Incorporating tick feeding behaviour into R₀ for tick-borne pathogens

Area of Science:

• Epidemiology
• Vector-borne diseases
• Mathematical modeling

Background:

• Tick-borne pathogens like Borrelia burgdorferi and TBE virus cause significant disease burdens in Europe and North America.
• Understanding tick distribution and abundance is crucial due to increasing human cases and emerging pathogens.
• Transmission between tick generations occurs via vertebrate hosts or direct co-feeding.

Purpose of the Study:

• To derive mathematical expressions for disease transmission parameters (R0 and T) accounting for tick co-aggregation behavior.
• To investigate the impact of tick aggregation and co-aggregation on pathogen transmission dynamics.
• To analyze how co-aggregation influences R0 and T for different transmission routes.

Main Methods:

• Developed expressions for the basic reproduction number (R0) and tick type-reproduction number (T).
• Modeled tick blood meals as a directed, acyclic, bipartite contact network.
• Simulated pathogen transmission (B. burgdorferi, TBE virus) on theoretical tick-mouse contact networks.

Main Results:

• Co-aggregation significantly increases R0 and T, with synergistic effects when combined with aggregation.
• Co-aggregation consistently enhances pathogen transmission, especially when larvae and nymphs co-aggregate.
• The impact of co-aggregation is greatest with high larval burdens and for pathogens relying on co-feeding transmission.

Conclusions:

• Tick co-aggregation is a key factor driving the persistence and spread of tick-borne pathogens.
• Co-aggregation increases the number of infected ticks per infectious tick, enhancing pathogen survival.
• Understanding tick feeding behavior is vital for predicting and controlling tick-borne disease dynamics.