Effect of using redberry juniper (Juniperus pinchotii) to reduce Haemonchus contortus in vitro motility and increase ivermectin efficacy

A modified larval migration inhibition assay was used to determine if redberry juniper (Juniperus pinchotii Sudw.) can reduce Haemonchus contortus in vitro motility and increase ivermectin (IVM) efficacy. Ruminal fluid was mixed with buffer solution and either no material (CNTL) or Tifton 85 Bermudagrass hay (T85), dried juniper (DRY), fresh juniper (FRE), or distilled juniper terpenoid oil (OIL) to make treatment solutions and anaerobically incubated for 16 h. For Trial 1, larvae were incubated in CNTL, T85, DRY, or IVM. During Trial 2, larvae were incubated in CNTL, DRY, FRE, or OIL for 4 h. Trials 3 (CNTL or OIL) and 4 (CNTL, DRY or FRE) evaluated larvae after incubation in treatment solution for 2 h, then incubated an additional 2 h in various IVM doses (0, 0.1, 1, 3, and 6 μg/mL IVM) and placed onto a screen. Larvae that passed through the 20-μm screen within a 96-well plate were considered motile. Larvae incubated in CNTL or T85 had similar (P = 0.12) motility, but larvae incubated in DRY were less (P < 0.02) motile than larvae incubated in CNTL or T85 (Trial 1). During Trial 2, adding DRY, FRE, or OIL reduced (P < 0.001) larval motility as compared to CNTL. A treatment × IVM dose interaction (P = 0.02) was observed during Trial 3, due to OIL unexpectedly decreasing IMV efficacy at IVM concentrations of 1 (P = 0.07), 3, and 6 (P < 0.002) μg/mL. No treatment × IVM dose interaction (P = 0.57) was observed during Trial 4, but larvae incubated in DRY had less (P < 0.004) total motility than larvae incubated in CNTL or FRE. Juniper forage material reduced in vitro H. contortus larval motility, but IVM efficacy was increased only by initially incubating larvae in DRY.