Natural History of Sin Nombre Virus in Western Colorado

Abstract

A mark-recapture longitudinal study of immunoglobulin G (IgG) antibody to Sin Nombre virus (SNV) in rodent populations in western Colorado (1994—results summarized to October 1997) indicates the presence of SNV or a closely related hantavirus at two sites. Most rodents (principally deer mice, Peromyscus maniculatus, and pinyon mice, P. truei) did not persist on the trapping webs much beyond 1 month after first capture. Some persisted more than 1 year, which suggests that even a few infected deer mice could serve as transseasonal reservoirs and mechanisms for over-winter virus maintenance. A positive association between wounds and SNV antibody in adult animals at both sites suggests that when infected rodents in certain populations fight with uninfected rodents, virus amplification occurs. At both sites, male rodents comprised a larger percentage of seropositive mice than recaptured mice, which suggests that male mice contribute more to the SNV epizootic cycle than female mice. In deer mice, IgG antibody prevalence fluctuations were positively associated with population fluctuations. The rates of seroconversion, which in deer mice at both sites occurred mostly during late summer and midwinter, were higher than the seroprevalence, which suggests that the longer deer mice live, the greater the probability they will become infected with SNV.

Persistent hantavirus infections: characteristics and mechanisms

“…The presence of viral antigen in the kidneys was most common in deer mice that did not have antibodies to Sin Nombre virus, suggesting that virus shedding is greatest in the early stages of infection 32 . Also analogous to findings with the Old World hantaviruses, a higher sero-prevalence rate for Sin Nombre virus was observed in old deer mice than in young deer mice, with males infected more often than females [33][34][35] . Although these data are consistent with horizontal transmission by aggressive interactions and biting, they could also reflect the larger home range of adult males compared with adult females and the resulting increased risk of aerosol exposure 33 .…”

Do Unusual Site-Specific Population Dynamics of Rodent Reservoirs Provide Clues to the Natural History of Hantaviruses?

“…Numerous studies have demonstrated an age-related prevalence of antibody, often favoring males (Glass et al, 1988;Childs et al, 1994;Mills et al, 1997;Calisher et al, 1999), indicating that virus is maintained in reservoir populations via horizontal transmission, perhaps most frequently through aggressive encounters among adult males. Populations consisting of older individuals may have much higher prevalences of infection than populations comprising mostly young mice.…”

“…Populations consisting of older individuals may have much higher prevalences of infection than populations comprising mostly young mice. It has been hypothesized that transseasonal maintenance of hantaviruses in reservoir populations in temperate environments occurs via longlived resident animals, which maintain infection from the previous season and reintroduce virus to susceptible animals each spring (Abbott, et al, 1999;Calisher et al, 1999;Mills et al, 1999a).…”

Longitudinal studies of Sin Nombre virus in deer mouse-dominated ecosystems of Montana.

“…After the discovery of this disease in the southwestern United States 1,2 in 1993, several long-term studies of reservoir populations were initiated-in part, to develop measures to control and prevent human infection. 3 Four studies were conducted in the Southwestern United States [4][5][6][7] and one in Montana. 8 An important potential tool for preventing HPS is the use of models based on environmental and ecological conditions that predict risk of HPS.…”