Viral and squamous papillomas in captive polar bears (Ursus maritimus).

Area of Science:

• Veterinary Pathology
• Virology
• Wildlife Disease

Background:

• Papillomas are common skin lesions in many species, often virally induced.
• Distinguishing viral from non-viral papillomas relies on characteristic histologic cytopathic changes.
• A novel papillomavirus, Ursus maritimus papillomavirus-type 1, was previously reported in a polar bear without confirmed association to papilloma formation.

Purpose of the Study:

• To investigate the presence and causative agent of papillomas in polar bears.
• To determine if a novel papillomavirus is associated with papilloma development in this species.
• To differentiate between viral and non-viral papilloma pathogenesis in polar bears.

Main Methods:

• Histologic examination of papilloma tissues from three polar bears.
• Polymerase chain reaction (PCR) with broad-spectrum papillomavirus primers and amplicon sequencing.
• In situ hybridization (ISH) to detect viral nucleic acid within tissue samples.

Main Results:

• One polar bear exhibited papillomas with koilocytosis, indicative of viral infection.
• Novel papillomavirus DNA sequence (<70% identity to known types) was detected in the affected bear via PCR and sequencing.
• In situ hybridization confirmed viral nucleic acid presence in papilloma cells but not adjacent normal skin.
• Papillomas in the other two bears lacked histologic cytopathic changes and were negative for papillomavirus by PCR and ISH.

Conclusions:

• Cytopathic effect in polar bear papillomas is associated with the presence of a novel papillomavirus.
• The absence of histologic cytopathic change may indicate a non-viral etiology for papillomas in polar bears.
• Further genomic sequencing of the novel virus is crucial for understanding its role in polar bear health and conservation.