Epidemiological performance and subsequent costs of different surveillance strategies to control bovine herpesvirus type 1 in dairy farms

Control and Eradication Programs for Non-EU Regulated Cattle Diseases in the Netherlands

Within the European Union, infectious cattle diseases are categorized in the Animal Health Law. No strict EU regulations exist for control, evidence of disease freedom, and surveillance of diseases listed other than categories A and B. Consequently, EU member states follow their own varying strategies for disease control. The aim of this study was to provide an overview of the control and eradication programs (CPs) for six cattle diseases in the Netherlands between 2009 and 2019 and to highlight characteristics specific to the Dutch situation. All of these diseases were listed as C,D or E in the New Animal Health Law. In the Netherlands, CPs are in place for six endemic cattle diseases: bovine viral diarrhea, infectious bovine rhinotracheitis, salmonellosis, paratuberculosis, leptospirosis, and neosporosis. These CPs have been tailored to the specific situation in the Netherlands: a country with a high cattle density, a high rate of animal movements, a strong dependence on export of dairy products, and a high-quality data-infrastructure. The latter specifically applies to the dairy sector, which is the leading cattle sector in the Netherlands. When a herd enters a CP, generally the within-herd prevalence of infection is estimated in an initial assessment. The outcome creates awareness of the infection status of a herd and also provides an indication of the costs and time to achieve the preferred herd status. Subsequently, the herd enrolls in the control phase of the CP to, if present, eliminate the infection from a herd and a surveillance phase to substantiate the free or low prevalence status over time. The high-quality data infrastructure that results in complete and centrally registered census data on cattle movements provides the opportunity to design CPs while minimizing administrative efforts for the farmer. In the CPs, mostly routinely collected samples are used for surveillance. Where possible, requests for proof of the herd status are sent automatically. Automated detection of risk factors for introduction of new animals originating from a herd without the preferred herd status i.e., free or unsuspected, is in place using centrally registered data. The presented overview may inspire countries that want to develop cost-effective CPs for endemic diseases that are not (yet) regulated at EU level.

Overview of Cattle Diseases Listed Under Category C, D or E in the Animal Health Law for Which Control Programmes Are in Place Within Europe

The COST action “Standardising output-based surveillance to control non-regulated diseases of cattle in the European Union (SOUND control),” aims to harmonise the results of surveillance and control programmes (CPs) for selected cattle diseases to facilitate safe trade and improve overall control of cattle infectious diseases. In this paper we aimed to provide an overview on the diversity of control for these diseases in Europe. A selected cattle disease was defined as an infectious disease of cattle with no or limited control at EU level, which is not included in the European Union Animal health law Categories A or B under Commission Implementing Regulation (EU) 2020/2002. A CP was defined as surveillance and/or intervention strategies designed to lower the incidence, prevalence, mortality or prove freedom from a specific disease in a region or country. Passive surveillance, and active surveillance of breeding bulls under Council Directive 88/407/EEC were not considered as CPs. A questionnaire was designed to obtain country-specific information about CPs for each disease. Animal health experts from 33 European countries completed the questionnaire. Overall, there are 23 diseases for which a CP exists in one or more of the countries studied. The diseases for which CPs exist in the highest number of countries are enzootic bovine leukosis, bluetongue, infectious bovine rhinotracheitis, bovine viral diarrhoea and anthrax (CPs reported by between 16 and 31 countries). Every participating country has on average, 6 CPs (min–max: 1–13) in place. Most programmes are implemented at a national level (86%) and are applied to both dairy and non-dairy cattle (75%). Approximately one-third of the CPs are voluntary, and the funding structure is divided between government and private resources. Countries that have eradicated diseases like enzootic bovine leukosis, bluetongue, infectious bovine rhinotracheitis and bovine viral diarrhoea have implemented CPs for other diseases to further improve the health status of cattle in their country. The control of the selected cattle diseases is very heterogenous in Europe. Therefore, the standardising of the outputs of these programmes to enable comparison represents a challenge.

Review of Infections With Bovine Herpesvirus 1 in Slovenia

In the 1950s, infectious bovine rhinotracheitis/infectious pustular vulvovaginitis (IBR/IPV) disease was clinically detected and documented in cattle for the first time in Slovenia. The bovine herpes virus 1 (BoHV-1) was confirmed several times from infected herds by virus isolation on cell cultures. To keep the IC virus-free, high biosecurity measures were introduced. Before entering the IC, all calves are serologically tested and quarantined. Bulls in Slovenian insemination centres (IC) have been negative for IBR /IPV infection since 1979. From 1985 to 1991, few large-scale studies of the prevalence of IBR/IPV were carried out. In 1985, a high percentage (56.9%) of serologically positive animals were found in large state farms with Holstein Friesian cattle. Epidemiological studies in farm with bulls' mother herds were also carried out in the farms with Simmental and Brown cows. Antibodies against BoHV-1 were detected in the serum of 2.3% of Brown cattle and 3.5% of Simmental cattle. In the year 2000, 3.4% of bulk tank milk samples from 13,349 dairy farms were detected BoHV-1 antibodies positive. The highest percentage of positive animals was found in regions with an intensive grazing system (6.2% positive) and the lowest percentage in the east part of Slovenia (0.9% positive) on farms with mostly Simmental cattle. In 2006, a total 204,662 sera of cattle older than 24 months were tested for the presence of BoHV-1 antibodies and positive cattle were detected in 3.6% of tested farms. These farms kept 34,537 animals that were potential carriers of the BoHV-1. Most of the positive farms kept Holstein Friesian cattle, descendants from the state-owned farms, which were privatised or closed after 1990. In 2015, the Administration of the Republic of Slovenia for Food Safety, Veterinary and Plant Protection issued a rule that describes the conditions for granting and maintaining the status of BoHV-1 free holdings. The rule provides a voluntary control programme for breeders who want to obtain BoHV-1 free status and are willing to cover all the cost of acquiring and maintaining that status. There has been very little response from breeders.

Key Learnings During the Development of a Generic Data Collection Tool to Support Assessment of Freedom of Infection in Cattle Herds

Various European Member States have implemented control or eradication programmes for endemic infectious diseases in cattle. The design of these programmes varies between countries and therefore comparison of the outputs of different control programmes is complex. Although output-based methods to estimate the confidence of freedom resulting from these programmes are under development, as yet there is no practical modeling framework applicable to a variety of infectious diseases. Therefore, a data collection tool was developed to evaluate data availability and quality and to collect actual input data required for such a modeling framework. The aim of the current paper is to present the key learnings from the process of the development of this data collection tool. The data collection tool was developed by experts from two international projects: STOC free (Surveillance Tool for Outcome-based Comparison of FREEdom from infection, www.stocfree.eu) and SOUND control (Standardizing OUtput-based surveillance to control Non-regulated Diseases of cattle in the EU, www.sound-control.eu). Initially a data collection tool was developed for assessment of freedom of bovine viral diarrhea virus in six Western European countries. This tool was then further generalized to enable inclusion of data for other cattle diseases i.e., infectious bovine rhinotracheitis and Johne's disease. Subsequently, the tool was pilot-tested by a Western and Eastern European country, discussed with animal health experts from 32 different European countries and further developed for use throughout Europe. The developed online data collection tool includes a wide range of variables that could reasonably influence confidence of freedom, including those relating to cattle demographics, risk factors for introduction and characteristics of disease control programmes. Our results highlight the fact that data requirements for different cattle diseases can be generalized and easily included in a data collection tool. However, there are large differences in data availability and comparability across European countries, presenting challenges to the development of a standardized data collection tool and modeling framework. These key learnings are important for development of any generic data collection tool for animal disease control purposes. Further, the results can facilitate development of output-based modeling frameworks that aim to calculate confidence of freedom from disease.

A survey of biosecurity measures and serological status for bovine viral diarrhoea virus and bovine herpesvirus 1 on dairy cattle farms in north-west and north-east Spain

BACKGROUND

Biosecurity is a key measure to reduce and prevent the introduction of diseases to farms and minimise spread of diseases within a herd. The aim of the study was to characterise the current application of biosecurity measures on dairy cattle farms in Spain along with their bovine viral diarrhoea and infectious bovine rhinotracheitis status.

METHODS

Data on biosecurity measures for 124 dairy herds were collected using a questionnaire. The sanitary status of these farms for bovine viral diarrhoea and infectious bovine rhinotracheitis was also assessed using antibody ELISA. Data were analysed using multiple correspondence analysis and a two-step cluster analysis.

RESULTS

Three main clusters of farms were identified: clusters 1 and 2 included herds of small and intermediate sizes. These, particularly cluster 1, showed the most deficiencies in the control of vehicles and visitors. However, laboratory tests were always performed on purchased animals. Cluster 3 had the largest herd sizes, with somewhat better biosecurity control of vehicles and visitors. However, farms in this cluster also purchased the most animals, sometimes without testing, and hired external workers more often.

CONCLUSION

The study indicated that, in the study population, there are serious shortcomings in the application of biosecurity measures on dairy farms, exposing them to disease transmission. This survey also highlights regional and herd size-related differences in the implementation of biosecurity. Collecting data is an important first step to identification of specific weaknesses in different farm typologies, and an adequate follow-up is needed to ensure that measures are implemented correctly on farms.

Assessment of bovine tuberculosis surveillance effectiveness in French wildlife: An operational approach

Bovine tuberculosis (bTB) is a chronic, zoonotic, bacterial disease mostly caused by Mycobacterium bovis, which can affect both domestic and wild species. France was officially declared bTB-free in 2001 but faced since 2004 an increase of the prevalence in cattle. Since 2001, bTB has been detected in several wild species: red deer (Cervus elaphus), roe deer (Capreolus capreolus), wild boar (Sus scrofa) and badger (Meles meles). Infected wild species constitute a major threat, because they may contribute to the maintenance of the infection in cattle and prevent eradication. In 2011, a surveillance system, Sylvatub, was implemented nationwide, to monitor the epidemiological status of bTB in mainland France. Our objective in this study was to assess the effectiveness of one of Sylvatub's passive surveillance system components (SSCs), which is based on the visual inspection of hunted animals (wild boars, red and roe deer) throughout mainland France. The following effectiveness criteria were evaluated: individual-level and component group-level positive and negative predictive values, and individual-level and component group-level probabilities of type I error ("false-positive" error) and type II error ("false-negative" error). These criteria were estimated quantitatively, at the scale of the département (a French administrative area of similar size to a county), with a stochastic scenario tree model. Individual negative predictive values were high, whereas individual positive predictive values were poor, whatever the species considered, and the training of hunters did not improve these effectiveness criteria sufficiently. The individual-level probability of type I error was relatively low, but the individual-level probability of type II error was generally high and was therefore an issue. However, increasing the proportion of trained hunters decreased this probability effectively. At group level, the size of the population surveyed had a marked impact on the effectiveness criteria: both the component group-level negative predictive value and the component group-level probability of type II error decreased rapidly with increasing population size. The conclusions drawn from such rationale may directly benefit stakeholders and actors in the field in their day to day practice of the surveillance processes. Thus, the assessment method used in this article presents the advantage of being operational, as well as being applicable to any surveillance system.

Field application of an indirect gE ELISA on pooled milk samples for the control of IBR in free and marker vaccinated dairy herds

BACKGROUND

The aim of the present study was to assess the reliability of a new strategy for monitoring the serological response against Bovine Herpesvirus 1 (BoHV1), the causative agent of infectious bovine rhinotracheitis (IBR). Bulk milk samples have already been identified as cost effective diagnostic matrices for monitoring purposes. Nevertheless, most eradication programs are still based on individual standard assays. In a region of northwestern Italy (Piedmont), the voluntary eradication program for IBR has become economically unsustainable. Being the prevalence of infection still high, glycoprotein E-deleted marker vaccines are commonly used but gE blocking ELISAs are less sensitive on bulk milk samples compared to blood serum.

RESULTS

A recently developed indirect gE ELISA showed high versatility when applied to a wide range of matrices. In this study, we applied a faster, cost effective system for the concentration of IgG from pooled milk samples. The IgG enriched fractions were tested using a gE indirect ELISA for monitoring purposes in IBR-positive and IBR-marker-vaccinated herds. Official diagnostic tests were used as gold standard. During a 3 years study, a total 250 herds were involved, including more than 34,500 lactating cows. The proposed method showed a very good agreement with official diagnostic protocols and very good diagnostic performances: only 37 positive animals were not detected across the entire study.

CONCLUSIONS

The results highlighted the ability of the proposed method to support the surveillance of IBR in the Piedmont region, reducing the costs without affecting the diagnostic performances.