Evaluation of the association between the introduction of data-driven tools to support calf rearing and reduced calf mortality in dairy herds in the Netherlands.

Between 2009 and 2017, calf mortality in the Dutch dairy sector showed a slight but steady increase. The Dutch dairy industry decided to act and supported the development of several data-driven tools that were implemented from 2018 on. The tools informed farmers about their calf mortality rates and stimulated them to improve. The Trend Analysis Surveillance Component of the Dutch cattle Health Surveillance System provided the possibility to evaluate the calf mortality in Dutch dairy herds before and after implementation of these tools. The aim of this study was to evaluate the association between calf mortality and i) all actions that were taken by the Dutch dairy industry to improve the quality of calf rearing and ii) other potential management or environmental factors associated with calf mortality in Dutch dairy herds. Census data from approximately 98 % of all Dutch dairy herds were available from July 2014 until June 2019. Four different calf mortality indicators were defined: perinatal calf mortality risk (i.e., mortality before, during, or shortly after the moment of birth up to the moment of ear-tagging), postnatal calf mortality risk (ear-tagging till 14 d), preweaned calf mortality rate (15 d-55 d) and weaned calf mortality rate (56 d-1 yr.). All data were aggregated to herd and monthly level and were analysed using Population-Averaged Generalized Estimating Equations (PA GEE models) with a Poisson distribution and log link function. When the period before implementation of the tools (2016-2017) was compared to the period thereafter (2018-2019), all four calf mortality indicators decreased. The relative decrease varied from 3 % (postnatal calves) and 10 % (perinatal calves) up to 18 % and 30 % in preweaned and weaned calves, respectively. Registrations of veterinary treatments such as antimicrobial use, vaccinations (calf or cow) and antiparasitic treatments were associated with calf mortality. Additionally, herds with a higher level of metabolic problems in transition cows had a higher calf mortality and also extreme outside temperatures were associated with higher calf mortality. Given that the different tools were implemented nation-wide and a control group was lacking, we could not prove that implementing the different tools caused the reduction in calf mortality. We do however, believe that all the actions and communication towards improvement of calf rearing in dairy herds led to an increased awareness among farmers towards the importance of calf rearing management and therefore a reduction in calf mortality on national level.

Surveillance of cattle health in the Netherlands: Monitoring trends and developments using routinely collected cattle census data.

Since 2002, a national cattle health surveillance system (CHSS) is in place that consists of several surveillance components. The CHSS combines enhanced passive reporting, diagnostic and post-mortem examinations, random surveys for prevalence estimation of endemic diseases and quarterly data analysis. The aim of the data-analysis component, which is called the Trend Analysis Surveillance Component (TASC), is to monitor trends and developments in cattle health using routine census data. The challenges that were faced during the development of TASC and the merits of this surveillance component are discussed, which might be of help to those who want to develop a monitoring and surveillance system that includes data analysis. When TASC was developed, there were process-oriented challenges and analytical related issues that had to be solved. Process-oriented challenges involved data availability, confidentiality, quality, uniformity and economic value of the data. Analytical issues involved data validation, aggregation and modeling. Eventually, the results had to provide information on cattle health that was intuitive to the stakeholders and that could support decision making. Within TASC, both quarterly analysis on census data and, on demand, additional in-depth analysis are performed. The key monitoring indicators that are analyzed as part of TASC all relate to cattle health and involve parameters such as mortality, fertility, udder health and antimicrobial usage. Population-Averaged Generalized Estimating Equations, with the appropriate distribution (i.e. Gaussian, Poisson, Negative Binomial or Binomial) and link function (independent, log or logit), are used for analysis. Both trends in time and associations between cattle health indicators and potential confounders are monitored, discussed and reported to the stakeholders on a quarterly level. The flexibility of the in-depth analyses provides the possibility to conduct additional analyses when anomalies in trends of cattle health occur or when developments in the cattle industry need further investigation. In addition, part of the budget for the in-depth analysis can also be used to improve the models or add new data sources. The TASC provides insight in cattle health parameters, it visualizes trends in time, can be used to support or nuance signals that are detected in one of the other surveillance components and can provide warnings or initiate changes in policy when unfavorable trends occur.

Schmallenberg virus in Dutch dairy herds: potential risk factors for high within-herd seroprevalence and malformations in calves, and its impact on productivity.

In November 2011, the new orthobunyavirus Schmallenberg virus (SBV) was identified in dairy cows that had induced fever, drop in milk production and diarrhoea in the Netherlands (Muskens et al., 2012. Tijdschrift voor Diergeneeskunde 137, 112-115) and a drop in milk production in cows in Northwestern Germany (Hoffmann et al., 2012. Emerging Infectious Diseases 18 (3), 469-472), in August/September 2011. This study aimed at quantifying risk factors for high within-herd prevalence of SBV and SBV-induced malformations in newborn calves in dairy herds in the Netherlands. Additionally, the within-herd impact of SBV infection on mortality rates and milk production was estimated. A case-control design was used, including 75 clinically affected case herds and 74 control herds. Control herds were selected based on absence of malformations in newborn calves and anomalies in reproductive performance. SBV-specific within-herd seroprevalences were estimated. Risk factors for high within-herd SBV seroprevalence (>50%) and the probability of malformed newborn calves in a herd were quantified. In addition, within-herd impact of SBV with regard to milk production and mortality was estimated. Animal-level seroprevalence was 84.4% (95% confidence interval (CI): 70.8-92.3) in case herds and 75.8% (95% CI: 67.5-82.5) in control herds. Control herds that were completely free from SBV were not present in the study. Herds that were grazed in 2011 had an increased odds (OR 9.9; 95% CI: 2.4-41.2)) of a high seroprevalence (>50%) compared to herds that were kept indoors. Also, when grazing was applied in 2011, the odds of malformations in newborn calves tended to be 2.6 times higher compared to herds in which cattle were kept indoors. Incidence of malformations in newborn calves at herd level was associated with both within-herd seroprevalence and clinical expression of the disease in adult cattle. The rate of vertical transmission of SBV to the fetus once a dam gets infected seemed low. A total of 146 stillborn or malformed calves were submitted by 65 farmers during the study period, of which 19 were diagnosed as SBV-positive based on pathological investigation and/or RT-qPCR testing of brain tissue. Based on these results combined with calving data from these herds we roughly estimated that at least 0.5% of the calves born between February and September 2012 have been infected by SBV. A drop in milk production was observed between the end of August 2011 and the first half of September (week 35-36), indicating the acute phase of the epidemic. During a 4-week period in which SBV infection was expected to have occurred, the total loss in milk production in affected dairy herds was around 30-51 kg per cow. SBV had no or limited impact on mortality rates which was as expected given the relatively mild expression of SBV in adult cows and the low incidence of malformations in newborn calves.

[Diarrhea and loss of production on Dutch dairy farms caused by the Schmallenberg virus]. / Diarree en productiedaling op Nederlandse melkveebedrijven door het Schmallenbergvirus.

At the end of August and the first two weeks of September 2011 dozens of veterinary practitioners reported to GD Veekijker (Animal Health Service) several dairy herds with cows with sudden decreased milk production, watery diarrhea and sometimes fever. In the beginning these reports came from the Eastern region of the Netherlands, after that also from the other three regions. The percentages of diseased herds per veterinary practice varied from a few till dozens per cent. Extensive bacteriological, virological and parasitological testing of the feces of sick cows did not reveal an infectious cause of the clinical problems. Recently, 50 stored blood samples of clinically diseased cattle were tested for the Schmallenbergvirus using a PCR, and 36% (18/50) tested positive. A large group of control cows (n=115) was also tested with the PCR and all cattle tested negative. Likely the Schmallenbergvirus was the primary cause of the clinical symptoms in the Dutch dairy herds. Further research will be done to confirm this.

Vertical transmission of bluetongue virus serotype 8 virus in Dutch dairy herds in 2007.

In February 2008, evidence was found for transplacental infection of bluetongue virus serotype 8 (BTV-8) in PCR negative, seropositive heifers in Northern Ireland originating from the Netherlands. The relevance of this route of transmission was studied in Dutch cow-calf combinations in the Netherlands of which the calves were born in the same time period of the year as the calves from the exported heifers, the first quarter of 2008. Blood samples were tested from 385 cows and their calves, housed in 43 dairy farms that became naturally infected with BTV-8 for the first time in 2007. All calves were at least 10 days old at the moment of first testing. In total 229 cows tested seropositive for BTV-8. Eight of these cows were still PCR positive. Out of the 229 seropositive cows, 37 calves (16.2%; 95% CI: 11.4-21.0) were tested PCR positive in the first sample taken in April 2008. In the first week of June, 34 out of the 37 PCR positive calves were still available for resampling. Three calves were still PCR positive; one was 5 months old, the other two were 3 months old. One month later, in the first week of July, all initially PCR positive calves, including the three still tested positive 1 month earlier, were PCR negative. We showed that BTV-8 can be vertically transmitted from cow to calf and can result in healthy looking viraemic calves remaining PCR positive for up to 5 months. These PCR positive calves could play a role in the epidemiology, and in particular in overwintering of BT. However, further investigations are needed to evaluate the importance of this route of transmission.

[Abortions, fertility problems and mastitis on a cattle farm and a sick farmer: a zoonosis? Infection with Staphylococcus aureus phagetype T543]. / Verwerpen, vruchtbaarheidsproblemen en mastitis op een rundveebedrijf en een zieke veehouder: een zoonose? Infectie met Staphylococcus aureus faagtype T543.

On a dairy farm the herdsman got a pustular dermatitis and in the herd in a year several abortions occurred, the somatic cell count of the bulk milk increased and the fertility results decreased. The cause appeared to be an infection in both the herdsman and the herd with Staphylococcus aureus type T543.

[Parafilariasis: a new parasitic disease of cattle in The Netherlands]. / Parafilariose, een nieuwe parasitaire ziekte bij het rund in Nederland.

In March 2007, cutaneous nodules were observed on the neck, shoulder and back of a breeding bull imported from France in November 2006. The nodules opened spontaneously and produced a haemorrhagic exudate. The cause was Parafilaria bovicola, a filariid nematode not endemic to The Netherlands. The worm can cause substantial economic loss because of the need to trim carcasses and because of the diminished value of hides. The infection is spread by the fly Musca autumnalis, which is common in The Netherlands. Because treatment does not stop the infection from spreading, the bull was culled to prevent the risk of infection of the national herd. To our knowledge, this is the first case of Parafilaria bovicola in The Netherlands.

[Bluetongue in The Netherlands; description of the first clinical cases and differential diagnosis. Common symptoms just a little different and in too many herds]. / Bluetongue voor het eerst in Nederland: beschrijving van de klinische verschijnselen en differentiaaldiagnose.

For the first time Bluetongue (BT) has been diagnosed in the Netherlands. The clinical symptoms of BT on five farms during the first outbreak ever in the Netherlands are described. Fever and swollen sensitive coronets leading to reluctance to stand and walk were sometimes the first symptoms. Later lesions in the mouth occurred with foamy salivation and respiratory problems. In other cases a swollen head with swollen lips and foamy salivation were the first clinical signs. Also sudden death occurred. In the first sixteen confirmed cases morbidity and mortality were lower than described in outbreaks in other countries. Good collaboration between practitioners, specialists of the Animal Health Service (GD-Deventer), and specialists of the Food and Consumer Product Safety Authority (VWA) and CIDC-Lelystad (Wageningen UR) led to a rapid notification and ultimately confirmation of the suspected diagnosis BT.

[First case of pithomycotoxicosis (facial eczema) in the Netherlands]. / Pithomycotoxicosis of facial eczema bij het rund voor de eerste maal aangetoond in Nederland. Zonnebrand als koppelprobleem op rundveebedryjven.

Between mid September and the beginning of November 2005, the Animal Health Service (AHS) received thirteen reports offarms on which several animals showed severe symptoms of solar eczema. Blood chemistry showed very high levels of GOT/AST and GGT indicative of severe liver damage. Farm visits to eight farms showed that the animals--previous to the start of the symptoms--had been grazing 24 hours/day and received no additional feed. Ingestion of poisonous plants or medications was considered unlikely to have caused the liver damage, and liver fluke infections were present on only two farms. Microscopic examination of specimens of grass revealed the presence of spores of Pithomyces chartarum in samples taken from six of nine farms. This fungus produces the mycotoxin sporidesmin, which causes severe liver damage and pithomycotoxicosis (facial eczema). This article is the first to describe Pithomyces chartarum in cattle in mainland Europe. Further research on the distribution and re-occurrence of Pithomyces chartarum infection and sporidesmin survival in grass silage is recommended.

[Suffocating, slow calves with a thick neck. Iodine deficiency in cattle]. / Benauwde, slome kalveren met een dikke hals. Jodiumdeficiëntie bij rundvee.

On a dairy farm situated 200 km from the sea on sandy soil an increasing problem arose during 3 years with new-born calves showing a thickness over the larynx. The calves and close-in heifers proved to be severely deficient in trace elements. The new born calves had goitre. The clinical picture, diagnosis and therapy/prevention are discussed.

[Alcohol poisoning in dogs]. / Alcoholvergiftiging bij de hond.

The clinical symptoms of ethanol intoxication in a Jack Russell terrier dog of 5 kg, that consumed 50 ml of whisky (40%) within 15 minutes on an empty stomach are described. The clinical case is completed with literature information on clinic, pathogeneses and therapy.

[Botulism poisoning in cattle, a case report, diagnosis and prevention]. / Botulismevergiftiging bij runderen, een case, diagnostiek en preventie.

On a dairy farm 22 animals die in 14 days. After 10 days the clinical diagnosis is confirmed: clostridium botulinum type D intoxication. The clinical, diagnosis, therapy and prevention are discussed.

[She does behave funny, but she is no 'crazy cow' (BSE)]. / Ze doet wel raar, maar is geen 'gekke koe' (BSE).

Since 1999 18 cows with 'crampiness' were presented for clinical inspection. Most animals were called upon because of clinically 'suspected BSE' by the local veterinary practitioner. The clinical picture of the disease and the differences with BSE are discussed.

[BSE: clinical diagnosis and field experience]. / BSE: klinische diagnostiek en veldervaringen.

The clinical diagnosis 'suspected of having BSE' is difficult. Cows older than 2.5 years, presented to the private veterinary practitioner with disturbed locomotion present for more than 14 days and with no detectable cause, should be investigated with suspicion. Questions on changes in behaviour of the animal and during the examination attention on exaggerated responses to handling and sound can give additional information. Notification of suspected cases and gained field experiences are discussed.

[Outbreak of bovine virus diarrhea on Dutch dairy farms induced by a bovine herpesvirus 1 marker vaccine contaminated with bovine virus diarrhea virus type 2]. / Uitbraak van bovine virus diarree op Nederlandse rundveebedrijven na vaccinatie met een met BVDV type 2 gecontamineerd BHV1 markervaccin.

On 23 February 1999, the Dutch Animal Health Service advised all Dutch veterinary practices to postpone vaccination against bovine herpesvirus 1 (BHV1) immediately. The day before severe disease problems were diagnosed on four dairy farms after vaccination with the same batch of BHV1 marker vaccine. Using monoclonal antibodies, bovine virus diarrhoea virus (BVDV) type 2 was found in the vaccine batch. This paper describes an outbreak of BVDV type 2 infection caused by the use of a batch of modified live BHV1 marker vaccine contaminated with BDVD. Sources of information used were reports of farm visits, minutes of meetings, laboratory results, and oral communications from the people involved. The first symptoms of disease were observed on average six days after vaccination. Morbidity was high on 11 of the 12 farms. On five farms more than 70% of the animals became ill, while on one farm no symptoms could be detected. During the first week after vaccination, feed intake and milk production decreased. During the second week, some animals became clinically diseased having nasal discharge, fever, and diarrhoea. At the end of the second week and at the start of the third week, the number of diseased animals increased rapidly, the symptoms became more severe, and some animals died. Mortality varied among herds. Necropsy most often revealed erosions and ulcers of the mucosa of the digestive tract. In addition, degeneration of the liver, hyperaemia of the abomasum, and swollen mesenterial lymph nodes and swollen spleen were found. On 11 of the 12 farms all animals were culled between 32 and 68 days after vaccination after an agreement was reached with the manufacturer of the vaccine. This was the third outbreak of BVD in cattle after administration of a contaminated vaccine in the Netherlands. The possibilities to prevent contamination of a vaccine as a consequence of infection of fetal calf serum with BVDV are discussed. Improvement of controls to prevent contamination before and during vaccine production, and improvement of the monitoring of side-effects is necessary.

[Analysis of symptoms associated with bovine herpesvirus 1 vaccination]. / Analyse van gezondheidsklachten na BHV1 vaccinatie.

Between 1 May 1998 and 22 February 1999, it was compulsory for Dutch cattle farmers to take measures against bovine herpesvirus 1 (BHV1). Cattle on farms that were not certified as infectious bovine rhinotracheitis (IBR)-free had to be vaccinated twice a year. During the vaccination programme, both farmers and veterinarians reported side-effects of the vaccine. These reports were collected by the Stichting IBR/BVD Schade (SIS; Foundation for IBR/BVD Damage) in order to draw up a damage report. In 1999 in total 6977 cattle farmers lodged complaints which they considered to be related to the vaccination against BHV1. On these farms, 15,150 herd vaccinations had been performed, 10,269 of which were associated with one or more symptoms. During the compulsory vaccination period, 13% of the herd vaccinations led to symptoms and complaints. In March 1999, a number of vaccine batches were found to be contaminated with bovine virus diarrhoea (BVD) virus. For the purposes of this analysis, a 'known contaminated' herd vaccination was defined as one in which at least one 'known contaminated' batch or lot of vaccine was used. In total, 987 of 1007 herds vaccinated with 'known contaminated' vaccines developed one or more symptoms compatible with acute BVD. There were no commonly seen combinations of symptoms. For this reason, and because the start and end dates were not reported for 55% of the symptoms, it was not possible to detect a symptom pattern. Therefore there were no 'suspect' batches of vaccine which, although not contaminated with BVD virus, gave rise to symptoms. The number of BVD symptoms was determined for those herds with vaccination-related symptoms. There was no difference in the distribution frequency between batch numbers or between 'known contaminated' batches and 'non-suspect' batches. The farmers' definition of chronic wasting was used in this investigation, with the inevitable large differences in definition. The symptom chronic 'wasting' was reported for 3209 of the 10,269 herds with vaccination-related symptoms. On 161 farms (164 herd vaccinations) 'chronic wasting' accounted for more than 20% of the symptoms. As expected, other symptoms were reported in addition to wasting. The symptom 'chronic wasting' was reported more often on forms where a 'known contaminated' vaccine was used. Inactivated vaccine was used for 154 herd vaccinations. In 34 cases, one or more symptoms of acute BVD were reported. The frequency was the same as that for live vaccines. The frequency of reported symptoms tended to be lower with the inactivated vaccine. On the basis of the SIS data, no relationship was found between vaccine batch and reported symptoms. This may be because (i) the classification of a vaccine as 'known contaminated', 'non-suspect', and 'not known' may not have been in keeping with the real status of the vaccine, (ii) farmers may have reported symptoms selectively, and (iii) there is no relationship with vaccination against BHV1.