In their primary rodent reservoir hosts, naturally occurring and experimentally induced hantavirus infections are subclinical and chronic (14
). Experimental infection of striped field mice and bank voles with HTNV and PUUV, respectively, is characterized by transient viremia and short-lived shedding of virus in oropharyngeal secretions; prolonged excretion of virus in urine, feces, or both; and virus persistence in tissues, particularly lung (14
). PUUV has been serially passaged only in laboratory-bred bank voles (17
), and strains Hällnäs and K27 of PUUV cause an asymptomatic persistent infection in Mongolian gerbils (21
) and Syrian hamsters (22
), respectively. Horizontal intracage transmission has been demonstrated for HTNV and PUUV, but vertical transmission does not appear to occur (15
). In infant mice and rats experimentally infected with HTNV and SEOV, respectively, fatal meningoencephalitis develops (24
). In contrast, mice and rats >14–21 days of age are generally resistant to experimental HTNV and SEOV infection (26
). Conversely, infant mice are resistant to experimental infection with PUUV (18
), PHV (L.J. Baek, unpub. data), and SNV, the prototype sigmodontine rodentborne hantavirus that causes HPS (28
To determine the host range of experimental TPMV infection and to ascertain whether susceptibility of small laboratory animals to disseminated TPMV infection is age-dependent, we infected NIH Swiss mice and Mongolian gerbils of different ages, as well as infant deer mice and gray short-tailed opossums (Monodelphis domestica), by the intracerebral route with 6,000 PFU of TPMV (). Infant Swiss NIH mice, deer mice, and gerbils were equally susceptible to fatal TPMV infection. Moreover, susceptibility to disseminated TPMV infection in NIH Swiss mice and gerbils was not age-dependent, as shown by lethal meningoencephalitis (characterized by hyperexcitability, ataxia, limb paralysis, and seizures) in animals infected at 1–21 days of age. TPMV antigen was detected in cryostat-cut sections of lung, brain, kidney, spleen, and liver of experimentally infected, moribund NIH Swiss mice and gerbils (). Thus, unlike HTNV, SEOV, PUUV, PHV, and SNV, TPMV appears to have a much broader experimental host range in small laboratory animals.
Susceptibility of small laboratory animals of various ages to fatal Thottapalayam virus meningoencephalitis*
Figure 1 Intracytoplasmic virus-specific fluorescence in brain tissues of an 11-day-old Mongolian gerbil (A) and a 10-day-old NIH Swiss mouse (B) injected intracerebrally with 6,000 PFU of Thottapalayam virus (TPMV) strain VRC-66412 from serum of an adult rat (more ...)
Studies now in progress on experimental TPMV infection in laboratory-reared Asian house shrews should provide information about virus carriage and shedding. In addition, experimental demonstration of subclinical and chronic TPMV infection in Asian house shrews would also support the nonrodent reservoir host status.