ABSTRACT

Background and Aim: Bovine trichophytosis is a contagious zoonotic dermatophytosis that adversely affects animal health and livestock productivity and poses an occupational risk to people in contact with infected cattle. Although live attenuated vaccines have contributed to disease control, evidence for bivalent formulations targeting multiple Trichophyton species remains limited. This study evaluated the prophylactic activity and post-infection outcomes of a live attenuated bivalent vaccine candidate containing Trichophyton verrucosum and a member of the Trichophyton mentagrophytes species complex in an experimental rabbit model.

Materials and Methods: Thirty-three clinically healthy rabbits were allocated to a prophylactic group (Group I, n = 10), therapeutic group (Group IIa, n = 10), infected untreated histopathology subgroup (Group IIb, n = 3), and intact control group (Group III, n = 10). Group I received two intramuscular vaccinations 14 days apart and was challenged 21 days after the second vaccination, whereas Group IIa was experimentally infected before therapeutic vaccination. Clinical manifestations, body weight, rectal temperature, hematological parameters, mycological culture, and histopathological changes were evaluated. Clinical and histopathological assessments were descriptive and non-blinded.

Results: Following experimental challenge, no clinically visible dermatophytosis lesions occurred in prophylactically vaccinated rabbits (0/10), whereas all infected untreated reference rabbits developed lesions (3/3; two-sided Fisher’s exact test, p = 0.0035), supporting prophylactic activity. Therapeutically vaccinated rabbits showed progressive regression of visible crusting and hair regrowth; however, the absence of a longitudinal untreated infected group and positive treatment comparator precluded attribution of recovery specifically to vaccination. Dermatophyte growth was recovered from challenged skin after 5–7 days, although species-specific identification and quantitative fungal burden were not determined. Hematological indices showed limited descriptive variation. Histopathology demonstrated inflammatory and degenerative cutaneous lesions in untreated infected rabbits and nonspecific reactive lymphoid changes in vaccinated animals.

Conclusion: The live attenuated bivalent vaccine candidate demonstrated promising prophylactic activity against experimental dermatophytosis in rabbits. Post-infection clinical improvement provides preliminary evidence warranting further investigation but cannot establish therapeutic efficacy. Controlled studies in the target host should incorporate adequate comparator groups, standardized lesion scoring, quantitative and species-specific mycology, immunological endpoints, and comprehensive vaccine quality control and stability assessments before field application.

Keywords: bivalent vaccine, bovine trichophytosis, dermatophytosis, live attenuated vaccine, One Health, rabbit model, Trichophyton mentagrophytes, Trichophyton verrucosum.