Effects of permethrin and amitraz on gas exchange and water loss in unfed adult females of Amblyomma americanum (Acari: Ixodidae)

• Published in: Pesticide biochemistry and physiology Vol. 107; no. 2; pp. 153 - 159
• Main Authors: Zheng, Hongyuan, Li, Andrew Y., Fielden, Laura J., Liu, Jingze, Seshu, Janakiram, Pérez de León, Adalberto A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2013
• Subjects: Acaricide; Carbon dioxide; Lone star tick; Metabolism; Water balance; Acaricide; Water balance; Lone star tick; Metabolism; Carbon dioxide
• ISSN: 0048-3575; 1095-9939
• DOI: 10.1016/j.pestbp.2012.12.004

[Display omitted] ► Permethrin treatment of ticks increased discontinuous gas exchange frequency and caused significant water loss. ► Amitraz abolished the normal rhythmic CO2 release pattern, resulting in an elevated and long-lasting CO2 release. ► Acaricide mixture elicited the strongest CO2 release and water loss. ► This study provided new insights into acaricide modes of action and mechanism of synergism. Effects of two acaricides, permethrin and amitraz, with different modes of action, on gas exchange and water balance of the lone star tick, Amblyomma americanum, were examined using a flow-through carbon dioxide (CO2) and water vapor analyzer. Untreated adult female ticks exhibited a distinct discontinuous gas exchange pattern (DGEP) with no measurable water loss. Similarly, ticks with acetone (a solvent) showed little change in gas exchange and water loss. Topical treatment of ticks with a lethal dose of permethrin caused immediate major water loss and long-lasting high frequency DGEP, with increased amplitude of CO2 release. A small water loss spike was observed for each CO2 release. Treatment of ticks with amitraz abolished the DGEP and elicited a long-lasting continuous gas exchange pattern, indicating significantly increased tick metabolism. No detectable water loss was observed during amitraz-elicited continuous gas exchange. Treatment of ticks with a mixture of sub-lethal doses of permethrin and amitraz caused a similar initial major water loss, as in permethrin-treated ticks, followed by a second period of water loss activity at 10–14h after treatment. Mixture of the two acaricides caused immediate onset of major chaotic CO2 release activities with a significantly elevated baseline CO2 emission level. The standard metabolism rate (SMR, VCO2) of acetone-treated ticks (0.452μlh−1) was similar to that of the untreated ticks (0.461μlh−1). Compared to untreated control ticks, permethrin-, amitraz-, and the acaricide mixture-treated ticks exhibited significantly increased SMR (1.054, 1.392 and 1.520μlh−1 respectively (P<0.05). Results obtained from this study clearly demonstrated the detrimental effects of permethrin and amitraz on CO2 gas exchange and water balance in A. americanum ticks. The data also revealed subtle differences between permethrin and amitraz in their effects on tick metabolism, specifically gas exchange and water loss. In addition, the study may provide insight into the modes of action of these two acaricides in tick physiology. The results may also help understand the mechanism of synergism between permethrin and amitraz that was reported previously in other ticks and insects.