In Lepus timidus -
- Lesions of mucocutaneous junctions: Proliferative lesions with
marked formation of crusts.
- Usually on the lips and nose, sometimes the prepuce, vulva, and
conjunctiva, also sometimes the extremities.
In Lepus timidus -
- Fully developed acute lesions:
- Epidermis hyperplastic, with clusters of swollen keratocytes.
Pathological changes extended as far as the follicular
infundibulum. Keratocytes large and pale due to severe hydropic
swelling. Presence of numerous eosinophilic intracytoplasmic
inclusion bodies, often floccular, particularly found in cells
with ballooning degeneration. Many inclusion bodies were found in
28% of cases.
- Dermis oedematous with mild, superficial perivascular
infiltration of lymphocytes.
- Later lesions:
- Epidermis necrotic to the follicular infundibulum. Ulceration,
marked neutrophil transmigration into exudate, forming crusts,
often with large numbers of cocci in the crust surface. Rarely
inclusion bodies present. Occasional hair follicle rupture and
associated pyogranulomaous inflammatory reaction in the dermis.
Inflammation mild (three cases, 7%), moderate (nine cases, 20%) or
severe (33 cases, 72%).
- Chronic advanced lesions:
- Dermal fibrosis, variable (marked in three cases, 7%). Epidermal
hyperplasia; mild or minimal plasma cell infiltration and fewer
lymphocytes and neutrophils.
- Electron microscopy revealed numerous virions in the
intracytoplasmic inclusion bodies. The virions were ovoid, 300 x
130-150 nm, with a biconcave nucleocapsid core, two lateral bodies and
an outer lipoprotein capsule which was clearly discernable. They were
considered to be typical poxviruses.
- Bacterial cultures were commonly grown, paricularly Staphylococcus
warneri, often in pure culture, but also other Staphylococcus
spp. and the yeast Candida albicans. It was noted that Treponema
spp. were not found.
- It was considered that the lesions showed development from acute
viral dermatitis through secondary pyoderma to cutaneous scarring.