[Food hygiene and safety - What is your diagnosis?] / Lebensmittelhygiene ­ Was ist Ihre Diagnose?

INTRODUCTION: A healthy, 1,5 year old female wild boar (Sus scrofa) was shoot in a hunting district in Switzerland on June 22, 2023. The meat inspection revealed noticeable skin changes on all four distal extremities which were described histologically as multifocal epidermal hyperplasia and moderate orthokeratotic hyperkeratosis. The rest of the animal body, the organs and the lymph nodes were without any obvious lesions. The diagnosis of papilloma virus-associated exophytically growing papillomas was made. The venison was approved as fit for human consumption.

INTRODUCTION: Un sanglier femelle (Sus scrofa) en bonne santé, âgé d'un an et demi, a été abattu dans le nord de la Suisse le 22 juin 2023. L'inspection de la viande a révélé des modifications cutanées notables sur les quatre extrémités distales des membres qui ont été décrites histologiquement comme une hyperplasie épidermique multifocale et une hyperkératose orthokératosique modérée. Le reste du corps de l'animal, les organes et les ganglions lymphatiques ne présentaient aucune lésion évidente. Le diagnostic de papillomes à croissance exophytique associés à des papillomavirus a été posé. La venaison a été déclarée propre à la consommation humaine.

[Equine Infectious Anaemia - a review from an official veterinary perspective]. / Die Equine Infektiöse Anämie ­ eine Besprechung aus amtstierärztlicher Sicht.

INTRODUCTION: Equine infectious anaemia (EIA) is a sporadic viral disease in many countries. Every single case has, however, a dramatic impact: infected animals have to be put down, and quarantine restrictions on horse movements lasting three months lead to substantial economic losses. In Switzerland, the mandatory notification was introduced in 1994 in order to facilitate international traffic. A year later, the "new" Ordinance on epizootics of 1995 classified EIA as a "disease to be eradicated". An infected polo horse in the canton of Argovia in summer 2017 thus represented Switzerland's first official case. It served as a starting point to review the legal frameworks of the EU and Switzerland. Recent publications suggest that there might be some potential to optimize the current diagnostic protocols. EIA is transmitted by virus-containing blood and blood products. Introductions in previously disease-free regions are mostly due to human activities, while blood feeding insects as horse flies or other biting flies act as mechanical vectors only locally within some 100 meters. As before, the new EU Regulations governing animal health do not prescribe national monitoring and control plans, allowing member states to shape them according to their particular situation. However, they have to ensure that equids intended for intracommunity movements comply with specific guarantees. In this context, a fine-tuning of current international standards seems conceivable. Mandatory testing preceding each movement would not be a proportionate option even for the future. Regardless their final wording, it would be a great step for all the actors involved in animal traffic if it were possible to adopt rules that are accepted and uniformly implemented by all competent authorities at national, regional and local level. However, the official system will never be able to guarantee absolute safety. Since there are neither effective vaccines nor treatment protocols, it is crucial that all owners, stablehands, veterinarians, associations, and organizers of horse contests are aware of the disease risks, minimizing them as far as possible by adequate biosecurity measures.

INTRODUCTION: L'anémie infectieuse des équidés (AIE) est une maladie virale sporadique dans de nombreux pays. Chaque cas a pourtant de graves conséquences: les animaux infectés doivent être éliminés, et les interdictions de mouvements d'équidés pendant trois mois causent des pertes économiques substantielles. En Suisse, la notification obligatoire a été introduite en 1994 pour faciliter les échanges transfrontaliers. En 1995, la «nouvelle¼ ordonnance sur les épizooties a ensuite classé l'AIE dans la catégorie des «épizooties à éradiquer¼. Le cheval de polo infecté, qui a été découvert durant l'été 2017 dans le canton d'Argovie, représente donc le premier cas officiel d'AIE en Suisse. Il a servi de point de départ pour une appréciation de la réglementation de l'UE et du droit suisse. Des études récentes indiquent qu'il existerait un potentiel d'optimisation des protocoles de diagnostic. L'AIE est transmise par le sang et les produits sanguins contenant l'agent infectieux. L'introduction de la maladie dans une région indemne est souvent liée à des activités humaines, les insectes hématophages, comme les taons ou les mouches piquantes, peuvent servir de vecteurs mécaniques au niveau local, dans un rayon ne dépassant pas quelques centaines de mètres. Comme l'actuelle, la nouvelle réglementation de l'UE régissant la santé animale ne prescrira pas aux États membres une stratégie nationale de surveillance ou de lutte, qu'ils peuvent en conséquence adapter en fonction de leur situation particulière. Ils doivent toutefois assurer que les équidés destinés aux mouvements intracommunautaires remplissent des conditions spécifiées. A cet égard, un «ajustage¼ des normes internationales parait envisageable, mais comme c'est déjà le cas actuellement, un examen de laboratoire avant tout déplacement ne sera pas exigé. Indépendamment de leur formulation finale, des conditions de déplacement d'équidés généralement acceptées et appliquées uniformément par toutes les autorités compétentes aux échelles nationales, régionales et locales signifieraient un grand progrès pour tous les acteurs impliqués dans le trafic d'animaux. Les législations ne pourront jamais garantir une sécurité absolue. Considérant qu'il n'existe ni vaccination efficace ni traitement, il est crucial que les détenteurs, palefreniers, vétérinaires, associations et organisateurs de manifestations équestres soient conscients du danger d'épizootie, et qu'ils le réduisent autant que possible par des mesures de biosécurité adéquates.

Outbreak investigation: how to prevent laboratory contamination during high-throughput testing.

This is particularly important for outbreaks of highly contagious animal diseases. Efficient and correct testing as well as the reduction of technical breakdowns should be addressed by a laboratory contingency plan specially designed for the use of polymerase chain reactions (PCRs), i.e. PCR or reverse transcription PCR ([RT]-PCR) or the high-throughput quantitative real-time form of these tests([RT]-qPCR). Problems with contamination during outbreak investigations can negatively impact reliable diagnostics, and ultimately the eradication of the disease in the field. Therefore, well-defined standard procedures for preventing contamination are highly recommended, particularly in emergencies when a steep increase in the number of samples necessitates the use of additional, less-experienced laboratory support staff. In the context of an outbreak, the possible implementation of preclinical testing is an important point of discussion. Very sensitive methods, which are prone to contamination, are used for this type of testing, increasing the risk of false-positive results. Potential approaches to minimising contamination include standard protocols adapted for high-throughput analyses, different procedures for samples with an expected high or low viral load, and the prioritisation and treatment of samples with respect to epidemiological aspects (e.g. epidemic vs endemic situations). Although there may be pressure to perform outbreak investigations as soon as possible, the authors do not recommend preclinical testing in every case due to the severe consequences of false-positive results. Contingency plans should be discussed with the responsible authorities and communicated to relevant personnel before an outbreak occurs. The specific aim of this paper is the detailed description of solutions to prevent the laboratory contamination of samples and to avoid the generation of false-positive results.

L'identification précoce des maladies est un facteur essentiel pour mettre rapidement en place les mesures de (bio)sécurité et d'éradication appropriées. Ainsi, en cas d'apparition d'un foyer, il est indispensable de pouvoir compter sur un diagnostic à la fois rapide et précis. Cette condition est particulièrement importante lorsqu'il s'agit de foyers de maladies animales à forte contagiosité. Les objectifs d'efficacité et de justesse des protocoles d'essai et la réduction des défaillances techniques doivent faire l'objet d'un plan d'intervention d'urgence au laboratoire, conçu spécialement pour les amplifications en chaîne par polymérase (PCR) à haut débit en temps réel, c'est-à-dire la PCR simple ou couplée à une transcription inverse ([RT]­PCR) ou encore la forme quantitative de ces deux tests ([RT]­qPCR). Les problèmes de contamination pendant les enquêtes sur les foyers peuvent avoir un impact négatif sur la fiabilité du diagnostic et compromettre à terme les chances d'éradiquer la maladie sur le terrain. Il est donc vivement recommandé de mettre en place des procédures normalisées prédéfinies visant à empêcher tout risque de contamination, en particulier dans les situations d'urgence où l'augmentation soudaine du nombre d'échantillons à analyser impose de faire appel à un personnel de soutien, parfois moins expérimenté. La possibilité de procéder à des analyses précliniques dans le contexte d'un foyer est un élément important de la discussion. Pour ce type d'essais, il est fait appel à des méthodes extrêmement sensibles qui sont davantage exposées aux contaminations, ce qui accroît le risque d'obtenir des résultats faussement positifs. Les méthodes envisagées pour minimiser la contamination sont l'application de protocoles normalisés adaptés aux analyses à haut débit, le recours à des procédures différentes suivant que la charge virale attendue des échantillons est forte ou faible, et la priorisation et traitement différenciés des échantillons en fonction de leurs caractéristiques épidémiologiques (par exemple, situations d'épidémie versus d'endémie). Malgré les pressions exercées pour des enquêtes aussi rapides que possible sur les foyers, les auteurs ne recommandent pas que des analyses précliniques soient effectuées en toutes circonstances, compte tenu de la gravité des conséquences des résultats faussement positifs. Il convient d'examiner les plans d'urgence avec les autorités responsables et de les transmettre aux personnels en charge de les appliquer avant la survenue d'un foyer. L'objectif de l'article est de décrire en détail les solutions permettant de prévenir les contaminations au laboratoire et d'éviter la production massive de résultats faussement positifs.

La pronta identificación de las enfermedades es esencial para aplicar con rapidez medidas de (bio)protección y erradicación. En este sentido, ante un eventual brote el diagnóstico debe ser a la vez rápido y exacto, extremo de especial importancia en el caso de brotes de enfermedades animales muy contagiosas. Para garantizar una realización eficiente y correcta de las pruebas y reducir los percances técnicos es necesario contar con un plan de emergencia en laboratorio concebido especialmente para el uso de reacciones en cadena de la polimerasa (PCR) en tiempo real de alto rendimiento, esto es, PCR o PCR acoplada a retrotranscriptasa ([RT]­PCR), o de la versión cuantitativa de estas técnicas. Durante el estudio de un brote, los problemas de contaminación pueden influir negativamente en la fiabilidad del diagnóstico y, a la postre, lastrar la erradicación de la enfermedad sobre el terreno. Por ello se recomienda vivamente el uso de procedimientos normalizados perfectamente definidos para impedir la contaminación, sobre todo en el curso de emergencias, cuando el súbito aumento del número de muestras exige recurrir a personal auxiliar de laboratorio menos avezado. En el contexto de un brote, la posible realización de pruebas preclínicas es un punto importante que conviene abordar. Para este tipo de pruebas se emplean métodos de gran sensibilidad, especialmente vulnerables a la contaminación, cosa que eleva el riesgo de falsos resultados positivos. Entre las posibles soluciones para reducir al mínimo la contaminación están el uso de protocolos normalizados adaptados a los análisis de alto rendimiento, el de procedimientos distintos según se prevea que una muestra vaya a arrojar una carga viral baja o elevada y la priorización y el procesamiento de las muestras en función de aspectos epidemiológicos (p.ej. situaciones de epidemia frente a situaciones de endemismo). Aunque pueda haber presiones para que se empiece a investigar un brote cuanto antes, los autores no recomiendan la práctica de pruebas preclínicas en todos los casos, habida cuenta de las graves consecuencias que tienen los falsos resultados positivos. Los planes de emergencia deben ser examinados con las autoridades competentes y puestos en conocimiento del personal interesado antes de que se produzca un brote. Los autores se centran aquí específicamente en describir en detalle soluciones para prevenir la contaminación de muestras en laboratorio y evitar que se produzcan falsos resultados positivos.

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.

[Bluetongue disease in Swiss sheep breeds: clinical signs after experimental infection with bluetongue virus serotype 8]. / Blauzungenkrankheit bei Schweizer Schafrassen: Klinische Symptome nach experimenteller Infektion mit dem BTV-Serotyp 8.

Clinical disease of bluetongue (BT) in sheep may differ depending on breed, age and immunity of infected sheep and may also vary between serotype and strain of BT virus (BTV). Since there are no data available on the susceptibility of Swiss sheep breeds for BT, we performed experimental infection of the 4 most common Swiss sheep breeds and the highly susceptible Poll Dorset sheep with the BTV serotype 8 (BTV-8) circulating in Northern Europe since 2006. Clinical signs were assessed regarding severity, localisation, progression and time point of their appearance. The results clearly show that the Swiss sheep breeds investigated were susceptible to BTV-8 infection. They developed moderate, BT-characteristic symptoms, which were similar to those observed in Poll Dorset sheep. Regardless of breed, the majority of infected animals showed fever, swelling of the head as well as erosions of the mouth and subcutaneous haemorrhages.

[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.

Prevalence of classical swine fever, Aujeszky's disease and brucellosis in a population of wild boar in Switzerland.

During two survey rounds of a national surveillance system for infectious diseases in wild boar in Switzerland, each lasting four months from November to February, between 2001 and 2003, 1949 blood samples and 62 tissue samples from the spleen and 50 from the reproductive organs were collected from hunted wild boar. The survey was designed so that freedom from infection could be detected with a probability of 95 per cent at a threshold prevalence of less than 1 per cent for classical swine fever and Aujeszky's disease and less than 1.5 per cent for brucellosis. There was no serological evidence of classical swine fever or Aujeszky's disease, but brucellosis due to Brucella suis biovar 2 was confirmed serologically and by bacterial isolation.

No evidence of bluetongue virus in Switzerland.

We report the results of the first survey for antibody against bluetongue virus (BTV) that was conducted in Switzerland in the year 2003. In a nationwide cross-sectional study with partial verification, 2437 cattle sera collected from 507 herds were analysed using competitive enzyme-linked immunosorbent assays (c-ELISA). To adjust for misclassification, 158 sera, including 86 that were recorded equivocal in Switzerland, were sent to the Office Internationale des Epizooties designated regional reference laboratory in the UK for confirmation. No BTV antibody was detected in any of these samples, confirming the absence of BTV from Switzerland in 2003. The specificity of the c-ELISA used in Switzerland for individual Swiss cattle was calculated to be 96.5%. The mean herd sensitivity achieved in our survey ranged from 78.9% to 98.8% depending on the with-in herd prevalence and test sensitivity used for the calculations. The cumulated confidence level achieved with the survey based on a minimal expected prevalence of 2%, was 99.99% and therefore it was concluded that there was no evidence of BTV circulation in Switzerland in 2003.

Establishment of an early warning system against bluetongue virus in Switzerland.

Bluetongue (BT) is a vector-borne animal disease of economical importance due to the international trade restrictions likely to be put into place in a country once the infection is discovered. The presence of BT and its vectors in countries adjacent to Switzerland stresses the need of implementing a surveillance system and to raise disease awareness among potential stakeholders. A national survey in Switzerland 2003 indicated freedom of Bluetongue virus (BTV), although a single individual of the main BT vector Culicoides imicola was caught in the canton of Ticino. The survey also demonstrated that potential BT vectors, C. obsoletus and C. pulicaris are locally abundant in Switzerland. Therefore, a new surveillance method based on sentinel herds in high risk areas was implemented in 2004 for the early detection of both an incursion of BT vectors into Switzerland, and potential virus circulation among cattle.

Bluetongue surveillance in Switzerland in 2003: a serological and entomological survey.

At present, Switzerland is considered officially free from bluetongue (BT) disease. Recently reported outbreaks have recorded BT moving north as far as latitude 44 degrees 30'N in Europe and 49 degrees N in Kazakhstan. The absence of clinical disease does not prove freedom from BT virus (BTV) infection. In addition, the occurrence and distribution of the only known biological vector, certain species of Culicoides biting midges (Diptera: Ceratopogonidae), is poorly understood for Switzerland. Consequently the Swiss Veterinary Office initiated a project on BT surveillance in April 2003 on cattle farms. The study comprised serological and entomological activities; initial results are presented.

Quantitative TaqMan RT-PCR for the detection and differentiation of European and North American strains of porcine reproductive and respiratory syndrome virus.

Since two different types of porcine reproductive and respiratory syndrome virus (PRRSV), the European (EU) and the North American (US) strain, occur or coexist in European swine herds, their rapid and reliable detection and differentiation is essential for disease surveillance. A quantitative TaqMan reverse transcription-polymerase chain reaction (RT-PCR) is described for PRRSV detection and strain differentiation. Sensitivity and specificity were compared with a conventional PRRSV RT-PCR and to the detection of both PRRSV types in cell cultures and both were found to be equal or superior to the reference methods. Reproducibility was tested and proved that the assay was very reliable. Standard dilutions included in each test allowed absolute quantitation of the amount of viral RNA. The TaqMan assay described below is time-saving, easy to handle, exhibits a decreased risk of cross-contamination and is highly sensitive and specific. It is, therefore, considered to be a powerful tool for the rapid detection and differentiation of PRRSV.

Rescue of infectious classical swine fever and foot-and-mouth disease virus by RNA transfection and virus detection by RT-PCR after extended storage of samples in Trizol.

A method for storing samples containing classical swine fever virus (CSFV) or foot-and-mouth disease virus (FMDV), respectively, was developed, which abolishes the infectivity of both plus strand RNA viruses, and allows storage of samples above 0 degrees C for an extended time, yet preserves the viral RNA in a state which allows its detection by reverse transcription-polymerase chain reaction (RT-PCR), and even rescue of infectious virus after transfection of the extracted RNA into susceptible cells. Supernatants from infected cell cultures as well as organs from diseased animals were stored in Trizol(R) for 1-4 weeks at -20 degrees C, 4 degrees C, room temperature, or 37 degrees C. RNA was then extracted and used subsequently for RT-PCR, as well as transfection into susceptible cells to initiate the replication of progeny virus. Formaldehyde-fixed samples were also included in this study. Storage up to 4 weeks at 37 degrees C in Trizol(R) still yielded positive RT-PCR results and rescue of infectious virus upon RNA transfection. In contrast, formaldehyde fixation reduced drastically the detectability of viral RNA. This method represents a safe and inexpensive alternative to -70 degrees C (dry ice) storage or transport of samples, and abolishes the biosafety risks involved in shipping deep-frozen infectious materials.

Detection of Newcastle disease virus in organs and faeces of experimentally infected chickens using RT-PCR.

Newcastle disease (ND) is a highly contagious avian disease. Rapid diagnosis of ND plays an important role in controlling outbreaks. Until now, time-consuming isolation of ND virus (NDV) in embryonated chicken eggs was used for NDV detection. For rapid diagnosis, reverse transcription-polymerase chain reaction (RT-PCR) with RNA extracted from tissue samples and faeces originating from experimentally and contact-infected chickens was established. Conjunctiva, lung, caecal tonsil and kidney proved to be the most suitable organs. In infected animals, NDV was detected most frequently between day 4 and 6 post-infection. Contact-infected animals gave most positive results between day 6 and 13 after exposure. RT-PCR was also able to reproducibly detect NDV in faecal samples. The RT-PCR did not show any cross-reactivity with other avian paramyxovirus serotypes, and additionally offers the possibility of subsequent sequencing of the amplified DNA allowing pathotyping of the isolate.

[Classical swine fever in wild boars in Switzerland]. / Klassische Schweinepest beim Wildschwein in der Schweiz.

In May 1998, wild boars with classical swine fever (CSF) symptoms were detected in the southern part (Canton Ticino) of Switzerland. CSF virus was isolated from the submitted samples and RT-PCR followed by direct nucleotide sequencing of the 5' non-translated region showed that this virus was identical to the isolate previously recognized in wild boars from the area of Varese (Italy). In most animals, antibodies to CSF virus were detected as well. An immediate measurement was taken by limiting the movement of pigs and identifying both risk and surveillance zones. In order not to disturb potentially infected wild boars within their habitat a complete hunting prohibition for 2 months was enforced. The different possibilities of the control of CSF outbreaks in wild boars are discussed.

A survey of Newcastle disease in Swiss laying-hen flocks using serological testing and simulation modelling.

Newcastle disease (ND) is a highly contagious viral disease of birds particularly domestic poultry. Switzerland is currently declared free from ND; since vaccination is prohibited, the detection of antibodies against ND virus (NDV) results in the destruction of the respective flock (stamping-out policy). However, in 1995 and 1996, antibody-positive flocks were detected and sporadic ND outbreaks even occurred in Switzerland. Therefore, a serosurvey was done to look for evidence of NDV infections in Swiss laying-hen flocks. The survey was designed to provide 95% confidence of detecting at least one seropositive flock if the flock prevalence were 1%. Thirty blood samples from each of 260 commercial laying-hen flocks were collected during 1996 in a central poultry slaughterhouse. Sera were screened for NDV antibodies with a commercial blocking enzyme-linked immunosorbent assay (ELISA). Samples with a questionable or positive test result were retested with the same ELISA. A stochastic computer model was applied to define a cut-off number of test-positive samples to help to differentiate between true- and false-positive flocks and to estimate the true flock prevalence of infection. Four flocks were identified as NDV-seropositive and the NDV true seroprevalence among commercial laying-hen flocks in Switzerland was most likely between 1.35 and 1.55%. This indicates that Swiss laying-hen and parental flocks with more than 150 animals have been in contact with strains of NDV that cause subclinical infection in chicken, because no clinical symptoms have been observed. In this context, computer simulation was a useful technique to interpret survey results.

[Molecular and immunodiagnostic studies of bovine neosporosis in Switzerland]. / Molekular- und immundiagnostische Untersuchungen zur bovinen Neosporose in der Schweiz.

Cyst-forming coccidia may cause significant losses in livestock, primarily due to abortion, loss of young animals and neuromuscular diseases. Rather recently, Neospora caninum has been recognized as one of the major protozoal abortion-inducing parasites in cattle. The present study addressed the performance of different diagnostic tools (in vitro-cultivation; histology; immunohistochemistry; serology; PCR) suitable for the direct or indirect detection of N. caninum. By PCR, Neospora-DNA was detected in 24 brains (29%) from 83 bovine abortion, many of these brains were simultaneously characterized by histopathological findings typical for a protozoal, cerebral parasitosis. The diagnostic methods were furthermore assessed using samples of different tissues and body fluids from three experimentally Neospora-infected pregnant cows and their foetuses. The diaplacental passage of N. caninum to the foetus was successful in two of the three cases. In these two cases, PCR was positive for different foetal organs and, additionally, for the abomasal and amniotic fluid. The successfully infected cows developed anti-Neospora serum antibodies between 10 and 17 days post infection, foetuses remained serologically negative in all cases. The results obtained in the present study demonstrated the usefulness of PCR, complemented by serology, for the specific diagnosis of bovine neosporosis. Such tests may prove suitable to perform epidemiological investigations. Taken together, our data indicated that prenatal neosporosis may be an important cause of infectious bovine abortion in Switzerland.