Environmental change and Rift Valley fever in eastern Africa: projecting beyond HEALTHY FUTURES

Outbreaks of Rift Valley fever (RVF), a relatively recently emerged zoonosis endemic to large parts of sub-Saharan Africa that has the potential to spread beyond the continent, have profound health and socio-economic impacts, particularly in communities where resilience is already low. Here output from a new, dynamic disease model [the Liverpool RVF (LRVF) model], driven by downscaled, bias-corrected climate change data from an ensemble of global circulation models from the Inter-Sectoral Impact Model Intercomparison Project run according to two radiative forcing scenarios [representative concentration pathway (RCP)4.5 and RCP8.5], is combined with results of a spatial assessment of social vulnerability to the disease in eastern Africa. The combined approach allowed for analyses of spatial and temporal variations in the risk of RVF to the end of the current century. Results for both scenarios highlight the high-risk of future RVF outbreaks, including in parts of eastern Africa to date unaffected by the disease. The results also highlight the risk of spread from/to countries adjacent to the study area, and possibly farther afield, and the value of considering the geography of future projections of disease risk. Based on the results, there is a clear need to remain vigilant and to invest not only in surveillance and early warning systems, but also in addressing the socio-economic factors that underpin social vulnerability in order to mitigate, effectively, future impacts.

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Dynamic risk model for Rift Valley fever outbreaks in Kenya based on climate and disease outbreak data

Geospatial health ◽

10.4081/gh.2016.377 ◽

2016 ◽

Vol 11 (2) ◽

Cited By ~ 2

Author(s):

David Gikungu ◽

Jacob Wakhungu ◽

Donald Siamba ◽

Edward Neyole ◽

Richard Muita ◽

...

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Risk Model ◽

Early Warning Systems ◽

Sub Saharan Africa ◽

Weather Data ◽

Brier Score ◽

Valley Fever ◽

Dynamic Risk ◽

Normalised Difference Vegetation Index

Rift Valley fever (RVF) is a mosquito-borne viral zoonotic disease that occurs throughout sub-Saharan Africa, Egypt and the Arabian Peninsula, with heavy impact in affected countries. Outbreaks are episodic and related to climate variability, especially rainfall and flooding. Despite great strides towards better prediction of RVF epidemics, there is still no observed climate data-based warning system with sufficient lead time for appropriate response and mitigation. We present a dynamic risk model based on historical RVF outbreaks and observed meteorological data. The model uses 30-year data on rainfall, temperature, relative humidity, normalised difference vegetation index and sea surface temperature data as predictors. Our research on RVF focused on Garissa, Murang’a and Kwale counties in Kenya using a research design based on a correlational, experimental, and evaluational approach. The weather data were obtained from the Kenya Meteorological Department while the RVF data were acquired from International Livestock Research Institute, and the Department of Veterinary Services. Performance of the model was evaluated by using the first 70% of the data for calibration and the remaining 30% for validation. The assessed components of the model accurately predicted already observed RVF events. The Brier score for each of the models (ranging from 0.007 to 0.022) indicated high skill. The coefficient of determination (R2) was higher in Garissa (0.66) than in Murang’a (0.21) and Kwale (0.16). The discrepancy was attributed to data distribution differences and varying ecosystems. The model outputs should complement existing early warning systems to detect risk factors that predispose for RVF outbreaks.

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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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Pathologic Studies on Suspect Animal and Human Cases of Rift Valley Fever from an Outbreak in Eastern Africa, 2006–2007

American Journal of Tropical Medicine and Hygiene ◽

10.4269/ajtmh.2010.09-0463 ◽

2010 ◽

Vol 83 (2_Suppl) ◽

pp. 38-42 ◽

Cited By ~ 32

Author(s):

Wun-Ju Shieh ◽

Robert F. Breiman ◽

Fausta Mosha ◽

Peter Bloland ◽

Carol Y. Rao ◽

...

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Eastern Africa ◽

Valley Fever

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Sorafenib Impedes Rift Valley Fever Virus Egress by Inhibiting Valosin-Containing Protein Function in the Cellular Secretory Pathway

Journal of Virology ◽

10.1128/jvi.00968-17 ◽

2017 ◽

Vol 91 (21) ◽

Cited By ~ 9

Author(s):

Ashwini Brahms ◽

Rajini Mudhasani ◽

Chelsea Pinkham ◽

Krishna Kota ◽

Farooq Nasar ◽

...

Keyword(s):

Host Cell ◽

Golgi Complex ◽

Rift Valley ◽

Rift Valley Fever ◽

Secretory Pathway ◽

Rift Valley Fever Virus ◽

Fever Virus ◽

Sub Saharan Africa ◽

Microscopy Imaging ◽

Valley Fever

ABSTRACT There is an urgent need for therapeutic development to combat infections caused by Rift Valley fever virus (RVFV), which causes devastating disease in both humans and animals. In an effort to repurpose drugs for RVFV treatment, our previous studies screened a library of FDA-approved drugs. The most promising candidate identified was the hepatocellular and renal cell carcinoma drug sorafenib. Mechanism-of-action studies indicated that sorafenib targeted a late stage in virus infection and caused a buildup of virions within cells. In addition, small interfering RNA (siRNA) knockdown studies suggested that nonclassical targets of sorafenib are important for the propagation of RVFV. Here we extend our previous findings to identify the mechanism by which sorafenib inhibits the release of RVFV virions from the cell. Confocal microscopy imaging revealed that glycoprotein Gn colocalizes and accumulates within the endoplasmic reticulum (ER) and the transport of Gn from the Golgi complex to the host cell membrane is reduced. Transmission electron microscopy demonstrated that sorafenib caused virions to be present inside large vacuoles inside the cells. p97/valosin-containing protein (VCP), which is involved in membrane remodeling in the secretory pathway and a known target of sorafenib, was found to be important for RVFV egress. Knockdown of VCP resulted in decreased RVFV replication, reduced Gn Golgi complex localization, and increased Gn ER accumulation. The intracellular accumulation of RVFV virions was also observed in cells transfected with siRNA targeting VCP. Collectively, these data indicate that sorafenib causes a disruption in viral egress by targeting VCP and the secretory pathway, resulting in a buildup of virions within dilated ER vesicles. IMPORTANCE In humans, symptoms of RVFV infection mainly include a self-limiting febrile illness. However, in some cases, infected individuals can also experience hemorrhagic fever, neurological disorders, liver failure, and blindness, which could collectively be lethal. The ability of RVFV to expand geographically outside sub-Saharan Africa is of concern, particularly to the Americas, where native mosquito species are capable of virus transmission. Currently, there are no FDA-approved therapeutics to treat RVFV infection, and thus, there is an urgent need to understand the mechanisms by which the virus hijacks the host cell machinery to replicate. The significance of our research is in identifying the cellular target of sorafenib that inhibits RVFV propagation, so that this information can be used as a tool for the further development of therapeutics used to treat RVFV infection.

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Common Host-Derived Chemicals Increase Catches of Disease-Transmitting Mosquitoes and Can Improve Early Warning Systems for Rift Valley Fever Virus

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0002007 ◽

2013 ◽

Vol 7 (1) ◽

pp. e2007 ◽

Cited By ~ 24

Author(s):

David P. Tchouassi ◽

Rosemary Sang ◽

Catherine L. Sole ◽

Armanda D. S. Bastos ◽

Peter E. A. Teal ◽

...

Keyword(s):

Early Warning ◽

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Early Warning Systems ◽

Fever Virus ◽

Warning Systems ◽

Valley Fever

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Detection of Rift Valley Fever Virus RNA in Formalin-Fixed Mosquitoes by In Situ Hybridization (RNAscope®)

Viruses ◽

10.3390/v13061079 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1079

Author(s):

Sarah Lumley ◽

Laura Hunter ◽

Kirsty Emery ◽

Roger Hewson ◽

Anthony R. Fooks ◽

...

Keyword(s):

In Situ Hybridization ◽

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Mosquito Species ◽

Fever Virus ◽

Sub Saharan Africa ◽

Support Vector ◽

Valley Fever

Rift Valley fever virus (RVFV) causes a zoonotic mosquito-borne haemorrhagic disease that emerges to produce rapid large-scale outbreaks in livestock within sub-Saharan Africa. A range of mosquito species in Africa have been shown to transmit RVFV, and recent studies have assessed whether temperate mosquito species are also capable of transmission. In order to support vector competence studies, the ability to visualize virus localization in mosquito cells and tissue would enhance the understanding of the infection process within the mosquito body. Here, the application of in situ hybridization utilizing RNAscope® to detect RVFV infection within the mosquito species, Culex pipiens, derived from the United Kingdom was demonstrated. Extensive RVFV replication was detected in many tissues of the mosquito with the notable exception of the interior of ovarian follicles.

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Rift Valley fever virus MP-12 vaccine encoding Toscana virus NSs retains neuroinvasiveness in mice

Journal of General Virology ◽

10.1099/vir.0.051250-0 ◽

2013 ◽

Vol 94 (7) ◽

pp. 1441-1450 ◽

Cited By ~ 12

Author(s):

Sabarish V. Indran ◽

Olga A. Lihoradova ◽

Inaia Phoenix ◽

Nandadeva Lokugamage ◽

Birte Kalveram ◽

...

Keyword(s):

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Fever Virus ◽

Sub Saharan Africa ◽

Fetal Malformation ◽

Toscana Virus ◽

Valley Fever ◽

Live Attenuated Vaccine ◽

Viral Antigens

Rift Valley fever is a mosquito-borne zoonotic disease endemic to sub-Saharan Africa. Rift Valley fever virus (RVFV; genus Phlebovirus, family Bunyaviridae) causes high rates of abortion and fetal malformation in pregnant ruminants, and haemorrhagic fever, neurological disorders or blindness in humans. The MP-12 strain is a highly efficacious and safe live-attenuated vaccine candidate for both humans and ruminants. However, MP-12 lacks a marker to differentiate infected from vaccinated animals. In this study, we originally aimed to characterize the efficacy of a recombinant RVFV MP-12 strain encoding Toscana virus (TOSV) NSs gene in place of MP-12 NSs (rMP12-TOSNSs). TOSV NSs promotes the degradation of dsRNA-dependent protein kinase (PKR) and inhibits interferon-β gene up-regulation without suppressing host general transcription. Unexpectedly, rMP12-TOSNSs increased death in vaccinated outbred mice and inbred BALB/c or C57BL/6 mice. Immunohistochemistry showed diffusely positive viral antigens in the thalamus, hypothalamus and brainstem, including the medulla. No viral antigens were detected in spleen or liver, which is similar to the antigen distribution of moribund mice infected with MP-12. These results suggest that rMP12-TOSNSs retains neuroinvasiveness in mice. Our findings demonstrate that rMP12-TOSNSs causes neuroinvasion without any hepatic disease and will be useful for studying the neuroinvasion mechanism of RVFV and TOSV.

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Indigenous knowledge of Rift Valley Fever among Somali nomadic pastoralists and its implications on public health delivery approaches in Ijara sub-County, North Eastern Kenya

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0009166 ◽

2021 ◽

Vol 15 (2) ◽

pp. e0009166

Author(s):

Geoffrey Otieno Muga ◽

Washington Onyango-Ouma ◽

Rosemary Sang ◽

Hippolyte Affognon

Keyword(s):

Public Health ◽

Risk Factors ◽

Indigenous Knowledge ◽

Rift Valley ◽

Rift Valley Fever ◽

Signs And Symptoms ◽

Early Warning Systems ◽

Valley Fever ◽

Health Delivery ◽

Nomadic Pastoralists

Rift Valley Fever (RVF) is a zoonotic disease whose outbreak results in heavy economic and public health burdens. In East Africa, RVF is mainly experienced in arid and semi-arid areas predominantly inhabited by the pastoralists. These areas experience sudden, dramatic epidemics of the disease at intervals of approximately 10 years, associated with widespread flooding and the resultant swarms of mosquitoes. Pastoralists’ indigenous knowledge and experience of RVF is critical for public health interventions targeting prevention and control of RVF. The study adopted a descriptive cross-sectional design combining both quantitative and qualitative methods of data collection. A total of 204 respondents participated in questionnaire survey and 15 key informants and 4 focus group discussions were interviewed and conducted respectively. In addition, secondary data mainly journal publications, books, policy documents and research reports from conferences and government departments were reviewed. Findings indicated that the Somali pastoralists possess immense knowledge of RVF including signs and symptoms, risk factors, and risk pathways associated with RVF. Ninety eight percent (98%) of respondents identified signs and symptoms such as bloody nose, diarrhea, foul smell and discharge of blood from the orifices which are consistent with RVF. Heavy rains and floods (85%) and sudden emergence of mosquito swarms (91%) were also cited as the major RVF risk factors while mosquito bites (85%), drinking raw milk and blood (78%) and contact with animal fluids during mobility, slaughter and obstetric procedures (77%) were mentioned as the RVF entry risk pathways. Despite this immense knowledge, the study found that the pastoralists did not translate the knowledge into safer health practices because of the deep-seated socio-cultural practices associated with pastoralist production system and religious beliefs. On top of these practices, food preparation and consumption practices such as drinking raw blood and milk and animal ritual sacrifices continue to account for most of the mortality and morbidity cases experienced in humans and animals during RVF outbreaks. This article concludes that pastoralists’ indigenous knowledge on RVF has implications on public health delivery approaches. Since the pastoralists’ knowledge on RVF was definitive, integrating the community into early warning systems through training on reporting mechanisms and empowering the nomads to use their mobile phone devices to report observable changes in their livestock and environment could prove very effective in providing information for timely mobilization of public health responses. Public health advocacy based on targeted and contextually appropriate health messaging and disseminated through popular communication channels in the community such as the religious leaders and local radio stations would also be needed to reverse the drivers of RVF occurrence in the study area.

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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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