Control Tools

• Diagnostics availability

• Commercial diagnostic kits available worldwide

  -Sero-neutralisation tests (SNT) are not the gold standard anymore. Glycoprotein B (gB)-ELISAs are generally more sensitive and also highly specific.-ELISA (gB-blocking, indirect, glycoprotein E (gE)-blocking, gE discrimination BoHV1 with BuHV1)-PCR (conventional and real-time)-Direct or indirect immunofluorescence techniques-Immunoperoxidase staining-Electron microscope examination-Virus isolation in cell culture-Immunohistochemistry

• Diagnostic kits validated by International, European or National Standards

  Indirect, gB-specific and gE-specific blocking ELISAs are used for screening of BoHV-1 antibodies.

  The gE-specific blocking ELISA is of particular interest for the countries that use a DIVA vaccine in order to distinguish vaccinated from infected animals. However, due to the sensitivity values of the available gE-antibody tests false negative results do occur more often than with conventional test systems.

  In IBR free countries cross reaction of gB blocking and indirect ELISAs has been reported. BoHV-2 infection could be the cause of this cross reactivity (Böttcher et al., 2012). A second gB test, usually a cELISA gB or a SNT are used as confirmatory tests. An indirect BoHV-2 ELISA is now also available.

  However, gE-ELISAs are very specific and cross reactivity with non-BoHV-1 is very low.

  Bulk milk testing with gE blocking ELISA: positive reaction when more than 10-15% herd infected although the sensitivity can be increased by milk concentration protocols (Schroeder et al., 2012). An indirect gE ELISA with concentration (detection limit: one strong positive in a pool composed of 40 samples) is now available.

  Indirect ELISAs optimised for use with bulk milk samples of up to 50 individual cows (or up to 100 animals in BoHV-1-free regions) can indicate reliably the BoHV-1 status of these animals. These test systems are able to detect one weak positive sample in a pool of 50 milk samples or one strong positive milk in a pool composed of 100 samples.

  GAPS :

  An independent confirmatory test for the presence of gE-specific antibodies using different protocols does not exist. The development of an independent and sensitive confirmatory test would be an important advance.

  Cross reaction with gB ELISAs should be investigated.

  Creation of IBR standards for serum or milk

  • Validation of pooled serum: define numbers that can be defined for pooling serum.
  • Definition of Limit of detection (LOD) of kits re bulk samples, individual serum and milk for ELISA.
  • Commission Delegated regulation (EU) 2020/689:
    • Serum pool: detection limit of one weak positive.
    • Milk pool conv: max. pool size 100 = one strong positive.

  Milk pool gE: one strong positive as detection limit.

• Diagnostic method(s) described by International, European or National standards

  Yes. In France and Germany as in other European countries, the national reference laboratory (NRL) performs the control of commercial ELISA kit, batch to batch, according to an in-house developed process. Nevertheless, the AFNOR (French association for the normalization) currently works to implement a standard for the control and validation of ELISA kits.

  In Belgium, France and Germany and other countries, all ELISA kits have to be licensed by the NRL. Every batch is tested before release.

  The European standard serums (strong positive, weak positive and negative serum: EU1, EU2 and EU3 respectively) are used, as well as national standard samples, for the control of diagnostic kits. More and more national laboratories develop their own standards and references based on the international reference samples. The OIE laboratories in Germany and UK as well as the French NRL provide a wide range of reference materials like sera, milk samples and virus strains. German reference samples are internationally distributed. However, there is a need for modern OIE standards, that are widely available for NRLs (instead of EU1, EU2 and EU3).

  A test for differentiating BHV-1 serology from BuHV-1 seroconversion is now available. SNT can be used for supporting the ELISA test results.

  GAPS :

  There is a need to implement a harmonized process to verify the performance characteristics of test kits batches (indirect-, gB-blocking, gE-blocking ELISAs) used for routine laboratory diagnosis. There is also a need for the data exchange about the batch release results in the different countries.

  There is need to prepare additional reference samples e.g. of critical lyophilized serum (and milk) samples taken from infected as well as from vaccinated or vaccinated and subsequently infected animals. The panel of national and international (OIE) primary standards (gold standards) should be used and possibly distributed by the responsible laboratories at a national and international (OIE) level.

  The primary standards should be used to validate newly developed tests and to harmonise tests between responsible laboratories at a national level.

  Obtaining positive control milk sample is problematic and potentially serum-spike negative milk samples could be used. It is challenging to get EU2 milk samples for IBR Ab testing, currently only obtained through diluting strong milk positive with serum. Alternative processes should be investigated.

• Commercial potential for diagnostic kits in Europe

  High, especially in countries which have eradication programs running.

  GAP :

  Low, diversity of commercial tests available.

• DIVA tests required and/or available

  DIVA gE ELISA tests available to differentiate vaccinated from infected animals.

• Vaccines availability

• Commercial vaccines availability (globally)

  At the moment, there are live, attenuated or inactivated IBR vaccines available in Europe. They can be administered intramuscularly, subcutaneously or intranasally and are mostly used strategically, either to prevent clinical signs (e.g. in a feedlot) or in pursuit of eradication.

  One initial dose with annual boosters is adequate for cattle over three months of age. If younger calves are vaccinated, for example before transport to another farm, two doses, at a three to five week interval, should be given. Vaccination is approved from 2 weeks of age. Marker vaccine allows testing to differentiate between the immune reaction elicited by the vaccine and exposure to the virus.

  GAPS :

  Vaccines schemes should be further proven and compared (e.g. the use of modified live or inactivated preparations).

  The calf vaccination scheme should consider the presence of maternal immunity resulting from immunisation with marker vaccination. Booster vaccination at approximately 4 months of age is necessary following the latest data.

• Marker vaccines available worldwide

  In many European member states, the use of conventional vaccines is no longer permitted. gE-deleted vaccines were recently approved in the U.S. and are probably also available in other countries.

  In Europe, several products are licensed by a number of companies. Licensed vaccines include:

  • live gE negative vaccines,
  • inactivated gE negative vaccines,
  • inactivated recombinant gE negative vaccines,
  • inactivated vaccines,
  • glycoprotein E (gE)- and thymidine kinase (TK)-deleted modified live vaccines.

• Effectiveness of vaccines / Main shortcomings of current vaccines

  There are now multiple vaccine regimes for young and older animals and varying in the number of booster vaccinations and the (un)combined used of live and inactivated vaccines.Live-attenuated vaccines are administered either in one injection or two at a three to five weeks interval in a primary course. They can be used intranasally in calves. Inactivated vaccines require two administrations, three to five weeks apart, in a primary course. Booster vaccinations every 6 months thereafter. Some vaccines are licensed to provide immunity for 12 months. Special vaccination courses with live and inactived vaccines according to the summary of product characteristics (SPC). BoHV-1-vaccines can either be used for the reduction of clinical signs and on the repression of wild type BoHV-1 (in the absence of an eradication programme), to prevent reactivation and transmission and to reduce subclinical production losses.

  Furthermore, the live DIVA vaccines have been reported to become latent, and can be reactivated. The frequency of reactivation in the field is probably low and depends also on the site of injection (intramuscular or subcutaneous injection is less likely to be involved with latency and reactivation than intranasal application).

  Conventional vaccines should not be used any more, since no advantages over marker vaccines could be shown.

  Live marker vaccines should not be administered intra-nasally but intramuscularly, especially if the farm is becoming gE-antibody free, to avoid the shedding and spread of gE-deleted virus.

  Inactivated vaccines are recommended for infected animals. In infected holdings only vaccination of the whole herd is highly effective. Single animal immunization should be avoided.

• Commercial potential for vaccines in Europe

  There is a substantial market for both live and inactivated (marker) vaccines including countries and regions where vaccination forms an important element of compulsory eradication programmes.

• Regulatory and/or policy challenges to approval

  None unless genetically manipulated vaccines which may pose a problem in some countries. Some countries may be reluctant to use live virus vaccines, but alternatives are available.

  GAP :

  Recombinant gE-vaccines have to be licensed by EMA. A first GMO vaccine is available in the EU.

• Commercial feasibility (e.g manufacturing)

  Feasible.

• Opportunity for barrier protection

  Not applicable

• Pharmaceutical availability

• Current therapy (curative and preventive)

  As with other viral diseases, there is no direct treatment for the infection. Antibiotic treatment of secondary infections may be necessary. Since there are no antiviral agents commercially available, treatment of IBR is symptomatic. During an outbreak of IBR, sick animals should be identified and isolated. Very often live vaccines are used for emergency vaccination in IBR outbreaks.

• Future therapy

  In BoHV-1-free countries, infected animals are slaughtered or euthanized and there is no need for treatment.There might be an interest to use antivirals (anti-herpesvirus compounds) to face BoHV-1 outbreaks in free herds and countries, where vaccine is no longer used and not available. So far, the development of such antivirals retained low attention. Compounds developed against human herpesviruses could be screened for their activity against BoHV-1. However, their use will depend on a relatively low cost of production, which is not the case at the moment. The cost of the guanine analogues for large animal treatment is prohibitively high in this context. Moreover, Maximum Residue Limits (MRL) have to be established when using any pharmaceutical in food producing animals and this raises development costs considerably.

• Commercial potential for pharmaceuticals in Europe

  An antiviral may have a place in future as well as other agents that have a disease mitigating effect at low cost.

• Regulatory and/or policy challenges to approval

  Establishment of MRLs.

• Commercial feasibility (e.g manufacturing)

  Not applicable at present.

• New developments for diagnostic tests

• Requirements for diagnostics development

  There is a need for an independent confirmatory test for the gE ELISA.Non-specific reactions in the gE ELISA of multiple DIVA vaccinated animals have been observed.There is a need to address possible non-specific activity in commercially available gB blocking tests used in free states, regions or units.

  As a consequence of anomalous results in high value or export animals, and the need to detect SNLC calves, a better means of determining the true virus status of “doubtful” animals is required.

  In regions with a low BoHV-1-prevalence non-specific BoHV-1-ELISA results are problematic. In most cases single animals are detected as gB-ELISA or indirect ELISA reactors. Other herpesvirus-infections like BoHV-2 could be a possible reason. Therefore, differentiating assays (including multiplex ELISA tests) and test schemes should be developed.

  GAPS :

  Create a harmonised platform to share information about ELISA kits, batches for gB, gE, whole virus ELISA.

  Standardise protocols for SNT, PCR. International proficiency tests have driven harmonisation of these methods; OIE and leading NRLs should alternately organize ring tests for European NRLs.

  Standardise pooling strategies from serum and milk as well as

  Limit of detection (LOD) when testing bulk milk samples.

  Study in depth cross-reactions with BHV-2 and/or BHV-4 tests.

  Validation of each test batch, and batch release tests have to be implemented.

• Time to develop new or improved diagnostics

  Specificity and sensitivity of the available tests is already very high. Focus to improve diagnostics should be on harmonisation.

• Cost of developing new or improved diagnostics and their validation

  If reagents for test setup and especially field samples for test validation are available, which likely will be the case, then costs are low. If reagents as well as samples have to be generated costs will be much higher.

• Research requirements for new or improved diagnostics

  A confirmatory test for the gE ELISA could be helpful.

  GAP :

  In depth study of cross-reactions of conventional BHV-1 tests with BHV-2 and/or BHV-4 or other (yet unknown) herpesviruses.

• Technology to determine virus freedom in animals

  Marker vaccines and marker diagnostics.

• New developments for vaccines

• Requirements for vaccines development / main characteristics for improved vaccines

  Marker vaccines might be further improved.

  However, the existing vaccines are in general able to repress wild type virus and are a suitable tool to allow BoHV-1 eradication in regions with a high BoHV-1 prevalence.

  Potential further developments include:

  • Adjuvanted live attenuated vaccines for long lasting immunity (Kalthoff et al., 2010).
  • Vaccines which provide a longer duration of immunity.

  GAP :

  RNA vaccines could be further investigated together with screening of adjuvants.

• Time to develop new or improved vaccines

  Variable because of research time needed, but at least 4-5 years.

• Cost of developing new or improved vaccines and their validation

  High, not only because of research but also because of extensive animal studies needed for registration. However, the market size is substantial.

• Research requirements for new or improved vaccines

  Again, DIVA vaccines with a higher efficacy, i.e. inducing long term protection (> 1 year), and not becoming latent, would be a significant improvement to currently available vaccines.Research should be focussed on immunological aspects of interaction of BHV1 with the host immune system e.g. on viral genes down regulating the host immune system; immunomodulation (adjuvants, cytokines etc.), vaccine application, and factors involved in latency.Obviously, this involves multidisciplinary cooperation between universities, research institutes and industry.

• New developments for pharmaceuticals

• Requirements for pharmaceuticals development

  In general, there is no need for the development of antivirals to control BoHV-1 effectively.

• Time to develop new or improved pharmaceuticals

  Difficult to assess but could involve many years to develop, screen and obtain authorisation for use.

• Cost of developing new or improved pharmaceuticals and their validation

  Difficult to assess but would be very expensive.

• Research requirements for new or improved pharmaceuticals

  No high priority.

Disease details

• Description and characteristics

• Pathogen

  Infectious bovine rhinotracheitis / infectious pustular vulvovaginitis (IBR/IPV), sometimes called Red nose, is an infectious disease of cattle due to bovine herpesvirus-1 (BoHV-1). The virus can infect mainly the upper respiratory tract or the reproductive tract. BoHV-1 belongs to the order Herpesvirales, family Herpesviridae, subfamily Herpesvirinae, genus Varicellovirus. The virus has a double-stranded DNA genome of about 140 kb. The viral encodes for about 70 proteins, of which 33 structural and up to 15 non-structural proteins have been demonstrated. The viral glycoproteins, which are located in the envelope on the surface of the virion, play an important role in pathogenesis and immunity.

• Variability of the disease

  Restriction fragment length polymorphisms (RFLPs) were detected within BoHV1.1 and BoHV1.2 genomes using several restriction endonucleases. The genomic areas of these changes have not been previously reported. Partial sequencing of the genome is able to point out nucleotide substitutions between the two sub-types BoHV1-1 and BoHV-1.2. BoHV-5 responsible for bovine herpesvirus encephalitis was previously considered as subtype 3 of BoHV-1. It was now assigned to a distinct viral species. Several ruminant alphaherpesviruses are closely related, both genetically and antigenically, to BoHV-1: caprine herpesvirus 1 (CpHV-1), reindeer herpesvirus (CvHV-2) red deer herpesvirus (CvHV-1), buffalo herpesvirus (BuHV-1), elk herpesvirus (ElkHV-1). The natural host of BoHV-1 is the bovine species, although the virus was found to infected naturally goat, sheep, water buffalo, o.a. There are numerous species of ruminants that can be seropositive to BoHV-1 although it remains unclear if this sero-positivity is due to BoHV-1 or infection with another related alphaherpesvirus.

  GAPS :

  Develop herpesvirus-species specific serological tests.

  Use next-generation sequencing-based whole-genome sequencing and metagenomics for detailed genome analyses.

  Use modern real-time PCRs (qPCRs) for diagnostics (also differentiating marker vaccine strains or other bovine herpesviruses)

• Stability of the agent/pathogen in the environment

  BoHV-1 is an enveloped virus and has a moderate resistance in the environment.

• Species involved

• Animal infected/carrier/disease

  BoHV-1 infects cattle where it establishes a latent infection typically in the neurons of sensory ganglia, especially trigeminal ganglia. Latency was also demonstrated in the tonsils. The host range was already considered in the section “Description and characteristics - Variability of the disease”. However BoHV-1 associated disease is only observed in cattle. Infection in other ruminants is subclinical.There are reports showing that cattle is susceptible to BuHV-1 by experimental infection and by contact with infected buffalo Maidana et al 2016). In addition, buffalo is susceptible to BoHV-1 (Fusco et al 2015); both of which would have potential implications in mixed farms.

  GAP :

  There is little information available on virus reactivation under different circumstances- frequency, duration, levels of shedding. This would be very useful for disease modelling.

• Human infected/disease

  No.

• Vector cyclical/non-cyclical

  None.

• Reservoir (animal, environment)

  Bovidae. There is no proof of another domestic or wild ruminant reservoir, although BoHV-1 can establish latency in other species like goat and sheep.

  GAP :

  The susceptibility of some species (e.g. buffalo) to infection has not been fully explored.

• Description of infection & disease in natural hosts

• Transmissibility

  Transmission occurs mainly through direct and indirect contact (over a short period of time). It is estimated that approximately 50 percent of the adult cattle population has had experience with this infection in endemic situations. Wherever cattle are confined, or groups are permitted to commingle as in feedlots and collection points, the disease is rapidly spread to new arrivals from cattle already infected or those recovered latent carriers that serve as virus reservoirs and shedders of infection. IBR infection is spread primarily by contact transmission. Transplacental transmission is efficient after primary infection of a naive pregnant cow and may result in abortion. Another method of spread is venereal and by artificial insemination using contaminated materials. Under closed herd conditions, spontaneous and uncontrolled reactivation of BoHV-1 from a latent carrier, usually detectable by serology, can lead to virus circulation and virus spreading among the animals. Cases of BoHV-1 reactivation from a latent carrier are mostly stress-related (e.g. transport, social stress, other diseases such as BVD, etc.)

  GAPS :

  Abortion seems to be a relatively uncommon outcome of infection in Europe relative to elsewhere. It would be useful to have more information on this.

  Knowledge on R0 under different circumstances (herd type, ages, housed, at pasture, virus strain, …). This would be very useful for disease modelling.

• Pathogenic life cycle stages

  Not applicable.

• Signs/Morbidity

  Clinical signs of IBR, the respiratory form of BoHV-1 infection, are: an initial high fever accompanied by a red nose (inflammation of the muzzle and nostrils) and very often conjunctivitis. There is loss of appetite, depression, difficult or rapid respiration, and a profuse nasal discharge. The nasal discharge progresses from clear and watery to a sticky, yellow discharge that hangs in long strands from the nose.Usually there is an early clear, watery discharge from the eyes, which later becomes sticky as the inflammation of the eyelids develops. IBR is usually a herd infection with all animals in the group involved. Since only the upper respiratory tract involving the nasal turbinates, sinuses, pharynx, larynx, and trachea are affected, a dry, non-productive hacky cough is noted. Death is uncommon unless the disease is complicated by secondary infections due to the stresses of a severe winter or unusually hot weather. BoHV-1 respiratory outbreak can be associated with abortion in cows undergoing primary infection.Neonatal calves may develop a systemic disease with respiratory distress, small ulcers of the lining of the forestomaches, and peritonitis.Infectious pustular vulvovaginitis and infectious balanoposthitis can also occur, although has become rare in Europe.Often there are subclinical infections. Individual health aspects or housing conditions may determine the outcome of infection (clinical/subclinical). Virus strains with increased virulence have not been described.

  GAP :

  Need for more information on the role of BoHV-1 in abortions.

• Incubation period

  The incubation period is usually 4 to 6 days with the entire herd progressively involved and the infection lasting for 10 to 14 days.

• Mortality

  Mortality is low but the economic loss can be important due to subclinical infections.

• Shedding kinetic patterns

  Virus is shed for a period of 10 to 14 days in the nasal discharge after primary infection and for a shorter period (variable in time) during respiratory re-excretion following reactivation of latent virus. Shedding of the virus can also occur through amniotic liquid, placenta, foetus and semen of infected bulls (with a special concern for untested semen used in artificial insemination as the virus is well conserved in liquid nitrogen).

• Mechanism of pathogenicity

  Initially, this virus replicates in epithelial cells at the portal of entry. The signs of the acute diseases are often associated with the destruction of those epithelial cells. BoHV-1 may spread in the infected host by viraemia, gaining access to a broader range of tissues and organs, and especially reaching the placenta and the foetus in pregnant cow. BoHV-1 enters neuronal cells, establishing latent infection but, in rare occasions, also, acute and replicating infection leading to encephalitis. During latency, apparently no viral antigens are synthesized but the genomes of the latent viruses are present in the nuclei of long-living cells, e.g., neurones of the ganglia corresponding to the sites of peripheral replication. Upon reactivation, the virus re-establishes the lytic cycle of replication. Shielded from the effectors of the immune system, they migrate back to the peripheral tissues where they are re- excreted and may be transmitted. Although a strong immune response is provoked during primary viral replication, these mechanisms help the herpesviruses to escape from immune surveillance during latency and to a lesser degree during reactivation. It has been observed that certain herpesviruses may behave differently upon infection of different hosts.

• Zoonotic potential

• Reported incidence in humans

  None.

• Risk of occurence in humans, populations at risk, specific risk factors

  Not applicable.

• Symptoms described in humans

  Not applicable.

• Likelihood of spread in humans

  Not applicable.

• Impact on animal welfare and biodiversity

• Both disease and prevention/control measures related

  Affected animals should be isolated and treated to protect them from secondary bacterial infections, preferably with broad-spectrum antibiotics.

• Endangered wild species affected or not (estimation for Europe / worldwide)

  No.

• Slaughter necessity according to EU rules or other regions

  Generally none, but if the country is a Member State of the EU it may have an eradication programme as defined by the Commission Delegated Regulation (EU) 2020/689 (Chapter 2, Section 2). In that case slaughter will depend on the eradication programme. Positive animals were slaughtered in the Article 10 countries (the latest area receiving the article 10 status was Germany in June 2017 after a consequent detection, vaccination and slaughter programme).

• Geographical distribution and spread

• Current occurence/distribution

  Endemic, worldwide in the cattle population. Not present in countries or regions such as Austria, Bolzano (Italy), Denmark, Sweden, Finland, Switzerland, Germany etc. which have eradication programmes as specified under the new Animal Health Law.

• Epizootic/endemic- if epidemic frequency of outbreaks

  Endemic, worldwide in the cattle population in regions where there are no eradication programmes.

• Speed of spatial spread during an outbreak

  High to medium and may depend on strain differences.

  GAP :

  Assessment of transmissibility and R0 for different strains.

• Transboundary potential of the disease

  High, via the movement/trade of cattle and semen, if no diagnostic control is applied. Transmission by clinically inconspicuous carriers upon reactivation.

• Route of Transmission

• Usual mode of transmission (introduction, means of spread)

  After infection, nasal and ocular viral shedding is detected for 10-14 days. It is also present in amniotic liquid, placenta, foetus and semen of infected bulls. Transmission occurs through aerosols, contact direct and indirect (over short period of time) and artificial insemination.

• Occasional mode of transmission

  Intermittent recurrence of virus shedding occasionally occurs long after apparent recovery, indicating that the virus exists as a latent, reactivatable infection.

• Conditions that favour spread

  Latent infection, intercurrent disease and herd management practices (e.g. housing/close contact, mixing of animals), stress, birth.Absence of a stringent control programme.

• Detection and Immune response to infection

• Mechanism of host response

  Immunity to BoHV-1 is very complex. It involves local and systemic antibody production (humoral immunity) and cell-mediated immunity. The level of humoral antibody has been used as an indicator of previous infection, but the levels of antibodies are not indicative of resistance to disease because the cell mediated immunity may provide protection even if the antibody levels are low. Notably, calves acquire colostral antibodies that offer a good protection to the disease but not to viral infection. It is possible that this maternal antibody may interfere with successful vaccination of the calf as the passive immunity may persist for 6 months and sometimes longer. This however, is unlikely when live vaccines are used. Nutrition also plays a role in the calves’ ability to mount an immune response. For example, if the calf is deficient in B vitamins, its humoral response may be depressed.An infection normally elicits an antibody response and a cell-immune response within 7–10 days. The immune response is presumed to persist for life.

• Immunological basis of diagnosis

  Antibodies detection via SNT and various indirect and blocking ELISAs.

• Main means of prevention, detection and control

• Sanitary measures

  • Closed herd policy.
  • Purchase of replacement stock from herds certified free of IBR.
  • Quarantine all added animals for at least 4 weeks and test them for IBR antibodies before inclusion into the main herd, noting that seroconversion to gE may take longer than seroconversion to gB/whole virus.
  • Avoid direct or indirect contact with cattle from potentially infected farms (shows, markets, contact over fences, rented grazing, hired bulls, etc.).
  • Do not allow the introduction of disease via technicians, vets, hoof trimmers, visitors etc. (e.g. dedicated footwear and protective clothing for people who enter cattle housing) and limit access to essential visitors only.
  • Isolate delivery and pick-up points for trucks from cattle.

• Mechanical and biological control

  Vaccines and marker vaccines. (gE-deleted vaccines; live or inactivated).

• Prevention through breeding

  Not applicable.

• Diagnostic tools

  Seroneutralisation (SNT)

  Retrospective diagnosis of BoHV-1 infection can be made by measuring antibody titres in paired sera samples. First sample is collected during the clinical phase and a second sample is collected 4 weeks later for the detection of a specific seroconversion.

  ELISA

  There are BoHV-1 indirect and blocking ELISA tests currently available. Seroconversion can also be detected by ELISA. The use of marker vaccines is important in the differentiation of infected and vaccinated animals that can be made by the simultaneous use of ELISA detecting whole virus or glycoprotein B antibodies and ELISA detecting glycoprotein E antibodies.

  Negative gE- or gB-ELISA bulk milk test should be followed up with individual blood samples from all cattle in the herd. Indirect ELISAs optimised for use with bulk milk samples of up to 50 individual cows (or up to 100 animals in BoHV-1-free regions). These test systems are able to detect one weak positive sample in a pool of 50 milk samples or one strong positive milk in a pool composed of 100 samples.

  BoHV-1-free regions with single animals showing non-specific reactivity or cross reactivity in gB ELISAs have been reported:gE-ELISAs and SNTs should be used to further verify such singleton reactors.Recommended to repeat testing of those animals after 28 days in a gE-ELISA using a lower cut-off (e.g. positive/negative of 0.95) to increase the sensitivity. In the case of two negative gE-ELISA results, the animal is not classified as BoHV-1-positive, but it is recommended to slaughter the animal as diagnostic problems with other test systems may still occur (e.g. positive bulk milk results of the affected herd).

  In addition, nonspecific reactions are reported in gE ELISAs, which is due to batch variation, samples that are tested to soon after collection, or within 4 weeks after vaccination with a marker vaccine.

  GAPS :

  A further harmonisation of serological tests in Europe (EU ring trial) is needed.

  Strict evaluation of sensitivity and specificity of whole virus, gB and gE ELISA and this for different matrices (serum, milk, pooled samples).

  Reference sera and common standards (EU1, EU2, EU3).

  No OIE standards available, but national standards (e.g. Germany: R1, R2, R3 and also milk reference samples).

  Problem of unintended contact with a gE-deleted vaccine (contaminated syringes etc.).

  “Pseudovaccinees”: unvaccinated animals which are gB-ELISA positive and gE-ELISA negative.

• Vaccines

  Live-attenuated and inactivated vaccines are commercially available. Various sub-unit and vectored vaccines have been tested experimentally. Marker vaccines (gE-deleted) are commercially available.

• Therapeutics

  As with other viral diseases, there is no direct treatment for the infection. Antivirals were not developed specifically to BoHV-1 although some have been tested successfully experimentally. Antibiotic treatment of secondary infections may be necessary.

• Biosecurity measures effective as a preventive measure

  It is extremely important to establish efficient biosecurity measures in particular adequate quarantine periods. Effective (pre- or post-purchase) quarantine prevents the introduction of the virus into the main herd. Replacement animals for the farm should be sourced from herds that are free of the disease but nevertheless such animals should be submitted to a period of quarantine during which they should be tested for BoHV-1 and observed for the presence of any clinical signs. Paired serology with a 3-4-week interval should be performed. Animals that are sero-positive for BoHV-1 should never be released into the herd from quarantine as they must be regarded as lifelong potential shedders of the virus. Marker-vaccinated cattle have BoHV-1 antibodies (SNT, gB-ELISA, indirect ELISA), but are negative in gE-ELISA tests. These animals should be avoided in BoHV-1-free farms since there can raise problems with diagnostics using indirect ELISAs and pooled milk samples. BoHV-1 control programmes should differentiate “gE-antibody” free animals vs BHV-1-antibody-free cattle.

  In European states where IBR control is applied, these biosecurity measures have been well developed.

• Border/trade/movement control sufficient for control

  High constraints on trade because of movement control.

  From April 2021, Council Directive 64/432/EEC on animal health problems affecting intra-Community trade in bovine animals and swine has been replaced by Regulation EU 2016/429, (“Animal Health Law”). The Delegated Regulation (EU) 2020/689 provides for transitional arrangements for countries/regions with recognised free status or approved eradication programmes and details the basis on which programmes may now be approved and freedom recognised.The diagnostic methods for granting and maintaining disease-free status of IBR are laid down in section 4 of Annex III of the regulation EU 2016/429 of the European Parliament and the Council laying down rules for surveillance, eradication programmes and disease freedom for certain listed and emerging diseases.The disease-specific requirements for the granting, maintenance, suspension and withdrawal of the disease-free status is laid in annex IV , part IV, chapters 1 and 2: SANTE/7066/2019-EN ANNEX CIS Rev, 2 (europa.eu)

• Prevention tools

  The prevention and control of IBR is based either on preventing the virus from entering the herd or on vaccination. Several European countries have eradicated or are in the process of eradicating IBR.

  • Implement a closed herd policy.
  • If necessary, purchase replacement stock from herds certified free of IBR (i.e. accredited herds).
  • Quarantine all added animals for 4 weeks and test them for IBR antibodies before inclusion into the main herd.
  • Avoid direct or indirect contact with cattle from potentially infected farms (shows, markets, contact over fences, rented grazing, hired bulls, etc.). Talk to your neighbours.
  • Do not allow the introduction of disease via AI technicians, vets, hoof trimmers, visitors etc. (e.g. dedicated protective clothing and footwear for people who enter cattle housing) and limit access to essential visitors only.
  • Isolate delivery and pick-up points for trucks from cattle.

  Screening, eradication and accreditation

  It has also been shown that in closed herds the virus circulates from infected to non-infected animals, and disease eradication has been successfully carried out in beef herds by segregating the seropositive and sero-negative animals, but the risk of virus transfer by humans or inanimate vectors is high.

• Surveillance

  Screening.

• Past experiences on success (and failures) of prevention, control, eradication in regions outside Europe

  Eradication programmes are running in several countries. IBR/IPV has been eradicated during the nineties from a few European countries, e.g. Austria, Denmark, Finland and Sweden, and the autonomous region of Bolzano (Italy), and the disease-free status of these countries was last confirmed by the EU Commission in 2004. Switzerland, Norway and Germany are now also recognized as being free of the disease. These countries do not vaccinate against IBR/IPV.

  The production of semen is governed by EU rules affecting bulls on approved EU bull studs and mean that these animals must have no antibodies to BHV1, i.e. following infection with BHV1 or following use of any IBR vaccine (conventional or marker vaccine).

• Costs of above measures

  Not specified.

• Disease information from the WOAH

• Disease notifiable to the WOAH

  IBR is an OIE listed disease.

• WOAH disease card available

  No.

• WOAH Terrestrial Animal Health Code

  Link to OIE.

• WOAH Terrestrial Manual

  Link to OIE.

• Socio-economic impact

• Zoonosis: impact on affected individuals and/or aggregated DALY figures

  Not applicable.

• Zoonosis: cost of treatment and control of the disease in humans

  Not applicable.

• Direct impact (a) on production

  Medium to high, linked to morbidity and rarely mortality.

  GAP :

  Need for greater study of the economic impact of clinical and subclinical infection in various herd types and in particular in beef systems.

• Direct impact (b) cost of private and public control measures

  Cost of treatment can be high when secondary bacterial infections in the respiratory tract occur.

• Indirect impact

  High trade impact due to latent infection of breeding animals (live animals, frozen semen). General movement restrictions as well as a lower price for positive animals (in some regions; also for the export of cattle to third countries) has to be taken into consideration. In BoHV-1-free regions high costs for replacement of slaughtered/ culled cattle after a new outbreak.

• Trade implications

• Impact on international trade/exports from the EU

  High impact on trade between IBR-free countries and seropositive countries.

• Impact on EU intra-community trade

  High. Infectious Bovine Rhinotracheitis (IBR) is a OIE listed disease under EU legislation. A state or region that is certified IBR free) can limit trade and movement of cattle from areas that are not, by insisting on evidence of IBR freedom and blocking the importation of seropositive animals. Currently Sweden, Finland, Denmark, Austria, Bolzano province in Italy, and Germany are IBR free. Areas with EU approved national eradication schemes may also be able to impose restrictions.

• Impact on national trade

  Low in countries without mandatory control programme; high in countries and regions with an official control/eradication scheme.

• Main perceived obstacles for effective prevention and control

  Sero-negative latent BoHV-1 carriers (SNLC) have been experimentally demonstrated. Their importance for eradication is low due to the experiences in the countries with Article 10 status..

  However, recent evidence from IBR (IPB) outbreaks at 2 UK bull studs indicates that SNLC calves were the source of the infections. The policy of purchase of young bulls with maternal antibody to BoHV-1 presents an as yet unquantified risk of introducing SNLC calves into the stud.

  A confirmatory test for the presence of antibodies to gE, using a different principle than the currently used ELISA, does not exist. The development of such a confirmatory test would be an important advance for establishing the status of animals giving borderline responses in the gE ELISA. And would be of great advantage in eradication programs using gE based DIVA vaccines.

  Some problems have been observed with apparently anomalous or ambiguous results with commercially available gB blocking assays. In BoHV-1 free states, regions and units these assays are used for front line surveillance and certification purposes. The reasons for the anomalous results are unclear at the moment, although it is suspected that cross reactions with other bovine or ruminant herpesviruses may be responsible. In addition to potential loss of EU free status, the anomalies may result in significant extra costs in loss of production, costs of isolation facilities, extra bleeding/testing requirements and unnecessary culling.

  GAP

  Develop non invasive tests to detect sero-negative carriers The contribution of other ruminants to the epidemiology of viruses related to BoHV-1 is small but should not be discounted in unexplained outbreaks in cattle, particularly relating to goats, sheep, water buffalo, and wild ruminants.Additional test should be developed, allowing the detection of BoHV-1-specific antibodies with a high sensitivity and specificity, which are different from the gB-ELISAs (e.g. gC-ELISA or gG-ELISA or gD-ELISA). This kind of assays could allow the classification of unvaccinated gB-positive and gE-negative animals.

• Main perceived facilitators for effective prevention and control

  There is the need for diagnostic tests of higher sensitivity and specificity than the currently used gE blocking ELISA, for alternative gE-ELISAs as well as confirmatory tests.

  A gE assay with an improved sensitivity for bulk milk samples would facilitate marker vaccine control/eradication in dairy herds. There is a new cleaning kit

  which allows the use of pooled milk samples to be used in the gE-ELISA (LDL, Leipzig, Germany

• Links to climate

• Seasonal cycle linked to climate

  No. Seasonal variation in incidence is due to the management practice of assembling feedlot cattle rather than due to any true seasonal variance. In Europe, autumn and early winter are usually associated with a higher incidence of infectious respiratory diseases in calves where BoHV-1 can be one of the etiological agents. This is likely due to husbandry changes (e.g. housing with greater proximity between animals).

• Distribution of disease or vector linked to climate

  No.

• Outbreaks linked to extreme weather

  No.

• Sensitivity of disease or vectors to the effects of global climate change (climate/environment/land use)

  Not applicable.

• Main perceived obstacles for effective prevention and control

  Sero-negative latent BoHV-1 carriers (SNLC) have been experimentally demonstrated. Their importance for eradication is low due to the experiences in the countries with Article 10 status.

  However, recent evidence from IBR (IPB) outbreaks at 2 UK bull studs indicates that SNLC calves were the source of the infections. The policy of purchase of young bulls with maternal antibody to BoHV-1 presents an as yet unquantified risk of introducing SNLC calves into the stud.

  A confirmatory test for the presence of antibodies to gE, using a different principle than the currently used ELISA, does not exist. The development of such a confirmatory test would be an important advance for establishing the status of animals giving borderline responses in the gE ELISA, and would be a great advantage in eradication programmes using gE based DIVA vaccines.

  Some problems have been observed with apparently anomalous or ambiguous results with commercially available gB blocking assays. In BoHV-1 free states, regions and units these assays are used for front line surveillance and certification purposes. The reasons for the anomalous results are unclear at the moment, although it is suspected that cross reactions with other bovine or ruminant herpesviruses may be responsible. In addition to potential loss of EU free status, the anomalies may result in significant extra costs in loss of production, costs of isolation facilities, extra bleeding/testing requirements and unnecessary culling.

  GAPS :

  Develop non-invasive tests to detect sero-negative carriers. Difficulty is that the sites of latency are the trigeminal ganglia deep in the scull of the animal. Moreover, levels of LATs (latency associated transcripts) are low and undulating.

  Further work needed to quantify the frequency and impact of sero-negative carriers on disease transmission.

  The contribution of other ruminants to the epidemiology of viruses related to BoHV-1 is small but should not be discounted in unexplained outbreaks in cattle, particularly relating to goats, sheep, water buffalo, and wild ruminants.

  Additional test should be developed, allowing the detection of BoHV-1-specific antibodies with a high sensitivity and specificity, which are different from the gB-ELISAs (e.g. gC-ELISA or gG-ELISA or gD-ELISA). This kind of assays could allow the classification of unvaccinated gB-positive and gE-negative animals.

Global challenges

• Antimicrobial resistance (AMR)

• Mechanism of action

  Not Applicable.

• Conditions that reduce need for antimicrobials

  Effective control of IBR through vaccination and ultimately eradication will in turn reduce antimicrobial use and therefore development of resistance (prevention is better than cure).

• Alternatives to antimicrobials

  Vaccination.

• Impact of AMR on disease control

  No direct impact on IBR, given that it is a viral condition against which antibiotics are not effective.

• Established links with AMR in humans

  Not Applicable.

• Digital health

• Precision technologies available/needed

  Collection of data in special health databases (in Germany: HIT database collecting data from all cattle).

  GAP :

  Broader use should be supported.

• Data requirements

  Ear tag numbers, birth dates, selling and movement dates, health data including vaccinations and test results (also for BHV-1).

  GAP :

  Mapping of animal movements in the country and between countries.

• Data availability

  In some countries; Data available at various levels: farmers, veterinarians, official veterinarians.

  GAP :

  More transparency is necessary.

• Data standardisation

  Standardized on a national level.

  GAP :

  Should be standardized at EU level.

• Climate change

• Role of disease control for climate adaptation

  No data available.

  GAP :

  No data available. Research necessary.

• Effect of disease (control) on resource use

  IBR control will increase efficiency of production, which is beneficial in terms of greenhouse gas mitigation, requiring less resource per unit of output.

• Effect of disease (control) on emissions and pollution (greenhouse gases, phosphate, nitrate, …)

  Reducing the morbidity and mortality caused by IBR will in turn reduce the greenhouse gases (GHG) emitted per unit of output, providing an increased efficiency of production. In the scenario where total output remains constant this will deliver an absolute reduction in GHG emissions.

  GAP :

  There is currently a lack of detailed information on morbidity and mortality attributable to IBR specifically and of modelling to apply such data, if available, to GHG abatement.

• Preparedness

• Syndromic surveillance

  Prescribed by law (national and EU).

  GAP :

  Should be continuously updated.

• Diagnostic platforms

  Prescribed by law (national and EU).

  GAP :

  Communal platform to share protocols, controls (standards) and scientific advice between countries.

• Mathematical modelling

  Some models for the spread and efficacy of vaccines are available.

  GAP :

  New models with adapted parameters should be tested.

• Intervention platforms

  Regional, national and EU programmes.

  GAP :

  Gaps in the Animal Health Law have to be detected and considered.

• Communication strategies

  GAP :

  EU reference laboratory for BHV-1 (and BVDV) is missing. Need for establishment of an IBR discussion committee.

Conclusion

• BoHV-1 infections are still of major economic impact in the cattle industry. This not only as an infection of cattle standing on its own, but also as part of the Bovine respiratory disease complex, in which several viruses and bacteria are involved. Currently eradication programmes for BoHV-1 are running in several European countries, where gE negative DIVA vaccines are used in combination with the companion diagnostic gE ELISA test. The currently used DIVA vaccines and the accompanying diagnostic tests have been the basis of successful eradication programmes. In addition, the most important factors in any BoHV-1 eradication programme are farm management factors like separation, marking and fast slaughtering of BoHV-1 positive cattle. Despite this, both the available vaccines and diagnostics can/need to be further improved for more efficient control.

Sources of information

• Expert group composition

  Martin Beer, Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Germany - [Leader];

  Patricia König, Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Germany;

  Laura Garza Cuartero, Department of Agriculture, Food and the Marine, Ireland;

  David Graham, Animal Health Ireland, Ireland;

  Stephen Valas, ANSES, France;

  Stefano Petrini, IZS dell’ Umbria e delle Marche, Italy;

  Torsten Stepping, Zoetis Deutschland GmbH.

• Date of submission by expert group

  22 March 2021.

• References

  Böttcher J., Boje J., Janowetz B., Alex M., König P., Hagg M., Götz F., Renner K., Otterbein C., Mages J., Meier N., Wittkowski G. (2012). Epidemiologically non-feasible singleton reactors at the final stage of BoHV1 eradication: serological evidence of BoHV2 cross-reactivity. Vet. Microbiol., 159, 282–290.

  Fusco G., Amoroso M. G., Aprea G., Veneziano V., Guarino A., Galiero G., Viscardi M. (2015) First report of natural BoHV-1 infection in water buffalo. Vet. Rec. 177, 152.

  Kalthoff D. König P., Trapp S., Beer M. (2010). Immunization and challenge experiments with a new modified live bovine herpesvirus type 1 marker vaccine prototype adjuvanted with a co-polymer. Vaccine 28, 5871-5877.

  Maidana S.S., Delgado F., Vagnoni L., Mauroy A., Thiry E., Romera S. (2016). Cattle are a potential reservoir of bubaline herpesvirus 1 (BuHV1) Vet. Rec. Open 3, e000162.

  Petrini S., Iscaro C., and Righi C. (2019). Antibody Responses to Bovine Alphaherpesvirus 1(BoHV-1) in Passively Immunized Calves. Viruses, 2019, 11(1), 23. https://doi.org/10.3390/v11010023.

  Petrini S., Konig P., Iscaro C., Pierini I., Casciari C., Pellegrini C., Gobbi P., Giammarioli M., De Mia G.M. (2020). Serological Cross-Reactivity Between Bovine alphaherpesvirus 2 and Bovine alphaherpesvirus 1 in a gB-ELISA: A Case Report in Italy. Frontiers in Veterinary Science,https://doi.org/10.3389/fvets.2020.587885

  Petrini S., Righi C., Iscaro C., Viola G., Gobbi P., Scoccia E., Rossi E., Pellegrini C., De Mia G.M. (2020). Evaluation of Passive Immunity Induced by Immunisation Using Two Inactivated gE-deleted Marker Vaccines against Infectious Bovine Rhinotracheitis (IBR) in Calves. Vaccines, 2020, 8(1), 14.https://doi.org/10.3390/vaccines8010014.

  Schroeder C., Horner S., Bürger N., Engemann C., Bange U., Knoop E.V. & Gabert J. (2012). Improving the sensitivity of the IBR-gE ELISA for testing IBR marker vaccinated cows from bulk milk. Berl. Munch. Tierarztl. Wochenschr., 125, 290–296.

  Singer S., Hoffmann B., Hafner-Marx A., Christian J., Forster F., Schneider K., Knubben-Schweizer G., Neubauer-Juric A. (2020). Bovine alphaherpesvirus 2 infections in Bavaria: an analysis of the current situation - several years after eradicating Bovine alphaherpesvirus 1. BMC Veterinary Research, 16: 149, https://doi.org/10.1186/s12917-020-02310-w.

  Valas S., Brémaud I., Stourm S., Croisé B., Mémeteau S., Ngwa-Mbot D., Tabouret M. (2019). Improvement of eradication program for infectious bovine rhinotracheitis in France inferred by serological monitoring of singleton reactors in certified BoHV1-free herds. Preventive Veterinary Medicine, 171, https://doi.org/10.1016/j.prevetmed.2019.104743.

  Infectious bovine rhinotracheitis/infectious pustular vulvovaginitis. Terrestrial Manual OIE – 2018.

Conclusions

• Main perceived facilitators for effective prevention and control

  There is the need for independent confirmatory tests for the presence of gE-specific antibodies using different protocols.

  A gE assay with an improved sensitivity for bulk milk samples would facilitate marker vaccine control/eradication in dairy herds. There is a new concentration kit which allows the use of pooled milk samples to be used in the gE-ELISA.

  A more practical and efficient intra vitam means of determining the true virus status of “doubtful” reactors in high value herds, eg bull studs.Optimization of vaccination schemes i.e. type of marker vaccine, administration route and timing.