BACKGROUND: The objective of the study was to determine the sustained effectiveness of 10% imidacloprid (w/w)
and 4.5% flumethrin (w/w) incorporated in a slow-release matrix collar in preventing Dipylidium caninum infection
in cats following repeated laboratory-infestations with fleas infected with metacestodes.
METHODS: Efficacy against infection with D. caninum was evaluated by infesting 16 cats with the flea
Ctenocephalides felis felis infected with metacestodes of the tapeworm. Medicated collars were fitted to 8 of the cats
and infestation of each cat with 200 fleas from a suitably infected batch commenced 7 days later and continued at
weekly intervals until Day 28. Efficacy against fleas was evaluated 24 h after each infestation. Infection of the cats
with D. caninum was verified by daily examination of the cats’ faeces and immediate surroundings for proglottids
from Day 21 to Day 60. Calculation of the prophylactic effectiveness of the collars in preventing infection of the
cats with D. caninum was based on the difference in the geometric mean number of scoleces recovered from the
gastrointestinal tracts of collared compared to untreated cats at necropsy on Day 61.
RESULTS: Efficacy of the collars against infestation of the cats with fleas was 99.9% on Day 7 and 100% at each
subsequent weekly assessment. Infection of the fleas with metacestodes was ≥40% in 7 to 13 day old fleas, but
progressively decreased thereafter. At necropsy all the control cats were infected with D. caninum and harboured
between 19 and 346 scoleces with a geometric mean of 58.3. A single treated cat was infected and harboured
2 scoleces. Effective prevention of infection with D. caninum, based on a comparison of the geometric mean
numbers of scoleces recovered from control and treated cats, was 99.7%.
CONCLUSION: The insecticidal components of the medicated collars are capable of rapidly eliminating newlyacquired
infestations of fleas that are infected with the metacestodes of D. caninum, thus preventing infection with
the cestode in collared cats.