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.

An Outbreak of Porcine Reproductive and Respiratory Syndrome Virus in Switzerland Following Import of Boar Semen.

An outbreak of porcine reproductive and respiratory syndrome virus (PRRSV) occurred in November 2012 in Switzerland (CH), traditionally PRRSV-free. It was detected after a German boar stud informed a semen importer about the detection of PRRSV during routine monitoring. Tracing of semen deliveries revealed 26 Swiss sow herds that had used semen from this stud after its last negative routine monitoring and 62 further contact herds. All herds were put under movement restrictions and examined serologically and virologically. As a first measure, 59 sows from five herds that had previously been inseminated with suspicious semen were slaughtered and tested immediately. Investigations in the stud resulted in 8 positive boars with recent semen deliveries to CH (Seven with antibodies and virus, one with antibodies only). In one boar out of six tested, virus was detected in semen. Of the 59 slaughtered sows, five from three herds were virus-positive. In one herd, the virus had spread, and all pigs were slaughtered or non-marketable animals euthanized. In the remaining herds, no further infections were detected. After confirmatory testings in all herds 3 weeks after the first examination gave negative results, restrictions were lifted in January 2013, and Switzerland regained its PRRSV-free status. The events demonstrate that import of semen from non-PRRS-free countries--even from negative studs--poses a risk, because monitoring protocols in boar studs are often insufficient to timely detect an infection, and infections of sows/herds occur even with low numbers of semen doses. The outbreak was eradicated successfully mainly due to the high disease awareness of the importer and because immediate actions were taken before clinical or laboratory diagnosis of a single case in the country was made. To minimize the risk of an introduction of PRRSV in the future, stricter import guidelines for boar semen have been implemented.

[Does emergency vaccination make sense as a supporting element in control of foot-and-mouth disease in Switzerland]. / Ist die Notimpfung als unterstützende Massnahme zur Tilgung der Maul- und Klauenseuche in der Schweiz sinnvoll?

The outbreak of foot and mouth disease (FMD) in Great Britain in 2001 let to discussions and especially emergency vaccination was deemed as an alternative to the culling of vast numbers of healthy animals. The project emergency vaccination for FMD in Switzerland was conducted to compare the effectiveness of conventional control strategies during a FMD outbreak alone and with ring vaccination of 3 km and 10 km, respectively. The results of this project showed that emergency vaccination conducted at the beginning of an epidemic was not favorable compared to conventional disease control strategy in Switzerland. In case of an advanced FMD epidemic, a 10 km ring vaccination could support the disease control in a positive way. However, the goal of emergency vaccination to save animal live can hardly be achieved due to actual legal basis and the consequent restriction measures within vaccination zones which will lead to welfare culling.

L'épizootie de fièvre aphteuse en Grande Bretagne en 2001 a montré que les abatages de masse d'animaux sains sont plus en plus critiquée. On discute régulièrement de la vaccination d'urgence comme mesure permettant de réduire le nombre d'animaux à tuer en cas d'épizootie. Dans le cadre du projet vaccination d'urgence FA suisse, on a comparé l'effet de la seule lutte conventionnelle avec celui d'une vaccination d'urgence «vaccination to live¼ dans un périmètre de 3 km (GV3) respectivement 10 km (GV10) quant à la durée et à l'importance du foyer. Au début d'une épizootie, la vaccination d'urgence supplémentaire n'apporte pas d'avantage face à la lutte conventionnelle. Si une vaccination V10 est pratiquée plus tardivement, elle peut dans certains cas amener une diminution et un raccourcissement de l'épizootie. Le but visant, grâce à la vaccination d'urgence, à tuer moins d'animaux ne peut toutefois pas, dans les conditions actuelles, être atteint car vu les fortes limitations du trafic d'animaux à l'intérieur des zones de vaccination, on doit compter avec des abattages pour des raisons de protections des animaux.

[Infectious bovine rhinotracheitis (IBR) in the canton of Jura: an epidemiological outbreak investigation]. / Rhino-trachéite infectieuse bovine (IBR) dans le canton du Jura: enquête épidémiologique.

Following an abortion in a beef herd in the summer of 2009, three outbreaks of infectious bovine rhinotracheitis (IBR) were diagnosed in the cantons of Jura and Neuchatel. An epidemiological outbreak investigation was conducted with the aims to identify the source of introduction of the bovine herpes virus 1 (BoHV-1) into the affected herds and to prevent further spread of the disease. The attack rates in the three outbreak farms were 0.89, 0.28 and 0, respectively. BoHV-1 could be isolated from nasal swabs of two animals originating from one of the affected farms. Comparative restriction enzyme analysis revealed slight differences between the isolates of the two animals, but a high similarity to previous BoHV-1 isolates from the canton of Jura, as well as to a French BoHV-1 isolate. This IBR outbreak has shown the importance of reporting and analyzing abortions. The current disease outbreaks recall the main risk factors for the spread of IBR in Switzerland: purchase and movement of bovines and semen of often unknown IBR status.

[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.

[Livestock owners with specifically increased disease awareness for Bluetongue: A new approach to disease surveillance]. / Tierhalter mit gezielt erhöhter "Disease Awareness" für die Blauzungenkrankheit: Ein neuer Ansatz in der Seuchenüberwachung.

For the first time in Switzerland, specifically trained livestock owners were included in a national disease surveillance program by the Federal Veterinary Office. A questionnaire on data about clinical and epidemiological aspects of Bluetongue Disease (BT) as well as on herd management was completed by 26 sheep owners three months after they had attended a training course about BT. The control group, consisted of 264 randomly selected sheep and cattle owners who had not visited a training course. Results showed that disease awareness for BT after attending the training course was considerably increased. This was especially evident in the better knowledge of the participants about the great number of possible symptoms. Training courses with the objective of increased disease awareness of livestock owners are an efficient, cost-effective instrument in control programs for exotic diseases.

[Serological and clinical proof of freedom from Equine Infectious Anemia (EIA) in imported and domestic horses in Switzerland]. / Serologischer und klinischer Nachweis der Freiheit von Equiner Infektiöser Anämie (EIA) bei importierten und einheimischen Pferden in der Schweiz.

Since 1991, no cases of Equine Infectious Anemia (EIA) have been reported in Switzerland. Risk factors for introduction of the virus into Switzerland are still present or have even increased as frequent inapparent infections, large numbers of imported horses, (since 2003) absence of compulsory testing prior to importation, EIA cases in surrounding Europe, possible illegal importation of horses, frequent short-term stays, poor knowledge of the disease among horse owners and even veterinarians. The aim of this study was to provide evidence of freedom from EIA in imported and domestic horses in Switzerland. The serum samples from 434 horses imported since 2003 as well as from 232 domestic horses fifteen years of age or older (since older horses have naturally had a longer time of being exposed to the risk of infection) were analysed using a commercially available ELISA test. All samples were seronegative, indicating that the maximum possible prevalence that could have been missed with this sample was 0.5% (95% confidence).

[Bluetongue disease reaches Switzerland]. / Blauzungenkrankheit erreicht die Schweiz.

Since 2006 bluetongue disease is rapidly spreading across Europe and reached Switzerland in October 2007. In the present article a short overview about the disease and the virus is given, and the first three clinical bluetongue disease cases in cattle, and the respective laboratory findings are presented.

Risk factors for the infection of Swiss goat herds with small ruminant lentivirus: a case-control study.

In the mid-1980s, Switzerland started a programme to eradicate caprine arthritis-encephalitis - an infectious disease of goats caused by the small ruminant lentivirus (srlv). Since 1996, progress towards eradication has slowed down, owing to infections occurring on farms from which the infection had previously been eliminated. To investigate specific risk factors for these new infections and to improve the eradication programme, a case-control study was conducted. Cases consisted of farms that had been officially free of srlv for at least three consecutive years but on which at least one srlv-seropositive animal had been detected during the annual serological surveys of 2001 and 2002. On all the case and control farms where sheep were housed together with goats, a subset of sheep was screened for antibodies to srlv. Potential risk factors were analysed in a logistic regression model; the results indicated that close contact with srlv-seropositive sheep was highly correlated with seroconversion in srlv-seronegative goat herds (odds ratio=26.9), supporting the hypothesis that srlv can be transmitted between sheep and goats, and suggesting that the measures taken so far will not lead to the complete eradication of srlv from Switzerland within the next few years.

[Beyond BSE: Transmissible spongiform encephalopathies in other animal species]. / Jenseits von BSE: Transmissible spongiforme Enzephalopathien bei anderen Tierarten.

There are several other diseases besides BSE which belong to the group of transmissible spongiform encephalopathies (TSE). Although most mammals can be experimentally infected with the agent of these diseases, generally only single representatives of the orders Artiodactyla (cloven-hoofed animals), Carnivora (carnivores) and Primates (humans and monkeys) are naturally infected in the field. An overview of the current state of knowledge on TSE in several species like exotic ruminants, deer, mink and cats is presented. Etiological, clinical, anatomic-pathological and epidemiological aspects are described.

[A method to identify BSE suspects in emergency slaughtered cattle during ante mortem examination]. / Eine Methode zur Erkennung von BSE-Verdachtsfällen in der Gruppe der krankgeschlachteten Rinder während der ante mortem Untersuchung.

A method is presented by which a maximal number of BSE-infected cattle that had escaped the filter of clinical examination are identified during ante mortem examination. This approach might prove to be an efficient and cost-effective method for veterinary and non-veterinary meat inspectors to remove infected animals prior to slaughter. In a case-control study, the clinical signs of 224 randomly selected sick slaughtered animals were compared with the clinical signs of 26 sick slaughtered animals in which BSE infection was diagnosed using a rapid test post mortem. In addition, the clinical signs of the sick slaughtered BSE-positive animals were compared with the clinical signs of a group of BSE suspects identified during the same time period and in which BSE infection could be confirmed. As a result of this study a mathematical model was developed to identify BSE suspects. This model contains a total of 7 variables (clinical signs) that proved to be of importance. These signs were aggressive behaviour, grinding of teeth, protruding eyeballs, reduced rumination, inability to stand, overexcitability, and difficulty in standing up. The presented model has a sensitivity of 61.5% (16 out of 26 BSE-positive animals slaughtered while sick were identified) and a specificity of 99.6% when compared to a rapid test conducted post mortem.

[The eradication of BSE: a touch stone for the veterinary services]. / Die Bekämpfung der BSE: Ein Prüfstein für den Veterinärdienst.

The eradication of BSE is proving to be a lengthy task. Undisputedly, it has become one of the highest priority tasks of the Veterinary Services in Europe since the disease first occurred in the mid eighties. However, the effects of the ongoing eradication effort also impair important economic agricultural sectors. Risk analysis has never before been such a critical tool in the decision-making processes for eradication of animal diseases, despite the problem that many risk analyses are being conducted in the face of incomplete knowledge about BSE. In the focus are the measures minimizing the risk for humans (such as the ban on specified risk material) and the measures implemented to prevent the spread of the disease in animals with the ban on feeding meat and bone meal to ruminants. Due to the long incubation period, implementation of insufficient measures may not be noticed for many years. Implementation of drastic measures is needed, if the eradication of the disease is to be pursued purposefully.

Bovine viral diarrhoea virus and bovine herpesvirus-1 prime uninfected macrophages for lipopolysaccharide-triggered apoptosis by interferon-dependent and -independent pathways.

The flavivirus bovine viral diarrhoea (BVD) virus exists in two biotypes, cytopathic (cp) and non-cytopathic (ncp), defined by their effect on cultured cells. Cp BVD virus-infected cells undergo apoptosis and may promote apoptosis in uninfected cells by an indirect mechanism. Macrophages (Mφ) infected with cp, but not ncp, BVD virus release a factor(s) in the supernatant capable of priming uninfected Mφ for activation-induced apoptosis in response to lipopolysaccharide. A possible role of interferon (IFN) type I was suggested previously by the observation that this cytokine primed for activation-induced apoptosis and was present in supernatants of Mφ infected with cp, but not ncp, BVD virus. Here, supernatants of both Mφ infected with a wider range of cp BVD virus and Mφ infected with bovine herpesvirus-1 are shown to contain such priming activity. Two lines of evidence indicate that factors in addition to IFN type I prime uninfected Mφ for apoptosis. First, supernatants of Mφ infected with cp BVD virus contained much less IFN than is required for priming for apoptosis. Second, whereas antiviral activity was neutralized by a vaccinia virus-encoded IFN type I receptor, B18R, the capacity of the supernatant to prime for apoptosis was unaffected by this treatment. The apparent molecular mass of the factor(s) priming for apoptosis was between 30 and 100 kDa. Priming of uninfected cells for activation-induced apoptosis may add a new facet to virus pathogenesis and may contribute to the formation of lesions not related directly to virus replication.

[Ten years of BSE in Switzerland. The development of an extraordinary disease]. / 10 Jahre BSE in der Schweiz. Der Verlauf einer aussergewöhnlichen Krankheit.

The first case of bovine spongiform encephalopathy (BSE) in Switzerland was diagnosed in November 1990. BSE is--in particular considering its eradication--different from many other livestock diseases. Strict disease control measures were taken from the very beginning by the Swiss authorities in order to protect public as well as animal health. In addition, BSE has stimulated enormous media interest and public concern. The occurrence of the born after the ban (BAB) cases, increasing questions about the zoonotic potential of the disease and trade restrictions against Switzerland led to the "BSE-crisis". In 1999, Switzerland internationally took a leading role in the surveillance of BSE by active investigation of targeted risk population.

A bioassay for interferon type I based on inhibition of Sendai virus growth.

The expression of type I interferons (IFNs) in eukaryotic cells represents a first line of defense against viral infection. Cells pretreated by IFNs do not support viral replication and are protected from virus-induced cell destruction. A challenge of IFN-pretreated cells with vesicular stomatitis virus (VSV) is frequently used to quantitate this cytokine because, on the one hand, the replication of VSV is highly sensitive to IFNs and, on the other hand, in unprotected cells this virus induces a rapid cytopathic effect that can readily be quantified. However, as VSV may infect humans and is known to cause severe disease in a variety of animal species, this virus must be considered a biohazard. In this paper, we describe a bioassay for bovine IFN using Sendai virus, a paramyxovirus that grows readily in MDBK cells yet is released from these cells in a non-infectious form. The sensitivity and dynamic range of this assay are similar to those of the popular VSV-based IFN assay. We demonstrate that the Sendai-virus-based IFN assay permits rapid quantitation of recombinant bovine type I IFN, and also of native type I IFNs which are present in the supernatants of monocyte-derived macrophages infected with various pathogens. In view of the possible artifacts induced by viruses in samples to be assayed for IFN activity, we evaluated several methods of virus inactivation. Treatment with beta-propiolactone led to virus inactivation without affecting the bioactivity of IFNs as detected in the Sendai-virus-based assay.

Supernatants of virus-infected macrophages prime uninfected macrophages for lipopolysaccharide-induced apoptosis by both an interferon-dependent and an independent mechanism.

Virus-infected macrophages (M phi) release factors priming uninfected M phi for LPS-induced apoptosis. This was shown for bovine M phi infected with cytopathogenic bovine virus diarrhea (BVD) virus or with bovine herpes virus-1 (BHV-1) but not for M phi infected with noncytopathogenic BVD virus. The former two viruses also induced interferon type I in M phi, which also primes macrophages for LPS-induced apoptosis. However, several lines of evidence suggested that virus-infected M phi produce IFN-independent factors priming for apoptosis. For example, a soluble IFN type I receptor abrogated the antiviral activity, but not the ability of supernatants to prime uninfected M phi for LPS-induced apoptosis. It is suggested that the production of factors priming uninfected cells for apoptosis plays a part in virus-induced pathogenesis, e.g. in cattle afflicted with mucosal disease, or with infectious bovine rhinotracheitis, or in viral diseases inducing a marked lymphopenia.