References of "Theron, Léonard"
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See detailMediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections
Detilleux, Johann ULg; Theron, Léonard ULg; Duprez, Jean-Noël ULg et al

in Animal (2016)

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e ... [more ▼]

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e. indirect losses). Test-day milk somatic cell counts (SCC) and number of bacterial colony forming units (CFU) found in milk samples are putative measures of the level of immune response and of the bacterial load, respectively. Mediation models, in which one independent variable affects a second variable which, in turn, affects a third one, are conceivable models to estimate direct and indirect losses. Here, we evaluated the feasibility of a mediation model in which test-day SCC and milk were regressed toward bacterial CFU measured at three selected sampling dates, 1 week apart. We applied this method on cows free of clinical signs and with records on up to 3 test-days before and after the date of the first bacteriological samples. Most bacteriological cultures were negative (52.38%), others contained either staphylococci (23.08%), streptococci (9.16%), mixed bacteria (8.79%) or were contaminated (6.59%). Only losses mediated by an increase in SCC were significantly different from null. In cows with three consecutive bacteriological positive results, we estimated a decreased milk yield of 0.28 kg per day for each unit increase in log2-transformed CFU that elicited one unit increase in log2-transformed SCC. In cows with one or two bacteriological positive results, indirect milk loss was not significantly different from null although test-day milk decreased by 0.74 kg per day for each unit increase of log2-transformed SCC. These results highlight the importance of milk losses that are mediated by an increase in SCC during mammary infection and the feasibility of decomposing total milk loss into its direct and indirect components. © The Animal Consortium 2016 [less ▲]

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See detailReconstruction of the Schmallenberg virus epidemic in Belgium: Complementary use of disease surveillance approaches
Poskin, A; Theron, Léonard ULg; Hanon, JB et al

in Veterinary Microbiology (2016), 183

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See detailL'échographie bovine: une autre utilité ... chez le veau
Sartelet, Arnaud ULg; Knapp, Emilie ULg; Rao, Anne-Sophie ULg et al

Conference given outside the academic context (2015)

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See detailPatologie okresu poporodowego u krow
Hanzen, Christian ULg; Rao, Anne-Sophie ULg; Theron, Léonard ULg et al

in Gajewski, Zdzislaw; Wehrend, Axel (Eds.) Rozrod i mastitis u bydla (2015)

Conférence donnée le 10 octobre 2015 à la faculté de Médecine vétérinaire de Varsovie .Les questions suivantes ont été développées 1. In which context are we working ? 1 2. Is puerperium important for cow ... [more ▼]

Conférence donnée le 10 octobre 2015 à la faculté de Médecine vétérinaire de Varsovie .Les questions suivantes ont été développées 1. In which context are we working ? 1 2. Is puerperium important for cow reproductive performances ? 2 3. How to define these pathologies ? 3 1.1. Dystocia 3 1.2. Placental retention 3 1.3. Uterine involution and uterine involution delay. 4 1.4. Uterine infections 4 1.5. The postpartum anestrus 5 4. What’s the prevalence of these pathologies ? 6 5. How to diagnose the pathologies of the puerperium ? 7 6. When detect these pathologies ? 7 7. What kind of relations exist between these pathologies? The example of uterine infections. 8 8. How to treat these pathologies ? 9 [less ▲]

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See detailChronic Toxic Hepatitis in Beef Calves due to Mycotoxins in Mixed Feed
Theron, Léonard ULg; Callebaut, Alfons; Bayrou, Calixte ULg et al

in Zemljic, Borut; Podpecan, Ozbalt; Zmljic-Jokhadar, Spela (Eds.) Proceedings of the XV middle European Buiatric Congress (2015, June 10)

Mycotoxins intoxination is an emerging disorder in Belgium, due to evolution of cultural practices and harvesting weather conditions. These intoxinations are difficult to diagnose for the vet practioners ... [more ▼]

Mycotoxins intoxination is an emerging disorder in Belgium, due to evolution of cultural practices and harvesting weather conditions. These intoxinations are difficult to diagnose for the vet practioners, since unspecific clinical signs, and their impact on ruminant disorder remains controversial. Although legal concentrations have been established for mycotoxins in the EU, farm forages are most of the time not tested (EU 2006/576/EC). In January 2015, a 500 calvings cross-bred Belgian blue cattle herd (BVDV free) referred a second (the first was directly sent to the rendering-plant) unexplained fatal case of jaundice on a 2 months-old calf to the Clinic for Ruminants of the University of Liège for necropsy. In 2013, a case of jaundice due to a Salmonella dublin hepatocholecystitis had previously diagnosed in this farm (Ronzoni et al., 2014), but so far preventions measures were implemented. Necropsy revealed generalized icterus, mild bilirubinuria, splenomegaly, but no precise etiology. On February a second 2 month old calf with jaundice is referred, lethargic, normothermic with a mild diarrhea, Calf shown generalized jaundice, anemia, elevation of leukocytes (neutrophils, eosinophils and monocytes), TGO, bilirubinemia, total biliary acids and Globulins (alpha2). He had also diminished erythrocytes and albuminemia. Copraemia, leptospirosis serology, leademia, hemoculture and pancreatic enzymes were within normal ranges, ruling out classic causes of jaundice in calf. Abdomen ultrasonography revealed a mild hyperechogenicity of the liver but no gall bladder modifications. Symptomatic treatment was based on symptoms, with fluidotherapy and choleretics. A third calf was referred three days after in a worst clinical condition, with also a severely modified liver enzymes, but no anemia. Three days after, this calf died and a necropsy revealed petechiae and hemorrhages in the abomasum, congestive mucosae in the distal bowel, white depot in the kidney medulla, modified urine and splenomegaly. Bile bacteriology and leptospirosis PCR was negative and liver histopathology revealed a severe histopathological liver degeneration associated with a disruption of the parenchyma and marked hyperplasia of the bile ducts compatible with chronic metabolic disorder. Meanwhile, the anemic calf recovered from anemia without any treatment after 4 days and was discharged from the Clinic for Ruminants. Considering the weird clinical patterns of these jaundice cases, and the fact that only calves from 2 to 3 months were affected, a nutritional origin as etiology was suspected. To test it, eight clinically healthy two to three months-old calves, of two different pens were sampled. TGO, GLDH, GGT or biliary acids were either modified and the values tended to increase with the age of the calves. The water was analyzed for classic toxics, and cultured for total germ content and everything were within recommended values. The calves fed with a milk replacer (30 % milk powder), and a commercial calf starter until one month of age. Then, they were given a mixed feed (containing cereal mix, cocoa, beet pulp, soja, maize), made at the farm from primary product/byproducts bought from different sources. The mix was tested for mycotoxins presence and ranged from 0.8 to 1.5 ppm of Desoxynivalenone (DON), and 115-215 ppb of Zearalenone (ZEA). The principal source of DON was maize (3.1 to 6.2 ppm), as for ZEA (0.3-0.6 ppm), but several compounds contained small dose of DON (0.2-0.7 ppm) for Barley feed, Tanned soja. Cacao contained 2.7 to 5.9 ppb of Ochratoxine (OTA). Nutritionnal recommendations were immediately given with a change in the source of maize and an addition of clay and yeast at 40g/calf/day and hay. Since, any other hypothetic origin to this progressive hepatic intoxination was demostrated, and that the doses founded, even if barely legal in the mix, are not accounted for toxic in the EU regulation, we believe that the calves were chronically exposed to these toxins. However, some mycotoxins experts still claim that various clinical signs would be observed in ruminants, if the rumen is partially defaunated, like in our case with the lake of forage. We propose that monitoring of subclinical liver health could be a key to screen DON effects. [less ▲]

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See detailLes utilités de l’échographie chez le bovin en dehors du suivi de reproduction
Sartelet, Arnaud ULg; Knapp, Emilie ULg; Rao, Anne-Sophie ULg et al

Scientific conference (2014, November 17)

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See detailWound management of a pregnant Belgian blue cow with severe toxic cutaneous necrosis affecting the limbs.
Gaillot, Claire; Claeys, Stéphanie ULg; Douffet, François ULg et al

Scientific conference (2014, October 17)

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See detailCarnet Clinique de Médecine de Troupeau
Guyot, Hugues ULg; Theron, Léonard ULg; Frisee, Vincent ULg et al

Book published by ULG - FMV - DCP - 4ème édition (2014)

L’agriculture évolue, la médecine vétérinaire suit le même chemin. Les troupeaux d’hier ressemblent de moins en moins à ceux d’aujourd’hui. Hier, la médecine vétérinaire se concentrait sur l’urgence et ... [more ▼]

L’agriculture évolue, la médecine vétérinaire suit le même chemin. Les troupeaux d’hier ressemblent de moins en moins à ceux d’aujourd’hui. Hier, la médecine vétérinaire se concentrait sur l’urgence et donc le cas individuel. Dès aujourd’hui, et encore plus demain, il faut voir l’individu dans sa globalité et donc dans son troupeau. L’unité épidémiologique n’est plus l’individu mais le troupeau. La médecine devient davantage préventive que curative. De là est né le concept Herd Health & Production Management (HH&PM) alliant à la fois des mesures préventives et curatives dans le but d’améliorer la productivité et la rentabilité du troupeau. Cette forme de médecine garde toutefois à l’esprit les attentes du consommateur en termes de qualité des denrées alimentaires d’origine animale (résidus, qualités organoleptiques et microbiologiques) et de bien-être animal. Le concept HH&PM peut se définir comme « l’expression maximale du potentiel génétique d’un animal individuel et du troupeau comme un tout, en optimisant le management de l’exploitation, ainsi que les conditions de la ferme et en conséquence, les entrées économiques de la ferme ». L’examen global d’un troupeau requiert toutefois des connaissances élargies : alimentation, médecine, thériogénologie, bioclimatologie, parasitologie, bactériologie, épidémiologie, économie, zootechnologie. Il est essentiel de ne pas segmenter ses connaissances à l’approche du troupeau tant les problèmes rencontrés peuvent être multifactoriels. La 4ème édition de ce carnet clinique se veut toujours plus pratique et calquée sur le modèle des visites HH&PM que le Département Clinique des Animaux de Production (DCP) de l’Université de Liège réalise quotidiennement sur le terrain. De nombreux rappels sont proposés ainsi que des pistes et/ou canevas permettant d’appréhender au mieux une problématique de troupeau. Cependant, il est très difficile d’être exhaustif pour un carnet de poche (cet outil est avant tout un aide-mémoire en exploitation) et le lecteur prendra soin de compléter ses connaissances dans les livres/cours ad hoc. Par ailleurs, les informations contenues dans ce carnet ne sont pas fixées une fois pour toutes. Les législations, normes, spécialités pharmaceutiques peuvent évoluer et le détenteur de ce carnet clinique de médecine de troupeaux veillera à se tenir informé de ces modifications potentielles. Enfin, bien que les normes établies constituent des repères objectifs, le praticien sera attentif à ne pas émettre de jugement ou diagnostic définitif sur base de simples normes, mais analysera la situation dans sa globalité, en tenant compte de l’aspect clairement multifactoriel des maladies de production dans les élevages bovins laitiers ou viandeux. Enfin, j’adresse mes remerciements aux Profs Emile Bouchard et Luc DesCôteaux, (Université de Montréal, St-Hyacinthe Québec, Canada), et leurs collaborateurs, au Dr. Virginie Filteau (DSAHR Inc., Québec, Canada), à mes collègues du DCP et de la FMV, et à MSD pour l’inspiration, l’impulsion et l’aide à la réalisation de ce carnet clinique. Pour l’Equipe, Pr. Hugues Guyot 4ème édition – Liège – Janvier 2014 Editions précédentes : 1ère édition (2002), 2ème édition (2006), 3ème édition (2011) [less ▲]

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See detailEvaluating somatic cell scores with a Bayesian Gaussian linear state-space model.
Detilleux, Johann ULg; Theron, Léonard ULg; Reding, E. et al

in Animal (2014), 8(3), 477-83

Because accurate characterization of health state is important for managing dairy herds, we propose to validate the use of a linear state-space model (LSSM) for evaluating monthly somatic cell scores ... [more ▼]

Because accurate characterization of health state is important for managing dairy herds, we propose to validate the use of a linear state-space model (LSSM) for evaluating monthly somatic cell scores (SCSs). To do so, we retrieved SCS from a dairy database and collected reports on clinical mastitis collected in 20 farms, during the period from January 2008 to December 2011 in the Walloon region of Belgium. The dependent variable was the SCS, and the independent variables were the number of days from calving, year of calving and parity. The LSSM also incorporated an error-free underlying variable that described the trend across time as a function of previous clinical and subclinical status. We computed the mean sum of squared differences between observed SCS and median values of the posterior SCS distribution and constructed the receiver operating characteristic (ROC) curve for SCS thresholds going from 0 to 6. Our results show SCS estimates are close to observed SCS and area under the ROC curve is higher than 90%. We discuss the meaning of the parameters in light of our current knowledge of the disease and propose methods to incorporate, in LSSM, this knowledge often expressed in the form of ordinary differential equations. [less ▲]

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See detailComprendre la mammite bovine comme une enzootie dynamique
Theron, Léonard ULg; Hanzen, Christian ULg

Article for general public (2013)

Health disorders in bovine herds are, in essence, multifactorial. They are based on the equilibrium among various factors. The major difficulty in managing endemias in livestock production emerges from ... [more ▼]

Health disorders in bovine herds are, in essence, multifactorial. They are based on the equilibrium among various factors. The major difficulty in managing endemias in livestock production emerges from two elements: the extreme variability of practices among farms and over time on one hand and on the other hand, the crossed impact of various factors producing the same result. A simple example will illustrate the two problems: Mastitis has epidemiological components that govern their own response to means of prevention. Because no two dairy farms ever have fifty per cent of their livestock production practices in common, the establishment of the usual means of prevention will never have the same dosable impact in each of the two farms (Bradley et al. 2007; Théron et al. 2009). Further, in view of the variability of certain practices or adjustments over time, a situation can vary while all other factors remain constant, due to a neglected invisible factor, thus diminishing the strength of the prevention argument. Each of us has known situations in which post-dipping did not generate the anticipated effects, and situations in which, after a transitory improvement linked to milking practices, the situation degrades again for a cause associated with the milking machine or feeding. The conclusion of this introduction is both simple and complex: the integrated control of mastitis is based on long-term monitoring. This monitoring is justified by the economic and societal impact of this disease. Good monitoring implies the definition of key measurable control points. The aim of this article will be to define the indicators and epidemiological objectives that enable the level of mammary health and its evolution to be defined over time. [less ▲]

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See detailAnalyse de l'efficience des traitements de mammites de 50 fermes de Wallonie dans la base LAECEA
Theron, Léonard ULg; Reding, Edouard; Detilleux, Johann ULg et al

Conference (2013, October 11)

Mastitis is the most “antibiotic consuming” pathology in dairy medicine. Though antibiotics and antibiograms are known to vets since the early fifties, our practices did not evolved a lot from empiric ... [more ▼]

Mastitis is the most “antibiotic consuming” pathology in dairy medicine. Though antibiotics and antibiograms are known to vets since the early fifties, our practices did not evolved a lot from empiric antibiotic therapy. Indeed, the need for a treatment, the cost and the delay for an antibiogram are most of the time incoherent with a routine practice. Nevertheless, there is a surge for rational use of antibiotics. Our study was based on 1100 mastitis events from 30 Belgian farms collected between January 2011 and June 2012. We chose to compare tissular cure (TC) based on the threshold of 200.000 somatic cells/ml in milk at milk control at least 60 days after the clinical mastitis event. Regarding the mastitis event, severity (according 3 grades: alteration of milk as grade 1, alteration of quarter as grade 2 and alteration of general state as grade 3), quarter, treatments were recorded. We also assessed a chronicity status based on previous somatic cell count (SCC) of the cow. It was considered a new case a cow which at least 15 days before had an SCC <200.000 cells/ml, other were marked as chronic cases. In our distribution, we see a seasonal rise of incidence between January and May. This period would represent twice as many mastitis as the summer period. Overall TC reaches 46% of all mastitis events, which is quite poor. Rear quarters had significantly lower TC (p<0,05%). Grade 3 mastitis had lower TC, 42,6% (p<0.05%) versus 48,9 % for grade 2 and 44,2% for grade 1. Almost 49% of all mastitis was considered as chronic cases, which TC was 33% on average, whereas new cases reached 55,3% TC. Study of treatment was frustrating given the high number of different combinations of treatments. It was underlined that 4th generation cephalosporins (C4G) were the most used in our cohort, followed by aminopenicillin/methicillin association (PENA/PENM) and 1st generation cephalosporins/aminoglycosids (C1G/AG) association. Of these intramammary treatments, 20% of the cases were submitted to a second intramammary drug, mostly C1G or C1G/AG. One third of the cases were treated parenterally with antimicrobials, mostly macrolids, fluoroquinolones and penethacillin. Finally, 10% of mastitis was treated with anti-inflammatory drugs, mostly tolfenamic acid and flunixin-meglumin. Comparing mastitis without use of a secondary intramammary drug, only PENA and C1G/AG reached more than 60% TC. Considering new cases, then C1G/AG, PENA/PENM and Prednisolone containing specialties were above 60% TC. Use of a parenteral injections increased TC only on new cases (+12%), but not on chronic cases. Refining by severity, TC improved with a parenteral on new cases, mainly in grade 1 (+20%). Regarding associated factors, TC was negatively affected by chronicity, parity and lactation stage. Indeed, TC was lower on cases from more than 4 month in milk, third lactation (OR = 2.8 for no cure) compared with previous, and chronic cases (OR=2,6). Seemingly, chronicity was positively associated with parity and season. The 3rd parity cases had higher chances to be chronic ones (OR = 1,7), as well as cases from April to September (OR = 1,6). This evaluation of cure is rather simple and has a good variability which allows several questions about the real match between antimicrobial treatment for mastitis and the udder inflammation. Based on our epidemiological data, we can modify routine management of mastitis, as some cases might not worth the antimicrobial treatment. [less ▲]

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See detailFluidothérapie chez le veau
Sartelet, Arnaud ULg; Lecomte, Denis; Theron, Léonard ULg et al

Conference (2013, September 27)

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