Etsuko Nonaka

Publication Date

2-19-2010

Abstract

Infectivity periods of different tick-borne pathogens in host species can vary widely, and the variation affects how the pathogens are maintained in tick populations. In addition to systemic and vertical transmission, cofeeding transmission has been proposed as an important route for the persistence of pathogens with short infectivity (e.g., tick-borne encephalitis causing viruses, TBEv). Because cofeeding transmission requires ticks to feed simultaneously, the temporal dynamics of tick populations become important. Existing models of tick-borne diseases do not fully incorporate all three transmission pathways (systemic, vertical, and cofeeding transmission) and tick seasonality. We developed a comprehensive stage-structured population model that includes seasonality and evaluated the relative importance of the three transmission pathways for pathogens with short infectivity. We used the next generation matrix method to calculate R0 and performed elasticity analyses for complex disease systems. We found that cofeeding transmission is a critically important route for such pathogens to persist in seasonal tick populations over the reasonable range of parameter values. At higher but still plausible rates of vertical transmission, our model suggests that vertical transmission can be a strong enhancer of pathogen prevalence when it operates in combination with cofeeding transmission. We discuss potential mechanisms behind consistent but low prevalence of TBEv observed in tick populations in the field.

Degree Name

Mathematics

Level of Degree

Masters

Department Name

Mathematics & Statistics

First Committee Member (Chair)

Helen Wearing

Second Committee Member

Pedro Embid

Third Committee Member

Stanly Steinberg

Language

English

Keywords

Tick-borne diseases in animals--Transmission--Mathematical models, Tick-borne encephalitis--Transmission--mathematical models, Encephalitis--Seasonal variations--Mathematical models.

Document Type

Thesis

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