Within- and between-pen transmission of Classical Swine Fever Virus: a new method to estimate the basic reproduction ratio from transmission experiments

-Transmission of encephalomyocarditis-virus (EMCV) has been estimated in experiments, but never using field data. In this field study, a farm in Belgium was selected where the presence of EMCV was confirmed by necropsy and virus isolation. Serology was used to estimate the transmission parameter R 0 . In one compartment with 630 pigs, 6 pens were fully sampled, in the remaining 38 pens, 2 randomly selected pigs were bled. The 151 pigs were bled twice and their serum was tested in a virus neutralisation test. Seroprevalence at the first and second sampling was 41 and 43% respectively, with a cut off value of 1:40. R 0 was estimated for 2 scenarios, in-and excluding mortality based on the final sizes from the serological results of the second sampling. The R 0 for the fully sampled pens was estimated between 0.6 and 1.7, the combined estimated R 0 of these 6 pens was 1.36 (95%-CI 0.93-2.23). The median of the estimated R 0 of the partially sampled pens was 1.3 and 1.4. Sampling two pigs per pen provided insight into the spread of the virus in the compartment, while the fully sampled pens provided an accurate estimation of R 0 . The low R 0 strongly suggests that EMCV is not very effectively transmitted between pigs. The number of seropositive pigs in a pen and the spread in the compartment suggests that other routes of infection are more important, in this case most likely rodents. Preventing viral spread should therefore be focussed on rodent control instead of reduction of contact between pigs. encephalomyocarditis virus / pigs / transmission / R 0 / field data

Section: Discussionmentioning

confidence: 95%

Transmission of encephalomyocarditis virus in pigs estimated from field data in Belgium by means of R₀

Kluivers

Maurice

Vyt³

et al. 2006

“…Oropharyngeal fluid and faeces were collected at days 0, 3,4,5,6,7,8,10,11,12,13,14,15,17,19,21,24,26,28,31, 33, and 35 p.i. Oropharyngeal fluid was obtained with a gauze tampon held by a 30 cm long forceps, which was scrubbed against the dorsal wall of the pharynx behind the soft palatum.…”

Section: Sampling Proceduresmentioning

confidence: 99%

“…This requires assumptions regarding the start and duration of the infectious period of infected animals and the moment of infection of contact pigs. In previous studies, mostly viraemia was used to determine this 1 [8,[13][14][15]. The main problem with viraemia is that the virus is isolated from a site from which it cannot be transmitted to other pigs, and viraemia does not necessarily coincide with virus excretion in secretions and excretions [28].…”

Section: Introductionmentioning

confidence: 99%

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Effect of strain and inoculation dose of classical swine fever virus on within-pen transmission

Weesendorp

Backer²,

Stegeman

et al. 2009

-To improve the understanding of the dynamics and options for control of classical swine fever (CSF), more quantitative knowledge is needed on virus transmission. In this study, virus excretion and within-pen transmission of a strain of low, moderate and high virulence were quantified. Furthermore, the effect of inoculation dose on excretion and transmission were studied. The transmission was quantified using a stochastic susceptible-exposed-infectious-recovered (SEIR) model. Five transmission trials were conducted with ten pigs each. In each trial, three pigs were inoculated with the low virulent strain Zoelen, a low (10 2 TCID 50 ), middle (10 3.5 TCID 50 ), or high dose (10 5 TCID 50 ) of the moderately virulent strain Paderborn, or the highly virulent strain Brescia. The other seven pigs in each trial served as contact pigs. None of the pigs inoculated with the low dose of the Paderborn strain were infected. When it was assumed that the infectiousness of the pigs coincided with virus isolation positive oropharyngeal fluid and/or faeces, no significant differences in transmission rate b and basic reproduction ratio R 0 between the high inoculation dose of the Paderborn strain (b = 1.62/day, R 0 = 35.9) and the Brescia strain (b = 2.07/day, R 0 = 17.5) were observed. When the middle dose of the Paderborn strain was used for inoculation, the b (5.38/day) was not significantly higher than the Brescia strain or the high inoculation dose of the Paderborn strain, but the R 0 (148) was significantly higher. Infection with the Zoelen strain resulted in a significantly lower b and R 0 (b = 0/day, R 0 = 0) than the other strains.classical swine fever / transmission parameter / virus excretion / within-pen transmission

“…where I x (t) gives the number of infectious animals in subgroup x = {A,B} at time t, and N x (t) gives the number of animals in subgroup x at time t, the log likelihood for β w and β b based on the daily data is [11] in which the previously quantified value for β w was used.…”

Section: Quantification Of Virus Transmissionmentioning

confidence: 99%

Quantification of within- and between-pen transmission of Foot-and-Mouth disease virus in pigs

Eblé¹,

Koeijer

Bouma

et al. 2006

-Quantified transmission parameters of Foot-and-Mouth Disease Virus (FMDV) are needed for epidemic models used for control and surveillance. In this study, we quantified the within-and between-pen transmission of FMDV in groups of pigs by estimating the daily transmission rate β, i.e. the number of secondary infections caused by one infectious pig during one day, using an SIR (susceptible-infectious-removed) model. Within-pen transmission was studied in four groups of ten pigs in which 5 infected and 5 susceptible pigs had direct contact; betweenpen transmission was studied in one group of ten pigs in which 5 infected and 5 susceptible pigs had indirect contact. Daily results of virus isolation of oropharyngeal fluid were used to quantify the transmission rate β, using Generalised Linear Modelling (GLM) and a maximum likelihood method. In addition, we estimated the expected time to infection of the first pig within a pen T w and in the indirect-contact pen T b . The between-pen transmission rate β b was estimated to be 0.59 (0.083-4.18) per day, which was significantly lower than the within-pen transmission rate β w of 6.14 (3.75-10.06). T w was 1.6 h, and T b was 16 h. Our results show that the transmission rate is influenced by contact structure between pigs.foot-and-mouth disease / pigs / transmission / transmission rate / modelling