HFRS antigen and antibody in two species of Swedish voles

Hemorrhagic fever with renal syndrome (nephropathia epidemica) in Norway: seroepidemiology 1981-1985

An indirect fluorescent antibody technique (IFAT) was applied to serologically confirm the clinical diagnosis in 507 nephropathia epidemica (NE) suspected patients. Hantaan virus (HV), the agent of Korean hemorrhagic fever, which is serologically related to the NE agent, was used as antigen. Both IgG and IgM reactions were detected. High levels of IgG antibodies to HV were common, even in the acute phase of illness. Over a 5-year period, a total of 35% of the NE suspected patients revealed antibodies to HV, but this varied considerably in the different years. In 2 endemic areas the serological confirmation of the NE diagnosis was 60%. 82% of the seropositive NE patients lived in 4 endemic areas. The bank vole (Clethrionomys glareolus) was common in all areas and predominant in 2. The wood mouse (Apodemus sylvaticus) was abundant in the other 2. In years with high bank vole population, the number of seropositive NE cases increased, with a peak in October/November. When the bank vole population was low, the relatively few seropositive NE cases occurred more regularly throughout the year. Subclinical infections were common. Antibodies to HV were detected in 74% male and 26% female NE patients, but the ratio varied between age groups.

Serological survey of Prospect Hill virus infection in indigenous wild rodents in the USA

We found serological evidence of infection with Prospect Hill virus, a Hantaan-like virus isolated from meadow voles (Microtus pennsylvanicus), in microtine and cricetid rodents trapped in Maryland, West Virginia, Minnesota and California, USA. Fluorescent antibodies were detected in sera from M. pennsylvanicus (74/277), M. californicus (39/185), Clethrionomys gapperi (5/51), Peromyscus maniculatus (4/22) and P. truei (1/11). Sera from seropositive P. maniculatus contained neutralizing antibodies against Prospect Hill virus, confirming that infection with Prospect Hill virus or antigenically related viruses is not restricted to microtine rodents in the USA. Despite the widespread distribution of Prospect Hill virus in indigenous rodents, the recent demonstration that American mammalogists are only rarely infected supports the view that the overall risk of Prospect Hill virus infection in man is low.

Experimental infection with Puumala virus, the etiologic agent of nephropathia epidemica, in bank voles (Clethrionomys glareolus)

Subclinical chronic infections characterized by transient viremia, prolonged virus shedding in oropharyngeal secretions and feces, and virus persistence in tissues (particularly lung) developed in laboratory-bred weanling bank voles (Clethrionomys glareolus) inoculated intramuscularly with Puumala virus (strain Hällnäs), the etiologic agent of nephropathia epidemica. Viral antigen, as evidence by granular fluorescence, was detected in the lungs, liver, spleen, pancreas, salivary glands, and small intestine. Infectious virus was found in the lungs from 14 to 270 days postinoculation, and feces and urine collected 35 to 130 days postinoculation were regularly and sporadically infectious, respectively. Horizontal transmission coincided with virus shedding in oropharyngeal secretions. Suckling voles also developed asymptomatic persistent infections after intracerebral inoculation, and histopathological changes were absent despite widespread infection. Our data resemble findings in Apodemus agrarius experimentally infected with Hantaan virus, the prototype virus of hemorrhagic fever with renal syndrome, suggesting that the mechanisms of maintenance and transmission of Puumala and Hantaan viruses are similar in their respective wild-rodent hosts.

Propagation of nephropathia epidemica virus in Mongolian gerbils

Nephropathia epidemica virus, the etiological agent of hemorrhagic fever with renal syndrome in Scandinavia, was serially propagated in Mongolian gerbils (Meriones unguiculatus). Intracerebrally inoculated suckling gerbils developed subclinical infections, with viral antigen found in lung, brain, liver and spleen. The distribution of viral antigen was similar to that seen in experimentally infected bank voles (Clethrionomys glareolus), the principal wild rodent reservoir of nephropathia epidemica virus. This model provides a readily available animal host for the study of experimental nephropathia epidemica virus infection.

Isolation and propagation of nephropathia epidemica virus in bank voles

Three strains of nephropathia epidemica (NE) virus were isolated from lung tissues of bank voles (Clethrionomys glareolus) and a grey-sided vole (C. rufocanus) trapped in Västerbotten county, Sweden. Two of these isolates were serially passaged in seronegative laboratory-bred bank voles. Experimentally infected animals developed a subclinical infection characterized by virus persistence, particularly in lung tissue. Attempts to infect other species of colonized rodents with NE virus and to isolate NE virus from acute phase patient blood were unsuccessful. The serial propagation of NE virus in colonized bank voles provides opportunities to study experimental infection in its reservoir rodent host.