Authors

Discussion

Cercarial dermatitis (CD), also known as swimmer’s itch, is a waterborne allergic disease caused by avian schistosome larvae penetrating mammalian skin. Trichobilharzia franki has been identified as a major contributor to human CD cases in Europe. However, little is known about its interactions with mammals, as previous research focused on less prevalent species like T. regenti and T. szidati. To address this gap, we infected C57BL/6J female mice with T. franki cercariae collected during human CD outbreaks in Czechia in July–August 2023. Mice were sacrificed at 2 and 7 days post-infection (dpi), and parasitological, histopathological, and immunological analyses were performed. In infected pinnae, migrating schistosomula and extensive epidermal lesions were observed at both time points. Additionally, the parotid lymph nodes exhibited significant enlargement. Surprisingly, schistosomula were not detected in the lungs, where visceral schistosomes typically lodge; instead, hemorrhages were observed at 2 dpi, followed by eosinophil-rich pulmonary lesions at 7 dpi. Infected mice displayed spleen enlargement, and splenocytes, when restimulated with T. franki cercarial homogenate, secreted a mixture of Th1/Th2/Treg cytokines robustly. Notably, splenocytes also reacted to protein lysates from other avian schistosome species, indicating significant cross-reactivity. No parasite-specific serum IgG was detected at 7 dpi, suggesting limited utility of serological diagnostics in early infections. In summary, our study provides novel insights into the migration, pathogenicity, and immunobiology of T. franki in mice. These findings contribute to a better understanding of the implications of cercarial dermatitis caused by this species.

Acknowledgment: This study was supported by the Czech Science Foundation (GA24-11031S): “Swimmer’s itch: From detection to protection”.