Betaretrovirus-induced transmissible respiratory tumors in sheep arise at 2 distinct anatomic locations, either deep in the lung tissue caused by jaagsiekte sheep retrovirus (JSRV) or in the nasal cavity induced by ovine enzootic nasal tumor virus (ENTV-1). JSRV and ENTV-1 are found in many countries worldwide and have a significant economic and animal health impact. Although JSRV is endemic in sheep in the British Isles, ENTV-1 has not been reported. We report herein a nasal adenocarcinoma in a cull 8-y-old Belclare ewe from Ireland. The gross and microscopic features and immunohistochemistry results were consistent with an ENTV-1-associated tumor. However, differential PCR, using primers specific to regions of divergent sequence between the viruses, was performed on different parts of the adenocarcinoma and produced consistent results: positive for JSRV and negative for ENTV-1. An association of JSRV with nasal adenocarcinoma in sheep has not been reported previously, to our knowledge. Our case shows the necessity of using PCR in combination with immunohistochemistry to reach an accurate etiologic diagnosis, which is of importance in countries currently free of ENTV-1.
Keywords: enzootic nasal tumor virus; jaagsiekte sheep retrovirus; nasal adenocarcinoma; sheep.