Modelling the time-dependent transmission rate for porcine circovirus type 2 (PCV2) in pigs using data from serial transmission experiments.
Six successive transmission trials were carried out from 4 to 39 days post inoculation (DPI) to determine the features of the infectious period for PCV2-infected pigs. The infectiousness of inoculated pigs, assessed from the frequency of occurrence of infected pigs in susceptible groups in each contact trial, increased from 4 to 18 DPI (0, 7 and 8 infected pigs at 4, 11 and 18 DPI, respectively) and then decreased slowly until 39 days post infection (4, 2 and 1 pigs infected at 25, 32 and 39 DPI, respectively). The estimated time-dependent infectiousness was fitted to three unimodal function shapes (gamma, Weibull and lognormal) for comparison. The absence of infected pigs at 4 DPI revealed a latency period between 4 and 10 DPI. A sensitivity analysis was performed to test whether the parametric shape of the transmission function influenced the estimations. The estimated time-dependent transmission rate was implemented in a deterministic SEIR model and validated by comparing the model prediction with external data. The lognormal-like function shape evidenced the best quality of fit, leading to a latency period of 8 days, an estimated basic reproduction ratio of 5.9 [1.8,10.1] and a mean disease generation time of 18.4 days [18.2, 18.5].
Andraud
M
M
AFSSA-site de Ploufragan, B.P. 53, F22440 Ploufragan, France. m.andraud@afssa.fr
Grasland
B
B
Durand
B
B
Cariolet
R
R
Jestin
A
A
Madec
F
F
Pierre
J S
JS
Rose
N
N
D000818:Animals; D018173:Circoviridae Infections / Q000635:transmission / Q000662:veterinary*; D017925:Circovirus / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D016013:Likelihood Functions; D008954:Models, Biological; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D034421:Sus scrofa; D013553:Swine Diseases / Q000635:transmission*; D013997:Time Factors
D017931:DNA Primers