[BVD situation on farms with high serological values in the tank milk - individual animals have a greater influence than previously known]. / BVD-Situation auf Betrieben mit hohen serologischen Werten in der Tankmilch ­ Einzeltiere haben einen grösseren Einfluss als bisher bekannt.

INTRODUCTION: Bovine virus diarrhea (BVD) is an economically important disease in cattle. Switzerland started an eradication program in 2008. After the initial virological examination of all cattle followed by the examination of all newborn calves, the BVD prevalence in 2012 was low enough to start serological monitoring. An unusually high number of increased tank milk values were observed during this serological monitoring in autumn 2019. No seropositive animals were found on most farms in the follow-up cattle group testing. The present study was designed in the form of a multiple case report to better assess the BVD situation in a herd after a serological tank milk result above the cut-off value. The tank milk of 13 farms with serological values above the cut-off value from the analyses in autumn 2019 was examined again with two different ELISA tests in spring 2020. In addition, at the same time blood samples were taken to obtain serological values of all adult cattle on the farm. The results of the two tests that were used to examine the tank milk samples correlated well with each another. The results of the tank milk serology showed a low correlation with the seroprevalence in the lactating cows, but no correlation with the seroprevalence of all adult animals in the herd. A single seropositive animal had a major influence on the results of the tank milk serology in some herds. In addition, correct tank milk sampling must be ensured because the representativeness of the tank milk sample is decisive for a meaningful result for the investigated farm. If the result of the tank milk test is above the cut-off value, the examination of a group of cattle is still the best way to identify a current infection in a herd.

INTRODUCTION: La diarrhée virale bovine (BVD) est une maladie des bovins économiquement importante. En Suisse, cette maladie fait l'objet d'un programme d'éradication depuis 2008. Après l'examen virologique initial de tous les bovins, suivi de l'examen de tous les veaux nouveau-nés, la prévalence de la BVD en 2012 était suffisamment faible pour permettre d'adapter le programme de surveillance et de procéder à un suivi sérologique des exploitations laitières. Un nombre inhabituellement grand de valeurs élevées dans les examens de lait de citerne a été observé lors de cette surveillance sérologique en automne 2019. Dans de nombreuses exploitations, aucun animal séropositif n'a pu être découvert lors des tests de suivi des groupes de bovins. Cette étude a été conçue sous la forme d'un rapport de cas multiples pour mieux évaluer la situation de la BVD dans un troupeau après un résultat sérologique de lait de citerne supérieur à la valeur limite. Le lait de citerne de 13 exploitations avec des valeurs sérologiques supérieures à la valeur limite en automne 2019 a été analysé à nouveau avec deux tests ELISA différents au printemps 2020. De plus, des échantillons de sang ont été prélevés en même temps pour obtenir les valeurs sérologiques de tous les bovins adultes présents sur l'exploitation. Les résultats des deux tests utilisés pour examiner les échantillons de lait de citerne montraient une bonne corrélation entre les deux tests. Les résultats de la sérologie du lait de citerne ont montré une faible corrélation avec la séroprévalence chez les vaches en lactation mais pas avec la séroprévalence de tous les animaux adultes du troupeau. Un seul animal séropositif pouvait avoir à lui seul une forte influence sur les résultats de la sérologie du lait de citerne dans certains troupeaux. De plus, un prélèvement correct du lait de citerne doit être assuré car la représentativité de l'échantillon est décisive pour obtenir un résultat significatif pour l'exploitation étudiée. Si le résultat du test est supérieur à la valeur limite, l'examen d'un groupe de bovins reste le meilleur moyen d'identifier une infection dans un troupeau.

Diagnostic response to a cross-border challenge for the Swiss caprine arthritis encephalitis virus eradication program.

INTRODUCTION: Animal trading between countries with different small ruminant lentivirus infectious status is a potential danger for the reintroduction of eradicated genotypes. This was the case in 2017 with the importation of a large flock of seropositive goats into Switzerland. The handling of this case permitted us to test the preventive measures in place. The coordination between the local veterinarian and the cantonal and federal veterinary authorities worked efficiently and rapidly involved the national reference center in the investigations. This case posed a challenge for the reference center and enabled scrutiny of the applied diagnostic tests. ELISA and western blot provided consistent results and pointed to an unusually high infection rate in the flock. This was confirmed by the isolation of several viruses from different organs and cells, demonstrating that the spleen is particularly well suited for isolation of small ruminant lentiviruses. The SU5-ELISA, designed to predict the subtype of the infecting virus, correctly pointed to a B1 subtype as the infectious agent. We confirmed that with this test it is necessary to analyze a representative number of samples from a flock and not just individual sera to obtain reliable results. This analysis permitted us to identify particular amino acid residues in the SU5 peptides that may be crucial in determining the subtype specificity of antibody binding. Different gag-pol and env regions were amplified by PCR using primers designed for this purpose. The phylogenetic analysis revealed a surprisingly high heterogeneity of the sequences, pointing to multiple infections within single animals and the entire flock. In conclusion, this case showed that the defense of the CAEV negative status of the Swiss goat population with respect to the virulent, prototypic B1 subtype of small ruminant lentiviruses, requires, among other measures, a diagnostic facility capable of performing a thorough analysis of the collected samples.

INTRODUCTION: Le commerce d'animaux entre pays où le statut infectieux des lentivirus des petits ruminants est différent constitue un danger potentiel pour la réintroduction de génotypes éradiqués. Ce fut le cas en 2017 avec l'importation d'un grand troupeau de chèvres séropositives en Suisse. Le traitement de cette affaire nous a permis de tester les mesures préventives mises en place. La coordination entre le vétérinaire local et les autorités vétérinaires cantonales et fédérales a été efficace et a impliqué rapidement le centre de référence national dans les enquêtes. Ce cas a constitué un défi pour le centre de référence et a permis d'examiner de près les tests de diagnostic appliqués. Les tests ELISA et Western blot ont fourni des résultats cohérents et ont mis en évidence un taux d'infection anormalement élevé dans le troupeau. Cela a été confirmé par l'isolement de plusieurs virus provenant d'organes et de cellules différents, démontrant que la rate est particulièrement bien adaptée à l'isolement des lentivirus des petits ruminants. Le SU5-ELISA, conçu pour prédire le sous-type du virus infectant, désignait correctement un sous-type B1 en tant qu'agent infectieux. Nous avons confirmé qu'avec ce test, il était nécessaire d'analyser un nombre représentatif d'échantillons d'un troupeau et pas seulement des sérums individuels pour obtenir des résultats fiables. Cette analyse nous a permis d'identifier des résidus d'acides aminés particuliers dans les peptides SU5 qui pourraient jouer un rôle crucial dans la détermination de la spécificité de sous-type de la liaison à l'anticorps. Différentes régions gag-pol et env ont été amplifiées par PCR en utilisant des amorces conçues à cet effet. L'analyse phylogénétique a révélé une hétérogénéité étonnamment élevée des séquences, indiquant de multiples infections chez les animaux isolés et dans l'ensemble du troupeau. En conclusion, cette affaire a montré que la défense du statut négatif CAEV de la population de chèvres suisses vis-à-vis du virus virulent, sous-type B1 des lentivirus des petits ruminants, nécessite, entre autres mesures, un système de diagnostic capable d'effectuer une analyse approfondie des échantillons collectés.

Evaluation of control and surveillance strategies for classical swine fever using a simulation model.

Classical swine fever (CSF) outbreaks can cause enormous losses in naïve pig populations. How to best minimize the economic damage and number of culled animals caused by CSF is therefore an important research area. The baseline CSF control strategy in the European Union and Switzerland consists of culling all animals in infected herds, movement restrictions for animals, material and people within a given distance to the infected herd and epidemiological tracing of transmission contacts. Additional disease control measures such as pre-emptive culling or vaccination have been recommended based on the results from several simulation models; however, these models were parameterized for areas with high animal densities. The objective of this study was to explore whether pre-emptive culling and emergency vaccination should also be recommended in low- to moderate-density areas such as Switzerland. Additionally, we studied the influence of initial outbreak conditions on outbreak severity to improve the efficiency of disease prevention and surveillance. A spatial, stochastic, individual-animal-based simulation model using all registered Swiss pig premises in 2009 (n=9770) was implemented to quantify these relationships. The model simulates within-herd and between-herd transmission (direct and indirect contacts and local area spread). By varying the four parameters (a) control measures, (b) index herd type (breeding, fattening, weaning or mixed herd), (c) detection delay for secondary cases during an outbreak and (d) contact tracing probability, 112 distinct scenarios were simulated. To assess the impact of scenarios on outbreak severity, daily transmission rates were compared between scenarios. Compared with the baseline strategy (stamping out and movement restrictions) vaccination and pre-emptive culling neither reduced outbreak size nor duration. Outbreaks starting in a herd with weaning piglets or fattening pigs caused higher losses regarding to the number of culled premises and were longer lasting than those starting in the two other index herd types. Similarly, larger transmission rates were estimated for these index herd type outbreaks. A longer detection delay resulted in more culled premises and longer duration and better transmission tracing increased the number of short outbreaks. Based on the simulation results, baseline control strategies seem sufficient to control CSF in low-medium animal-dense areas. Early detection of outbreaks is crucial and risk-based surveillance should be focused on weaning piglet and fattening pig premises.

Economic evaluation of the surveillance and intervention programme for bluetongue virus serotype 8 in Switzerland.

Empirical analyses founded on sound economic principles are essential in advising policy makers on the efficiency of resource use for disease mitigation. Surveillance and intervention are resource-using activities directed at mitigation. Surveillance helps to offset negative disease effects by promoting successful intervention. Intervention is the process of implementing measures (e.g. vaccination or medication) to reduce or remove a hazard in a population. The scale and ratios in which the two are combined affect the efficiency of mitigation, its costs, benefits, and thus net effect on society's well-being. The Swiss national mitigation programme for bluetongue virus serotype 8 was used as case study to investigate the economic efficiency of mitigation. In 2008, Switzerland implemented a vaccination programme to avoid and reduce disease and infection in its ruminant population. To monitor the vaccination programme and the vector dynamics, a surveillance system consisting of serological and entomological surveillance was established. Retrospective analyses for the years 2008-2009 and prospective analyses for the years 2010-2012 were conducted to investigate if the mitigation programme was economically beneficial. In the retrospective analysis, the implemented programme (=comparative scenario) was compared to a hypothesised baseline scenario of voluntary vaccination and surveillance. In the prospective analysis, the comparative scenario assumed to continue was compared to two baseline scenarios: one of voluntary vaccination combined with surveillance and one of no vaccination combined with surveillance. For each scenario, monetary surveillance, intervention and disease costs were calculated. The comparison of baseline and comparative scenarios yielded estimates for the total benefit (=disease costs avoided), margin over intervention cost and the net value of the programme. For 2008-2009, in aggregate, the mean biannual total benefit was 17.46 m Swiss francs (CHF) (1CHF=0.66€ at the time of analysis) and the mean net benefit after subtraction of the intervention and surveillance cost was 3.95 m CHF. For the three years 2010-2012, overall net costs were estimated at 12.93 m and 8.11 m CHF, respectively, for comparison of the implemented mitigation programme with the two baseline scenarios. It was concluded that the surveillance and intervention programme implemented in 2008-2009 was economically beneficial, while its continuation in the same form in 2010-2012 would produce net costs. These costs were due to the mean intervention cost remaining constant at a level of approximately 11 m CHF per year while the mean total benefit would be gradually reduced in 2010-2012 due to the reduced occurrence of disease in a fully vaccinated population.

[Vaccination as a supporting measure to control animal disease outbreaks in Europe: Findings for Switzerland]. / Die Impfung als unterstützende Massnahme zur Tilgung von Tierseuchenausbrüchen in Europa: Erkenntnisse für die Schweiz.

Switzerland and the European Union have a non-vaccination policy for many animal diseases relevant for trade. Because of the relatively low animal density, disease control measures in Switzerland focus on the immediate culling of infected animals. However, the use of vaccines as a supporting measure can represent an effective option to promptly contain an epidemic and to reduce the number of animals to be killed. A prerequisite for the success of vaccination is its early, rapid and purposeful implementation. Vaccinations can be cost-intensive and can entail restrictions in international trade. For the choice of the appropriate control measure it is therefore important to thoroughly assess the epidemiology, the economic consequences of the control measures and the acceptance of these measures by the environment. Because of their special epidemiology, vaccination has clear advantages as a preventive measure for vector-borne diseases.

Antimicrobial resistance in bacteria from Swiss veal calves at slaughter.

Bacteria with antimicrobial resistance can be transferred from animals to humans and may compromise antimicrobial treatment in case of infection. To determine the antimicrobial resistance situation in bacteria from Swiss veal calves, faecal samples from 500 randomly selected calves originating from 129 farms were collected at four big slaughterhouses. Samples were cultured for Escherichia coli, Enterococcus sp. and Campylobacter sp. and isolated strains were tested for antimicrobial susceptibility to selected antimicrobial agents by the minimal inhibitory concentration technique using the broth microdilution method. From 100 farms, data on farm management, animal husbandry and antimicrobial treatments of the calves were collected by questionnaire. Risk factors associated with antimicrobial resistance were identified by logistic regression. In total, 467 E. coli, 413 Enterococcus sp. and 202 Campylobacter sp. were isolated. Of those, 68.7%, 98.7% and 67.8%, respectively, were resistant to at least one of the tested antimicrobial agents. Resistance was mainly observed to antimicrobials frequently used in farm animals. Prevalence of resistance to antimicrobials important for human treatment was generally low. However, a rather high number of quinupristin/dalfopristin-resistant Enterococcus faecium and ciprofloxacin-resistant Campylobacter sp. were detected. External calf purchase, large finishing groups, feeding of milk by-products and administration of antimicrobials through feed upon arrival of the animals on the farm significantly increased the risk of antimicrobial resistance at farm level. Participation in a quality assurance programme and injection of a macrolide upon arrival of the animals on the farm had a protective effect. The present study showed that veal calves may serve as a reservoir for resistant bacteria. To ensure food safety, veal calves should be included in the national monitoring programme for antimicrobial resistance in farm animals. By improving farm management and calf husbandry the prevalence of resistance may be reduced.