The aim of the investigation was to examine whether a single topical administration of a combination of imidacloprid and moxidectin to pregnant dogs could prevent neonatal infections with reactivated Ancylostoma caninum larvae. Three pregnant beagles, infected with A. caninum, were treated topically with the combination on day 56 of pregnancy. Three further dogs served as untreated controls. Treatment appeared to prevent neonatal infections in the puppies completely. Neither intestinal stages nor somatic larvae were found in two examined puppies per litter. All puppies and dams of the treatment group remained coproscopically negative. No side-effects in dams or puppies were observed. Two of three untreated dams showed a patent infection after parturition. Necropsy of two puppies of each negative control litter revealed seven intestinal and five somatic A. caninum stages in total. One litter of the untreated dams showed a patent infection 33 days after parturition. In the other two litters, no representative sample sizes could be collected.