Geographical distribution

RVF is a disease listed in the World Organisation for Animal Health (WOAH) Terrestrial Animal Health Code and must be reported to the WOAH. The map to the right displays outbreak points reported to the WOAH early warning system since 2005.

As described in the WOAH Terrestrial Animal Health Code, the WOAH early warning system includes immediate notifications and follow-up reports on:

• First occurrences of a listed disease,
• Recurrence of an eradicated listed disease,
• First occurrences of new strain of a pathogenic agent of a listed disease,
• Recurrence of an eradicated strain,
• Sudden and unexpected changes in the distribution or increase in incidence or virulence of, or morbidity or mortality caused by the pathogenic agent of a listed disease
• Occurrence of a listed disease in an unusual host species.

Countries are coloured according to the available information regarding their stable disease situation (disease situation legend). This information is provided by countries through the WOAH monitoring system, which is a different reporting channel.
The disease situations (country/region colours) are prioritized in the following order: Present, Suspected and Absent if more than one is present in a country during the filtered period.
Immediate notifications (points) and disease situation (country/region colours) are reported to the WOAH in different spatial and temporal scales, and therefore are displayed in the map as layers which can be filtered independently.

Available through the World Health Organization.

Last updated at: 2024-11-18

For more up to date reports, visit the original data source: WOAH-WAHIS.

Epi studies

The panel to the right shows the distribution of epidemiological studies collected in the literature review. Click on the map to see more information about the studies. The following study context categories are considered:

• Case reports
• Passive surveillance (reports of specific surveillance activities following reported cases)
• Evidence of disease freedom (investigations to confirm disease absence)
• Observational study (case-control or cohort studies)
• Active surveillance (active testing of animals and search for cases)
• Survey (designed sampling and testing of animals)

It is important to note that studies targetting humans were NOT included in the systematic literature reviews.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Disease

A summary of the disease in animal hosts is given in the WOAH Technical disease card.

The panel to the right summarizes evidence collected from published studies describing natural infections with this agent (as opposed to experimental infections, summarized in dedicated section).

It is important to note that studies targetting humans were NOT included in the systematic literature reviews.

This is a zoonotic disease. Humans may become infected through direct or indirect contact with the blood or organs of infected animals. For more details, visit the information from the European Centre for Disease Prevention and Control (ECDC) for Rift Valey Fever.

EFSA conducts regular systematic literature reviews covering studies investigating natural infections with this agent, and published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Experimental Inf.

Refer to the WOAH Technical Disease Card for a key summary of the disease in animal hosts.

The panel to the right summarizes all evidence collected by EFSA from published experimental infection studies describing the health effects of this pathogen in host animal species. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

• Host species
• Start of clinical signs (incubation period)
• Duration of clinical signs
• All diverse types of clinical signs reported in the different host species
• Case fatality
• Meta-analysis of the reported duration of observable clinical signs, accounting for censoring in the experimental infection study groups

EFSA conducts regular systematic literature reviews covering all experimental infections published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Agent

Family: Phenuiviridae (Order Bunyavirales)

Genus: Phlebovirus

Species: Rift Valley fever phlebovirus

Serotypes: 1 recognised serotype

Refer to the WOAH Technical Disease Card for a key summary of the virus characteristics.

The panel to the right summarizes all evidence collected by EFSA from published experiments on pathogen survival. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

• Survival plots indicating the maximum number of days the virus was detected in different matrices under different conditions (temperature)
• Half-life studies which documented virus viability decay over time under different temperatures
• Meta-analysis of the reported virus survival period for matrices in which a sufficient number of studies were found

EFSA conducts regular systematic literature reviews covering pathogen survival studies. To date, no studies fitting the eligibility criteria were found which studies survival of the RVF virus. The full review protocol, explaining the eligibility criteria, can be downloaded here.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu.

Transmission

Refer to the WOAH Technical Disease Card for a key summary of the disease transmission and epidemiological parameters.

The panel to the right summarizes all evidence collected by EFSA from published experimental infection studies describing host infectiousness. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

• Evidence of Host-host transmission
• Evidence of transplacentary transmission
• Meta-analysis of the reported duration of the infectious period, accounting for censoring in the experimental infection study groups
• Data for all animal matrices in which agent presence was demonstrated.

EFSA conducts regular systematic literature reviews covering all experimental infections published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Diagnosis

According to the WOAH Terrestrial Manual, laboratory confirmation of clinical cases should require a combination of at least two positive results from two different diagnostic test methods; either positive for virus/viral RNA and antibodies or positive for IgM or IgG antibodies with demonstration of rising titres between paired sera samples collected 2–4 weeks apart.

RVFV can be isolated from blood and several organs. The recommended tests by the WOAH for confirmation of clinical cases are the virus isolation in cell culture and the RT-PCR (WOAH, 2021).

Suitable tests for detection of immune response, immune status of individual pre- and post-vaccinated animals, identification of prevalence of infection and individual animal freedom from infection prior to movement include enzyme-linked immunosorbent (ELISA) assay and PRNT (WOAH,2021). Identification of specific antibodies is mostly achieved by IgM and IgG detection ELISAs or the plaque reduction neutralization test (PRNT); the latter is the most specific but can only be performed with live virus. IgM ELISAs and virus neutralization tests can detect earlier antibodies (4 days post-infection) than IgG ELISAs (from 8 days post-infection) (Kortekaas et al., 2013).

EFSA conducts regular systematic literature reviews covering peer-reviewed literature in English since 1970, covering diagnostic tests approved for use in the European Union (EU).

Data were collected from all evaluations of performance of those tests which provided sensitivity or specificity (or enough data to estimate those needed to be provided). You can browse through the data collected scrolling the panel to the right.

We have chosen not to aggregate and summarize the results because the study conditions can vary greatly. Instead, we present the results for all the articles retrieved from the literature individually, grouped by type of test, diagnostic target and, when relevant, animal species.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Vectors

RVFV is transmitted by a broad range of mosquito species. Aedes mosquitoes preferably feed on domestic and wild ruminants, who act as amplifier of RVFV, leading to expansion of disease (WOAH technical disease card). Rodents and bats have also been suggested to be somehow involved in the cycle (Hubálek et al., 2014). Visit the Transmission section of this story map for further information.

The map on the right shows the reported presence of various species of Aedes, Anopheles, and Culex mosquitoes in primary sources.

Visit the VectorNet resources directly for further information on disease vectors, including expert opinion

*To consider an arthropod species as a vector for viruses, the following four criteria should be satisfied (World Health Organization, 1967): (1) the species should be repeatedly associated with the disease in the field (season and places); (2) the virus should be recovered from field-collected adult females that do not have a fresh blood meal in the abdomen; (3) the species should be able to become infected after oral infection; and (4) the species should be able to transmit the infection biologically. However, based on the literature finding, all these criteria could be satisfied for only very few arthropod species, which could then be called a vector in this strict sense. Furthermore, other vector species could be present which were never tested for this pathogen.

Vector control

The panel to the right summarizes all evidence collected by EFSA from published studies of the efficacy of various substances available for control of MOSQUITOES. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

• The efficacy of various substances on mosquito mortality, when applied to animal hosts by different routes (modes of treatment)
• The efficacy of various substances in experiments where mosquitoes were directly exposed

Studies that presented substance effects through outcomes other than mosquito mortality (for instance infestation prevention)

EFSA conducts regular systematic literature reviews covering vector control studies (for selected vectors: midges, mosqtuitoes, sandflies and ticks) published in peer-reviewed literature in English since 1970.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

*The review was last updated in January 2018. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Vaccination

At present, no vaccines have been authorised for use in the EU by the European Medicine Agency (EMA, online). However, both inactivated and live vaccines are available and used frequently in Africa. Inactivated vaccines are normally used in non-endemic RVFV countries (CFSPH, online; DISCONTOOLS, 2016). In these countries, vaccination is a key strategy for control of RVFV outbreaks. In 2011, FAO (2011) produced a detailed report on the shortcomings of two existing vaccines then, namely the need for annual vaccination for the inactivated whole RVFV vaccine; and the residual virulence of the live-attenuated alternative. Kortekaas (2014) reviewed the progress in the development of next-generation veterinary vaccines of improved efficacy and safety, as well as the progress in overcoming hurdles to the development of a vaccination strategy also for humans.

An inactivated vaccine for human use has been created, but currently is not licensed and not commercially available. It has been tested in workers with high risk of exposure under the strict control of health authorities (WHO, 2016).

EFSA conducts regular systematic literature reviews covering peer-reviewed literature in English since 1970, covering commercial vaccines approved for use in the European Union (EU) or third countries.

Data were collected from all evaluations of vaccine performance which met the inclusion criteria specified in the Systematic Literature Review Protocol, COVETLAB consortium. Review Protocol 2021. You can browse through the data collected scrolling the panel to the right.

Two main types of performance evaluation studies are reported in literature:

• (i) those which evaluated vaccine efficacy
• (ii) those which reported vaccine coverage after animals were challenged with the disease agent.

Results for these two types of evaluations are presented separately.

We have chosen not to aggregate and summarize the results because the study conditions can vary greatly. Instead, we present the results for all the articles retrieved from the literature individually, grouped by vaccine and animal species.

You can download all data collected through systematic literature review here. Data fields are explained in this read-me file.

The review was last updated in November 2023. The complete list of references is available for download here. If important references to primary studies are missing, contact animal-diseases@efsa.europa.eu. The full review protocol can be downloaded here.

Treatments

There are no specific curative treatments for RFV infections (MSD MANUAL, online).

Picture on the right: RVF depression. A courtesy of Dr Assane G Fall and Dr Modou Moustapha LO.

Animal Health Law Risk Assessments

RVF is listed as a category A diseases in the "Animal Health Law" - Regulation (EU) 2016/429 of the European Parliament and of the Council of 9 March 2016 on transmissible animal diseases and amending and repealing certain acts in the area of animal health.

EFSA has published a series of Scientific Opinions on risk assessment of several scientific topics within the framework of AHL, upon request by the European Comission (EC). You can browse through the AHL legislations and EFSA’s Scientific Opinions on the right panel.

Other Risk Assessments

The EFSA Animal Health and Welfare Panel assessed the risk of RVFV for the four regions of the EU for 2017, using EFSA’s VBD risk assessment model.

The outcomes of the risk assessment model estimated the overall rate of entry to be very low, depending on the region in the EU.

After entry, the risk assessment model estimated the level of transmission to be moderate in the four regions. The probability of establishment was estimated to be very high/high in all four regions of the EU.

The overall rate of introduction of RVFV (being the combination of the rate of entry, the level of transmission and the probability of establishment) was estimated to be very low; hence, the extent of spread and potential impact after introduction was not assessed.

Acknowledgments

The CoVetLab consortium has been responsible for the systematic literature reviews since 2015, and has delivered story maps to EFSA since 2021. Partners are: Swedish National Veterinary Institute (SVA, Sweden); Wageningen Bioveterinary Research (WBVR, The Netherlands); Animal and Plant Health Agency (APHA; UK) and the University of Surrey (UK).

Geographical distribution data has been kindly provided by the World Organisation of Animal Health (WOAH). WOAH-WAHIS (WOAH World Animal Health Information System) is the original source of these data.

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References

The list of references displayed in this storymap is available on the right panel.

You can also download the complete list of references for each of the seven specific knowledge domains for which EFSA carries out systematic literature reviews regularly (living reviews):

• Experimental Infections (complete list of references, complete dataset, Read me file)
• Pathogen Survival (complete list of references, complete dataset, Read me file)
• Diagnostic Tests (complete list of references, complete dataset, Read me file)
• Vaccines (complete list of references, complete dataset, Read me file)
• Treatments (complete list of references, complete dataset, Read me file)
• Vector Control (complete list of references, complete dataset, Read me file)
• Geographical distribution (complete list of references, complete dataset, Read me file)