Serologic and virologic evidence of a prospect hill-like hantavirus in Wisconsin and Minnesota

The purposes of this study were to determine if hantaviruses were present in the Great Lakes port areas of Wisconsin and Minnesota and if so, to identify which virus and which rodent host species were involved. Rodents were trapped in Duluth, Minnesota, Superior, Green Bay, and Milwaukee, Wisconsin, all ports of call for international maritime shipping. A total of 675 wild rodents were captured and tested, including 310 meadow voles (Microtus pennsylvanicus), 173 Norway rats (Rattus norvegicus), 179 Peromyscus spp., (including white footed mice [P. leucopus] and deer mice [P. maniculatus gracilis and P. maniculatus bairdii]), and 13 house mice (Mus musculus). Twenty percent of the rats, 17% of the meadow voles, 8% of the house mice, and 3% of the Peromyscus spp. had antibody to a hantavirus by immunofluorescent antibody assay (IFA). By the plaque-reduction neutralization test (PRNT), nine of 36 meadow voles, one of 4 P. leucopus, and one of 34 rats had hantavirus antibody, with the highest titers to Prospect Hill (PH) virus. All of the PRNT-seropositive individuals were from the twin cities of Superior and Duluth. Hantavirus antigen was detected in lung tissue by IFA in M. pennsylvanicus and Peromyscus spp., but not in rats. Two hantaviruses, designated SD-1 and SD-2, were isolated from M. pennsylvanicus captured in Duluth and found to be very similar to prototype PH virus by cross-IFA and cross-PRNT. Virus isolation attempts were unsuccessful from tissues of the Peromyscus spp. and the rats.