Rift Valley fever
Rift Valley fever | |
---|---|
Arabia[1] |
Rift Valley fever (RVF) is a
The disease is caused by the RVF
Prevention of the disease in humans is accomplished by vaccinating animals against the disease. This must be done before an outbreak occurs because if it is done during an outbreak it may worsen the situation. Stopping the movement of animals during an outbreak may also be useful, as may decreasing mosquito numbers and avoiding their bites. There is a human vaccine; however, as of 2010 it is not widely available. There is no specific treatment and medical efforts are supportive.[1]
Signs and symptoms
In humans, the virus can cause several syndromes. Usually, they have either no symptoms or only a mild illness with fever,
Other signs in livestock include vomiting and diarrhea, respiratory disease, fever, lethargy, anorexia and sudden death in young animals.[3]
Cause
Virology
Rift Valley fever phlebovirus | |
---|---|
Phlebovirus virion and genome | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Negarnaviricota
|
Class: | Ellioviricetes |
Order: | Bunyavirales |
Family: | Phenuiviridae |
Genus: | Phlebovirus |
Species: | Rift Valley fever phlebovirus
|
The virus belongs to the
The virus' G(C) protein has a class II membrane fusion protein architecture similar to that found in flaviviruses and alphaviruses.[4] This structural similarity suggests that there may be a common origin for these viral families.[citation needed]
The virus' 11.5
Transmission
The virus is transmitted through mosquito
Pathogenesis
Although many components of the RVFV's RNA play an important role in the virus' pathology, the nonstructural protein encoded on the S segment (NSs) is the only component that has been found to directly affect the host. NSs is hostile and combative against the host interferon (IFNs) antiviral response.[13] IFNs are essential in order for the immune system to fight off viral infections in a host.[14] This inhibitory mechanism is believed to be due to a number of reasons, the first being, competitive inhibition of the formation of the transcription factor.[13] On this transcription factor, NSs interacts with and binds to a subunit that is needed for RNA polymerase I and II.[13][15] This interaction cause competitive inhibition with another transcription factor component and prevents the assembly process of the transcription factor complex, which results in the suppression of the host antiviral response.[13][15] Transcription suppression is believed to be another mechanism of this inhibitory process.[13] This occurs when an area of NSs interacts with and binds to the host's protein, SAP30 and forms a complex.[13][15] This complex causes histone acetylation to regress, which is needed for transcriptional activation of the IFN promoter.[15] This causes IFN expression to be obstructed. Lastly, NSs has also been known to affect regular activity of double-stranded RNA-dependent protein kinase R. This protein is involved in cellular antiviral responses in the host. When RVFV is able to enter the host's DNA, NSs forms a filamentous structure in the nucleus. This allows the virus to interact with specific areas of the host's DNA that relates to segregation defects and induction of chromosome continuity. This increases host infectivity and decreases the host's antiviral response.[13]
Diagnosis
Diagnosis relies on viral isolation from tissues, or serological testing with an
Prevention
A person's chances of becoming infected can be reduced by taking measures to decrease contact with blood, body fluids, or tissues of infected animals and protection against mosquitoes and other bloodsucking insects. Use of mosquito repellents and bed nets are two effective methods. For persons working with animals in RVF-endemic areas, wearing protective equipment to avoid any exposure to blood or tissues of animals that may potentially be infected is an important protective measure.[18] Potentially, establishing environmental monitoring and case surveillance systems may aid in the prediction and control of future RVF outbreaks.[18]
No vaccines are currently available for humans.[18][1] While a vaccines have been developed for humans, it has only been used experimentally for scientific personnel in high-risk environments.[1] Trials of a number of vaccines, such as NDBR-103 and TSI-GSD 200, are ongoing.[19] Different types of vaccines for veterinary use are available. The killed vaccines are not practical in routine animal field vaccination because of the need of multiple injections. Live vaccines require a single injection but are known to cause birth defects and abortions in sheep and induce only low-level protection in cattle. The live-attenuated vaccine, MP-12, has demonstrated promising results in laboratory trials in domesticated animals, but more research is needed before the vaccine can be used in the field. The live-attenuated clone 13 vaccine was recently registered and used in South Africa. Alternative vaccines using molecular recombinant constructs are in development and show promising results.[18]
A vaccine has been conditionally approved for use in animals in the US.[20] It has been shown that knockout of the NSs and NSm nonstructural proteins of this virus produces an effective vaccine in sheep as well.[21]
Epidemiology
RVF outbreaks occur across sub-Saharan Africa, with outbreaks occurring elsewhere infrequently. Outbreaks of this disease usually correspond with the warm phases of the EI Niño/Southern Oscillation. During this time there is an increase in rainfall, flooding and greenness of vegetation index, which leads to an increase in mosquito vectors.[22] RVFV can be transmitted vertically in mosquitos, meaning that the virus can be passed from the mother to her offspring. During dry conditions, the virus can remain viable for a number of years in the egg. Mosquitos lay their eggs in water, where they eventually hatch. As water is essential for mosquito eggs to hatch, rainfall and flooding cause an increase in the mosquito population and an increased potential for the virus.[23]
The first documented outbreak was identified in Kenya in 1931, in sheep, cattle and humans; in 2022 an outbreak is ongoing in Burundi.
Biological weapon
Rift Valley fever was one of more than a dozen agents that the
Research
The disease is one of several identified by
See also
References
- ^ a b c d e f g h i j k l m n o p "Rift Valley fever". Fact sheet N°207. World Health Organization. May 2010. Archived from the original on 15 April 2014. Retrieved 21 March 2014.
- ISBN 9780198570028. Archivedfrom the original on 2017-09-08.
- ^ a b Rift Valley Fever Archived 2012-05-08 at the Wayback Machine reviewed and published by WikiVet, accessed 12 October 2011.
- PMID 23319635.
- ^ "ViralZone: Phlebovirus". viralzone.expasy.org. Archived from the original on 2016-10-03. Retrieved 2016-09-14.
- PMID 17192303.
- PMID 12243225.
- PMID 8619436.
- S2CID 36591701.
- PMID 9621201.
- ISBN 978-0195761702.
- PMID 3607999.
- ^ PMID 21450816.
- S2CID 27209861.
- ^ PMID 21666766.
- ISBN 978-1-4511-0563-6.
- ^ "Kemri develops kit for rapid test of viral disease". Archived from the original on 2016-09-06. Retrieved 2016-09-14.
- ^ a b c d "Prevention: Rift Valley Fever | CDC". US Centers for Disease Control and Prevention. Retrieved 24 September 2018. This article incorporates text from this source, which is in the public domain.
- PMID 30736362.
- PMID 25948740.
- PMID 21976656.
- from the original on 2016-12-02.
- ^ "Rift Valley Fever | CDC". www.cdc.gov. Archived from the original on 2016-12-04. Retrieved 2016-12-01.
- .
- S2CID 41617078.
- S2CID 46918400.
- PMID 561445.
- S2CID 31753926.
- S2CID 16239209.
- ^ "At least 75 people die of Rift Valley Fever in Kenya". International Herald Tribune. 7 January 2007. Archived from the original on 9 January 2007.
- ^ "Deadly fever spreads Kenya Panic". BBC. 26 January 2007. Archived from the original on 1 May 2008.
- ^ ProMED-mail Archived 2011-07-28 at the Wayback Machine. ProMED-mail. Retrieved on 2014-05-12.
- ^ "Rift Valley fever in South Africa". WHO. Archived from the original on 2010-04-12.
- ^ "Outbreak Summaries | Rift Valley Fever | CDC". 2019-02-15.
- ^ "Rift Valley fever – Kenya". WHO. 18 June 2018. Archived from the original on June 23, 2018. Retrieved 1 July 2018.
- ^ "Rift Valley Fever – Mayotte (France)". WHO. 13 May 2019. Archived from the original on July 1, 2019. Retrieved 15 May 2019.
- ^ "Rift Valley fever – Kenya". World Health Organization. 12 February 2021. Archived from the original on February 12, 2021. Retrieved 24 February 2021.
- ^ "Chemical and Biological Weapons: Possession and Programs Past and Present", James Martin Center for Nonproliferation Studies, Middlebury College, April 9, 2002, accessed November 14, 2008.
- ^ "Select Agents and Toxins" (PDF). USDA-APHIS and CDC: National Select Agent Registry. 2011-09-19. Archived from the original (PDF) on 2012-02-25.
- ^ Kieny MP. "After Ebola, a Blueprint Emerges to Jump-Start R&D". Scientific American Blog Network. Archived from the original on 20 December 2016. Retrieved 13 December 2016.
- ^ "List of Pathogens". World Health Organization. Archived from the original on 20 December 2016. Retrieved 13 December 2016.
External links
- CDC RVF Information Page
- Rift Valley Fever disease card at OIE
- "Rift Valley fever". Fact sheet N°207. World Health Organization. May 2010. Retrieved 21 March 2014.
- "Rift Valley fever virus". NCBI Taxonomy Browser. 11588.