Epidemiological studies investigating disease dynamics and measures of disease frequency

Data collected through systematic literature review are presented in the right panel, mapped separately according to the study context eligible:

A summary of all epidemiological study references reviewed for this agent is shown to the right. More detailed information for each of those is presented in individual sections below when data is available. All references are listed in a dedicated section following further.

Note that this is a disease reportable to WOAH, and therefore case reports and passive surveillance were NOT considered eligible in the literature review. For the geographical distribution of reported cases of this disease, please refer to the Geographic Distribution data.

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.

The table on the right lists the main features of eligible studies reporting active testing of animals and search for cases. It has one row per study group from all studies reviewed. This means that the same reference may appear in several rows if several target species or different tests were reported.

• RefID: the paper unique ID, which can be used to get full bibliographical details in the References table for this section, further below.
• Country: where the investigation was conducted.
• Year: year when the study was conducted (start year when multiple years are reported).
• Target species
• Reason for sampling: the reported trigger for animals being tested, when reported.
• Sampling strategy: how sampling was designed.
• Lab target: target of the test for laboratorial confirmation. It specifies whether the agent or antibodies were detected.
• Sample size: number of units tested.
• N Pos: number of units tested which were found positive. This was only reported as prevalence when there was a specific sampling strategy used, and the article reported the result as a prevalence estimation.
• Prevalence: documented only when reported in the reviewed references as a prevalence estimation.
• Sampling point: where in the animal production chain samples were taken, for example farms, abattoirs, etc.

The table on the right lists the main features of eligible studies reporting designed sampling and testing of animals. It has one row per study group from all studies reviewed. This means that the same reference may appear in several rows if several target species or different tests were reported.

• RefID: the paper unique ID, which can be used to get full bibliographical details in the References table for this section, further below.
• Country: where the investigation was conducted.
• Year: year when the study was conducted (start year when multiple years are reported).
• Target species
• Lab target: target of the test for laboratorial confirmation. It specifies whether the agent or antibodies were detected.
• Sample size: number of units tested.
• Prevalence: documented only when reported in the reviewed references as a prevalence estimation.
• Sampling strategy: how sampling was designed.
• Sampling point: where in the animal production chain samples were taken, for example farms, abattoirs, etc.

The table on the right lists the main features of eligible studies reporting results from passive surveillance activities.

Case reported and reports of specific surveillance activities following reported cases were included in the literature review in cases of diseases not reportable to WOAH, or when additional information on disease burden and impact on animal health were reported on the study.

• RefID: the paper unique ID, which can be used to get full bibliographical details in the References table for this section, further below.
• Country: where the investigation was conducted.
• Year: year when the study was conducted (start year when multiple years are reported).
• Target species
• Lab target: target of the test for laboratorial confirmation. It specifies whether the agent or antibodies were detected.
• Sample size: number of units tested. Sampling designs can vary a lot, and are usually in two-stages for disease freedom. Visit the reference or the full dataset for details.
• N Pos: number of units tested which were found positive. This was only reported as prevalence when there was a specific sampling strategy used, and the article reported the result as a prevalence estimation.
• Reason for sampling: the reported trigger for animals being tested, when reported.
• Sampling point: where in the animal production chain samples were taken, for example farms, abattoirs, etc.

The table on the right lists the main features of eligible studies reporting results from outbreak investigations.

For official data on reported outbreaks, please visit the Geographical distribution section of this animal disease profile (menu on the top of the page).

Data from papers reported as outbreak investigations was only collected for (i) diseases not reportable to WOAH, or (ii) when the paper contained additional information regarding measures of disease frequency or burden, that is, when it was not simply a case or outbreak report.

• RefID: the paper unique ID, which can be used to get full bibliographical details in the References table for this section, further below.
• Country: where the investigation was conducted.
• Year: year when the study was conducted (start year when multiple years are reported).
• Target species
• Prevalence: the reported prevalence found (which can be apparent prevalence or seroprevalence, according to the "Lab target").
• Incidence: documented when studies specifically reported investigating incidence.
• Epi unit: the epidemiological unit reported (for example herd or individual animals).
• Outcome reported: when the study reported any additional measure of disease burden, this was recorded during data collection unting the 3 next fields - data collectors documented what was the outcome (for instance mortality rate), the value reported , and the unit of measurement used. For example mortality rate, 30%; or number of deaths, 5 animals.

The table to the right shows references for all the studies included in the epidemiological studies section. You can find specific papers by their RefID.

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 evidence collected from published studies describing natural infections with this agent (as opposed to experimental infections, summarised in dedicated section).

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.

The table to the right summarises the clinical signs or severity described in epidemiological studies on field occurrence of this pathogen.

When reviewing eligible articles for the epidemiological studies section, if descriptions of the clinical signs observed were provided those were copied (as free-text) and compiled in the table to the right.

• RefID: the paper unique ID, which can be used to get full bibliographical details in the References table for this section, further below.
• Target species
• Clinical signs: text copied as reported in the articles reviewed.
• Severity: if a specific severity score or categorization was reported, this was also documented (but no attempt to categorize severity was made by those collecting data from the literature).

This table shows references for all the studies included in this section. You can find specific papers by their RefID.

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

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 epizootic haemorrhagic disease in host animal species.

Summaries of available scientific evidence are provided concerning:

• Host species
• Duration of clinical signs
• Clinical signs observed
• Case fatality
• Meta-analysis of reported duration of observed clinical signs, accounting for censoring in the experimental infection study groups

The panel to the right shows the animal species in which experimental infection has been demonstrated.

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.

The panel to the right shows the duration of clinical signs in host species. Experimental infections are usually done in animal groups, so two values are reported: the first day any animal in the group showed signs, and the last day any animal showed signs. This means the results show the range of days when signs can appear, not the exact duration for a single animal.

For each host species, the plot shows the distribution of start and end days of clinical signs for each animal group studied.

• The boxes represent the interquartile range (the middle 50% of data), with a line for the median (the middle value). The first quartile (Q1) is the 25th percentile, and the third quartile (Q3) is the 75th percentile.
• Dots represent outliers, which are values outside the range of Q1 minus 1.5 times the interquartile range, or Q3 plus 1.5 times the interquartile range.

Animals might still show signs on the last day of the experiment, so the maximum value is the highest observed, not the true maximum (censored data). The meta-analysis section recalculates the incubation period, considering this censoring.

The panel to the right shows, for each animal host, the percentage of individual animals with clinical signs in the animal group.

The panel on the right shows case fatality rates for various animal groups infected with epizootic haemorrhagic disease. Case fatality is the percentage of animals that died or were euthanised due to severe symptoms. If no animals died, the fatality rate is recorded as 0%.

• Grey dots represent individual animal groups studied. The x-axis shows the fatality rate, and the y-axis groups this data by animal species and, if relevant, by pathogen subtype.
• The coloured box plots display the distribution of fatality rates for each species and subtype combination, with detailed metrics visible when hovering over the bars.

Data aggregation by pathogen subtype is provided for additional context, especially where subtypes have distinct geographical distributions. Note that pathogenicity is not determined by subtype alone, so this should not imply a direct link between subtype and fatality.

Further details on case fatality data are available in the meta-analysis section.

Duration of clinial signs: Meta-analysis accounting for censoring

Evidence was available through systematic literature review for a minimum of 4 animal groups studied through experimental infections.

Kaplan-Meier curves were fit to the data, in order to estimate confidence intervals (CI) and interquartile ranges (IQ) for the duration of clinical signs. This methodology explicitly takes into account the data censoring issue (lack of information about true maximum when experiments ended while the agent was still detectable).

• The plot to the right shows the survival curves with confidence intervals (CI; parametric assumption). Keep scrolling down to find a table with the exact calculated CI.

• The plot to the right shows the survival curves with interquartile ranges (IQ; non-parametric). Keep scrolling down to find a table with the exact calculated IQ.

• The table to the right shows the exact calculated confidence intervals (CI) and interquartile ranges (IQ) accounting for censoring (lack of information about true maximum when experiments ended while the agent was still detectable).

LCL and UCL stand for the lower and upper control limit of a 95% confidence interval accounting for censoring.

N.groups is the number of animal groups from which experimental infection data was available.

The table to the right shows the number of groups (N.groups) for which experimental infection data was available, and gives a summary of the fatality observed within these experimentally infected groups.

For each combination of animal species and, when relevant, agent subtype, three rows of information are available:

• The within-group fatality, summarized for all animal groups in which the reference explicitly gave information about whether deaths were observed or animals were euthanised due to advanced clinical signs (groups with mortality information). This therefore can include groups in which no animals died or were euthanised, as long as this information was explicitily observed and reported. The within-group percentage displayed in the table is the median of all observations available (one observation = % dead within one animal group experimentally infected and followed).
• The within-group fatality only for groups in which mortality was observed (only groups with deaths). That is, when disease was observed to cause deaths, what was the percentage fatality within animal groups.
• The number of animal groups for which no fatality information is available (no mortality information). This is, the reference did not report deaths, but it was not possible to determine whether no deaths were observed, or this information was simply not reported.

The table to the right presents the information for the specific references used in this section of the disease profile.

Virus taxonomy

Family: Reoviridae

Genus: Orbivirus

Species: Epizootic haemorrhagic disease virus (Epizootic haemorrhagic disease virus and Ibaraki virus)

Serotypes: Eight serotypes or 10 numbered or named serotypes/strains (EHDV-1 to EHDV-8, EHDV 318, Ibaraki virus (atypical EHDV-2))

Agent characteristics

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

Agent survival outside living hosts

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

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 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.

There are no survival or half-life plots to show for this agent.

There are no plots based on meta-analysis available for this agent.

When evidence was available through systematic literature review for a minimum of 4 data points per animal matrix, this evidence was subjected to meta-analysis. In such cases, Kaplan-Meier curves would be fit to the data,in order to estimate confidence intervals (CI) and interquartile ranges (IQ) for the duration of the pathogen survival explicitly taking into account the data censoring issue (lack of information about true maximum when experiments ended while the agent was still detectable).

The specific references for this agent, and used in this section are listed in the right panel.

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.

Please note that experimental infections are generally conducted in animal groups.

Species listed are those for which evidence was available in peer-reviewed literature (in English).

Plots are interactive, hover to see more information, drag to zoom.

• Infectious period cannot be measured directly unless transmission experiments are also conducted. Infection experiments reviewed in the literature actually measured the period of time during which the pathogen/genetic material could be detected in specific body matrices.
• All data were recorded per ANIMAL GROUP, not individually. As a result, the periods were recorded in the form of minimum and maximum values (in days) observed in the group. The values therefore do not reflect a distribution of infectivity in a single animal, but the earliest and latest day in which the pathogen/genetic material could possibly be detected in specific body matrices.
• Animals could still be infectious on the last day of the experiment. Data in this case is censored - the maximum represents the maximum observed, not the true maximum.

Data collected from matrices other than blood, and calculations of the infectious period accounting for censoring (lack of information about true maximum when experiments ended while virus was still detectable) are available further below.

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.

The right panel gives a summary of findings on host-host transmission.

The right panel gives a summary of findings on transplacental transmission.

Duration of the infectious period: Meta-analysis accounting for censoring

Kaplan-Meier curves were fit to the data in order to estimate parametric confidence intervals (CI) and interquartile ranges (IQ) that explicitly take into account the data censoring issue (lack of information about true maximum when experiments ended while virus was still detectable). Further below you will find a table with the numerical values

Meta-analysis have been applied separately for VIRUS ISOLATION, detection of genetic material (DNA/RNA), and detection of virus ANTIGENS in species/matrices combinations where data was available for at least FOUR animal groups. The median minimum and maximum days during which virus/genetic material were detected in other matrices are listed in a table further below.

The plot to the right shows the survival curves with confidence intervals (CI; parametric assumption) for virus isolation. Keep scrolling down to find a table with the exact calculated CI.

Please note: Some data is organized across multiple tabs. If additional tabs are present, click through to explore each slide for a complete view of the data.

The plot to the right shows the survival curves with interquartile ranges (IQ; non-parametric) for virus isolation. Keep scrolling down to find a table with the exact calculated IQ.

Please note: Some data is organized across multiple tabs. If additional tabs are present, click through to explore each slide for a complete view of the data.

The table to the right shows the exact calculated confidence intervals (CI) and interquartile ranges (IQ) accounting for censoring (lack of information about true maximum when experiments ended while the agent was still detectable).

LCL and UCL stand for the lower and upper control limit of a 95% confidence interval accounting for censoring (lack of information about true maximum when experiments ended while virus was still detectable).

N.groups is the number of animal groups from which experimental infection data was available.

The plot to the right shows the survival curves with confidence intervals (CI; parametric assumption) for DNA/RNA detection. Keep scrolling down to find a table with the exact calculated CI.

Please note: Some data is organized across multiple tabs. If additional tabs are present, click through to explore each slide for a complete view of the data.

The plot to the right shows the survival curves with interquartile ranges (IQ; non-parametric) for DNA/RNA detection. Keep scrolling down to find a table with the exact calculated IQ.

Please note: Some data is organized across multiple tabs. If additional tabs are present, click through to explore each slide for a complete view of the data.

LCL and UCL stand for the lower and upper control limit of a 95% confidence interval accounting for censoring (lack of information about true maximum when experiments ended while virus was still detectable)

N.groups is the number of animal groups from which experimental infection data was available.

As pointed out above, meta-analyses were conducted only when data were available for at least four animal groups. Median values for all detection data collected in the systematic literature review (even when no meta-analyses were performed) are reported in the table to the right.

N.groups is the number of animal groups from which experimental infection data was available. The entire dataset can be downloaded through the link on the left panel.

The specific references for this agent, and used in this section are listed in the right panel.

WOAH-prescribed tests for epizootic haemorrhagic disease (WOAH,Terrestrial Manual) are the following:

• For the detection of the agent: Real-time RT-PCR, RT-PCR and isolation in cell culture.
• For the detection of immune response: C-ELISA (serogroup specific), virus neutralization (serotype specific), agar gel immunodiffusion (AGID) and Complement fixation test (CFT).

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).

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.

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).

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.

The figure to the right presents all the results from studies in which thediagnostic sensitivitywas actually reported. The number of occurrences for each diagnostic test is reported in square brackets. Please note that the range of values might refer to different target species.

The figure to the right presents all the results from studies in which thediagnostic specificity was actually reported. The number of occurrences for each diagnostic test is reported in square brackets. Please note that the range of values might refer to different target species.

Here you can find a summary of the main features of each study:

• RefID: Reference ID (to be used to retrieve full reference in the reference table below)
• Species: in which animal species the diagnostic assays have been tested
• Target: Antigen, Antibody, Nucleic acid or Virus
• Lab test: type diagnostic assays evaluated in the study
• Study type: Cohort, Cross-sectional, Diagnostic test validation, Longitudinal
• Nr tested: number of samples tested within the study. When multiple groups were tested, the range of sample sizes is reported
• Nr positive: number of samples that tested positive. When multiple groups were tested, the range of positive results is reported
• Se: whether an estimate of diagnostic test sensitivity was reported in the article
• Sp: whether an estimate of diagnostic test specificity was reported in the article

This table report the specific references that were used in this section of the disease profile.

Known vectors

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

Vector status estimations

Arthropod species	Vector status	Field results	Laboratory results
Culicoides insignis	Potential		Positive
Culicoides obsoletus s.l.	Potential		Positive
Culicoides scoticus	Potential		Positive
Culicoides sonorensis	Potential		Positive

The map on the right shows the reported presence of midges in primary sources.

The data were collected in the VectorNet project, which covers a geographical scope extending across Europe and the Mediterranean basin. Refer directly to the Scientific Report and the VectorNet resources for further information on disease vectors, including expert opinion.

Visit the Vector control - biting midges for further information on vector control.

*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.

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 next update of the SLR for vaccines is scheduled to be carried out in 2024.

Data were collected from all studies that evaluated the performance of commercial vaccines. For those studies meeting the inclusion criteria, vaccines were classified into the following types:

• Inactivated (dead)
• Live attenuated
• Live recombinant
• Recombinant (subunit vaccines)
• Other

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 2024. 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.

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:

• 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 following metrics are reported (whenever available):

• Percentage of infected hosts
• Host mortality

Please note that having a control group was one of the inclusion criteria for studies to be included in this literature review. The full review protocol 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.

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.

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 Veterinary Agency (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.

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)