Modelling infectious viral diseases in swine populations: a state of the art

Abstract

Mathematical modelling is nowadays a pivotal tool for infectious diseases studies, completing regular biological investigations. The rapid growth of computer technology allowed for development of computational tools to address biological issues that could not be unravelled in the past. The global understanding of viral disease dynamics requires to account for all interactions at all levels, from within-host to between-herd, to have all the keys for development of control measures. A literature review was performed to disentangle modelling frameworks according to their major objectives and methodologies. One hundred and seventeen articles published between 1994 and 2020 were found to meet our inclusion criteria, which were defined to target papers representative of studies dealing with models of viral infection dynamics in pigs. A first descriptive analysis, using bibliometric indexes, permitted to identify keywords strongly related to the study scopes. Modelling studies were focused on particular infectious agents, with a shared objective: to better understand the viral dynamics for appropriate control measure adaptation. In a second step, selected papers were analysed to disentangle the modelling structures according to the objectives of the studies. The system representation was highly dependent on the nature of the pathogens. Enzootic viruses, such as swine influenza or porcine reproductive and respiratory syndrome, were generally investigated at the herd scale to analyse the impact of husbandry practices and prophylactic measures on infection dynamics. Epizootic agents (classical swine fever, foot-and-mouth disease or African swine fever viruses) were mostly studied using spatio-temporal simulation tools, to investigate the efficiency of surveillance and control protocols, which are predetermined for regulated diseases. A huge effort was made on model parameterization through the development of specific studies and methodologies insuring the robustness of parameter values to feed simulation tools. Integrative modelling frameworks, from within-host to spatio-temporal models, is clearly on the way. This would allow to capture the complexity of individual biological variabilities and to assess their consequences on the whole system at the population level. This would offer the opportunity to test and evaluate in silico the efficiency of possible control measures targeting specific epidemiological units, from hosts to herds, either individually or through their contact networks. Such decision support tools represent a strength for stakeholders to help mitigating infectious diseases dynamics and limiting economic consequences.

Modeling the transmission and vaccination strategy for porcine reproductive and respiratory syndrome virus

“…Modelling individual PRRSV strain dissemination was beyond the scope of this study, but this is likely a potentially important future consideration as part of our active research focus area. In the current modelling framework, we were interested in the between-farm transmission, in which we did not include more detailed dynamics of individual pigs within farms, thus futures studies including within-farm dynamics at animal level will be an important component of future studies (Andraud and Rose, 2020). In addition, the model was calibrated on the incidence across all farm types for the temporal model calibration, while we decided to fit the spatial component to infected sow farms only, largely because PRRSV outbreaks records in sow farms were more consistent allowing for a more confident assessment of model sensitivity.…”

“…In the last two decades, epidemiological studies have described the between-farm PRRSV transmission dynamics (Dee et al, 2003a, 2004; Rosendal et al, 2014; Thakur, Revie et al, 2015; Jara et al, 2020; Andraud and Rose, 2020). Direct contact among farms through pig transportation together with indirect contacts often defined as local spread or local transmission, (e.g.…”

“…Currently, the industry relies heavily on vaccination and biosecurity practices as control and prevention strategies (Silva et al, 2019), with the vaccination of weaned pigs and gilts with modified-live vaccines (MLV) being among the most common (Kroll et al, 2018; Garcia-Morante et al, 2020; Rawal et al, 2020). Several studies have evaluated the efficacy of vaccines in increasing the immunity level and reducing shedding magnitude and duration (Pileri et al, 2015; Chase-Topping et al, 2020); however the absence of studies quantifying the effect of vaccination programs on between-farm PRRSV transmission, has limited our capacity to investigate the effectiveness of current vaccination strategies and the development of new, or the enhancement of existing PRRSV vaccination protocols (Andraud and Rose, 2020).…”

African Swine Fever Detection and Transmission Estimates Using Homogeneous Versus Heterogeneous Model Formulation in Stochastic Simulations Within Pig Premises

“…For highly transmissible and fast-spreading swine diseases like foot and mouth disease, homogeneous mixing within the barn can be a reasonable simplifying assumption (Kinsley et al, 2018). Detailed descriptions of how these approaches may differ have been reported elsewhere (Hethcote, 1996;Bansal et al, 2007;Burr and Chowell, 2008;Keeling and Rohani, 2008;Kong et al, 2016;Andraud and Rose, 2020).…”

Bibliometric analysis on the evolution of knowledge structure of African swine fever

“…There are some bibliometric studies in the field of pig disease studies. Those studies presented a research impact index or research production trends, but it is difficult to understand the overall field of ASF field due to the fragmentary quantitative analysis in the studies (Díaz et al, 2016;Andraud and Rose, 2020;Tian, 2020). Although some studies analyzed patterns through keyword analysis, the analysis of correlations between keywords is quite limited because it is impossible to identify related subthemes and keywords (Sinclair et al, 2020;Tian, 2020).…”