Pathological studies and detection of co-infection of bovine papilloma viruses in cattle cutaneous and teat warts

Abstract

Bovine papillomas are benign tumors of the cutaneous and mucosal epithelia and are commonly found in cattle. The productivity loss and economic impact depends on the location and degree of infection. The present study was undertaken to investigate the pathology and association of different bovine papilloma virus (BPV) types in cattle cutaneous and teat warts. Grossly, the warts were of variable size and shape (rice grain, cauliflower and finger-like horny growths or irregular). Histopathologically, the warts were diagnosed as fibropapilloma, papilloma, fibrosarcoma and hyperplasia. Fibropapilloma was the most frequent histological type observed and was characterized by hyperkeratosis, parakeratosis and acanthosis. PCR revealed the presence of either BPV-1, -2 and -5 DNA or their co-infections. Transmission electron microscopy on negative staining showed BPV-like particles. Varied copy numbers of viral DNA of BPV-1, -2 and -5 were detected by real-time PCR. Immunohistochemistry revealed the expression of Ki-67 mainly in the proliferating cells of stratum spinosum and a few basal cells in papilloma and fibropapilloma. Cyclooxygenase-2 immunostaining was observed in the cytoplasm and cell membrane of suprabasal cells. In conclusion, cutaneous and teat warts in cattle in India are more frequently associated with BPV-1/ -2 and their mixed infections, with the rare presence of BPV-5. The DNA of BPV-5 was detected for the first time in warts in India. Co-infection with two or three different viral types demonstrated the diversity of BPV types involved in warts. The frequent expression of Ki-67 in suprabasal layers may be indicative of its association with viral replication and that they are as proliferation sites.