚；5）薄膜 1+百里酚；6）薄膜 2+百里酚；7）蒸馏水；8）10%乙醇溶液；9）薄膜 1；和 10）薄膜 2。在实验组 1-6 中，评估了蒈烯和百里酚（游离或掺入两种不同的可生物降解薄膜配方中）的相同浓度（5.0mg/mL）。每组蜱虫分别浸入各自的溶液中 5 分钟。幼虫试验的结果表明，薄膜 1+百里酚和薄膜 2+蒈烯制剂具有最低的致死浓度（分别为 0.076 和 0.255mg/mL），比在配方外测试的单萜低 9.0 倍。在测试浓度下，蒈烯和百里酚对饱血雌蜱有效，控制率分别为 32.2%和 63.8%。当掺入可生物降解的薄膜配方中时，这些单萜表现出更大的功效。薄膜 1+蒈烯和薄膜 2+蒈烯的控制率分别为 71.6%和 97.2%，而薄膜 1+百里酚和薄膜 2+百里酚的控制率分别为 96.9%和 100.0%。壁虱 R. microplus 的幼虫和饱血雌蜱的高死亡率证明了这些生物聚合物配方具有很好的控制效果。因此，实验结果表明，这些配方具有很大的控制潜力，主要是因为在体外试验中，饱血雌蜱的控制率高达 100%。
