scholarly journals It’s risky to wander in September: modelling the epidemic potential of Rift Valley fever in a Sahelian setting

2020 ◽  
Author(s):  
Hélène Cecilia ◽  
Raphaëlle Métras ◽  
Assane Gueye Fall ◽  
Modou Moustapha Lo ◽  
Renaud Lancelot ◽  
...  
Keyword(s):  
At Risk ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Small Ruminants ◽  
Time Interval ◽  
List Type ◽  
Temperature Dependent ◽  
Valley Fever ◽  
The Impact

AbstractEstimating the epidemic potential of vector-borne diseases, along with the relative contribution of underlying mechanisms, is crucial for animal and human health worldwide. In West African Sahel, several outbreaks of Rift Valley fever (RVF) have occurred over the last decades, but uncertainty remains about the conditions necessary to trigger these outbreaks. We use the basic reproduction number (R0) as a measure of RVF epidemic potential in Northern Senegal, and map its value in two distinct ecosystems, namely the Ferlo and the Senegal river delta and valley. We consider three consecutive rainy seasons (July-November 2014, 2015 and 2016) and account for several vector and animal species. Namely, we parametrize our model with estimates of Aedes vexans arabiensis, Culex poicilipes, Culex tritaeniorhynchus, cattle, sheep and goats abundances. The impact of RVF virus introduction is assessed every week, in 4367 pixels of 3,5km2. The results of our analysis indicate that September was the month with highest epidemic potential in each study area, while at-risk locations varied between seasons. We show that decreased vector densities do not highly reduce R0 and that cattle immunity has a greater impact on reducing transmission than small ruminants immunity. The host preferences of vectors and the temperature-dependent time interval between their blood meals are crucial parameters needing further biological investigations.HighlightsSeptember is a period of high Rift Valley fever epidemic potential in northern Senegal regardless of the year, but exact locations where epidemics might start change between rainy seasons.Decreased vector densities during the rainy season did not highly reduce the epidemic potential of at-risk locations.High levels of immunity in cattle populations reduce more Rift Valley fever virus transmission than a high immunity in small ruminants in our study area. This aspect should be investigated further for targeted vaccination campaigns.Precise estimates of vector feeding preferences and the temperature-dependent lenght of their gonotrophic cycle are key to ensure a good detection of at-risk pixels.

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

2020 ◽  
Vol 117 (39) ◽  
pp. 24567-24574 ◽  
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.

A novel indirect ELISA based on glycoprotein Gn for the detection of IgG antibodies against Rift Valley fever virus in small ruminants

2013 ◽  
Vol 95 (2) ◽  
pp. 725-730 ◽  
Author(s):  
S. Jäckel ◽  
M. Eiden ◽  
A. Balkema-Buschmann ◽  
M. Ziller ◽  
P. Jansen van Vuren ◽  
...  
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Indirect Elisa ◽  
Rift Valley Fever Virus ◽  
Small Ruminants ◽  
Fever Virus ◽  
Igg Antibodies ◽  
Valley Fever

scholarly journals 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

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.

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

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.

Serological Evidence for the Circulation of Rift Valley Fever Virus in Domestic Small Ruminants in Southern Gabon

2017 ◽  
Vol 17 (6) ◽  
pp. 443-446 ◽  
Author(s):  
Gael Darren Maganga ◽  
Andre Lea Abessolo Ndong ◽  
Clency Sylde Mikala Okouyi ◽  
Sheila Makiala Mandanda ◽  
Nadine N'Dilimabaka ◽  
...  
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Rift Valley Fever Virus ◽  
Small Ruminants ◽  
Fever Virus ◽  
Serological Evidence ◽  
Valley Fever

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

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Warren S. D. Tennant ◽  
Eric Cardinale ◽  
Catherine Cêtre-Sossah ◽  
Youssouf Moutroifi ◽  
Gilles Le Godais ◽  
...  
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Animal Movement ◽  
Rift Valley Fever Virus ◽  
Virus Transmission ◽  
Control Measures ◽  
Environmental Drivers ◽  
Animal Movements ◽  
Valley Fever ◽  
The Impact

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.

scholarly journals Detection of Rift Valley Fever Virus Interepidemic Activity in Some Hotspot Areas of Kenya by Sentinel Animal Surveillance, 2009–2012

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Jacqueline Kasiiti Lichoti ◽  
Absolomon Kihara ◽  
Abuu A. Oriko ◽  
Leonard Ateya Okutoyi ◽  
James Ogaa Wauna ◽  
...  
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Control Strategies ◽  
Rift Valley Fever Virus ◽  
Virus Transmission ◽  
Small Ruminants ◽  
Fever Virus ◽  
Eastern Africa ◽  
Mosquito Vector ◽  
Valley Fever

Rift Valley fever virus causes an important zoonotic disease of humans and small ruminants in Eastern Africa and is spread primarily by a mosquito vector. In this region, it occurs as epizootics that typically occur at 5–15-year intervals associated with unusual rainfall events. It has hitherto been known that the virus is maintained between outbreaks in dormant eggs of the mosquito vector and this has formed the basis of understanding of the epidemiology and control strategies of the disease. We show here that seroconversion and sporadic acute disease do occur during the interepidemic periods (IEPs) in the absence of reported cases in livestock or humans. The finding indicates that previously undetected low-level virus transmission during the IEPs does occur and that epizootics may also be due to periodic expansion of mosquito vectors in the presence of both circulating virus and naïve animals.

scholarly journals Rift Valley fever virus in small ruminants in the Democratic Republic of the Congo

2019 ◽  
Vol 86 (1) ◽  
Author(s):  
Georges M. Tshilenge ◽  
Mfumu L.K Mulumba ◽  
Gerald Misinzo ◽  
Rob Noad ◽  
William G. Dundon
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Democratic Republic ◽  
Rift Valley Fever Virus ◽  
Small Ruminants ◽  
Rt Pcr ◽  
Recent Infection ◽  
Valley Fever ◽  
Sheep And Goats ◽  
Republic Of The Congo

Rift Valley fever (RVF) is a zoonotic viral disease caused by the RVF phlebovirus (RVFV) that infects a variety of animal species including sheep and goats. Sera (n = 893) collected between 2013 and 2015 from randomly selected indigenous sheep and goats in seven provinces of the Democratic Republic of the Congo (DRC) were tested for the presence of specific immunoglobulin G (IgG) and M (IgM) against RVFV, using two commercially available enzyme-linked immunosorbent assays. The reverse transcription polymerase chain reaction (RT-PCR) was also used to detect RVFV nucleic acid. There was significant variation in true seroprevalence of RVFV for both sheep and goats between the seven provinces investigated. Values ranged from 0.0 (95% confidence interval [CI] 0.0–6.55) to 23.81 (95% CI 12.03–41.76) for goat and 0.0 (95% CI 0.0–7.56) to 37.11 (95% CI 15.48–65.94) for sheep, respectively. One serum (1.85%) out of 54 that tested positive for IgG was found to be IgM-positive. This same sample was also positive by RT-PCR indicating an active or recent infection. These findings report the presence of RVFV in small ruminants in the DRC for the first time and indicate variations in exposure to the virus in different parts of the country.

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