Closing the gap on gapeworm: experimental infection of Mammomonogamus ierei in domestic cats

Background Mammomonogamus ierei is a nasal nematode of domestic cats, for which the life cycle and route of infection have remained unknown. Experimental oral infections have historically failed, leading to speculation regarding the involvement of an intermediate host and uncertainty about transmission pathways. The aim of this study was to determine the route of infection of M. ierei in domestic cats. Methods Twenty kittens (6–12 weeks old) were exposed to infective third-stage larvae (L3) via six routes: per os ( n = 3), oral mucosa ( n = 3), nasal mucosa ( n = 3), subcutaneous ( n = 3), percutaneous (abdominal region) ( n = 2), external auditory canal ( n = 2), and an unexposed control group ( n = 4). Kittens were randomized across litters to minimize litter-associated effects and monitored using serial fecal examinations for 70 days post-inoculation to assess establishment of infection and egg shedding. Results Motile L3 developed within 9 days in culture and exhibited morphometric characteristics consistent with previous descriptions. Two of 20 kittens developed patent M. ierei infections, first shedding eggs 48–51 days post-inoculation. Both infected animals belonged to the subcutaneous inoculation group, whereas no infections resulted from other inoculation routes. Mild, transient respiratory signs were observed in some kittens, including one prior to patency. Conclusions These findings demonstrate, for the first time, a viable route of infection for M. ierei and provide the first experimental evidence of route of transmission for any species within the genus Mammomonogamus . The results suggest a direct life cycle, as infection was established in the absence of an intermediate host, but do not preclude the occurrence of paratenic hosts. Infection via subcutaneous exposure was successfully achieved; however, its relevance under natural conditions remains to be confirmed. This study advances the current understanding of Mammomonogamus biology and may have implications for parasite control and for transmission models of zoonotic species such as Mammomonogamus laryngeus .