Predictability of the Normalized Difference Vegetation Index in Kenya and Potential Applications as an Indicator of Rift Valley Fever Outbreaks in the Greater Horn of Africa

2006 ◽  
Vol 19 (9) ◽  
pp. 1673-1687 ◽  
Author(s):  
Matayo Indeje ◽  
M. Neil Ward ◽  
Laban J. Ogallo ◽  
Glyn Davies ◽  
Maxx Dilley ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Horn Of Africa ◽  
Valley Fever ◽  
Wide Range ◽  
Potential Applications ◽  
Greater Horn Of Africa

Abstract In this paper the progress made in producing predictions of the Normalized Difference Vegetation Index (NDVI) over Kenya in the Greater Horn of Africa (GHA) for the October–December (OND) season is discussed. Several studies have identified a statistically significant relationship between rainfall and NDVI in the region. Predictability of seasonal rainfall by global climate models (GCMs) during the OND season over the GHA has also been established as being among the best in the world. Information was extracted from GCM seasonal prediction output using statistical transformations. The extracted information was then used in the prediction of NDVI. NDVI is a key variable for management of various climate-sensitive problems. For example, it has been shown to have the potential to predict environmental conditions associated with Rift Valley Fever (RVF) viral activity and this is referred to throughout the paper as a motivation for the study. RVF affects humans and livestock and is particularly economically important in the GHA. The establishment of predictability for NDVI in this paper is therefore part of a methodology that could ultimately generate information useful for managing RVF in livestock in the GHA. It has been shown that NDVI can be predicted skillfully over the GHA with a 2–3-month lead time. Such information is crucial for tailoring forecast information to support RVF monitoring and prediction over the region, as well as many other potential applications (e.g., livestock forage estimation). More generally, the Famine Early Warning System (FEWS), a project of the U.S. Agency for International Development (USAID) and the National Aeronautics and Space Administration (NASA) and other specialized technical centers routinely use NDVI images to monitor environmental conditions worldwide. The high predictability for NDVI established in this paper could therefore supplement the routine monitoring of environmental conditions for a wide range of applications.

scholarly journals Climate-disease connections: Rift Valley Fever in Kenya

2001 ◽  
Vol 17 (suppl) ◽  
pp. S133-S140 ◽  
Author(s):  
Assaf Anyamba ◽  
Kenneth J. Linthicum ◽  
Compton J. Tucker
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Southern Oscillation ◽  
Close Association ◽  
Enso Event ◽  
Infected Mosquito ◽  
Valley Fever

All known Rift Valley fever(RVF) outbreaks in Kenya from 1950 to 1998 followed periods of abnormally high rainfall. On an interannual scale, periods of above normal rainfall in East Africa are associated with the warm phase of the El Niño/Southern Oscillation (ENSO) phenomenon. Anomalous rainfall floods mosquito-breeding habitats called dambos, which contain transovarially infected mosquito eggs. The eggs hatch Aedes mosquitoes that transmit the RVF virus preferentially to livestock and to humans as well. Analysis of historical data on RVF outbreaks and indicators of ENSO (including Pacific and Indian Ocean sea surface temperatures and the Southern Oscillation Index) indicates that more than three quarters of the RVF outbreaks have occurred during warm ENSO event periods. Mapping of ecological conditions using satellite normalized difference vegetation index (NDVI) data show that areas where outbreaks have occurred during the satellite recording period (1981-1998) show anomalous positive departures in vegetation greenness, an indicator of above-normal precipitation. This is particularly observed in arid areas of East Africa, which are predominantly impacted by this disease. These results indicate a close association between interannual climate variability and RVF outbreaks in Kenya.

scholarly journals The Nonstructural Protein NSs Induces a Variable Antibody Response in Domestic Ruminants Naturally Infected with Rift Valley Fever Virus

2011 ◽  
Vol 19 (1) ◽  
pp. 5-10 ◽  
Author(s):  
José-Carlos Fernandez ◽  
Agnès Billecocq ◽  
Jean Paul Durand ◽  
Catherine Cêtre-Sossah ◽  
Eric Cardinale ◽  
...  
Keyword(s):  
Antibody Response ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Nonstructural Protein ◽  
Rift Valley Fever Virus ◽  
High Rate ◽  
Antibody Detection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Valley Fever ◽  
Wide Range

ABSTRACTRift Valley fever (RVF) is an emerging zoonosis in Africa which has spread to Egypt, the Arabian Peninsula, Madagascar, and Comoros. RVF virus (RVFV) (Bunyaviridaefamily,Phlebovirusgenus) causes a wide range of symptoms in humans, from benign fever to fatal hemorrhagic fever. Ruminants are severely affected by the disease, which leads to a high rate of mortality in young animals and to abortions and teratogenesis in pregnant females. Diagnostic tests include virus isolation and genome or antibody detection. During RVFV infection, the nucleoprotein encapsidating the tripartite RNA genome is expressed in large amounts and raises a robust antibody response, while the envelope glycoproteins elicit neutralizing antibodies which play a major role in protection. Much less is known about the antigenicity/immunogenicity of the nonstructural protein NSs, which is a major virulence factor. Here we have developed a competitive enzyme-linked immunosorbent assay (ELISA) enabling detection of low levels of NSs-specific antibodies in naturally infected or vaccinated ruminants. Detection of the NSs antibodies was validated by Western blotting. Altogether, our data showed that the NSs antibodies were detected in only 55% of animals naturally infected by RVFV, indicating that NSs does not induce a consistently high immune response. These results are discussed in light of differentiation between infected and vaccinated animals (DIVA) tests distinguishing naturally infected animals and those vaccinated with NSs-defective vaccines.

scholarly journals Safety and Efficacy Profile of Commercial Veterinary Vaccines against Rift Valley Fever: A Review Study

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Moataz Alhaj
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Clinical Manifestations ◽  
Effective Vaccine ◽  
Published Data ◽  
Inactivated Vaccine ◽  
Significant Information ◽  
Valley Fever ◽  
Wide Range ◽  
Efficacy Profile

Rift Valley Fever (RVF) is an infectious illness with serious clinical manifestations and health consequences in humans as well as a wide range of domestic ruminants. This review provides significant information about the prevention options of RVF along with the safety-efficacy profile of commercial vaccines and some of RVF vaccination strategies. Information presented in this paper was obtained through a systematic investigation of published data about RVF vaccines. Like other viral diseases, the prevention of RVF relies heavily on immunization of susceptible herds with safe and cost-effective vaccine that is able to confer long-term protective immunity. Several strains of RVF vaccines have been developed and are available in commercial production including Formalin-Inactivated vaccine, live attenuated Smithburn vaccine, and the most recent Clone13. Although Formalin-Inactivated vaccine and live attenuated Smithburn vaccine are immunogenic and widely used in prevention programs, they proved to be accompanied by significant concerns. Despite Clone13 vaccine being suggested as safe in pregnant ewes and as highly immunogenic along with its potential for differentiating infected from vaccinated animals (DIVA), a recent study raised concerns about the safety of the vaccine during the first trimester of gestation. Accordingly, RVF vaccines that are currently available in the market to a significant extent do not fulfill the requirements of safety, potency, and DIVA. These adverse effects stressed the need for developing new vaccines with an excellent safety profile to bridge the gap in safety and immunity. Bringing RVF vaccine candidates to local markets besides the absence of validated serological test for DIVA remain the major challenges of RVF control.

Rift Valley fever

2011 ◽  
Author(s):  
R. Swanepoel ◽  
J. T. Paweska
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Case Fatality ◽  
Febrile Illness ◽  
Horn Of Africa ◽  
Valley Fever ◽  
Domestic Ruminants ◽  
Inactivated Vaccines ◽  
Limited Scale ◽  
Haemorrhagic Disease

Rift Valley fever (RVF) is an acute disease of domestic ruminants in mainland Africa and Madagascar, caused by a mosquito borne virus and characterized by necrotic hepatitis and a haemorrhagic state. Large outbreaks of the disease in sheep, cattle and goats occur at irregular intervals of several years when exceptionally heavy rains favour the breeding of the mosquito vectors, and are distinguished by heavy mortality among newborn animals and abortion in pregnant animals. Humans become infected from contact with tissues of infected animals or from mosquito bite, and usually develop mild to moderately severe febrile illness, but severe complications, which occur in a small proportion of patients, include ocular sequelae, encephalitis and fatal haemorrhagic disease. Despite the occurrence of low case fatality rates, substantial numbers of humans may succumb to the disease during large outbreaks. Modified live and inactivated vaccines are available for use in livestock, and an inactivated vaccine was used on a limited scale in humans with occupational exposure to infection. The literature on the disease has been the subject of several extensive reviews from which the information presented here is drawn, except where indicated otherwise (Henning 1956; Weiss 1957; Easterday 1965; Peters and Meegan 1981; Shimshony and Barzilai 1983; Meegan and Bailey 1989; Swanepoel and Coetzer 2004; Flick and Bouloy 2005). In September 2000, the disease appeared in south-west Saudi Arabia and adjacent Yemen, and the outbreak lasted until early 2001 (Al Hazmi et al. 2003; Madani et al. 2003; Abdo-Salem et al. 2006). The virus was probably introduced with infected livestock from the Horn of Africa, and it remains to be determined whether it has become endemic on the Arabian Peninsula.

Risk assessment of the introduction of Rift Valley fever from the Horn of Africa to Yemen via legal trade of small ruminants

2010 ◽  
Vol 43 (2) ◽  
pp. 471-480 ◽  
Author(s):  
Shaif Abdo-Salem ◽  
Agnès Waret-Szkuta ◽  
François Roger ◽  
Marie-Marie Olive ◽  
Khalid Saeed ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Small Ruminants ◽  
Horn Of Africa ◽  
Valley Fever

scholarly journals Insights into the Pathogenesis of Viral Haemorrhagic Fever Based on Virus Tropism and Tissue Lesions of Natural Rift Valley Fever

Viruses ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 709
Author(s):  
Lieza Odendaal ◽  
A Sally Davis ◽  
Estelle H Venter
Keyword(s):  
Rift Valley ◽  
Rift Valley Fever ◽  
Multiorgan Failure ◽  
Current Understanding ◽  
Coagulation System ◽  
Future Research ◽  
Type I ◽  
Haemorrhagic Fever ◽  
Valley Fever ◽  
Wide Range

Rift Valley fever phlebovirus (RVFV) infects humans and a wide range of ungulates and historically has caused devastating epidemics in Africa and the Arabian Peninsula. Lesions of naturally infected cases of Rift Valley fever (RVF) have only been described in detail in sheep with a few reports concerning cattle and humans. The most frequently observed lesion in both ruminants and humans is randomly distributed necrosis, particularly in the liver. Lesions supportive of vascular endothelial injury are also present and include mild hydropericardium, hydrothorax and ascites; marked pulmonary congestion and oedema; lymph node congestion and oedema; and haemorrhages in many tissues. Although a complete understanding of RVF pathogenesis is still lacking, antigen-presenting cells in the skin are likely the early targets of the virus. Following suppression of type I IFN production and necrosis of dermal cells, RVFV spreads systemically, resulting in infection and necrosis of other cells in a variety of organs. Failure of both the innate and adaptive immune responses to control infection is exacerbated by apoptosis of lymphocytes. An excessive pro-inflammatory cytokine and chemokine response leads to microcirculatory dysfunction. Additionally, impairment of the coagulation system results in widespread haemorrhages. Fatal outcomes result from multiorgan failure, oedema in many organs (including the lungs and brain), hypotension, and circulatory shock. Here, we summarize current understanding of RVF cellular tropism as informed by lesions caused by natural infections. We specifically examine how extant knowledge informs current understanding regarding pathogenesis of the haemorrhagic fever form of RVF, identifying opportunities for future research.

scholarly journals Rift Valley Fever Outbreaks in Mauritania and Related Environmental Conditions

2014 ◽  
Vol 11 (1) ◽  
pp. 903-918 ◽  
Author(s):  
Cyril Caminade ◽  
Jacques Ndione ◽  
Mawlouth Diallo ◽  
Dave MacLeod ◽  
Ousmane Faye ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Rift Valley ◽  
Rift Valley Fever ◽  
Valley Fever
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