The invasive Cattle Fever Ticks (Rhipicephalus microplus and R. annulatus) were eradicated from United States in 1943, except from the Permanent Quarantine Zone maintained by the Cattle Fever Tick Eradication Program in South Texas on the border with Mexico where they cause outbreaks. Novel methods to keep the U.S. free of Cattle Fever Ticks (CFT) in a sustainable manner are needed. Previous laboratory studies showed that cattle treated according to label instructions with a product containing the macrocyclic lactone Moxidectin (10%, injectable formulation) would afford protection from CFT reinfestation for up to 50 days post-treatment, and that the estimated active ingredient serum levels for 100% elimination of feeding CFT was around 8 parts-per-billion (ppb). We hypothesized that an analytical method more refined than high performance liquid chromatography (HPLC) coupled to a fluorescence detector would provide a more sensitive assay. Here, a liquid chromatography/ tandem mass spectrometry (LC/MS-MS) method was adapted to test serum samples of cattle treated with the 10% Moxidectin injectable formulation. Extraction and clean-up methods were developed to optimize the LC/MS-MS method. Analytical results are reported and the findings discussed in comparison to the HPLC method.

LC/MS-MS method optimization for the detection and quantification of moxidectin in bovine serum

253rd National Meeting (2017)

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