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

AbstractThe 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.

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Drivers of Rift Valley fever virus persistence and the impact of control measures in a spatially heterogeneous landscape: the case of the Comoros archipelago, 2004–2015

10.1101/2021.03.10.434721 ◽

2021 ◽

Author(s):

Warren S. D. Tennant ◽

Eric Cardinale ◽

Catherine Cêtre-Sossah ◽

Youssouf Moutroifi ◽

Gilles Le Godais ◽

...

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Virus Transmission ◽

Control Measures ◽

Virus Persistence ◽

Valley Fever ◽

Grande Comore ◽

The Many ◽

The Impact

AbstractRift Valley fever (RVF) is one of the many zoonotic arboviral haemorrhagic fevers present in Africa. The ability of the pathogen to persist in multiple geographically distinct regions has raised concerns about its potential for spread to and persistence within currently disease-free areas. However, the mechanisms for which RVF virus persistence occurs at both local and broader geographical scales have yet to be fully understood and rigorously quantified. Here, we developed a mathematical metapopulation model describing RVF virus transmission in livestock across the four islands of the Comoros archipelago and fitted this model in a Bayesian framework to surveillance data conducted in livestock across those islands between 2004 and 2015. In doing so, we estimated the importance of island-specific environmental factors and animal movements between those islands on the persistence of RVF virus in the archipelago, and we further tested the impact of different control scenarios on reducing disease burden. We demonstrated that the archipelago network was able to sustain viral transmission over 10 years after assuming only one introduction event during early 2007. Movement restrictions were only useful to control the disease in Anjouan and Mayotte, as Grande Comore and Mohéli were able to self-sustain RVF viral persistence, probably due to local environmental conditions that are more favourable for vectors. We also evidenced that repeated outbreaks during 2004-2020 may have gone under-detected by local surveillance in Grande Comore and Mohéli. Strengthened longterm and coordinated surveillance would enable the detection of viral re-emergence and evaluation of different relevant vaccination programmes.

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Estimation of Rift Valley fever virus spillover to humans during the Mayotte 2018–2019 epidemic

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2004468117 ◽

2020 ◽

Vol 117 (39) ◽

pp. 24567-24574 ◽

Cited By ~ 1

Author(s):

Raphaëlle Métras ◽

W. John Edmunds ◽

Chouanibou Youssouffi ◽

Laure Dommergues ◽

Guillaume Fournié ◽

...

Keyword(s):

Rift Valley ◽

Direct Contact ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Animal Health ◽

Hemorrhagic Fever ◽

Control Measures ◽

Similar Reduction ◽

Valley Fever ◽

The Impact

Rift Valley fever (RVF) is an emerging, zoonotic, arboviral hemorrhagic fever threatening livestock and humans mainly in Africa. RVF is of global concern, having expanded its geographical range over the last decades. The impact of control measures on epidemic dynamics using empirical data has not been assessed. Here, we fitted a mathematical model to seroprevalence livestock and human RVF case data from the 2018–2019 epidemic in Mayotte to estimate viral transmission among livestock, and spillover from livestock to humans through both direct contact and vector-mediated routes. Model simulations were used to assess the impact of vaccination on reducing the epidemic size. The rate of spillover by direct contact was about twice as high as vector transmission. Assuming 30% of the population were farmers, each transmission route contributed to 45% and 55% of the number of human infections, respectively. Reactive vaccination immunizing 20% of the livestock population reduced the number of human cases by 30%. Vaccinating 1 mo later required using 50% more vaccine doses for a similar reduction. Vaccinating only farmers required 10 times as more vaccine doses for a similar reduction in human cases. Finally, with 52.0% (95% credible interval [CrI] [42.9–59.4]) of livestock immune at the end of the epidemic wave, viral reemergence in the next rainy season (2019–2020) is unlikely. Coordinated human and animal health surveillance, and timely livestock vaccination appear to be key to controlling RVF in this setting. We furthermore demonstrate the value of a One Health quantitative approach to surveillance and control of zoonotic infectious diseases.

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Estimation of Rift Valley fever virus spillover to humans during the Mayotte 2018-2019 epidemic

10.1101/2020.02.14.20022996 ◽

2020 ◽

Author(s):

Raphaëlle Métras ◽

W John Edmunds ◽

Chouanibou Youssouffi ◽

Laure Dommergues ◽

Guillaume Fournié ◽

...

Keyword(s):

Mathematical Model ◽

Rift Valley ◽

Rift Valley Fever ◽

Disease Risk ◽

Rift Valley Fever Virus ◽

Animal Health ◽

Control Measures ◽

Real World Data ◽

Valley Fever ◽

The Impact

AbstractRift Valley fever (RVF) is an emerging, zoonotic, arboviral haemorrhagic fever threatening livestock and humans mainly in Africa. RVF is of global concern, having expanded its geographical range over the last decades. The impact of control measures on epidemic dynamics using empirical data has not been assessed. Here, we combined seroprevalence livestock and human RVF case data from the 2018-2019 epidemic in Mayotte, with a dynamic mathematical model. Using a Bayesian inference framework, we estimated viral transmission potential amongst livestock, and spillover from livestock to humans, through both direct contact and vector-mediated routes. Model simulations were used to assess the impact of vaccination on reducing the human epidemic size. Reactive vaccination immunising 20% of the livestock population reduced the number of human cases by 30%. To achieve a similar impact, delaying the vaccination by one month required using 50% more vaccine doses, and vaccinating only humans required 20 times as more as the number of doses for livestock. Finally, with 53.92% (95%CrI [44.76-61.29]) of livestock estimated to be immune at the end of the epidemic wave, viral re-emergence in the next rainy season (2019-2020) was unlikely. We present the first mathematical model for RVF fitted to real-world data to estimate virus transmission parameters, and able to inform potential control programmes. Human and animal health surveillance, and timely livestock vaccination appear to be key in reducing disease risk in humans. We furthermore demonstrate the value of a One Health quantitative approach to surveillance and control of zoonotic infectious diseases.

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Diversity and Abundance of Potential Vectors of Rift Valley Fever Virus in the North Region of Cameroon

Insects ◽

10.3390/insects11110814 ◽

2020 ◽

Vol 11 (11) ◽

pp. 814

Author(s):

Poueme Namegni Rodrigue Simonet ◽

Njan-Nloga Alexandre Michel ◽

Wade Abel ◽

Eisenbarth Albert ◽

Groschup Martin Hermann ◽

...

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Fever Virus ◽

Control Measures ◽

Sub Saharan Africa ◽

Effective Control ◽

P Value ◽

Valley Fever ◽

The North

Rift Valley fever (RVF) is a major viral zoonosis transmitted by mosquitoes. The virus is endemic in most parts of sub-Saharan Africa and can affect humans, livestock, and wild ungulates. Knowledge of the biology of vectors of Rift Valley fever virus (RVFV) is essential for the establishment of effective control measures of the disease. The objective of this study was to determine the species diversity and relative abundance of potential RVFV vectors in the North Region of Cameroon. Adult mosquitoes were trapped during the wet and dry seasons from December 2017 to January 2019 with “EVS Light” traps with CO2 baits placed at selected sites. The captured mosquitoes were identified using dichotomous keys according to standard procedures. The abundance was calculated with regard to site, zone, and collection season. A total of 27,851 mosquitoes belonging to four genera (Aedes, Anopheles, Mansonia, and Culex) and comprising 31 species were caught (including 22 secondary vectors (98.05%) and nine primary vectors (1.94%). The total number of mosquitoes varied significantly depending on the locality (p-value < 0.001). The average number of mosquitoes collected per trap night was significantly higher in irrigated areas (p-value < 0.001), compared to urban and non-irrigated areas. The study revealed the presence of potential primary and secondary vectors of RVFV with varying abundance and diversity according to locality and ecological site in the North Region of Cameroon. The results showed that the genus Mansonia with the species Ma. uniformis and Ma. africana formed the dominant taxon (52.33%), followed by the genera Culex (45.04%) and Anopheles (2.61%). The need for molecular analysis (PCR) tests for RVFV RNA research and viral isolation methods on these vectors to determine their role in the epidemiology and control of RVF cannot be overemphasized.

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Rift Valley fever virus transmission by different Egyptian mosquito species

Transactions of the Royal Society of Tropical Medicine and Hygiene ◽

10.1016/0035-9203(87)90460-3 ◽

1987 ◽

Vol 81 (4) ◽

pp. 694-698 ◽

Cited By ~ 41

Author(s):

Adel M. Gad ◽

Mosaad M. Hassan ◽

Sharif El Said ◽

Mahmoud I. Moussa ◽

Owen L. Wood

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Mosquito Species ◽

Virus Transmission ◽

Fever Virus ◽

Valley Fever

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Co-housing of Rift Valley Fever Virus Infected Lambs with Immunocompetent or Immunosuppressed Lambs Does Not Result in Virus Transmission

Frontiers in Microbiology ◽

10.3389/fmicb.2016.00287 ◽

2016 ◽

Vol 7 ◽

Cited By ~ 5

Author(s):

Paul J. Wichgers Schreur ◽

Lucien van Keulen ◽

Jet Kant ◽

Nadia Oreshkova ◽

Rob J. M. Moormann ◽

...

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Virus Transmission ◽

Fever Virus ◽

Valley Fever

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Faculty Opinions recommendation of Spectrum of Rift Valley fever virus transmission in Kenya: insights from three distinct regions.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1084756.537673 ◽

2007 ◽

Author(s):

Tomas Jelinek

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Virus Transmission ◽

Fever Virus ◽

Valley Fever

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Modelling the use of impulsive vaccination to control Rift Valley Fever virus transmission

Advances in Difference Equations ◽

10.1186/s13662-016-0835-1 ◽

2016 ◽

Vol 2016 (1) ◽

Cited By ~ 2

Author(s):

Chen-Xia Yang ◽

Lin-Fei Nie

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Virus Transmission ◽

Fever Virus ◽

Valley Fever ◽

Impulsive Vaccination

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Threshold Dynamics in a Periodic Three-Patch Rift Valley Fever Virus Transmission Model

Complexity ◽

10.1155/2019/7896946 ◽

2019 ◽

Vol 2019 ◽

pp. 1-18 ◽

Cited By ~ 1

Author(s):

Buyu Wen ◽

Zhidong Teng ◽

Wenlin Liu

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Virus Transmission ◽

Operator Method ◽

Fever Virus ◽

Transmission Model ◽

Threshold Dynamics ◽

Valley Fever ◽

Threshold Conditions

This paper investigates a three-patch Rift Valley fever virus transmission model with periodic coefficients. The basic reproduction number Ri0i=1,2,3 is calculated for the model by using the next infection operator method. The threshold conditions on the extinction and permanence in the mean of the disease with probability one. The Rift Valley fever disease will be permanent in the j-th j=1,2,3 patch if j≥i,Ri0>1 and dies out in the j-th patch if j<i. The numerical simulations are given to confirm the theoretical results.

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