Model structure for the transmission of CCHFV amongst livestock.

The structure shows the compartments and state transitions for livestock. Births occur at a rate equal to the mortality rate to maintain a population at equilibrium. Mortality rates are estimated to achieve a known livestock age-distributed population (see S2 Text). Offspring from prevalent CCHFV animals acquire transient immunity at birth through first colostrum (R_i). This immunity lasts for an assumed average period of 6 months. After this period, livestock move to the susceptible stage (S₁). Susceptible livestock (S_a) acquire CCHFV with a force of infection λ_L that leads to an infectious period (I_a) with mean duration D_iL, expressed as inverse time rate D_iL^-1. We assume that livestock lose immunity at a rate D_mL.. Vaccination is implemented by recruiting susceptible animals at a rate ν(t). The effective number of immunised livestock is also defined by the efficacy of the vaccine (κ). At first, vaccination does not confer immunity V_a, which is only acquired after a period of length D_pV. In this structure, subscript a points to the age category within the age structure, over which transitions occurs as depicted with the shaded grey structure in the background

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