Periparturient infection with bovine viral diarrhea virus type 1 causes hemorrhagic proctocolitis in a cow.

After 3 cows of a dairy herd had died from severe hemorrhagic diarrhea, a 4th sick cow was transported to the clinic. Blood analyses revealed the complete absence of white blood cells, the presence of a type 1b strain of bovine viral diarrhea virus (BVDV), and seroconversion to BVDV.

Herd-level animal management factors associated with the occurrence of bovine neonatal pancytopenia in calves in a multi-country study.

Since 2007, mortality associated with a previously unreported haemorrhagic disease has been observed in young calves in several European countries. The syndrome, which has been named 'bovine neonatal pancytopenia' (BNP), is characterised by thrombocytopenia, leukocytopenia and a panmyelophthisis. A herd-level case-control study was conducted in four BNP affected countries (Belgium, France, Germany and the Netherlands) to identify herd management risk factors for BNP occurrence. Data were collected using structured face-to-face and telephone interviews of farm managers and their local veterinarians. In total, 363 case farms and 887 control farms were included in a matched multivariable conditional logistic regression analysis. Case-control status was strongly associated with the odds of herd level use of the vaccine PregSure® BVD (PregSure, Pfizer Animal Health) (matched adjusted odds ratio (OR) 107.2; 95% CI: 41.0-280.1). This was also the case for the practices of feeding calves colostrum from the calf's own dam (OR 2.0; 95% CI: 1.1-3.4) or feeding pooled colostrum (OR 4.1; 95% CI: 1.9-8.8). Given that the study had relatively high statistical power and represented a variety of cattle production and husbandry systems, it can be concluded with some confidence that no other herd level management factors are competent causes for a sufficient cause of BNP occurrence on herd level. It is suggested that genetic characteristics of the dams and BNP calves should be the focus of further investigations aimed at identifying the currently missing component causes that together with PregSure vaccination and colostrum feeding represent a sufficient cause for occurrence of BNP in calves.

[Mental notes in tracking BVDV carriers]. / Aandachtspunten bij het opsporen van BVDV-dragers.

The detection and elimination of animals persistently infected with bovine viral diarrhoea virus (BVDV) is the key to BVD control. This method has proven to be very efficient in eradicating BVDV in a herd. Several pitfalls in the detection procedure can make that some persistently infected (PI) animals do not get identified or are removed too late, supporting the assumption that circulation of the virus could be possible in absence of PI animals. Furthermore the risk of reintroduction is high since the prevalence of BVD is high in the Netherlands and Belgium. Based on both practical experience and literature, here we review critical control points in order to minimise the risk of a false negative BVDV screening.

A survey on biosecurity and management practices in selected Belgian cattle farms.

The shift from cure towards prevention in veterinary medicine involves the implementation of biosecurity, which includes all measures preventing pathogens from entering a herd and reducing the spread of pathogens within a herd. In Belgium no studies have considered the implementation of biosecurity measures in the daily management of cattle farms. Therefore the aim of the study was to map the current application of biosecurity measures in Belgian cattle farms in the prevention of disease transmission within and between farms. Between March 2011 and April 2013 the data were collected as part of a larger cross-sectional study, conducted to identify risk factors for reinfection with BVDV in cattle herds assumed free from BVDV. Questionnaire data from 33 dairy farms, 16 beef farms and 25 mixed (dairy and beef cattle) farms were analyzed using a combination of a linear scoring system, a categorical principal component analysis and a two-step cluster analysis to differentiate these farms based on their biosecurity levels and visit frequencies. Further enhancement of preventive measures considering external and internal biosecurity was still possible for each farm, as none of the farms obtained an overall high biosecurity level. Three groups of cattle farms were differentiated with a biosecurity level varying from low to high-medium, of which the group with the lowest biosecurity level mainly consisted of mixed farms. Animal-to-animal contacts with cattle from other herds were frequently possible as only 12% of the farmers purchasing cattle quarantined purchased animals at least three weeks and contacts over fences on pasture were possible in 70% of the herds. Basic biosecurity measures such as farm-specific protective clothing and boots were present in the majority of the farms, but they were insufficiently or incorrectly used. Cattle farms were very often visited by professional visitors of which the herd veterinarian, the AI technician and the cattle salesman most frequently entered the farm. It can be concluded that few biosecurity measures were undertaken by Belgian cattle farmers, thereby exposing themselves to the risk of disease transmission within and between farms. Especially in regions with a high cattle density, small distances to neighbouring farms and high frequencies of professional visits, a farm-specific preventive strategy should be developed, thereby using the facilities often already present on the farm.

Association between herd exposure to BVDV-infection and bulk milk somatic cell count of Flemish dairy farms.

The purpose of this study was to investigate the statistical association between herd bovine viral diarrhoea (BVD) status based on bulk milk antibody detection and monthly bulk milk somatic cell count (BMSCC) as a reflection of the udder health. A distinction was made between vaccinating and non-vaccinating herds via a questionnaire concerning BVD-vaccination. No significant difference in BMSCC was found between vaccinating (228,300 cells/ml; SD 180,019) and non-vaccinating (237,070 cells/ml; SD 77,900) herds. Non-vaccinating herds (n=243) were selected, and the relationship between a single BVDV-antibody titre and the BMSCC of each herd over a 12-month observation period evaluated. For this purpose, the non-vaccinating herds were divided into five groups depending on bulk milk BVDV-antibody titres. Overall, no significant relationship between the antibody titre and the BMSCC was found. Still, when comparing the category with the lowest S/P ratio (essentially BVDV-naïve herds; BMSCC=211,390 cells/ml) with the combined four other categories (BMSCC=242,790 cells/ml), a significant difference in BMSSC was observed (P=0.01).

Serological and virological BVDV prevalence and risk factor analysis for herds to be BVDV seropositive in Belgian cattle herds.

Bovine viral diarrhoea virus (BVDV) is a worldwide spread virus that most commonly infects cattle and can cause considerable economic losses. To determine the prevalence of BVDV in Belgium, a cross-sectional study was performed between November 2009 and March 2010. Young stock aged between 6 and 12 months from 773 randomly selected Belgian cattle herds were tested for BVDV-specific antibodies and antigen. With a target and maximum of 10 animals per sampled herd, a total of 5246 animals were selected. Additionally a questionnaire including different herd management topics and questions about participation in animal health programmes, including BVDV, was sent to 1100 Belgian cattle herds, including the 773 herds for BVDV testing. This paper focuses on results regarding these 773 herds. The true prevalence of BVDV-specific antibodies and antigen at herd level was respectively 47.4% and 4.4%, while at animal level this was respectively 32.9% and 0.3%. In 44.4% of the herds where BVDV-specific antibodies were detected at least 60% of the sampled young stock was BVDV seropositive. Interestingly, 83.4% of these farmers stated not to have suffered from problems related to BVDV. Moreover, only 8.4% of all farmers who completed the questionnaire (n=895) reported problems possibly related to BVDV the past 3 years. This demonstrates that farmers are often unaware of the presence of BVDV in their herd. Risk factors for a herd to be BVDV seropositive were identified by means of a multivariable logistic regression model. Large herds were significantly more likely to be BVDV seropositive (OR=1.004, p<0.01). The interaction between "Antigen positive animal detected in this study" and "BVDV vaccination in 2009" was significant (p<0.01). In non-vaccinating herds, the detection of antigen positive animals was significantly associated with BVDV seropositive herds (OR=13.8, p<0.01). In herds with no antigen positive animals detected, vaccination resulted in a significant risk factor to be BVDV seropositive compared to non-vaccinating herds (OR=3.4, p<0.01). Herds reporting BVDV-related problems the past 3 years were more likely to be BVDV seropositive (OR=1.9, p<0.05). This relation became non-significant (OR=1.8, p=0.08) when only a subset of herds with no vaccination of animals <12 months was taken into account. The results of the current study suggest an active circulation of BVDV in a considerable number of Belgian cattle herds.

Calf-level factors associated with bovine neonatal pancytopenia--a multi-country case-control study.

Bovine neonatal pancytopenia (BNP), a high fatality condition causing haemorrhages in calves aged less than 4 weeks, was first reported in 2007 in Germany and subsequently observed at low incidence in other European countries and New Zealand. A multi-country matched case-control study was conducted in 2011 to identify calf-level risk factors for BNP. 405 BNP cases were recruited from 330 farms in Belgium, France, Germany and the Netherlands by laboratory confirmation of farmer-reported cases. Up to four calves of similar age from the same farm were selected as controls (1154 calves). Risk factor data were collected by questionnaire. Multivariable modelling using conditional logistic regression indicated that PregSure®BVD (PregSure, Pfizer Animal Health) vaccination of the dam was strongly associated with BNP cases (adjusted matched Odds Ratio - amOR 17.8 first lactation dams; 95% confidence interval - ci 2.4, 134.4; p = 0.005), and second or more lactation PregSure-vaccinated dams were more likely to have a case than first lactation vaccinated dams (amOR 2.2 second lactation; ci 1.1, 4.3; p = 0.024; amOR 5.3 third or more lactation; ci 2.9, 9.8; p = <0.001). Feeding colostrum from other cows was strongly associated with BNP if the dam was not PregSure-vaccinated (amOR 30.5; ci 2.1, 440.5; p = 0.012), but the effect was less if the dam was PregSure-vaccinated (amOR 2.1; ci 1.1, 4.0; p = 0.024). Feeding exclusively dam's milk was a higher risk than other types of milk (amOR 3.4; ci 1.6, 7.5; p = 0.002). The population attributable fractions were 0.84 (ci 0.68, 0.92) for PregSure vaccination, 0.13 (ci 0.06, 0.19) for feeding other cows' colostrum, and 0.15 (ci 0.08, 0.22) for feeding dam's milk. No other calf-level factors were identified, suggesting that there are other important factors that are outside the scope of this study, such as genetics, which explain why BNP develops in some PregSure-colostrum-exposed calves but not in others.

Control of bovine virus diarrhoea at the herd level: reducing the risk of false negatives in the detection of persistently infected cattle.

The need to detect and eliminate cattle persistently infected (PI) with bovine viral diarrhoea virus (BVDV) is key to the control of BVD and has been shown to be very effective in eradicating BVDV from infected herds. However, because of pitfalls in the detection procedures, some PI animals can be missed and, as a result, are not identified and removal is delayed. The high prevalence of BVDV in cattle populations in some countries (such as Belgium and neighbouring countries) means there is a high risk of reinfection of a herd from which BVDV has been eradicated. Based on both practical experience and a literature study, this review considers those points that are critical to minimising the number of false negatives in the detection of PI cattle.