Sophie Roelandt

Prediction of respiratory disease and diarrhea in veal calves based on immunoglobulin levels and the serostatus for respiratory pathogens measured at arrival

Abstract Failure of passive transfer is a common problem in calves destined for veal production. At present it is unknown whether the risk for respiratory disease (BRD) or neonatal calf diarrhea (NCD) in the veal herd is associated with total immunoglobulin (Ig) and/or on the serostatus for respiratory pathogens measured at arrival. Therefore, the first objective of this prospective longitudinal cohort study was to determine associations between serum protein fractions as determined by routine electrophoresis (total protein, albumin, alpha-1 and -2 globulins, beta-globulins and Igs) at arrival and BRD and NCD in the first 3 weeks of the production cycle. The second objective was to determine whether the serostatus (seropositive/seronegative) of seven respiratory pathogens (bovine respiratory syncytial virus (BRSV), parainfluenzavirus-3, bovine coronavirus (BCV), bovine herpesvirus-1, bovine viral diarrhea virus, Mannheimia haemolytica and Mycoplasma bovis) of these arrival serum samples could be associated with the risk of having BRD. The third objective was to determine which of the electrophoresis proteins and respiratory serostatuses were associated with average daily gain (ADG) in the study period. The study population consisted of 150 rosé veal calves housed in a single air–space. The study period ended at day 18 post arrival, when BRD incidence was judged to be too high to further postpone a group treatment. A Cox regression model was used to determine the effect of the studied protein fractions and antibodies on the time to BRD and NCD occurrence. The effect of the studied predictors on ADG was determined by linear regression. Calves with Ig levels under 7.5g/L had an increased BRD hazard (hazard ratio (HR)=1.9 (95% confidence interval (CI)=1.2–3.0)). NCD was only positively associated with the alpha-2 globulin concentration. Calves with a negative serostatus for BCV (HR=1.7 (95% CI=1.0–2.8)) or BRSV (HR=2.0 (95% CI=1.0–3.9)) had an increased BRD hazard. Average daily gain (ADG) was 0.242kg/day (SD=0.142) and was not related to the occurrence of BRD or NCD. Calves with Igs below 7.5g/L and with increased levels of alpha-2 globulins showed a decrease in ADG. This study showed the importance of providing sufficient colostrum to veal calves and the potential benefit of the presence of BCV and BRSV antibodies at arrival to reduce the BRD hazard in the first 3 weeks.

Characterization of methicillin-resistant Staphylococcus aureus from healthy carrier chickens

Methicillin-resistant Staphylococcus aureus (MRSA) has long been recognized as an important pathogen in human medicine leading to hospital and community-acquired infections. However, it is now also considered a growing problem in veterinary medicine, although causing little or no disease. Although MRSA has already been detected in livestock including poultry, little is known about the epidemiology of MRSA in broiler and layer chickens. We therefore investigated 372 poultry farms in Belgium. We also compared the isolation method recommended by the European Food Safety Authority using two enrichment steps with an isolation method using only one enrichment step. Isolated MRSA was characterized by means of antimicrobial resistance profiling, spa typing, multi-locus sequence typing, and SCCmec typing. MRSA prevalence was 0.8% using the double broth enrichment method, while using the single broth enrichment method it was 1.8%. Five MRSA strains belonged to the livestock-associated (LA) MRSA ST398 (four with spa type t011 and one with t899), and three to the hospital-acquired MRSA ST239 spa type t037. The ST239 strains carried SCCmec type III while those belonging to ST398 carried SCCmec type IV or V. All isolates showed additional resistance to erythromycin and tetracycline apart from the expected resistance to cefoxitin and penicillin. All strains were susceptible to linezolid, mupirocin and vancomycin. In conclusion, a higher sensitivity for the isolation of LA-MRSA was obtained using only one enrichment step. While the typical LA-MRSA ST398 was present at low prevalence in poultry, human-associated strains have also been found.

Tick-Borne Encephalitis Virus Seropositive Dog Detected in Belgium: Screening of the Canine Population as Sentinels for Public Health

Tick-borne encephalitis virus (TBEV) is an important emerging tick-borne viral infection of humans and dogs in Europe. Currently, TBEV surveillance is virtually nonexistent in Belgium, which is considered nonendemic. A commercial enzyme-linked immunosorbent assay (ELISA) was adapted for the detection of TBEV-specific IgG-antibodies in canine sera. Serum samples of Belgian dogs were obtained from three diagnostic laboratories from Northern (n=688) and Southern Belgium (n=192). ELISA-positive and borderline samples were subjected to a TBEV rapid fluorescent focus inhibition confirmation test. One dog was confirmed TBEV seropositive. Several ELISA-positive and borderline sera underwent seroneutralization and hemagglutinin inhibition tests to rule out West Nile and Louping Ill viruses, but tested negative. The clinical history of the seropositive dog could not explain beyond doubt where and when TBEV infection was acquired. Further surveillance is necessary to determine whether this dog remains a single travel-related case or whether it represents an early warning of a possible future emergence of TBEV.

Wildtool, a flexible, first-line risk assessment system for wildlife-borne pathogens

We describe the prototype of an electronic tool for risk assessment with dynamic ranking of wildlife-borne pathogens in function of their need for surveillance. Data about pathogens, their hosts and occurrences are obtained from literature and are classified as qualitative scores under six main criteria with their sub-criteria, corresponding to the elements of a standard risk assessment. Pathogen-specific data are reviewed by experts. The information is processed per pathogen through an algorithm and through summing up of the values obtained by converting four-tiered qualitative sub-criteria scores to weighted five-tiered numerical values. For a consistent comparison between pathogens, the “unknown” sub-criteria scores are assigned a median value of 3, allowing preservation of the sub-criteria concerned and their weights for the risk assessment, but minimizing the effect of this score on the outcome. Irregular data availability is further accommodated by a different data processing for comprehensiveness and refinement requirements, which is realised by a respective first- and second-level ranking of pathogens, the latter using additional quantitative and qualitative data for the release assessment. Continuous data updates are necessary to reflect the current situation in the field. Output flexibility is implemented by the possibility to run queries based on the choice of a region, a specific target group susceptible to the pathogens and a set of weights for the sub-criteria.

Serologic screening for 13 infectious agents in roe deer ( Capreolus capreolus ) in Flanders

Introduction In order to investigate the role of roe deer in the maintenance and transmission of infectious animal and human diseases in Flanders, we conducted a serologic screening in 12 hunting areas. Materials and methods Roe deer sera collected between 2008 and 2013 (n=190) were examined for antibodies against 13 infectious agents, using indirect enzyme-linked immunosorbent assay, virus neutralisation, immunofluorescence, or microagglutination test, depending on the agent. Results and discussion High numbers of seropositives were found for Anaplasma phagocytophilum (45.8%), Toxoplasma gondii (43.2%) and Schmallenberg virus (27.9%), the latter with a distinct temporal distribution pattern following the outbreak in domestic ruminants. Lower antibody prevalence was found for Chlamydia abortus (6.7%), tick-borne encephalitis virus (5.1%), Neospora caninum (4.8%), and Mycobacterium avium subsp paratuberculosis (4.1%). The lowest prevalences were found for Leptospira (1.7%), bovine viral diarrhoea virus 1 (1.3%), and Coxiella burnetii (1.2%). No antibodies were found against Brucella sp., bovine herpesvirus 1, and bluetongue virus. A significant difference in seroprevalence between ages (higher in adults >1 year) was found for N. caninum. Four doubtful reacting sera accounted for a significant difference in seroprevalence between sexes for C. abortus (higher in females). Conclusions Despite the more intensive landscape use in Flanders, the results are consistent with other European studies. Apart from maintaining C. abortus and MAP, roe deer do not seem to play an important role in the epidemiology of the examined zoonotic and domestic animal pathogens. Nevertheless, their meaning as sentinels should not be neglected in the absence of other wild cervid species.

The Assessment of African Swine Fever Virus Risk to Belgium Early 2014, using the Quick and Semiquantitative Pandora Screening Protocol

&NA; A risk assessment was organized during the early EU ASF outbreaks of early 2014 (February–April) and performed in cooperation with 15 Belgian and European experts on ASFV and its epidemiology in pigs/wild boar. African swine fever (ASF) is considered as one of the most dangerous infectious pig diseases, causing many outbreaks. Since the end of 2013 – early 2014, several outbreaks within the European Union (Lithuania, Poland, Estonia and Latvia) were reported to OIE, which prompted several risk assessments by (inter)national bodies and scientists. In this study, the open source, semiquantitative Pandora risk assessment tool was used for a quick overall screening of the risk posed by ASF to Belgium early 2014. A set of integrated risk scores was calculated within the Pandora framework. Experts scored the questions and uncertainty levels in the Pandora modules individually, after which the calculations were performed and averaged scores were used within pre‐defined risk scales to define and visualize the ASF risk to Belgium. Emergence risk was considered low (Pandora score 0.29), while disease consequences were deemed high (0.93); the resulting multiplicative overall risk of ASFV for Belgium was low (0.27). The Belgian experts tended to give lower risk scores than the European experts, especially for entry risk and trade/public opinion consequences. These risk scores are further interpreted with a due consideration of the qualitative data in the expert remarks and of other ASF risk assessments. The results are similar to more extensive and elaborate risk assessment models/procedures which may require more time and resources. The Pandora tool allows sequential updates to monitor (rates of) increasing risk and provides information for risk managers to organize targeted control.

Serological diagnosis of bovine neosporosis: a Bayesian evaluation of two antibody ELISA tests for in vivo diagnosis in purchased and abortion cattle

Currently, there are no perfect reference tests for the in vivo detection of Neospora caninum infection. Two commercial N caninum ELISA tests are currently used in Belgium for bovine sera (TEST A and TEST B). The goal of this study is to evaluate these tests used at their current cut-offs, with a no gold standard approach, for the test purpose of (1) demonstration of freedom of infection at purchase and (2) diagnosis in aborting cattle. Sera of two study populations, Abortion population (n=196) and Purchase population (n=514), were selected and tested with both ELISAs. Test results were entered in a Bayesian model with informative priors on population prevalences only (Scenario 1). As sensitivity analysis, two more models were used: one with informative priors on test diagnostic accuracy (Scenario 2) and one with all priors uninformative (Scenario 3). The accuracy parameters were estimated from the first model: diagnostic sensitivity (Test A: 93.54 per cent–Test B: 86.99 per cent) and specificity (Test A: 90.22 per cent–Test B: 90.15 per cent) were high and comparable (Bayesian P values >0.05). Based on predictive values in the two study populations, both tests were fit for purpose, despite an expected false negative fraction of ±0.5 per cent in the Purchase population and ±5 per cent in the Abortion population. In addition, a false positive fraction of ±3 per cent in the overall Purchase population and ±4 per cent in the overall Abortion population was found.

First TBEV serological screening in Flemish wild boar.

In the frame of a Flemish wildlife surveillance in 2013, a serological screening was performed on sera from wild boar (Sus scrofa; n=238) in order to detect tick-borne encephalitis virus (TBEV)-specific antibodies. Neutralising antibodies were titrated with a seroneutralisation test (SNT), using two cut-off titres (1/10–1/15). Seven wild boars were found TBEV-seropositive and showed moderate (>1/15) to high (>1/125) SNT-titres; three individuals had borderline results (1/10–1/15). This study demonstrated the presence of TBEV-specific antibodies in wild boar and highlighted potential TBEV-foci in Flanders. Additional surveillance including direct virus testing is now recommended.

Veal Calves Produce Less Antibodies against C. Perfringens Alpha Toxin Compared to Beef Calves

Enterotoxaemia is a disease with a high associated mortality rate, affecting beef and veal calves worldwide, caused by C. perfringens alpha toxin and perfringolysin. A longitudinal study was conducted to determine the dynamics of antibodies against these toxins in 528 calves on 4 beef and 15 veal farms. The second study aimed to determine the effect of solid feed intake on the production of antibodies against alpha toxin and perfringolysin. The control group only received milk replacer, whereas in the test group solid feed was provided. Maternal antibodies for alpha toxin were present in 45% of the veal calves and 66% of the beef calves. In beef calves a fluent transition from maternal to active immunity was observed for alpha toxin, whereas almost no veal calves developed active immunity. Perfringolysin antibodies significantly declined both in veal and beef calves. In the second study all calves were seropositive for alpha toxin throughout the experiment and solid feed intake did not alter the dynamics of alpha and perfringolysin antibodies. In conclusion, the present study showed that veal calves on a traditional milk replacer diet had significantly lower alpha toxin antibodies compared to beef calves in the risk period for enterotoxaemia, whereas no differences were noticed for perfringolysin.

Evaluation of 16 commercial antibody ELISAs for the detection of bovine viral diarrhea virus–specific antibodies in serum and milk using well-characterized sample panels

We performed a thorough fit-for-purpose evaluation of commercial ELISAs for the detection of bovine viral diarrhea virus (BVDV)-specific antibodies in serum and in milk by testing 2 panels of well-characterized serum and milk samples. Sixteen ELISAs from 9 different manufacturers, available on the Belgian market at the time of our study, were assessed for their diagnostic and analytical sensitivity (DSe and ASe, respectively), diagnostic specificity (DSp), and repeatability relative to the virus neutralization (VN) test considered to be the gold standard assay. Using serum as a matrix, DSe was much lower for competitive (c)ELISAs (min. 45%, max. 65%) than for indirect (i)ELISAs (min. 85%, max. 100%), partly because of the lower detection of positive samples from vaccinated animals included in the panel. ASe was also better for iELISAs; DSp was >95% for all but 2 ELISAs. Repeatability, expressed as coefficients of variation (CV) of optical densities, was generally good, although 3 ELISAs had a mean CV >10%. With milk samples, as observed for serum, DSe was lower for cELISAs (min. 57%, max. 75%) than for iELISAs (min. 61%, max. 89%), and DSp was high for all ELISAs (min. 94%, max. 100%). Both DSe and ASe were lower when testing milk samples compared to serum samples. These results confirm that serologic monitoring of BVDV-free herds should be performed using serum samples of unvaccinated animals to avoid interference of vaccination and to maximize the chance of detecting seroconversion linked to BVDV infection. Further investigations using a larger collection of field samples are recommended.