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Mathematical models for the spread of foot and mouth disease (FMD) have been developed and used for a number of purposes in the recent literature. One important purpose is predicting the effect of strategies to combat between-farm epidemic spread, in support of decision-making on epidemic control. The authors briefly review the various modelling approaches, discussing the parameters used and how estimates may be obtained for these parameters. They emphasise that, in addition to the estimation of FMD transmission parameters, the choice of model structure (including the number and type of parameters used) is also crucial. Two gaps in the knowledge of FMD transmission, related to model construction and parameter quantification, are identified: transmission between different species and the way in which vaccination affects such transmission, and route-specific FMD transmission properties. In particular, the authors pay attention to the role that small-scale transmission experiments can play in bridging these gaps.

RESUMO O objetivo do presente trabalho foi verificar a presença de Erysipelothrix spp. em suínos abatidos em frigorífico, procedentes de granjas que usam ou não a vacinação e desenvolver técnica de nested PCR baseada na amplificação do gene do antígeno protetor de superfície (spaA) específico de Erysipelothrix rhusiopathiae e testar a sua utilização na análise de culturas padrão. Foram isoladas 56 (14,9%) amostras de Erysipelothrix spp. de tonsilas de suínos abatidos em frigorífico no Estado do Rio Grande do Sul, Brasil, sendo 13/275 de suínos vacinados (4,7%) entre 275 tonsilas e 43/100 de suínos não vacinados (43%), bem como foi obtido um isolado de lesão de pele também colhida em frigorífico. Os micro-organismos foram identificados por características fenotípicas por meio de exame bacteriológico e foi realizado teste de nested PCR em 13 isolados de suínos procedentes de granjas que utilizavam vacinação contra a erisipela suína, sendo positivo para 8 isolados, classificados como E. rhusiopathiae. As oito amostras confirmaram a classificação como E. rhusiopathiae também por exames sorológicos. Entre as amostras isoladas de suínos não vacinados, foram testados, por sorologia e PCR, 19 cultivos de Erysipelothrix spp., sendo classificados 9 como E. rhusiopathiae por ambos os testes, todos do sorotipo 2 e 7 negativos. Três isolados de Erysipelothrix sp. foram positivos somente por PCR e negativos por imunodifusão para os sorotipos 1A, 1B e 2, que são os encontrados com maior frequência em casos clínicos de erisipela suína. ABSTRACT The objective of the present work was to detect Erysipelothrix spp in slaughtered pigs, from erysipelasvaccinated and nonvaccinated herds, developing nested PCR based on the amplification of the surface protective antigen (spa A) gene specific for E. rhusiopathiae. Samples of Erysipelothrix spp. were isolated from the tonsils of slaughtered pigs in the state of Rio Grande do Sul, Brazil, respectively 13 (4.7%) from vaccinated (total of 275 tonsils examined) and 43 (43%) from nonvaccinated pigs (100 tonsils examined). Also 1 isolate from a skin lesion was obtained from the abattoir. Erysipelothrix rhusiopathiae isolated from vaccinated pigs (8 samples) were identified by phenotypic characteristics and by nested PCR. Identical results were obtained by serological classification, showing the usefulness of the molecular test. Nineteen strains isolated from nonvaccinated pigs were examined by serology and PCR. Results for both tests identified serotype 2 of E. rhusiopathiae in 9 samples, there being 7 nonreactors to the tests. Three isolates were positive only by PCR and negative by the immunodiffusion test.

A paper summarised in this week's Veterinary Record underlines the importance of biosecurity and of field data in understanding how FMD virus is transmitted between farms during outbreaks, as Aldo Dekker explains EUROPE is free of foot-and-mouth disease (FMD) without animals being vaccinated.

Mathematical models for the spread of foot and mouth disease (FMD) have been developed and used for a number of purposes in the recent literature. One important purpose is predicting the effect of strategies to combat between-farm epidemic spread, in support of decision-making on epidemic control. The authors briefly review the various modelling approaches, discussing the parameters used and how estimates may be obtained for these parameters. They emphasise that, in addition to the estimation of FMD transmission parameters, the choice of model structure (including the number and type of parameters used) is also crucial. Two gaps in the knowledge of FMD transmission, related to model construction and parameter quantification, are identified: transmission between different species and the way in which vaccination affects such transmission, and route-specific FMD transmission properties. In particular, the authors pay attention to the role that small-scale transmission experiments can play in bridging these gaps.

This paper describes a methodology to quantify the transmission of Actinobacillus (A.) pleuropneumoniae from subclinically infected carrier pigs to susceptible contact pigs, and to test the effect of possible interventions on the transmission. The methodology includes the design of a transmission experiment, and a method with which A. pleuropneumoniae transmission can be quantified and with which the effect of an intervention on the transmission can be tested. The experimental design consists of two parts. First, subclinically infected carrier pigs are created by contact exposure of specific-pathogen-free pigs to endobronchially inoculated pigs. Second, transmission is observed from the group of carrier pigs to a second group of susceptible contact pigs after replacing the inoculated pigs by new contact pigs. The presented analytical method is a generalised linear model (GLM) with which the effect of an intervention on the susceptibility and infectivity can be tested separately, if the transmission is observed in heterogeneous populations. The concept of the experimental transmission model is illustrated by describing an A. pleuropneumoniae transmission experiment in which the effect of vaccination on the susceptibility is quantified. Although it could not be demonstrated that vaccination has an effect on the susceptibility of pigs, it was demonstrated that nasal excretion of A. pleuropneumoniae is related to the infectivity of pigs. (C) 2003 Elsevier Science B.V. All rights reserved.

Foot-and-mouth disease virus (FMDV) infected animals can contaminate the environment with their secretions and excretions. To quantify the contribution of a contaminated environment to the transmission of FMDV, this study used calves that were not vaccinated and calves that were vaccinated 1 week prior to inoculation with the virus in direct and indirect contact experiments. In direct contact experiments, contact calves were exposed to inoculated calves in the same room. In indirect contact experiments, contact calves were housed in rooms that previously had held inoculated calves for three days (either from 0 to 3 or from 3 to 6 days post inoculation). Secretions and excretions from all calves were tested for the presence of FMDV by virus isolation; the results were used to quantify FMDV transmission. This was done using a generalized linear model based on a 2 route (2R, i.e. direct contact and environment) SIR model that included information on FMDV survival in the environment. The study shows that roughly 44% of transmission occurs via the environment, as indicated by the reproduction ratio \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {{\widehat{R}}_0}^{2R} environment $$\end{document}R^02Renvironment that equalled 2.0, whereas the sum of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {{\widehat{R}}_0}^{2R} contact $$\end{document}R^02Rcontact and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {{\widehat{R}}_0}^{2R} environment $$\end{document}R^02Renvironment equalled 4.6. Because vaccination 1 week prior to inoculation of the calves conferred protective immunity against FMDV infection, no transmission rate parameters could be estimated from the experiments with vaccinated calves. We conclude that a contaminated environment contributes considerably to the transmission of FMDV therefore that hygiene measures can play a crucial role in FMD control. Electronic supplementary material The online version of this article (doi:10.1186/s13567-015-0156-5) contains supplementary material, which is available to authorized users.