Bovine upper alimentary squamous cell carcinoma associated with bracken fern poisoning: Clinical-pathological aspects and etiopathogenesis of 100 cases

Upper digestive tract (UDT) cancer is rare in cattle, however in Southern Brazil, the UDT squamous cell carcinomas (SCCs) are relatively common and have been associated with bracken fern consumption and the presence of papillomas. Although a theory of pathogenesis considers bovine papillomavirus type 4 (BPV-4) as a cofactor in the development of these SCCs, some aspects of the etiopathogenesis of this disease need to be more investigated. In fact, detection of BPV-4 in UDT papillomas is scarce in other regions of the world and has not been performed in Brazil. Therefore, this study had two aims: 1) to analyze the epidemiological, clinical and pathological aspects of 100 natural cases of SCCs in the UDT of cattle grazing on bracken fern (Pteridium arachnoideum) highly contaminated areas, investigating the associations between these parameters; and 2) to investigate the presence of papillomavirus DNA by polymerase chain reaction (PCR) in the UDT papillomas (n = 47) from 30 cattle that also had UDT SCCs. There were statistically significant associations between clinical signs and tumor localization in the UDT; between histological grade of differentiation and tumor localization; and a trend towards significant association between histological grade of differentiation and presence of metastases. The average age of cattle with oropharyngeal SCCs was 7.39 years, with statistically significant difference comparing to cattle with esophageal SCCs (8.6 years). No statistical association was observed among other clinical-pathological parameters (growth pattern and primary site of the tumor) analyzed. No BPV DNA was detected in papillomas by PCR. Therefore, these results suggest the possibility that papillomas of the UDT are not necessarily associated with BPV infection.