Detection and molecular characterization of cultivable caliciviruses from clinically normal mink and enteric caliciviruses associated with diarrhea in mink

Enteric caliciviruses are emerging pathogens responsible for diarrhea or ga stroenteritis in their respective hosts. In this report, mink enteric calic iviruses (MEC) were detected in feces from diarrheic mink by both immune el ectron microscopy (IEM) and RT-PCR using a broadly reactive primer pair (p2 89/290) targeting the highly conserved RNA polymerase regions of the enteri c caliciviruses, Norwalk-like viruses (NLVs) and Sapporo-like viruses (SLVs ). The MEC possess classical caliciviral morphology with typical cup-shaped depressions on the viral surface. Sequence analyses based on nucleotide an d predicted amino acid (aa) sequences of the RT-PCR products indicated that MEC is most closely related genetically to SLVs of humans and animals. The MEC shared the highest aa identities (64-71%) in the RNA polymerase region with both human SLVs and the porcine enteric calicivirus (PEC) Cowden stra in SLV, indicating that MEC may belong to an individual genogroup or subgro up in the SLV genus. The MEC shared only limited aa identities in the RNA p olymerase region with vesiviruses (40-51%) and NLVs (29-33%). The RNA polym erase regions of the cultivable, non-enteric mink caliciviruses (MCV) were also amplified by RT-PCR using the primer pair Pol1/Pol3 based on sequences of vesiviruses, and the primer pair p289/290. Sequence analysis indicated that these MCV shared higher aa identities in the RNA polymerase region wit h vesiviruses (58-81%) than with SLVs (43-51%) including the MEC, lagovirus es (35-37%) and NLVs (27-35%), suggesting that they are most closely relate d genetically to vesiviruses. The MEC associated with diarrhea in mink are morphologically similar to but are genetically distinct from the cultivable MCV and likely represent a new member of the SLV genus.