Objective. The species Trichophyton benhamiae is now recognized as an agent of dermatophytosis frequently affecting guinea pigs and people in close contact with them (breeders or owners, especially children). In Europe, this dermatophyte species should be considered an emerging pathogen even though guinea pig breeding has a long tradition in some European countries, including France. Here, we report the results of a retrospective epidemiological survey based on the activity of the Mycology laboratory of the veterinary college of Alfort in France.

Methods. The survey was based on the results of the mycological analyses corresponding to 664 guinea pigs examined by vet practitioners in Ile-de-France region from 2003 to 2017. For each animal, the following parameters were documented: age, gender and owners' address. Sampling included scrubbing of animal's fur with a small piece of sterile carpet and culturing in Sabouraud dextrose agar for mycological cultures. Plates were incubated at 32°C for 10 days. Dermatophyte colonies were identified according to their macroscopic and microscopic features. Sequencing of ITS rDNA region was used for confirmation of species identification in selected isolates. 

Results. Dermatophyte colonies were detected from 36% of animals examined (238 out of 664 guinea pigs). For 7 animals, the dermatophyte species could not be clearly identified. Trichophyton mentagrophytes and T. benhamiae were detected in 111 and 121 guinea pigs, respectively. A co-infection with both species was reported once. DNA sequencing confirmed the phenotypic identification. The presence of T. benhamiae was observed for the first time in a guinea pig in June 2008. Since then, T. benhamiae progressively replaced T. mentagrophytes. In 2017, dermatophyte colonies were obtained from samples coming from 34 guinea pigs: T. benhamiae was detected in 33 cases whereas T. mentagrophytes was detected only once. The epidemiological situation is different in other rodents (mice, rats and chinchillas) and rabbits in which the infection by T. mentagrophytes remains largely predominant.

Conclusion. The present study confirms the emergence and the spread of the species T. benhamiae in companion guinea pig in Ile-de-France region since 2008.

5 / Emergence of Trichophyton benhamiae in guinea pigs: a retrospective study from the mycology laboratory of the veterinary college of Alfort