Outbreak of Cutaneous Papillomatosis in Buffaloes (Bubalus bubalis): Diagnosis by Transmission Electron Microscopy

Authors: Cappellaro, C.E.M.P.D.M; Catroxo, M.H.B.; Martins, A.M.C.R.P.F.
Outbreak of Cutaneous Papillomatosis in Buffaloes (Bubalus bubalis): Diagnosis by Transmission Electron Microscopy
DOI
10.25125/ijoear-aug-2026-28
DIN
IJOEAR-AUG-2026-28
Abstract

Papillomatosis is an emerging infectious disease that causes significant economic losses in intensive and semi-intensive buffalo production systems. In dairy herds, the disease impairs milking, causes cutaneous lesions and bleeding, and predisposes animals to mastitis. In beef production systems, the main impacts include reduced weight gain, hide damage, and increased veterinary care costs. The disease may occur in cutaneous and mucosal forms. The cutaneous form is characterized by the presence of warts or fibropapillomas distributed throughout different regions of the body, whereas the mucosal form is associated with bovine enzootic hematuria and urinary bladder carcinogenesis. The lesions observed include papillomas, fibropapillomas, and fibromas, as well as verrucous lesions affecting the mucosa of the rumen, oral cavity, esophagus, and amniotic membrane. Transmission occurs mainly from animal to animal and is facilitated by injuries to the skin and mucous membranes caused by fences, water troughs, feeding troughs, or instruments used for animal restraint. Bovine papillomaviruses are double-stranded DNA viruses belonging to the family Papillomaviridae. In 1993, fibropapilloma samples from five buffaloes (Bubalus bubalis) originating from a farm located in the municipality of Registro, São Paulo State, Brazil, were submitted to the Electron Microscopy Laboratory of the Biological Institute, São Paulo, Brazil. The samples were processed using transmission electron microscopy, negative staining, and resin embedding techniques. In all samples, a large number of non-enveloped papillomavirus particles with icosahedral symmetry were observed. These particles were characterized as "full" and "empty" virions, measuring approximately 60 nm in diameter. In ultrathin sections of papilloma fragments, intracytoplasmic viral particles measuring approximately 30 nm in diameter were observed, associated with thickening of the plasma membrane, which exhibited a serrated appearance. In addition, intranuclear viral particles and membrane-bound intracytoplasmic vacuoles were identified. In the reticular layer, a nucleus with an irregular contour, marginalized chromatin, and the presence of viral particles was observed. The results confirm the occurrence of papillomatosis in buffaloes and demonstrate the importance of electron microscopy for the rapid diagnosis and morphological characterization of the viral agent.

Keywords
Papillomatosis Buffaloes Transmission electron microscopy.
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Introduction

Bovine papillomatosis is an infectious disease of viral origin caused by bovine papillomavirus (BPV). Although it is more frequently described in cattle, it also affects buffaloes, in which it may occur in both cutaneous and mucosal forms. The cutaneous form is characterized by the presence of warts or fibropapillomas distributed across various regions of the body, including the head, neck, back, ears, abdomen, gluteal region, teats, udder, vulva, and perivulvar area (Silvestre et al., 2009). These tumors, which may occur as single or multiple lesions of varying sizes, tend to develop more frequently in previously traumatized areas, possibly due to the release of inflammatory cytokines, reactivation of latent viral infections, and stimulation of cellular proliferation (Silvestre et al., 2009; Al-Redah et al., 2021).

The mucosal form of the disease, mainly associated with BPV-2, is related to bovine enzootic hematuria and urinary bladder carcinogenesis in adult animals grazing on pastures containing bracken fern (Pteridium aquilinum). This condition results from a synergistic interaction between the virus and carcinogenic compounds present in the plant. In buffaloes, this form has been reported in both Brazil and Italy (Maiolino et al., 2013; Roperto et al., 2013; Rocha et al., 2022).

In Brazil, cutaneous papillomatosis was first described in buffaloes in 1993 in females raised in the municipality of Registro, São Paulo State, through transmission electron microscopy and histopathological analyses (Cappellaro et al., 1993; Cappellaro, 1994). Subsequently, cases have been reported in several countries, including Italy, Iraq, Turkey, India, Mexico, and Brazil, and have been more commonly observed in adult animals, although occasional cases have been described in young individuals (Singh et al., 2010). Transmission occurs mainly from buffalo to buffalo, without the need for an intermediate bovine host, and is facilitated by injuries to the skin and mucous membranes caused by fences, water troughs, feeding troughs, or instruments used for animal restraint (Somvanshi, 2011). In addition to horizontal transmission, vertical transmission has also been reported (Russo et al., 2017). Different types of lesions may be observed, including papillomas, fibropapillomas, and fibromas (Jangir et al., 2017), as well as verrucous lesions affecting the mucosa of the rumen, oral cavity, and esophagus (Kumar et al., 2012), and even the amniotic membrane (Russo et al., 2020).

Conclusion

This study confirms the occurrence of cutaneous papillomatosis in buffaloes in Brazil and demonstrates the utility of transmission electron microscopy for the rapid diagnosis and morphological characterization of bovine papillomavirus. The ultrastructural findings, including the visualization of non-enveloped, icosahedral viral particles with "full" and "empty" virions (45–55 nm), as well as intracytoplasmic and intranuclear viral particles (30 nm) and associated cellular alterations (serrated membranes, irregular nuclei with marginalized chromatin), provide detailed morphological evidence of papillomavirus infection in buffalo cutaneous fibropapillomas.

The results highlight the importance of electron microscopy as a diagnostic tool for emerging viral diseases in livestock. The high detection rate (100%) and the characteristic ultrastructural features confirm the presence of papillomavirus in the examined samples and contribute to the understanding of the pathogenesis of cutaneous papillomatosis in buffaloes.

Overall, this study provides valuable baseline information on the ultrastructural features of papillomavirus in buffaloes and emphasizes the need for integrated diagnostic approaches combining electron microscopy, histopathology, and molecular techniques for effective disease surveillance and control.

Agriculture Journal IJOEAR Call for Papers

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