The effect of heterogeneous infectious period and contagiousness on the dynamics of Salmonella transmission in dairy cattle

• Published in: Epidemiology and infection Vol. 136; no. 11; pp. 1496 - 1510
• Main Authors: LANZAS, C., BRIEN, S., IVANEK, R., LO, Y., CHAPAGAIN, P. P., RAY, K. A., AYSCUE, P., WARNICK, L. D., GRÖHN, Y. T.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.11.2008
• Subjects: Animals; Bacteriology; Basic Reproduction Number; Biological and medical sciences; Cattle; Cattle Diseases - epidemiology; Cattle Diseases - microbiology; Cattle Diseases - transmission; Computer Simulation; Fundamental and applied biological sciences. Psychology; Infection Control - methods; Microbiology; Miscellaneous; Models, Statistical; Original Papers; Prevalence; Salmonella; Salmonella Infections, Animal - epidemiology; Salmonella Infections, Animal - transmission; Time Factors; Human; Salmonella; Farming animal; Microbiology; Dairy cattle; Transmission; Epidemiology; Infection; Vertebrata; Mammalia; Bacteria; Artiodactyla; Ungulata; Enterobacteriaceae
• ISSN: 0950-2688; 1469-4409
• DOI: 10.1017/S0950268807000209

The objective of this study was to address the impact of heterogeneity of infectious period and contagiousness on Salmonella transmission dynamics in dairy cattle populations. We developed three deterministic SIR-type models with two basic infected stages (clinically and subclinically infected). In addition, model 2 included long-term shedders, which were defined as individuals with low contagiousness but long infectious period, and model 3 included super-shedders (individuals with high contagiousness and long infectious period). The simulated dynamics, basic reproduction number (R0) and critical vaccination threshold were studied. Clinically infected individuals were the main force of infection transmission for models 1 and 2. Long-term shedders had a small impact on the transmission of the infection and on the estimated vaccination thresholds. The presence of super-shedders increases R0 and decreases the effectiveness of population-wise strategies to reduce infection, making necessary the application of strategies that target this specific group.