Two-host, two-vector basic reproduction ratio (R(0)) for bluetongue.

Area of Science:

• Veterinary epidemiology
• Mathematical modeling
• Disease ecology

Background:

• Existing models for basic reproduction ratio (R(0)) often simplify vector-borne diseases to one-host, one-vector or two-host, one-vector systems.
• Many vector-borne diseases, like bluetongue, involve multiple co-occurring vector species, necessitating more complex formulations.
• Bluetongue poses significant economic threats to ruminants, with over a million sheep deaths in Europe since 1998.

Purpose of the Study:

• To derive and present a two-host, two-vector mathematical formulation for the R(0) of bluetongue.
• To investigate the impact of varying vector abundance, competence, and host preference on R(0).
• To highlight the potential for underestimation of R(0) with simplified models.

Main Methods:

• Developed a novel two-host, two-vector mathematical model for bluetongue transmission.
• Utilized data from South Africa, considering two primary hosts (sheep, cattle) and two distinct vector species.
• Analyzed the influence of differential vector ecology and transmission capabilities on R(0) calculations.

Main Results:

• R(0) can be significantly underestimated when assuming a single vector or overlooking vector host preferences.
• The accuracy of R(0) estimation depends on the level of cross-infection between vector species.
• A two-host, one-vector model is a fair approximation only when cross-infection is minimal.

Conclusions:

• Accurate bluetongue R(0) estimation requires complex models that account for multiple vectors and their specific interactions.
• Simplified models can lead to underestimations, impacting disease control strategies.
• The derived two-host, two-vector formulation is crucial for understanding and managing bluetongue outbreaks, particularly in regions with co-occurring vector species.