Modelling the persistence and control of Rift Valley fever virus in a spatially heterogeneous landscape

Abstract

The persistence mechanisms of Rift Valley fever (RVF), a zoonotic arboviral haemorrhagic fever, at both local and broader geographical scales have yet to be fully understood and rigorously quantified. We developed a mathematical metapopulation model describing RVF virus transmission in livestock across the four islands of the Comoros archipelago, accounting for island-specific environments and inter-island animal movements. By fitting our model in a Bayesian framework to 2004–2015 surveillance data, we estimated the importance of environmental drivers and animal movements on disease persistence, and tested the impact of different control scenarios on reducing disease burden throughout the archipelago. Here we report that (i) the archipelago network was able to sustain viral transmission in the absence of explicit disease introduction events after early 2007, (ii) repeated outbreaks during 2004–2020 may have gone under-detected by local surveillance, and (iii) co-ordinated within-island control measures are more effective than between-island animal movement restrictions.

Mechanistic models of Rift Valley fever virus transmission dynamics: A systematic review

“…Here, we highlight that theoretical and applied models can use different tools to contribute to a common objective. In 3 cases, parameter estimations were used further in the same model to help anticipate [48] or control [47,60] outbreaks, as a secondary objective. Fifty-five percent of models provided an estimation of a type of reproduction number (e.g., the basic reproduction number R O , the effective reproduction number R e , the seasonal reproduction number R st (phenomenological relationship estimated between environmental parameters and transmission rate) or the Floquet ratio R T (the expected number of cases caused by a primary case after one complete cycle of seasons [80]), most of which were obtained analytically (25/27).…”

“…Métras et al (2017) [48] suggested that import of infected livestock in 2007 was a major driver of RVF emergence in Mayotte in 2008-2010 and Gao et al (2013) [53] that a transport of only few infectious animals from Sudan to Egypt are sufficient to start an outbreak. In Grande Comore, the RVF virus seems to be able to circulate even in absence of new introduction [60].…”

“…The most common primary scientific objective of models was to understand epidemiological processes, in all model categories (from 72% of applied models to 79% of grey models, Table 1, Figure 3). Although in 11 cases, those models also aimed to anticipate or control outbreaks in a secondary part [32,47,48,[55][56][57][58]60,65,68,70]. In addition, in 30% of cases, model development in itself seemed to be a leading objective of the study.…”

“…Even if RVF virus circulation has been highlighted in several wildlife species, with clinical signs in some ruminants, the potential role of those species in the epidemiological sylvatic cycles in endemic areas is still poorly understood [97,98]. [47,48,60], the lack of data on vector densities urged the authors to use an environmental proxy (Normalized Difference Vegetation Index (NDVI) or rainfall) to drive vectorial transmission, without including an explicit vector compartment.…”

“…suggested that import of infected livestock in 2007 was a major driver of RVF emergence in Mayotte in 2008-2010 andGao et al (2013) [53] that a transport of only few infectious animals from Sudan to Egypt are sufficient to start an outbreak. In Grande Comore, the RVF virus seems to be able to circulate even in absence of new introduction[60].Original research questions stood out from the rest Beechler et al (2015) [37]. studied the impact of co-infections with another pathogen (Bovine tuberculosis, BTB).…”