, Volume 102, Issue 3-4, pp 187-196

The gerbil, Meriones unguiculatus, a model for Rift Valley fever viral encephalitis

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The gerbil,Meriones unguiculatus, was investigated as a model for the encephalitic form of Rift Valley fever. Resistance to necrotizing encephalitis was age-dependent with 100% mortality at 3 weeks, decreasing to approximately 20% by 10 weeks of age in outbred gerbils inoculated subcutaneously. Fatal encephalitis in the 10-week-old adults was dose-independent [1.0–7.0 log10 plaque forming units (PFU), subcutaneously]. Viral replication and histological lesions were followed serially throughout the course of the infection in young (4 week) and adult (10 week) gerbils. Viral replication was evident in the brain tissue of young gerbils from day 4 (3.0 log10 PFU/g) through day 7 (6.0 log10 PFU/g), the last day the young gerbils survived. Virus was only detected in the brain tissue of a single adult gerbil (day 7, 4.0 log10 PFU/g) of 26 studied in the sequential survey. In contrast, two moribund adult gerbils had approximately 7.0 log10 PFU/g of virus in the brain tissue on days 8 and 11. When young and adult gerbils were inoculated with a low dose (50 PFU) of virus intracranially, there were no detectable differences in the course of infection with all animals succumbing to fatal necrotizing encephalitis aproximately 7 days postinoculation. The young gerbil becomes the first animal model in which uniformly fatal RVFV-induced encephalitis is produced without significant extraneural lesions.

In conducting the research described in this report, the investigators adhered to the “Guide for Care and Use of Laboratory Animals”, as prepared by the Committee on Care and Use of Laboratory Animals of the Institute of Laboratory Animal Resources Commission on Life Sciences-National Research Council. The facilities are fully accredited by the American Association for Accreditation of Laboratory Animal Care.
The views of the author(s) do not purport to reflect the positions of the Department of the Army or the Department of Defence (Paragraph 4-3, AR 360-5).