Hantaviral infections of rodents: possible scenarios

Abstract

Virus–host interactions vary widely, depending on the hostspecies and the virus, and depend on age, dose and route ofexposure in determining whether the outcome will be achronic host infection with viral nucleic acid (genome) intarget organs such as brain, lung, liver or kidney, whetherinfectious virus will be excreted over time, and what theroute of excretion will be. In regard to viruses principallytransmitted among rodents, dominant transmission routesmay be affected by any or all of these or other variables indifferent rodent behavioral settings. Whereas characteris-tics of intraspecific aggressive behavior among weanedadults are thought to dominate mechanisms of reservoirinfection with hantaviruses [1, 2], there are many ways inwhich virus could spread among such communal rodents.The paper by Taruishi et al. [3] presents excellent evi-dence for lack of vertical transmission of Hantaan virus(family Bunyaviridae, genus Hantavirus) from dam tooffspring of persistently infected laboratory mice. Thoseauthors provide a comprehensive review of the literature,which indicates, among other things, that maternal anti-body to Seoul hantavirus in rats protects both the dam’sfetus and its neonates from infection and that no evidencefor vertical transmission has been presented for any rodent-hantavirus system. We believe the authors are correct inall their assumptions but emphasize here that the inbredlaboratory mouse strain used for their studies, bred andmaintained under laboratory conditions, is an artificial hostfor hantavirus studies, and that under natural conditions thetransmission of hantaviruses from dam to offspring could,and likely does, occur in complex ways and may not reflectresults from laboratory studies. We here suggest variousscenarios by which natural infections of young rodents byhantaviruses might occur; there may be more. All but oneof these scenarios would lead to horizontal transmission.Although our principal experiences have been with SinNombre hantavirus and deer mice (Peromyscus manicula-tus), we assume that many, if not most, but not all,hantaviruses are transmitted in similar manners. In con-trast, the data of Hutchinson et al. [4] at least suggest thepossibility of in utero transmission of Black Creek Canalhantavirus. There are no published data indicating thathantaviral infections of very young rodents engender per-sistent infections and subsequently shed virus persistently,but we speculate that that is the case.Scenario 1aDam uninfected with a hantavirus and without antibody tothat virus. Unless an infected male enters the nest area, theoffspring are not exposed to the virus until and unless theyexit the nest area and begin to exhibit adult behaviors, suchas fighting with infected individuals or by communallynesting with infected individuals or foraging with infectedindividuals. When infected as adults or subadults, they maybecome persistently infected (kidneys, lungs, other organscan be shown to harbor virus), may shed virus for a brief