First clinicopathological characterization of body wrinkle condition in Merino sheep and its association with Orf virus infection.

Merino sheep exhibit a high follicular density, enhancing wool yield but predisposing them to inherited cutaneous disorders, such as breech wrinkle, which is characterized by the appearance of multiple skin folds in the breech area. This study provides the first clinicopathological description of the so-called body wrinkle, a congenital skin condition in Merino lambs where the folds affect the whole-body skin. Four affected lambs displayed generalized alopecia with excessive skin folds. Hematological analysis showed neutrophilia, lymphopenia, and eosinopenia. Histological examination revealed follicular dysplasia, follicular keratinization and keratosis, and degeneration of follicular epithelium, particularly in the outer root sheath. The information obtained from pedigree analysis suggested an autosomal recessive inheritance pattern. All affected lambs exhibited severe OrfV lesions in the oral cavity and muzzle, persisting from 2 weeks of age until death at 1 to 2 months. Our results suggest that body wrinkle condition might favor a more prolonged clinical course and more severe outcome of OrfV infection in lambs. Further genetic and immunopathological investigations are needed.