mental infections in suckling and weanling F344 and WI (Wistar) rats, and named the virus rat coronavirus (RCV). [This virus is here considered a strain of sialodacryoadenitis virus (SDAV), the best studied of this group of closely related coronaviruses (Jacoby, 1986)].

1972: Bhatt et al. (1972) used primary rat kidney cells to isolate a virus from rats with sialodacryoadenitis, characterized the virus, identified it as a coronavirus, and named it SDAV.

1977: Weisbroth and Peress (1977) investigated an epizootic of SDAV infection in which lesions were limited to orbital tissues. They proposed the hypothesis that the variability in clinical and morphological expression of the disease due to SDAV was attributable to the occurrence of viral mutants with different tissue tropisms.

1982: Maru and Sato (1982) isolated and characterized a strain of SDAV from rats with sialoadenitis in Japan, and called it the causative agent of rat sialoadenitis (CARS). Unlike previous strains, it could be grown in 3T3 cells but not in primary rat kidney cells.

1986: Wojcinski and Percy (1986) demonstrated that SDAV produces significant albeit transient disease throughout the respiratory tract, and suggested that the respiratory disease due to SDAV had generally been overlooked except in the studies of RCV.

1987: Schoeb and Lindsey (1987) reported experimental evidence that SDAV can exacerbate murine respiratory mycoplasmosis in rats.

SDAV is an RNA virus, family Coronaviridae, genus Coronavirus. It is antigenically related to many other coronaviruses, including mouse hepatitis virus (MHV) (Machii et al., 1988) and human coronavirus (strain OG38). SDAV, RCV, CARS, and other similar coronavirus isolates from rats are considered different strains of the same virus (Bhatt et al., 1977; Jacoby, 1986).

Virions of SDAV measure approximately 114 nm in diameter and have characteristic projections from the surface, giving a crown-like appearance. The virus is relatively unstable. Infectivity is quickly lost at room temperature, freezing to -20°C, heating to 56°C, and exposure to lipid solvents. It has been stored at -60°C for at least 7 years (Jacoby et al., 1979).

SDAV and RCV can be propagated in primary rat kidney and LBC cells (Parker et al., 1970c; Bhatt et al., 1972; Hirano et al., 1985, 1986). CARS grows in 3T3 cells (Maru and Sato, 1982).

Rats. Mice have been shown to be susceptible experimentally (Bhatt et al., 1977; Percy et al., 1986, 1988a), but natural infection in mice has not

Front Matter (R1-R12)

I. Principles of Rodent Disease Prevention (1-2)

1. Objectives, Terminology, and Overview of Pathogen Status (3-12)

2. Breeding, Transportation, and Use of Pathogen-Free Rodents (13-16)

3. Barrier Programs (17-20)

4. Health Surveillance Programs (21-28)

II. Individual Disease Agents and Their Effects on Research (29-30)

5. Introduction (31-32)

6. Respiratory System (33-84)

7. Digestive System (85-163)

8. Skin and Joints (164-197)

9. Hemopoietic System (198-221)

10. Central Nervous System (222-230)

11. Genitourinary System (231-235)

12. Multiple Systems (236-256)

III. Indexes to Diagnosis and Research Complications of Infectious Agents (257-258)

Introduction (259-259)

Clinical Signs (260-265)

Pathology (266-274)

Research Complications (275-276)

References (277-386)

Index (387-397)