Bovine Papillomavirus Type 1 Infection in an Equine Congenital Papilloma

Abstract

Papillomas are benign epithelial lesions protruding on the epithelial surfaces as finger-like or warty projections. These lesions are often caused by papillomavirus (PV) infection. Congenital papillomas have been reported in foals. However, to date, no evidence of PV infection has been provided. In the present paper, we describe the main clinical-pathological features of a congenital papilloma observed in a foal. In addition, biomolecular tests demonstrated BPV1 infection in the case under study. Such data stimulate further investigations, even on archived samples, aiming to clarifying the etiology of equine congenital papilloma and the clinical relevance, if any, of BPV1 vertical transmission in horses.

Keywords: bovine papillomaviruses; congenital papilloma; horse.

Figure 1

Foal three days after birth. A globoid lesion is clearly seen, attached to the upper lip.

Figure 2

Excised lesion after formalin fixation. The mass is about 3 cm in diameter and shows a verrucous, “truffle-like” surface (a). In the cut section, the arborized stromal scaffold can be clearly observed (b).

Figure 3

Histopathological examination of the excised lesion. In this finger-like projection, a central fibrovascular backbone is clearly seen, which contains several blood and lymphatic vessels. The stroma is covered by a thickened epidermis, the stratum spinosum being markedly expanded. H and E stain. Final magnification ×200.

Figure 4

In these sections, evidence of koilocytosis was observed. The right panels reveal a close-up view of the inset. The arrows indicate some selected koilocytes. H and E stain. Final magnification ×200.

Figure 5

RNAscope assay. (A) Tissue sections hybridized with the probe targeting BPV-1 E5-E6-E7 mRNA (V-BPV-E). A close-up view of the inset is visible in the right panel. Specific staining was observed in the congenital papilloma under investigation. In detail, scattered red dots were detected within the cytoplasms (empty circles) and nuclei (black arrow) of epithelial cells. (B) On the contrary, no specific staining was observed in the negative control. Final magnification: ×400.