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Aerosol infection of calves and mice with Salmonella typhimurium
C M Wathes1, W A Zaidan, G R Pearson
1Department of Animal Husbandry, University of Bristol, Langford.
Abstract:
The likelihood of airborne spread and infection by Salmonella typhimurium was studied in calves and mice. S typhimurium survived in air sufficiently long to present a significant hazard of airborne spread. In a dry climate (32 per cent relative humidity) its predicted viability five minutes after aerosolization was 4 per cent relative to its initial value. This increased to 24.8 per cent in a humid atmosphere (72 per cent relative humidity). Inhalation of S typhimurium by mice caused disease and death at times dependent upon the dose. Even the lowest dose of about 150 colony forming units (cfu) produced disease. Inoculation of approximately 10(4) to 10(6) cfu S typhimurium by either 'mouth and nose only' or 'whole body' aerosol exposure caused infection in calves. The consequences for the control of salmonellosis in intensive calf husbandry are discussed in the light of this demonstration that airborne transmission can be a primary mode of infection of S typhimurium.
Insights
Salmonella typhimurium can spread through the air, posing a significant infection risk. This airborne transmission was confirmed in mice and calves, impacting disease control strategies.
Area of Science:
- Veterinary Microbiology
- Infectious Disease Transmission
- Environmental Health
Background:
- Salmonella typhimurium is a significant pathogen in livestock and can cause zoonotic infections.
- Understanding transmission routes is crucial for effective disease control in animal husbandry.
- Airborne transmission of bacterial pathogens is a recognized but often underestimated route.
Purpose of the Study:
- To investigate the potential for airborne spread and infection of Salmonella typhimurium.
- To determine the viability of airborne S. typhimurium under different humidity conditions.
- To assess the infectivity of aerosolized S. typhimurium in animal models.
Main Methods:
- Controlled aerosolization experiments with S. typhimurium in mice and calves.
- Assessment of bacterial viability at various relative humidity levels (32% and 72%).
- Inhalation exposure studies to determine dose-dependent infection and disease outcomes.
Main Results:
- S. typhimurium demonstrated significant survival in the air, with viability increasing in higher humidity.
- Inhalation of S. typhimurium caused disease and mortality in mice, even at low doses (approx. 150 colony forming units).
- Calves were infected by aerosol exposure (10^4 to 10^6 cfu), indicating susceptibility via inhalation.
Conclusions:
- Airborne transmission represents a primary and significant route for S. typhimurium infection in calves.
- Findings have critical implications for salmonellosis control in intensive calf farming environments.
- Enhanced biosecurity measures addressing airborne pathogens are recommended.