Figure 1
Flow diagram describing the modeled within-herd spread of C. burnetii. Flow diagram adapted from Courcoul et al. [15], describing the modeled within-herd spread of C. burnetii. The health states are the following: S, nonshedder apparently susceptible animal, I 1 , shedder which still has the possibility to eliminate the bacterium and to become S again, I 2 , shedder which no longer has the possibility to become S again, I 3 , shedder which no longer has the possibility to become S again and sheds in milk in a persistent way, C 1 , non-shedder but still infected individual and C 2 , non-shedder which was C 1 in the past but eliminated the bacterium. I animals are in the subcategory m if they shed in milk only, mf if they shed in vaginal mucus/faeces only and mmf if they shed in milk and vaginal mucus/faeces. Environment represents the environmental bacterial load expressed in dimensionless units, and p, the probability of infection or reinfection, is equal to 1 – exp(−Ê(t)/N). ϵ 1 , ϵ 2 , and ϵ 3 are the quantities of bacteria shed during a time step by an individual I 1 , I 2 , and I 3 respectively and contaminating the environment. For any shedder, ϵ represents the sum, for each shedding route, of the quantity of bacteria released, Qty, times ρ, its fraction reaching the herd environment. The definitions, values and sources of all parameters in the epidemiological model can be found in Additional file 1.