For their
biological and ecological characteristics, ticks are vectors of the widest variety of pathogens causing
tick-borne diseases (
TBDs). Little information is available about the ways in which time spent by ticks to feed on hosts, transmission times and TBD prevention are related and it is exclusively limited to laboratory reports on adult stages. In particular, the time required by immature stages to transmit pathogens has not been determined for most
TBDs. Considering their importance for animal and human health, effective control of immature ticks is advisable to reduce the damage ticks cause. Recently, the efficacy of a combination of
imidacloprid 10%/
permethrin 50% was compared with that of
fipronil 10%/S-
methoprene 9% against ticks when administered to naturally infected dogs. A semi-quantitative method was used to assess the methodological parameters to calculate
drug efficacy on immature stages. On adult ticks, the efficacy of both products was high and overall very similar, whereas for the immature stages the combination of
imidacloprid 10% and
permethrin 50% had a higher efficacy than
fipronil 10% and
methoprene 9% throughout the observation period (statistically significant difference on day + 28 only). The semi-quantitative method proposed for the evaluation of immature stages can be considered a useful tool for calculating the efficacy of a
drug in the field. Due the important role of immatures in the spread of
TBDs, the immature tick load should be calculated to assess the efficacy of acaricidal products both under laboratory and field conditions.