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Geographical distribution

Based on official disease reports to the WOAH

BTV is a disease listed in the World Organisation for Animal Health (WOAH) Terrestrial Animal Health Code. The map to the right displays occurrence reported to the WOAH-WAHIS 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.

Information on stable situations (disease present or absent in a zone or country) is provided by countries through the WOAH monitoring system, which is a different reporting channel. This information is available in a different spatial and temporal scale, which can be browsed on the map independently from the outbreak notification points.

Last updated at: 2023-05-26

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

Field studies

Field studies investigating disease dynamics and measures of disease frequency

EFSA conducts regular systematic literature reviews covering peer-reviewed literature in English since 1970. The map to the right shows countries of origin of published field studies which:

  • reported a specific disease frequency measure associated with field occurrence of this pathogen, such as number of cases, incidence, or prevalence;
  • reported a specific disease impact outcome, such as case fatality or mortality;
  • assessed disease spread, for example through mathematical models.

Click on a country to scroll through the list of references and the provided outcomes.

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 2022. 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

Animal Health Impact

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

The panel to the right summarizes all evidence collected by EFSA from published studies describing natural infections with this agent (as opposed to experimental infections, summarized in the next section). Scroll down to see summaries of the data collected according to the type of field investigation context. The following study context categories are considered, and summaries are shown in a dedicated section of the panel to the right if any references in the category were included in the literature review:

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

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 January 2022. 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.

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

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 January 2022. 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.

Public Health

Humans are not susceptible to BTVV and therefore there is no direct impact on public health (EFSA topic, BTV).

Agent

Virus taxonomy

Family: Reoviridae

Genus: Orbivirus

Species: Bluetongue virus

Recognised serotypes: 27

Virus characteristics

Refer to the WOAH Technical disease card for a key summary of the virus characteristics.

Virus survival outside living hosts

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 experiments 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 2022. 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.

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 January 2022. 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

WOAH-prescribed tests for international trade include (WOAH, Terrestrial Manual):

  • For the detection of the agent (confirmation of clinical cases and individual animal freedom from infection prior to movement): Real-time RT-PCR, RT-PCR and classical virus isolation.
  • For detection of immune response: C-ELISA (serogroup specific), virus neutralization (serogroup specific), and AGID.

    • 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.

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

  • (i) those which evaluated test performance using a set of samples from animals with known infectious status (samples from truly infected and non-infected animals);
  • (ii) those which compared test performance against a gold standard test, assuming the result of that test (positive or negative) to represent true infection status.

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 below the results for all the articles retrieved from the literature individually, grouped by type of test 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 January 2022. 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

Know vectors
  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Diptera
  • Family: Ceratopogonidae
  • Genus: Culicoides
  • Common name: biting midge, gnat, no-see-um, punky.

The map on the right shows the reported presence of biting midges 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 MIDGES control. Scroll down through the content.

Summaries of available scientific evidence are provided concerning:

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

Studies that presented substance effects through outcomes other than tick 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

EFSA conducts regular systematic literature reviews covering all vaccine efficacy studies published in peer-reviewed literature in English since 1970, when evaluating vaccines approved for use in the European Union.

The evidence collected from these references is summarized in the right panel.

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.

Treatments

The panel to the right summarizes all evidence collected by EFSA from published treatment efficacy studies. When available, evidence was collected from two main types of studies:

  • those in which the animals were subjected to a specific Pharmaceutical treatment, and the efficacy of the treatment in preventing infections in the treated group is reported in comparison to a control group;
  • and those in which a vector control substance (insecticide) was used, and its effect in preventing infections in hosts is reported.

    • For both types of studies the panel to the right presents reported results regarding:

  • Efficacy: efficacy is measured as 1-(percentage infection in the treated group/percentage infection in the control group)
  • Titer of neutralizing antibodies
  • Percentage of positive animals (after exposire to the agent)
  • Mortality

EFSA conducts regular systematic literature reviews covering treatment efficacy studies published in peer-reviewed literature in English since 1970, when substances used for treatment are approved for use in the European Union.

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.

Legislation

Council Directive 2000/75/EC lays down measures after suspicion and confirmation of a bluetongue outbreak in the EU. Measures to be taken in the event of an outbreak are, among others:

  • vector control (use of insecticides in animal housing and in the areas where these insects live, application of insect repellents on animals, use of mosquito nets, etc.);
  • restriction of the movements of live ruminants from affected to non-infected regions where the vector is present and the use of vaccines;
  • slaughtering animals when appropriate;
  • destruction of carcass/waste.

Specific requirements for testing animals, or fresh meat or meat products for the detection of BTV before importing them into the EU are laid down in Regulation EU/206/2010 .

Risk Assessments

EFSA regularly carries out risk assessments to support risk managers with their decision making on the prevention and control of diseases. Risk assessments of relevance for this disease are listed in the right panel.

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.

EFSA thanks the following experts for their specific contribution to this story map:

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):