NAVLE Rats-Mice

Epizootic Diarrhea of Infant Mice (EDIM) – NAVLE Study Guide

Epizootic Diarrhea of Infant Mice (EDIM) is a highly contagious viral infection of neonatal and suckling mice caused by murine rotavirus (Group A rotavirus).

Overview and Clinical Importance

Epizootic Diarrhea of Infant Mice (EDIM) is a highly contagious viral infection of neonatal and suckling mice caused by murine rotavirus (Group A rotavirus). The disease primarily affects mice between 0-14 days of age, with peak susceptibility at 4-14 days. Adult mice are asymptomatic carriers that shed virus to susceptible offspring.

While clinical disease is often subclinical in modern SPF colonies, EDIM can cause diarrhea, stunted growth, and mortality in affected litters. Understanding EDIM is important for the NAVLE as it represents a common research animal pathogen and illustrates rotavirus biology.

Age (Days) Susceptibility Clinical Outcome
0-3 days Low (23%) Maternal antibodies provide protection; minimal disease
4-14 days HIGH (95%) PEAK SUSCEPTIBILITY; clinical disease common (diarrhea, stunting)
15-17 days Moderate (41%) Decreasing susceptibility as weaning approaches
Greater than 18 days (post-weaning) Very Low to None Adults are ASYMPTOMATIC CARRIERS; shed virus without disease

Etiology and Viral Characteristics

Viral Classification

  • Family: Reoviridae
  • Genus: Rotavirus (Group A)
  • Genome: Double-stranded RNA, segmented (11 segments)
  • Morphology: Wheel-shaped virion (Latin: rota = wheel), 70 nm diameter, non-enveloped
  • Strains: Multiple strains identified with variable virulence

Environmental Stability

  • Highly stable in environment; persists in feces, bedding, and fomites
  • Resistant to many disinfectants; susceptible to bleach, formaldehyde, phenolics
  • Survives at room temperature for extended periods
NAVLE TipRemember: Rotavirus = Rota (wheel) shape. EDIM is a segmented dsRNA virus, similar to human rotavirus. If you see 'wheel-shaped virus causing diarrhea in infant mice,' think EDIM!
Method Specimen Notes
Serology (ELISA, IFA) Serum from adult dams MOST COMMON; detects antibodies indicating colony exposure; does not confirm active disease in pups
Histopathology Formalin-fixed intestine Demonstrates characteristic villous atrophy and vacuolar degeneration; highly diagnostic
PCR/RT-PCR Feces, intestinal contents Detects viral RNA; rapid, sensitive, specific
Electron Microscopy Feces, intestinal contents Demonstrates wheel-shaped rotavirus particles; rarely used now
Antigen Detection (ELISA) Feces Detects viral antigen in feces during acute infection

Epidemiology and Transmission

Age-Related Susceptibility

Susceptibility to EDIM is HIGHLY age-dependent:

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