Quantification of porcine circovirus type 2 (PCV-2) within- and between-pen transmission in pigsMathieu Andraud1, Béatrice Grasland1, Benoît Durand2, Roland Cariolet1, André Jestin1, François Madec1 and Nicolas Rose1
1 AFSSA-site de Ploufragan, B.P. 53, 22440 Ploufragan, France
2 AFSSA-site de Maisons-Alfort, 23 avenue du Général de Gaulle, Maisons Alfort Cedex, 94706, France
Received 19 October 2007; accepted 10 April 2008; published online 17 April 2008
Abstract - PCV-2 within- and between-pen transmission was quantified by estimating the daily transmission rate and the basic reproduction ratio (R0) using a stochastic SEIR (Susceptible, Exposed, Infectious, Removed) model fitted on experimental data. Within-pen transmission was quantified by using four groups of eight SPF (specific pathogen-free) pigs (four infected and four susceptible pigs having direct contact). Between-pen transmission was studied in two groups of 16 SPF pigs (eight infected and eight susceptible pigs having indirect contact (10 cm distance)). Pigs were monitored twice a week (blood samples) and were tested for PCV-2 antibodies (ELISA test) and viral genome load in sera (real-time PCR). Transmission parameters and were estimated using a maximum likelihood method and the duration of infectiousness, to compute R0, was estimated with a parametric survival model. Different assumptions were made to determine the end of infectiousness (seroconversion, seroconversion and decline in viral genome load, permanent infectiousness). (8.9 (5.1-15.4)) was greater when the end of infectiousness was assumed to be related to both seroconversion and a decline of PCV-2 genome load in sera (average duration of infectiousness = 32 days) compared with only seroconversion as the indicator of recovery ( = 5.5 (3.3-9.0)). Whatever the assumption, between-pen R0 (0.58 (0.23-1.47)) was always significantly lower than within-pen R0. Only was sensitive to the assumption on end of infectiousness and decreased with increasing duration of infectiousness. These results showed that PCV-2 transmission is influenced by contact structure that appears worth being taken into account in an epidemic model.
Key words: PCV-2 / pigs / transmission / modelling
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© INRA, EDP Sciences 2008