Barbieri A, Rico I B, Silveira C, Feltrin C, Dall Agnol B, Schrank A, Lozina L, Klafke G M, Reck J
Centro de Pesquisa em Saúde Animal, Instituto de Pesquisas Veterinárias Desidério Finamor (IPVDF), Estrada do Conde, 6000, Eldorado do Sul, RS 92990-000, Brazil.
EMATER/RS, Guaiba, RS, Brazil.
Ticks Tick Borne Dis. 2023 May;14(3):102147. doi: 10.1016/j.ttbdis.2023.102147. Epub 2023 Mar 7.
Rhipicephalus microplus tick is the main ectoparasite of cattle in Brazil. The exhaustive use of chemical acaricides to control this tick has favored the selection of resistant tick populations. Entomopathogenic fungi, as Metarhizium anisopliae, has been described as a potential biocontroller of ticks. Therefore, the aim of this study was to evaluate the in vivo efficacy of two oil based formulations of M. anisopliae for the control of the cattle tick R. microplus under field conditions using a cattle spray race as a method of treatment. Initially, in vitro assays were carried out with an aqueous suspension of M. anisopliae, using mineral oil and/or silicon oil. A potential synergism between oils and fungus conidia for tick control was demonstrated. Additionally, the usefulness of silicon oil in order to reduce mineral oil concentration, while improving formulation efficacy was illustrated. Based on the in vitro results, two formulations were selected for use in the field trial: MaO1 (10 conidia/mL plus 5% mineral oil) and MaO2 (10 conidia/mL plus 2.5% mineral oil and 0.01% silicon oil). The adjuvants concentrations (mineral and silicon oils) were chosen since preliminary data indicate that higher concentrations caused significant mortality in adult ticks. For this, 30 naturally infested heifers were divided into three groups based on previous tick counts. The control group did not receive treatment. The selected formulations were applied on animals using a cattle spray race. Subsequently, tick load was evaluated weekly by counting. The MaO1 treatment significantly reduced the tick count only on day +21, reaching approximately 55% efficacy. On the other hand, MaO2 showed significantly lower tick counts on days +7, +14, and +21 after treatment, with weekly efficacy achieving 66%. The results showed a substantial reduction of tick infestation, up to day +28, using a novel formulation of M. anisopliae based in the mixture of two oils. Moreover, we have shown, for the first time, the feasibility of employing formulations of M. anisopliae for large-scale treatment methods, such as a cattle spray race, which in turn, may increase the use and adhesion to biological control tools among farmers.
微小扇头蜱是巴西牛的主要体表寄生虫。为控制这种蜱而过度使用化学杀螨剂，促使了抗药蜱种群的产生。昆虫病原真菌，如绿僵菌，已被描述为蜱的一种潜在生物防治剂。因此，本研究的目的是在田间条件下，使用牛喷淋通道作为处理方法，评估两种基于油的绿僵菌制剂对牛蜱微小扇头蜱的体内防治效果。最初，用绿僵菌的水悬浮液、矿物油和/或硅油进行了体外试验。结果表明，油与真菌分生孢子在蜱防治方面存在潜在的协同作用。此外，还说明了硅油在降低矿物油浓度的同时提高制剂效果的作用。基于体外试验结果，选择了两种制剂用于田间试验：MaO1（10个分生孢子/毫升加5%矿物油）和MaO2（10个分生孢子/毫升加2.5%矿物油和0.01%硅油）。选择佐剂（矿物油和硅油）的浓度是因为初步数据表明，较高浓度会导致成年蜱大量死亡。为此，根据先前的蜱计数，将30头自然感染的小母牛分为三组。对照组未接受处理。将选定的制剂通过牛喷淋通道施用于动物。随后，每周通过计数评估蜱负荷。MaO1处理仅在第21天显著减少了蜱的数量，达到约55%的防治效果。另一方面，MaO2在处理后的第7天、第14天和第21天显示蜱的数量显著减少，每周防治效果达到66%。结果表明，使用基于两种油混合的新型绿僵菌制剂，蜱虫感染在第28天前大幅减少。此外，我们首次证明了采用绿僵菌制剂进行大规模处理方法（如牛喷淋通道）的可行性，这反过来可能会增加农民对生物防治工具的使用和接受度。
