Ungenaue Erkenntnis? Die Bedeutung von Wahrscheinlichkeit für die medizinische Praxis

Robert Kochs Postulate für Kausalität haben ihre Gültigkeit bei singulären Geschehen, das heisst, wenn ein Erreger eine bestimmte Krankheit auslöst, sind diese Postulate anwendbar. Koch wendete seine Postulate bei den Mykobakterien, den Verursachern der Tuberkulose, an. Kochs letztes Postulat, demzufolge der Erreger bei keiner anderen Krankheit vorkommen dürfe, stösst beim heutigen Wissensstand auf Kritik. Die Ursache eines Symptoms lässt sich besser mit den Postulaten erklären, die Austin Bradford Hill auf der Grundlage der Wahrscheinlichkeitstheorie von Thomas Bayes entwickelt hat. Klinisches Handeln, das immer einer gewissen Ungenauigkeit unterworfen ist, kann mithilfe des Bayes-Theorems objektiviert werden. In der Medizin gibt es keine Wahrheit, sondern nur hohe Wahrscheinlichkeit. Sie muss an die Stelle der Wahrheit treten, damit der Arzt handlungsfähig bleibt. Denn für die medizinische Praxis gilt der Grundsatz der «intention to treat», und zwar zum Wohl der Patientinnen und Patienten

Gesunde Tiere dank Antibiotika?

Mastkälber erkranken vor allem bis zum Alter von sechs Wochen an Jungtierkrankheiten wie Pneumonie und Diarrhöe. Sie werden in dieser Zeit zwischen Geburt und Mastbetrieb oft über mehrere Stationen verstellt, das heisst, sie werden willkürlich zu neuen Gruppen zusammengefügt. Diese Tierhaltung mit Verstellung in einer Zeit, in der ein erhebliches Risiko besteht, dass das Kalb erkrankt, und der finanzielle Druck auf die Kälbermäster führen dazu, dass es in der industriellen Kälbermast fast nicht ohne Antibiotika geht. Antibiotika töten dabei aber nicht nur pathogene, also krankmachende Bakterien ab, sondern auch die für die Verdauung notwendigen Bakterien, was oft zu Folgekrankheiten führt. Durch selektiven Einsatz von Antibiotika kann die Effizienz vorhandener Antibiotika erhöht werden. Eine gezielte Anlehnung an die Vorgaben der Natur, das heisst, indem die Jungtiere in der Herde belassen werden, kann den Antibiotikaeinsatz reduzieren. Dies würde aber zu einer späteren Mastperiode führen. Damit die Kälbermast dennoch rentiert, müssten diese Kälber älter auf den Markt kommen, weil ein Mäster vom Fleischzuwachs zwischen Aufstallung und Schlachtung lebt. Damit aber die auf den Markt gebrachte Fleischmenge konstant gehalten werden kann, müsste weniger Endmast und mehr Baby-Beef produziert werden, was die allgemeine Fleischqualität sogar erhöhen würd

Blauzungenkrankheit und Covid-19. Parallelitäten und Differenzen

Was die Faktenlage betrifft, bestehen signifikante Unterschiede zwischen der Blauzungenkrankheit beim Wiederkäuer und Covid-19 beim Menschen. Daher sind diesbezüglich auch unterschiedliche Bekämpfungsstrategien erforderlich, die in der Schweiz im Epidemiengesetz und im Tierseuchengesetz festgelegt sind. Ungeachtet der wichtigen Differenzen soll in der folgenden Arbeit das Augenmerk vor allem auf die Parallelitäten gelegt werden, namentlich bezüglich der Selbst- und Fremdbestimmung im Umgang mit Seuchen und Pandemien

Immunodiagnosis of primary Toxoplasma gondii infection in sheep by the use of a P30 IgG avidity ELISA

Abstract.: Toxoplasma gondii is a protozoan parasite with a worldwide distribution. In both sheep and humans, if the parasite is encountered during pregnancy, fetal infection and abortion can occur. Therefore, Toxoplasma infection in sheep has a major economic impact upon sheep farming. Clinically, there is a need to distinguish recent (acute) infections from longstanding (chronic) infections. However, current serological techniques, such as detection of anti-T. gondii IgG, cannot discriminate between acute and chronic infections. Increasing immunoglobulin avidity is a good determining factor of how recent an infection is. In this study, we describe the application and validation of a T. gondii IgG avidity ELISA, based on the use of an affinity-purified, native T. gondii P30 antigen. The assay was used to examine sera from eight sheep experimentally infected with T. gondii and found that all seroconverted within 21days post-infection (p.i.), beginning with avidities that were initially low but that increased over time, with all sheep reaching high IgG avidity within 10weeks p.i. In addition, sera from clinically healthy but T. gondii-seropositive lambs and ewes and seropositive ewes with a history of abortion were also subjected to a preliminary serological investigation. High IgG avidities were found in 80% of the seropositive lambs, in 90% of the clinically healthy ewes and in 97% of the ewes with abortion problems. These findings indicate that the animals had most likely contacted the parasite a longer time ag

Messung von Herzfrequenzen und Kotcortisolmetaboliten bei Pferden am Zürcher Sechseläuten

The Zurich’s Sechseläuten is a traditional festival of the Zurich guilds, in which around 500 horses take part. After a parade through the old town of Zurich, the riders gather at a big square to canter around a burning woodpile topped with an exploding effigy (the «Böögg»). The level of stress experienced by the horses partaking in this event is subjected to increasing scrutiny. The aim of this study was to evaluate the stress load of the horses participating in the Sechseläuten procession more objectively by measuring heart rate and faecal cortisol metabolites. Twenty-three horse-rider pairs were voluntarily recruited from the guilds for participation in the study. For comparison purposes, three sections of the procession were simulated in terms of gait and distance travelled in a normal riding environment during a test day and observed during the Sechseläuten itself 16 days later: Counter march Bahnhofstrasse, parade Limmatquai and parade around the burning «Böögg». All horses were equipped with a heart rate measuring system with GPS tracking (Polar Team Pro®, Polar Electro Oy, Finland). Faecal samples for measuring cortisol metabolites were taken rectally immediately before and 24 hours after the events. Thirteen of the 23 horses were sedated during the Sechseläuten (Acepromazine, 0,1–0,2 mg/kg p.o.). The differences between the observation periods and groups (sedated/unsedated) were tested by analysis of variance (P<0,05). Walking and cantering speeds in the three sections did not differ between the test day and the Sechseläuten itself. Compared to the test day, the average heart rate was increased in all sections of the real event. However, neither the initial cortisol metabolite value nor the increase after the events showed a significant difference between the test day and the Sechseläuten. The average heart rate of the sedated group did not differ from the unsedated group during the walking sections but was elevated during canter around the Böögg. The increase in heart rate at the Sechseläuten indicated a stress load, but together with the unchanged cortisol responses, this can be classified as moderate. The influence of a sedation were inconclusive and should be further investigated

Infection of cattle with Border disease virus by sheep on communal alpine pastures

The purpose of this study was to investigate whether sheep grazing communal alpine pastures with cattle can transmit Border disease virus (BDV) to cattle. A total of 1170 sheep and 923 cattle were tested for BDV using RT-PCR (sheep) and for pestivirus antibodies using an ELISA (cattle), respectively, before being moved to one of 4 pastures (A, B, C and D). Eight sheep from pasture C were viraemic. 396 of 923 cattle examined before the pasture season were seronegative. The latter were re-examined after the pasture season and 99 were seropositive or indeterminate. Antibody specificity was determined in 25 of these using a serum neutralization test (SNT). BDV infection was confirmed in 10 cattle and was considered likely in 8 others. BVDV infection was confirmed in 4 cattle and considered likely in 3 after pasturing. The study has shown that the transmission of BDV from sheep to cattle is possible on communal alpine pastures

Evaluation of an electrolyte analyser for measurement of concentrations of ionized calcium and magnesium in cats

The goal of this study was to evaluate the Nova CRT 8 electrolyte analyser for determination of concentrations of ionized calcium (Cai) and magnesium (Mgi) in cats, todetermine the effects of sample handling and storage and to establish reference ranges. The precision and analytical accuracy of the Nova CRT 8 analyser were good. The concentrations of Cai and Mgi were significantly lower in aerobically handled serum samples than in those handled anaerobically. The concentrations of Cai and Mgi differed significantly among whole blood, plasma and serum. In anaerobically handled serum, the concentration of Cai was stable for 8 h at 22°C, for 5 days at 4°C and for 1 week at −20°C. The concentration of Mgi was stable for 4 h at 22°C but for less than 24 h at 4°C and for less than 1 week at −20°C. In serum from 36 cats, the reference ranges were 1.20-1.35 mmol/L for Cai and 0.47-0.59 mmol/L for Mgi. The Nova CRT 8 electrolyte analyser is suitable for determination of Cai and Mgi concentrations in cats. Anaerobically handled serum samples are recommended and, stored at room temperature, they yield accurate results when analysed within 4