Rift Valley Fever Outbreaks in Mauritania and Related Environmental Conditions

Caminade, Cyril; Ndione, Jacques André; Diallo, Mawlouth; MacLeod, Dave; Faye, Ousmane; Bâ, Yamar; Dia, Ibrahima; Morse, Andrew P.

doi:10.3390/ijerph110100903

Cited by 46 publications

(51 citation statements)

References 23 publications

(42 reference statements)

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“…Thus, we assumed that the high variability of rainfall in arid areas (i.e. low monthly amount; Le Barbé and Lebel, ; Tramblay et al., ) contributed more to the emergence of mosquito populations and the occurrence of RVF epizootics (Vignolles et al., ; Caminade et al., ) than excessive or continuous rainfalls occurring in high‐rainfall areas.…”

Section: Methodsmentioning

confidence: 99%

Identifying Areas Suitable for the Occurrence of Rift Valley Fever in North Africa: Implications for Surveillance

Arsevska

Hellal²,

Mejri³

et al. 2015

Transbound Emerg Dis

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Rift Valley fever (RVF) is a vector-borne zoonotic disease that has caused widespread outbreaks throughout Africa and the Arabian Peninsula, with serious consequences for livestock-based economies and public health. Although there have never been any reports of RVF in Morocco, Algeria, Tunisia and Libya, it is a priority disease in the Maghreb, due to the threat of introduction of the virus through transboundary livestock movements or infected mosquito vectors. However, the implementation of surveillance activities and early warning contingency plans requires better knowledge of the epidemiological situation. We conducted a multicriteria decision analysis, integrating host distribution with a combination of important ecological factors that drive mosquito abundance, to identify hotspots and suitable time periods for RVF enzootic circulation (i.e. stable transmission at a low to moderate level for an extended period of time) and an RVF epizootic event (i.e. a sudden occurrence of a large number of infected animals over a large geographic area) in the Maghreb. We also modelled vector species distribution using available information on vector presence and habitat preference. We found that the northern regions of the Maghreb were moderately suitable for RVF enzootics, but highly suitable for RVF epizootics. The vector species distribution model identified these regions as the most favourable mosquito habitats. Due to the low density of animal hosts and arid conditions, the desert region showed low RVF suitability, except in oases. However, the presence of competent vectors in putative unsuitable areas underlines the need for further assessments of mosquito habitat preference. This study produced monthly RVF suitability maps useful for animal health managers and veterinary services involved in designing risk-based surveillance programmes. The suitability maps can be further enhanced using existing country-specific sources of information and by incorporating knowledge - as it becomes available - on the epidemiology of the disease and distribution of vectors in the Maghreb.

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Section: Methodsmentioning

confidence: 99%

Identifying Areas Suitable for the Occurrence of Rift Valley Fever in North Africa: Implications for Surveillance

Arsevska

Hellal²,

Mejri³

et al. 2015

Transbound Emerg Dis

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“…This underlying circulation of the virus is supported by the transovarial transmission of Aedes and the dormancy of infected eggs during dry spells. Under the right environmental conditions, such as uncharacteristically late, heavy rainfall preceded by a dry period at the end of a rainy season, low-level transmission can be amplified and a major outbreak of the disease can occur (Ndione et al, 2003(Ndione et al, , 2008Nderitu et al, 2011;Caminade et al, 2014b). This epizootic transition follows a sequence of large-scale mosquito proliferation events as large numbers of dormant infected Aedes emerge following flooding followed by a great increase in the Culex population due to the flooding-induced emergence of abundant favourable breeding sites (Bicout and Sabatier, 2004).…”

Section: Introductionmentioning

confidence: 99%

A dynamic, climate-driven model of Rift Valley fever

et al. 2016

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Outbreaks of Rift Valley fever (RVF) in eastern Africa have previously occurred following specific rainfall dynamics and flooding events that appear to support the emergence of large numbers of mosquito vectors. As such, transmission of the virus is considered to be sensitive to environmental conditions and therefore changes in climate can impact the spatiotemporal dynamics of epizootic vulnerability. Epidemiological information describing the methods and parameters of RVF transmission and its dependence on climatic factors are used to develop a new spatio-temporal mathematical model that simulates these dynamics and can predict the impact of changes in climate. The Liverpool RVF (LRVF) model is a new dynamic, process-based model driven by climate data that provides a predictive output of geographical changes in RVF outbreak susceptibility as a result of the climate and local livestock immunity. This description of the multi-disciplinary process of model development is accessible to mathematicians, epidemiological modellers and climate scientists, uniting dynamic mathematical modelling, empirical parameterisation and state-of-the-art climate information.

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“…Previous studies mapping RVF risk in West African Sahel overlapped climate anomalies and host densities, but without linking mechanistically the underlying processes to the disease outcome (Caminade et al, 2011(Caminade et al, , 2014. At very local scales, in particular around the village of Barkedji in the Ferlo region of Senegal, different approaches such as remote-sensing (Lacaux et al, 2007;Ndione et al, 2009) or statistical models (Bicout and Sabatier, 2004;Vignolles et al, 2009;Talla et al, 2016) were used.…”

Section: Introductionmentioning

confidence: 99%

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

Cecilia

Métras

Fall

et al. 2020

Preprint

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Estimating 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.

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Rift Valley Fever Outbreaks in Mauritania and Related Environmental Conditions

Cited by 46 publications

References 23 publications

Identifying Areas Suitable for the Occurrence of Rift Valley Fever in North Africa: Implications for Surveillance

Identifying Areas Suitable for the Occurrence of Rift Valley Fever in North Africa: Implications for Surveillance

A dynamic, climate-driven model of Rift Valley fever

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

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