ROLE OF INBORN RESISTANCE FACTORS IN MOUSE POPULATIONS INFECTED WITH BACILLUS ENTERITIDIS

Area of Science:

• Immunology
• Infectious Disease Epidemiology

Background:

• Understanding host susceptibility is crucial for controlling infectious diseases.
• Mouse typhoid provides a model to study innate resistance and disease transmission.

Purpose of the Study:

• To investigate the role of innate resistance in mouse typhoid survival.
• To determine if herd exposure confers immunity in susceptible individuals.

Main Methods:

• Naturally spreading mouse typhoid in mouse populations with varying proportions of resistant and susceptible individuals.
• Introducing susceptible and resistant recruits into established populations.
• Assessing survival rates and infection status post-exposure.

Main Results:

• Innately susceptible mice had 85-95% mortality, while resistant mice had <5% mortality.
• Survivors were predominantly innately resistant individuals, though some harbored bacteria.
• Susceptible recruits added to resistant populations experienced sporadic or epidemic mortality.
• No evidence of acquired immunity in susceptible mice following natural exposure or sublethal dosing.

Conclusions:

• Innate resistance is the primary determinant of survival in mouse typhoid.
• Susceptible individuals do not develop immunity through herd exposure or sublethal doses.
• Environmental stressors can increase mortality in both resistant and susceptible mice.