Die Paratuberkulose (Johne′sche Erkrankung) ist eine chronische bakterielle Darmerkrankung mit weltweiter Bedeutung, hervorgerufen durch Mycobacterium avium subsp. paratuberculosis (MAP). Neben selten ausgeprägten klinischen Symptomen wie Durchfall und Abmagerung führen vor allem Milchleistungsabfall, erhöhte Krankheitsanfälligkeit und verminderte Schlachterlöse zu ökonomischen Verlusten. Ein Zusammenhang zwischen einer Infektion mit MAP und Morbus Crohn, einer chronischen Darmerkrankung des Menschen, wird seit langem diskutiert. Die Anzucht auf Festkultur HEYM (Herrolds Egg Yolk Agar) ist aufgrund von mäßiger Sensitivität und langer Anzuchtdauer bis zu 16 Wochen keine optimale Referenzmethode, bietet jedoch eine hohe Testspezifität. Die Anzucht in Flüssigkultur wird als Alternative mit kürzerer Anzuchtdauer und höherer Sensitivität beschrieben. Für den Erregernachweis wird neben der Anzucht der DNA-Nachweis aus Kot mittels PCR-Verfahren (Direkt-PCR) als schnelle, automatisierbare Methode in der Paratuberkulose-Diagnostik verwendet. Die fäkal-orale Übertragung von MAP von der Kuh auf das Kalb gilt als wichtige Infektionsquelle innerhalb einer Herde. Die Kenntnis über den MAP-Status des Muttertieres vor der Geburt ist besonders hilfreich, um frühzeitig Maßnahmen zum Schutz des Kalbes treffen zu können. Vorrangiges Ziel dieser Arbeit war die optimierte Verwendung und Validierung von Methoden für einen raschen, sensitiven und automatisierbaren Nachweis von MAP innerhalb von maximal acht Wochen und unter Berücksichtigung der Anwendbarkeit für Paratuberkulose-Kontrollprogramme. Zu Beginn wurden 20 Kotproben mit Direkt-PCR-Verfahren (DNA-Extraktion und DNA-Nachweis direkt aus Kot) untersucht: Konkret wurden zwei kommerzielle Kombinatonskits (DNA-Extraktionskit für Kotproben mit real-time PCR in einem Kit) mit sechs weiteren DNA-Extraktionskits mit publizierter real-time PCR verglichen. Die zwei Kombinationskits dienten im Nachgang zur Untersuchung von 107 positiven und 50 negativen Kotproben. Parallel wurden diese Proben auf Festkultur HEYM und in Flüssigmedium M7H9C für 12 Wochen kultiviert. Für die anschließende Feldstudie wurden 245 Einzelkotproben und 12 Sockentupfer aus drei Milchviehbetrieben mit Laufstallhaltung entnommen und mit einer Direkt-PCR (Kombinationskit) und dem Flüssigmedium M7H9C nach 6-wöchiger Anzucht untersucht. Der statistische Vergleich der positiven und negativen Ergebnisse der Methoden sowie der Vergleich der Anzahl positiver Kulturröhrchen und der PCR-Signalstärke nach Kultivierung wurden mit dem Fishers Exakt-Test durchgeführt. Ein Typ 1-Fehler α von < 0,05 wurde als signifikant gewertet. Die Kombinationskits zeigten signifikant mehr positive Ergebnisse als die anderen sechs getesteten Extraktionskits (p < 0,04). Beide Kombinationskits erreichten eine Sensitivität von 86 % bzw. 89 % bei 100 % Spezifität im Vergleich zur Anzucht in dem Flüssigmedium M7H9C, welches nach 6-wöchiger Anzucht 97 % und nach 12 Wochen 100 % der positiven Proben erkannte, ebenfalls bei 100 % Spezifität. Auf Festkultur HEYM (12-wöchige Anzucht) gelang bei 74 % der Proben ein Erregernachweis. In der Feldstudie wurde MAP-DNA in Sockentupfer-Proben von allen Betrieben mit Direkt-PCR und Flüssigkultur nachgewiesen. Bei der Untersuchung der Einzelkotproben stimmten 74 % der positiven Ergebnisse beider Methoden überein. Die Stärke des PCR-Signals nach Kultivierung unterschied sich signifikant zwischen Proben mit positivem Signal in nur einem Röhrchen und Proben mit positivem Signal in zwei oder drei Röhrchen (p < 0,01). Die Direkt-PCR ist bei Verwendung von Kombinationskits gut geeignet als schnelle automatisierbare Methode für die Detektion von MAP-Ausscheidern. In Herden mit niedriger Ausscheidungsrate wird die Anzucht in dem Flüssigmedium M7H9C als Methode mit höherer Nachweisrate und Ergebnissen nach acht Wochen empfohlen. Dieses Zeitfenster ermöglicht zusätzlich die Untersuchung während der Trockenstehphase und bietet Informationen zum MAP-Status der Mutterkuh bereits vor der Abkalbung.:INHALTSVERZEICHNIS 1 EINLEITUNG 1 2 LITERATURÜBERSICHT 2 2.1 PARATUBERKULOSE 2 2.1.1 Ätiologie 2 2.1.2 Krankheitsbild 3 2.1.3 Das zoonotische Potenzial 3 2.2 DIAGNOSTIK 4 2.2.1 Diagnostische Herausforderungen des Erregernachweises 4 2.2.2 Nachweis des Erregers mittels PCR-Verfahren und Kultivierung 5 2.2.3 Nachweis von Antikörpern mittels ELISA 5 2.2.4 Probenart und Entnahme 6 2.3 BEKÄMPFUNG DER PARATUBERKULOSE 7 2.3.1 Risikofaktoren einer Infektion 7 2.3.2 Bestehende Bekämpfungsprogramme 8 2.3.3 Hygiene und Herdenmanagement 10 3 ZIELSETZUNG 11 4 PUBLIKATIONEN 12 4.1 PUBLIKATION 1 12 Stellungnahme zum Eigenanteil der Arbeit an der Publikation 1: 12 4.2 PUBLIKATION 2 22 Stellungnahme zum Eigenanteil der Arbeit an der Publikation 2: 22 5 DISKUSSION 31 6 ZUSAMMENFASSUNG 41 7 SUMMARY 43 8 LITERATURVERZEICHNIS 45 DANKSAGUNG 54

Crohn's disease (CD) is a chronic granulomatous inflammatory bowel disease involving Mycobacterium avium subspecies paratuberculosis (MAP). Other microorganisms such as adherent-invasive Escherichia coli (AIEC) have also been proposed in CD association. To date, only one study investigated both MAP and AIEC simultaneously using peripheral blood but not in affected intestinal tissues. A standardized and effective antibiotic therapy against MAP and/or AIEC is needed for better treatment. Three antibiotic drugs – Clarithromycin (CLA), Rifabutin (RIF), and Clofazimine (CLO) have been used to treat CD patients suspected with MAP infection. However, the outcome has been controversial. The treatment dosage is high, the duration is long, and the reported drug side effects resulted in patient non-compliance; therefore, a lower and effective drug dosage is needed. In this study, we developed two aims 1) to evaluate RHB 104, a drug formula comprised of low dosages of CLA, RIF, and CLO, against clinical MAP strains in-vitro using fluorescence quenching method, and 2) to develop a fluorescence in-situ hybridization method to detect both MAP and AIEC simultaneously in intestinal tissues of CD patients. A total of 16 clinical MAP strains and 19 non-MAP strains were tested against varied concentrations of RHB 104, CLA, RIF, and CLO. Although the MIC for all drugs ranged between 0.5-20 ?g/ml, the MIC for RHB 104 was significantly lower against most MAP strains. The effect of RHB 104 against MAP was bactericidal. Unlike RHB-104 formula, CLA, CLO, and RIF dosage similar to those in RHB-104 did not inhibit MAP growth when trialed individually and in dual-drug combinations. The data illustrated the presence of synergistic anti-MAP activity of low dosage of the three antibiotics in RHB-104. We also developed a rapid and sensitive multicolor in-situ hybridization technique that can detect MAP and AIEC using tagged-oligonucleotide probes. Non-pathogenic Escherichia coli (npEC) was used as a control for the study. Specifically, cultured MAP and npEC were fixed and hybridized with MAP488 and EC647 probes, respectively. Confocal laser scanning microscope (CLSM) revealed specific signals at 488nm for MAP and 647nm for npEC, indicating probe binding to each bacteria. This was confirmed with hybridization of MAP with EC647 and npEC with MAP488 resulting in absence of signals. Intestinal tissue samples from 9 CD patients were then analyzed using our technique. Preliminary data indicated positive results in 6/6 samples for MAP, 6/6 for npEC, 3/3 for AIEC, and 2/2 for both MAP and AIEC with MAP being more dominant. This protocol shortened the FISH procedure from multiple days to short-hours. The protocol allows the investigation of more than one pathogen simultaneously in the same clinical sample. A quantitative measurement of the signals is needed.

No description available.

Mycobacterium avium subsp. paratuberculosis (MAP) is a very slow growing bacterium that is the causative agent of Johne's disease (JD) in ruminants and has long been suggested to be associated with complications of Crohn's disease (CD) in humans. Although there is no direct evidence that MAP is the primary etiological agent for CD, most CD patients are found to have MAP in their intestinal tissues. The current control measures for JD in cattle, sheep, and goats have only been minimally effective, and there are only medications to treat the symptoms of mycobacterial infections associated with CD in humans. Along with not being able to cure MAP infections, there is no established laboratory animal model for testing therapeutics. When mice are infected with MAP they develop systemic infection and do not mimic disease observed in ruminants. J774A.1 murine macrophages typically have a very short lifespan of about 4-6 days, however MAP infected cell cultures can survive up to about 10 days. Using a modified protocol of Estrella et al. (2011), we have been able to establish a 45-60 day long-term MAP infected J774A.1 murine macrophage cell culture model. With the addition of retinoic acid (RA), vitamin D (VD), and phorbol myristate acetate (PMA) in combination in cell culture, we were able to screen novel therapeutics before embarking on in vivo testing in animals. This is a significant step forward in Crohn's and Johne's disease treatment research. We are not only able to test various drugs against specific strains of MAP to determine susceptibility, but we are also able to test a wide variety of drugs at the same time, with relatively minimal cost. We have evaluated the efficacy of clarithromycin, azithromycin, isoniazid, amikacin, ethambutol, ciprofloxacin, levofloxacin, rifampicin, clofazimine, as well as a combination of clarithromycin, rifampicin, and clofazimine using our MAP infected macrophage cell culture model. We were able to determine the drugs' differential ability to kill intracellular MAP in the early stages of infection, versus chronic stages of infection, and against two different strains of MAP, 43015 and 19698 that affect humans and cattle respectively. The minimal inhibitory concentration (MIC) of each drug was determined as per NCCLS protocol in vitro, and the drugs were tested at the MIC value, along with one concentration above and below the MIC in our cell culture model. The antimicrobials were found to be effective at different stages of cell culture infection and in different strains of MAP. Some drugs were more effective at early stages of MAP infection, whereas others were more effective in chronic or latent stages of infections. It is important to note that although a drug may be effective at a certain stage of infection, it may not necessarily be effective against all strains of MAP. The most promising results were seen with a combination of clarithromycin, clofazimine, and rifampicin, which was effective at all stages of infection with both strains of MAP tested. This long term cell culture model will provide researchers with important screening tools for evaluating new therapeutics before embarking on costly in vivo testing, and allow the assessment of therapeutics at different stages of MAP infection but also against an array of intracellular pathogens. / Ph. D.

Submitted by Edisangela Bastos (edisangela@ufpa.br) on 2014-02-03T21:22:32Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_DiagnosticoParatuberculoseBovinos.pdf: 264056 bytes, checksum: 5ce068ca20fbd8e870ce142990c3a769 (MD5) / Approved for entry into archive by Ana Rosa Silva(arosa@ufpa.br) on 2014-02-04T14:47:40Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_DiagnosticoParatuberculoseBovinos.pdf: 264056 bytes, checksum: 5ce068ca20fbd8e870ce142990c3a769 (MD5) / Made available in DSpace on 2014-02-04T14:47:40Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_DiagnosticoParatuberculoseBovinos.pdf: 264056 bytes, checksum: 5ce068ca20fbd8e870ce142990c3a769 (MD5) Previous issue date: 2005 / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / 514 amostras de sangue bovino foram analisadas para detecção de anticorpos anti-Mycobacterium avium (subsp.) paratuberculosis, utilizando um kit comercial do teste ELISA indireto. Os animais eram todos mestiços, machos e fêmeas, classificados em dois grupos, de acordo com a idade, menores ou iguais a 36 meses e maiores de 36 meses, provenientes de 23 municípios do Estado do Pará. Além deste teste, também foram colhidas 100 amostras de fragmentos de intestino delgado e de linfonodo mesentérico para análise bacteriológicaatravés da coloração de Ziehl-Neelsen, a fim de identificar o Mycobacterium avium (subsp.) paratuberculosis. As amostras foram colhidas aleatoriamente em matadouro da região metropolitana de Belém. No teste ELISA indireto, das 514 amostras de sangue bovino 182 (35,4%) foram reagentes para anticorpos anti-Mycobacterium avium (subsp.) paratuberculosis e 332 (64,6%) foram não-reagentes. Em todas as mesorregiões encontraramse animais soropositivos. As fêmeas com idade superior a 36 meses mostraram maior respostas ao teste , 92,06% de animais soropositivos. Entre os machos, a maior prevalência (76,79%), foi obtida nos mais novos, com idade abaixo de 36 meses. Das 100 lâminas coradas através do método de Ziehl-Neelsen, nenhum Mycobacterium sp. foi identificado. Conclui-se assim, que o elevado número de animais com anticorpos anti-Mycobacterium avium (subsp.) paratuberculosis indica a presença da doença em todas as mesorregiões estudadas, devendo-se atentar aos riscos desta enfermidade, através de pesquisas mais abrangentes sobre a Paratuberculose, com aplicação de métodos diagnósticos diretos e indiretos. / 514 blood samples from beef cattle were examined of to find anti- M. avium (subsp.) paratuberculosis antibodies, using commercial ELISA test kit. The animals from samples were all compous from cross between Indicus x Taurus race, between male and female, with two age class, over 36 months old and below 36 months old, from of the 23 municipality of Para State. Also were collected 100 samples of small intestine and mesenteric lymph nodes of bacteriological test through Ziehl-Neelsen method to detect the M. avium (subsp.) paratuberculosis. Were at random collected in slaughterhouse of Belem. In ELISA test, through these 514 samples, 182 (35,4%) were seropositive and 332 (64,6%) samples were seronegative. All the middle region were found soropositives animals. The female with over 36 months old presented larger response test, of the 92,06% seropositives animals. Among male the prevalency larger (76,79%,) were obtained between the most new, with below 36 months old. Of 100 samples stained through Ziehl-Neelsen method, not were found either Mycobacterium spp.. The conclusion, is the biggest number of seropositive animals of anti- M. avium (subsp.) paratuberculosis sign of disease is presented in all the regions studied, watching the risks of this disease with the elaborate more covering stud ies about the paratuberculosis with the appling of directs and indirects diagnosis methods.

Submitted by Ubirajara Cruz (ubirajara.cruz@gmail.com) on 2017-03-28T16:35:14Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_Leticia_Fiss_Resumo.pdf: 132018 bytes, checksum: bf6cc9a5c580e6d6228123ddca70c8d1 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-03-28T21:01:19Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_Leticia_Fiss_Resumo.pdf: 132018 bytes, checksum: bf6cc9a5c580e6d6228123ddca70c8d1 (MD5) / Made available in DSpace on 2017-03-28T21:01:19Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_Leticia_Fiss_Resumo.pdf: 132018 bytes, checksum: bf6cc9a5c580e6d6228123ddca70c8d1 (MD5) Previous issue date: 2015-09-30 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Esta tese relata um surto de paratuberculose diagnosticado em bovinos de corte em uma propriedade na região Sul do Rio Grande do Sul. Foram descritos os aspectos epidemiológicos e clínico-patológicos da doença. Os animais eram criados extensivamente e apresentaram quadro de emagrecimento progressivo e diarreia crônica. O diagnóstico foi realizado pelas lesões macroscópicas e pela histopatologia. Fragmentos dos órgãos foram fixados em formalina 10%, incluídos em parafina, cortados com 5 μm de espessura e corados pela técnica de hematoxilina e eosina (HE) e Ziehl-Neelsen (ZN). Fezes foram encaminhadas ao Departamento de Medicina Veterinária, Área de Medicina Veterinária Preventiva da Universidade Federal Rural de Pernambuco para o cultivo de Mycobacterium avium subsp. paratuberculosis em meio Löwenstein Jensen com micobactina e para realização da PCR. Histologicamente havia enterite granulomatosa principalmente no dudeno, jejuno, íleo, ceco, colon e reto. Havia, ainda, linfangite e linfaadenite granulomatosa. Pela coloração de ZN foram observados numerosos bacilos álcool-ácido resistentes (BAAR) no interior de macrófagos, células gigantes de Langhans e nos linfonodos mesentéricos no duodeno, jejuno, íleo ceco e reto. Não houve crescimento bacteriano nas amostras de fezes e cinco amostras amplificaram a sequência genética IS900 específica do Mycobacterium avium subesp. paratuberculosis. Concluiu-se que a paratuberculose ocorre, também, em bovinos de corte criados extensivamente no sul do Rio Grande do Sul e pode ter uma prevalência maior do que se supõe na região, sendo necessárias medidas efetivas de controle desta doença que, por vezes, ainda é considerada exótica no Brasil. Por ser uma doença ainda pouco diagnosticada e pouco conhecida na região e que apresenta sinais clínicos inespecíficos, um segundo trabalho foi realizado visando determinar as principais doenças que ocorrem na região Sul do Rio Grande do Sul, que cursam com diarreia e afetam bovinos de corte maiores de dois anos de idade. Para isso realizou-se um levantamento nos arquivos do Laboratório Regional de Diagnóstico identificando-se os protocolos de necropsia nos quais era mencionada a diarreia como um sinal clínico relevante. Observou-se que as causas de diarreia em bovinos com dois anos ou mais de idade são poucas e bem conhecidas na região, sendo de fácil diagnóstico. Destaca-se a intoxicação por Senecio spp., em bovinos maiores de três anos, que causa prejuízos econômicos relevantes devido a sua ampla distribuição na região do estudo e ao seu difícil controle. Com relação aos bovinos entre dois e três anos as parasitoses de modo geral foram as mais importantes causas de diarreia representando 70% dos casos. / This thesis reports an outbreak of paratuberculosis diagnosed in beef cattle at a farm in the southern region of Rio Grande do Sul.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2008. / Commercial production of sweet cherries has recently increased in South Africa, with more than 400 ha planted by 2006. Cherry, a high chilling fruit variety, is however not suited for the mild winter climate of South Africa. This was recognizable through common observed symptoms of delayed foliation and poor fruit set. In addition, cherry is exposed to long and hot summers in the postharvest period. The objective of this study was to evaluate cherry cultural practices that can manipulate (reduce) the trees chilling requirement under South African conditions. Cultural practices where aimed at increasing reserves (nitrogen, cytokinin and carbohydrates) in the tree. In addition, bud dormancy progression of cherry buds was quantified to determine the bud dormancy progression pattern under mild winter conditions. This was achieved through sampling of cherry shoots from different cherry production areas which was then forced in the growth cabinets. A model was developed to identify possible factors and groupings that can explain the cherry bud dormancy pattern. A model, comprising two joined straight lines, was fitted in order to characterize bud dormancy behaviour for sweet cherry cultivars under mild winter conditions. All cherry cultivars followed the expected pattern of entrance and exit from dormancy. Factor analysis showed that factors related to the entrance into dormancy primarily characterize bud dormancy behaviour. Bud dormancy patterns were also a function of environmental conditions within a year as shown by cluster analysis. In addition, buds entered dormancy in mid-summer and remained dormant until chilling accumulation commenced. Bud dormancy release was generally extended over a three to five-month period for all cultivars. Prior to spring budburst exit of both lateral and terminal buds occurred rapidly. Data indicate that there is no ecodormant phase for cherry under the prevalent climatic conditions in South Africa. Further experimentation was aimed at increasing reserves within the trees through cultural practices. In the nitrogen trials, fertilization in the postharvest period had no significant effect on field budburst or bud dormancy progression in one-year-old shoots. Time of flowering was advanced in N treatments during 2007 only. Yield was not significantly increased. Therefore, in this trial, N fertilization in the postharvest period did not significantly reduce the chilling requirement of mature sweet cherry trees under mild winter conditions. Application of particle films (Surround® and Raynox®) or ethylene inhibitors (Retain®) in the summer did not reduce the heat stress the trees experienced. Treatments had no significant effect on carbon assimilation, stomatal conductance, leaf surface temperature, fluorescence, bud dormancy, budburst, flowering and fruit set. Cytokinins sprays (benzyladenine) in autumn did not affect bud dormancy progression, spring budburst or flowering. Hydrogen cyanamide application in spring significantly advanced budburst, time to full bloom and increased yield. Promalin® and Retain®, however, had no significant effect on budburst, flowering or yield. It is therefore evident that cherry, due to its unexpected bud dormancy behaviour and its inability to be significantly influenced by several cultural practices, adapts poorly to South African climatic conditions through not reducing its chilling requirement significantly.

No description available.

Presented thesis evaluates the risk of ongoing hybridization (antropohybridization) in highly endangered Prunus fruticosa in the Czech Republic and selected adjacent countries. Absolute genome size analysis (estimated by flow cytometry) combined with both numeric and geometric morphometrics were used for evaluation of hybridization. Prunus fruticosa frequently hybridize with naturalized Prunus cerasus (emerging tetraploid hybrid Prunus ×eminens) and native Prunus avium (forming triploid hybrid Prunus ×mohacsyana). Discrimination between P. ×eminens and P. ×mohacsyana is difficult, when using leaf morphology characters only, so the occurrence of triploid hybrids was strongly underestimated in the Czech Republic (only tetraploid hybrids were reported). Both hybrids are surely differentiated using flow cytometry analysis (based on different ploidy level). The majority of analyzed populations is formed by either individuals of pure P. fruticosa or one of the mentioned hybrids. Only four populations were mixed. Continuous variability in absolute genome size was found in two of them, which may indicate hybrid swarm forming (incl. primary hybrids and backcrosses). Our findings can be considered only as indirect evidence for introgression, which needs to be confirmed by molecular markers (for example...

La paratuberculose est une maladie entérique incurable causée par la bactérie Mycobacterium avium subsp. paratuberculosis (MAP) endémique dans la plupart des régions du monde. Cette affection ciblant les ruminants est responsable d’importantes pertes économiques dans les productions animales et son contrôle est particulièrement difficile. L’ingestion de matières contaminées (fèces, lait et colostrum) est considérée comme la voie principale de transmission. La situation épidémiologique de la paratuberculose dans les troupeaux ovins du Québec demeure inconnue. Ce projet visait à évaluer la prévalence de MAP et à caractériser les facteurs de risque associés aux statuts positifs des ovins du Québec. Au total, 2942 brebis provenant de 70 fermes ovines, dont 10 productions laitières et 60 productions de boucherie, ont été échantillonnées dans le cadre de ce projet entre février 2020 et mars 2022. La prévalence réelle des moutons positifs dans la province a été estimée à 8.3% (IC 95% 4.7-14.1%) alors que la prévalence apparente de troupeaux positifs a été estimée à 29.9% (IC 95% 25.7-34.1%). L’analyse multivariée des facteurs de risque a permis d’identifier la présence de signes cliniques comme facteur de risque à un statut positif individuel (RC = 3.0; IC 95% 1.3-7.4) et l’utilisation d’un logiciel de régie pour les données de santé des animaux comme un facteur protecteur à un statut de troupeau positif (RC = 0.1; IC 95% 0.0-0.6). Les résultats de cette étude permettront l’exploration de mesures de contrôle de l’infection dans les troupeaux ovins de la province. / Paratuberculosis is an incurable enteric disease caused by Mycobacterium avium subsp. paratuberculosis (MAP), which is endemic in most parts of the world. This disease affecting ruminants is responsible for significant economic losses in livestock production and is particularly difficult to control. Ingestion of contaminated material (e.g., faeces, milk, colostrum) is considered the main route of transmission of MAP. The epidemiological situation of paratuberculosis in Quebec sheep flocks remains unknown. Hence, the purpose of this project was to evaluate the prevalence of MAP as well as to characterize the risk factors associated with positive status within Quebec sheep. A total of 2942 ewes from 70 sheep farms, including 10 dairy and 60 meat farms, were sampled between March 2020 and March 2022. The true prevalence of positive sheep in the province was estimated at 8.3% (IC 95% 4.7-14.1%) while the apparent prevalence of positive flocks was estimated at 29.9% (95% IC 25.7-34.1%). Multivariable analysis of risk factors identified the presence of clinical signs as risk factor for a positive ewe status (OR = 3.0; 95% CI 1.3-7.4) and the use of animal health data management software as a protective factor for positive flock status (OR = 0.1; 95% CI 0.0-0.6). The results of this study will enable the implementation of MAP-tailored infection control measures in the province's sheep flocks.