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Coxiella burnetii infections are mostly subclinical in cattle, but can occasionally be associated with abortion. In the present study, 100 aborted fetuses or stillborn calves that were submitted for postmortem examination between September 2007 and March 2008 were examined for infection with C burnetii. Samples of both pooled fetal tissues and placental cotyledon were tested using a real-time PCR assay. In addition, the sections of placental cotyledon were examined using immunohistochemistry (IHC). The IHC of four placentas was positive. The PCR results of the IHC-positive placentas were high positive (HP); the PCR results of the organs of these four fetuses and calves varied from low positive (LP) to HP. The four IHC-positive fetuses had a gestation length of seven to nine months. All four placentas had histological signs of inflammation, but only one of four placentas had gross pathological signs of inflammation possibly due to a concomitant infection with Bacillus licheniformis. Five other IHC-negative placentas had (high) positive PCR results; the PCR results of the organs of these fetuses were LP or negative. The present study indicates that C burnetii infections are detected in a limited percentage of aborted fetuses and stillborn calves by IHC. To assess the importance of placentas with PCR-positive and IHC-negative test results, more research is needed. [ABSTRACT FROM AUTHOR]

Abstract: In cattle, Coxiella burnetii infections are generally asymptomatic but can also be associated with reproductive disorders. Metritis is considered as one of the symptoms of C. burnetii infections, but reliable information is lacking. Therefore, information on the presence of C. burnetii in the uterine content of cows with metritis is important to increase our knowledge on this pathogen. In this study, the uterine content of 45 dairy cows with metritis belonging to 12 herds was tested for C. burnetii with a real-time PCR assay. Only one uterine sample tested PCR (highly) positive, all other samples were PCR negative. The PCR positive cow tested also positive for antibodies. Three other cows from other herds tested antibody positive. The bulk milk (BM) samples of these 12 herds were tested by real-time PCR assay and antibody-ELISA. Six BM samples (50%) were positive in PCR and 10 (83%) were positive in ELISA. Culturing the uterus samples by bacteriology, the most frequently cultured bacteria were arcanobacterium (n =24), E. coli (n =16), other streptococci (n =10), Streptococcus uberis (n =8) and Streptococcus dysgalactiae (n =5). This study indicates that C. burnetii is not an important cause for metritis in dairy herds, although apparently C. burnetii was or had been present in most of these herds. [ABSTRACT FROM AUTHOR]

Summary We describe the paratuberculosis management practices applied in dairy herds in the Netherlands. The findings from paratuberculosis seronegative and seropositive herds were compared to discover possible risk factors. In total, 370 randomly selected herds with ≥20 dairy cows were surveyed. A questionnaire was used to collect data on current and previous paratuberculosis management practices. All cattle aged ≥3 years were serologically tested for paratuberculosis using an enzyme-linked immunosorbent assay. Herds with >33 tested cattle, of which only one was seropositive, were excluded to reduce the risk of including false-positive herds in the analysis. A comparison of the management data of the seronegative herds (n = 166) and the seropositive herds (n = 143) showed that in both groups important management measures for the prevention of paratuberculosis, such as calving in a cleaned calving area, removing the calf immediately after birth, and feeding paratuberculosis non-suspect roughage to calves, were used only rarely. However, such measures should be regarded as the critical first step to control the disease and/or reduce its prevalence. Using univariable analysis, four factors were statistically different between seronegative and seropositive herds: herd size, cows with clinical signs of paratuberculosis, prompt selling of clinically diseased cattle and feeding milk replacer. Using a multivariable logistic regression model, only herd size was a significantly different factor. These results indicate that most of the paratuberculosis preventive management measures were executed on these Dutch dairy farms only to a limited extent. [ABSTRACT FROM AUTHOR]

Summary A total of 15 822 cattle aged 3 years and older, belonging to 378 randomly selected herds, were tested for paratuberculosis using an absorbed enzyme-linked immunosorbent assay (ELISA); 3.3% tested positive. This percentage was lowest for the group of cattle aged 3–4 years (2.3%) and highest for cattle with the age of 5–6 years (4.5%). The mean Sample to Positive (S/P) ratio of seropositive cattle vaccinated against paratuberculosis was higher (0.75 ± 0.33) than that of seropositive, non-vaccinated cattle (0.58 ± 0.26). Faecal samples of 422 ELISA-positive cattle were cultured for the presence of Mycobacterium avium subsp. paratuberculosis , 12% of these were contaminated. The percentage of non-contaminated samples with positive culture results was 17.3%, with a substantial difference between vaccinated (1.7%) and non-vaccinated cattle (20.2%). Of the positive cultures, the number of colonies varied from 1–10 (22% of cultures), 11–100 (22%), to more than 100 (55%). The percentage of ELISA-positive, non-vaccinated cattle tested culture-positive was positively correlated with the magnitude of the S/P ratio. This percentage varied from 12% (S/P ratio 0.3–0.5) to 58% (S/P ratio > 1.1), a result that might have implications for interpretation of the test. In this study, the percentage of ELISA-positive cattle with positive faecal culture results was limited and these individuals were mostly moderate to heavy shedders. [ABSTRACT FROM AUTHOR]

Paratuberculosis is a chronic and progressive disease of the intestine in ruminants caused by Mycobacterium avium subsp. paratuberculosis (Map). The bacterium is transmitted to young animals, becomes manifest in adulthood and leads to economic losses. The aim of this study is to investigate if cows shedding Map possess oocytes and embryos that are carriers of the bacterium. New genetical material can enter the dairy farm using embryo transfer but the question as to whether this technique is safe with respect to transmission of paratuberculosis has yet to be addressed. We selected and bought 16 cows, all proven to be moderate shedders of the bacterium in the faeces immediately prior to the experiment but none were clinically sick. One sample of uterine content was collected from each animal by flushing the uterus on the day of heat and five samples of homogenised uterine tissue were collected on the eighth day of the same cycle by biopsy. In addition, 217 cumulus–oocyte complexes (COCs), ranging from 3 to 35 COCs per animal, were collected using ultrasound guided transvaginal puncture of the ovarian follicles (OPU). On the seventh day of the subsequent cycle 31 embryos were obtained using the classic technique of super ovulation induction, artificial insemination (AI), followed by flushing of the uterus. These embryos have been washed and trypsinised. Fourteen of the 16 cows were treated again for super ovulation in the subsequent cycle and 19 foetuses were collected by opening of the uterus after euthanasia on Days 35–49 of the cycle. All samples were cultured for presence of Map and checked every 2 months during 1 year for bacterial growth. None of the samples showed growth of Map after 12 months of culture. Pathological examination of the cows revealed different degrees of severity of pathological alterations of the intestinal tract and mesenteric lymph nodes. However, the results suggest that neither in vivo embryo’s nor oocytes are carriers of the bacteria and do not form an extra risk at transfer. However, due to the limited size of the experiment (sample size of 16 cows), a certain margin for error remains. [Copyright &y& Elsevier]

In the past decades, vaccination against paratuberculosis in cattle was performed in The Netherlands only on a limited scale. Because of its interference with the diagnosis of bovine tuberculosis, vaccination was restricted to herds with a high prevalence of clinical cases of paratuberculosis and was meant to aid in the economical survival of the farm. Recently, a voluntary paratuberculosis certification program has started, based in part on serological screening of cattle of at least 3 years of age. Herds that have been vaccinated against paratuberculosis are, therefore, likely to encounter problems when entering this program.The aim of this study was to evaluate the immune response resulting from vaccination with a heat-killed paratuberculosis vaccine. Over a period of 12–14 years, new-born calves were vaccinated in two herds. The B-cell response was evaluated using both the complement-fixation test (CFT) and an enzyme-linked immunosorbent assay (ELISA) and the cell-mediated immune response was evaluated using the γ-interferon assay.Data obtained show a marked and prolonged effect of the vaccination on both cellular and humoral immune responses, in particular to the paratuberculosis antigen but also to the bovine tuberculosis antigen, using the respective tests. These responses were detected rapidly after vaccination. The individual responses were highly variable between animals with respect to both the level and to the duration of the evoked immune response. No relation between the results obtained with the ELISA and the CFT was observed. In conclusion, for a large number of vaccinated cattle, a long lasting interference is to be expected with the presently available immunodiagnostic methods for both bovine tuberculosis and paratuberculosis. [Copyright &y& Elsevier]

In the Dutch national surveillance system, an increasing number of reports were received in the summer of 2017 from farmers about unusual behavior of their cows. The cows were grouping during the day in summer in one part of the barn and did not move for several hours, which, according to the farmers, led to reduced food and water intake and lying time and resulted in decreased milk production and increased risk of lameness. Many farmers perceived magnetic fields from, for instance, high-voltage lines, automated milking systems, or solar panels as possible causes for the behavior of their cows. Our aim for the study was to study potential factors such as magnetic fields and other factors such as barn climate and insect burden for adverse grouping behavior of dairy cows in the barn. For each case herd, 2 control herds were selected in the same postal area code. A case was a herd in which cattle grouped at least on 7 occasions in a month for several hours. In a control herd, the cows were in the barn during the same time period as in the matching case herd but did not show adverse grouping behavior. A questionnaire was administered by telephone in 31 case herds and 62 control herds. The questionnaire gathered information on behavior of the cows and potential risk factors. In addition, data on the distance of the herd to high-voltage lines was obtained. From a total of 74 variables, all variables with a P -value ≤0.10 were included in full multivariable logistic regression model. Backward selection was carried out at P ≤ 0.10. The grouping behavior of the cows started in most herds in June, was seen only during the day, and lasted mostly 6 to 8 h, with cows often grouped in the northern part of the barn. Identified risk factors appeared to be recently constructed barns, measured stray voltage in barns, and presence of fans in barns. Given the cross-sectional design of the case-control study, causality for these risk factors leading to adverse behavior of the cows could not be proven. Dissemination of the results to farmers hopefully results in measures that can prevent the unusual grouping behavior of cows. [ABSTRACT FROM AUTHOR]

A study using an ELISA and a real-time PCR assay based on the detection of the repetitive transposon-like gene of revealed that infection with the bacterium was widespread among Dutch dairy herds, with antibodies detected in bulk tank milk (BTM) from 268 of 341 herds (78.6 per cent) and bacterial DNA detected in 193 of 341 herds (56.6 per cent). The BTM samples were taken in November and December 2007. Serological and molecular studies in young and adult cattle selected from 100 herds showed that antibodies were present in the blood of 470 of 2936 (16.0 per cent) lactating cows but only in 19 of 1831 (1.0 per cent) young animals. Bacterial DNA was detected in the milk of 254 of 2925 (8.7 per cent) lactating cows; bacterial DNA was not detected in any of the faecal samples obtained from youngstock. The blood and milk samples were taken from the cattle in the period January to April 2008. [ABSTRACT FROM PUBLISHER]

Longevity of a herd is defined as the average age of all cattle over two years old at the moment of death (either natural, by euthanasia or by slaughter), and is increasing since 2018. The aim of this study was to evaluate the association between longevity and cattle health indicators in Dutch dairy herds. Anonymized census data were available for 16,200 Dutch dairy herds (∼98 % of the dairy herds) between 2016 and 2020. All herds were categorized into one of six longevity groups: herds with a high longevity (>seven years old), increasing longevity (mean increase of one year and two months between 2017 and 2020), median longevity (∼five years and eight months, without major fluctuations in longevity), decreasing longevity (mean decrease eight months), low longevity (

Abstract: The aim of the study was to investigate the effect of BVDV-free certification of dairy herds on fertility and udder health. Cases were defined as dairy herds that had at least one BVDV-antigen positive animal, subsequently gained the BVDV-free status by participating in the BVDV-control programme of the Animal Health Service (AHS) and maintained this status for at least 2 years. Controls had an unknown status for BVDV and two controls were matched to one case by region and herd size. Data concerning fertility and milk production of all herds were provided by The Dutch Royal Cattle Syndicate (NRS). After validation, data of 79,607 cows of 392 case herds and 124,831 cows of 730 control herds were analysed on ten fertility and three udder health parameters. For the analyses all observations were aggregated at herd level. To account for the matching, differences for fertility parameters were calculated between each of the two pairs of case–control within a matching code. The analyses were performed with these differences as dependent variables. Mixed models and GEE models were used for the statistical analyses of fertility and udder health. Case herds had a significantly lower abortion rate in the BVDV-free period than controls herds (10.3% versus 11.6%, P <0.01) while there was no significant difference for the other fertility parameters. There was no effect on mastitis prevalence or bulk-milk SCC but the mastitis incidence significantly decreased for case herds in the BVDV-free period (cases 0.6 % lower than controls, P <0.05). In our study the effect of getting the BVDV-free status may have been underestimated for several reasons like an unknown status for control herds, not knowing when an acute infection occurred in case herds and not knowing the management for both cases and controls. Interestingly, both significant variables, being abortions and mastitis incidence, are parameters that are more difficult to influence by the farmer than the other parameters (e.g. calving interval). [Copyright &y& Elsevier]

The ELISA tests that are available to detect an infection with Mycobacterium avium subsp. paratuberculosis (MAP) have a limited validity expressed as the sensitivity (Se) and specificity (Sp). In many studies, the Se and Sp of the tests are treated as constants and this will result in an underestimation of the variability of the true prevalence (TP). Bayesian inference provided a natural framework for using information on the test variability (i.e., the uncertainty) in the estimates of test Se and Sp when estimating the TP.Data from two prevalence studies for MAP using an ELISA in several regions in two locations were available for the analyses. In location 1, all cattle of at least 3 years of age were sampled in approximately 90 randomly sampled herds in each of the four regions of the country. In location 2, in 30 randomly sampled herds in each of three regions, approximately 30 randomly selected cows were sampled. Information about the unknown test Se and Sp and MAP prevalence was incorporated into a Bayesian model by joint prior probability distributions. Posterior estimates were obtained by combining the actual likelihood with the prior distributions using Bayes’ formula.The corrected cow-level TP (proportion of infected cows in a herd) was low, 5.8 and 3.6% in locations 1 and 2, respectively. Certain regions within a location differed significantly in herd-level TP (proportion of infected herds). The herd-level TP was 54.3% in location 1 (95% credible interval (CI) 46.1, 63.3%) and 32.9% in location 2 (95% CI: 14.4, 73.3%). The variation in the herd-level TP estimate for location 2 was more than three times as large as the variation in location 1 mainly because of the relatively small number of investigated herds in location 2. In future prevalence studies for MAP, sample size calculations should be based on a very low cow-level prevalence. Approximately 50 and 90% of the herds in the current study had an estimated cow-level TP below 4 and 10%, respectively. [Copyright &y& Elsevier]

• Introduction of data-driven tools provides insight in calf mortality for farmers. • Increased awareness among farmers was associated with decreased mortality. • Other factors are found that may further decrease calf mortality in dairy herds. 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. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented about the prevalence of hydranencephaly in calves after the bluetongue serotype 8 epidemic in the Netherlands.