Abstract:
BACKROUND: We evaluated the efciency of an ex vivo feeding technique using a silicone membrane-based feeding
chamber to (i) assess the anti-feeding and acaricidal efcacy of a spot-on combination of dinotefuran, pyriproxyfen
and permethrin (DPP, Vectra® 3D) against adult Ixodes scapularis and Ixodes ricinus ticks, and to (ii) explore its efect on
blocking the acquisition of Borrelia burgdorferi sensu stricto.
METHODS: Eight purpose-bred dogs were randomly allocated to two equal-size groups based on body weight
assessed on day 2. DPP was administered topically, as spot-on, to four dogs on day 0. Hair from the eight dogs was
collected individually by brushing the whole body on days 2, 7, 14, 21, 28 and 35. On each day of hair collection,
0.05 g of sampled hair was applied on the membrane corresponding to each feeding unit (FU). Seventy-two FU
were each seeded with 30 adults of I. scapularis (n=24 FU) or I. ricinus ticks (n=48 FU). Bovine blood spiked with
B. burgdorferi sensu stricto (strain B31) was added into each unit and changed every 12 h for 4 days. Tick mortality was
assessed 1 h after seeding. One additional hour of incubation was added for live/moribund specimens and reassessed
for viability. All remaining live/moribund ticks were left in the feeders and tick engorgement status was recorded at
96 h after seeding, and the uptake of B. burgdorferi s.s. was examined in the collected ticks by applying quantitative
real-time PCR.
RESULTS: Exposure to DPP-treated hair was 100% efective in blocking B. burgdorferi s.s. acquisition. The anti-feeding
efcacy remained stable (100%) against both Ixodes species throughout the study. The acaricidal efcacy of DPP
evaluated at 1 and 2 h after exposure was 100% throughout the study for I. ricinus, except the 1-h assessment on day
28 (95.9%) and day 35 (95.3%). The 1-h assessment of acaricidal efcacy was 100% at all time points for I. scapularis.
CONCLUSIONS: The ex vivo feeding system developed here demonstrated a protective efect of DPP against the acquisition of B. burgdorferi without exposing the animals to the vectors or to the pathogen.
