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• W2128819125 abstract "En aquesta Tesis, sha estudiat per una banda, 1) la dinamica de infeccio de Mycoplasma hyopneumoniae (M. hyopneumoniae) a nivell de granja i la seva relacio amb els diferents sistemes de produccio i 2) la correlacio entre la deteccio daquest patogen a diferents nivells del tracte respiratori (cavitat nasal, tonsil.la, i bronqui) amb la seroconversio, i presencia de lesions macroscopiques i microscopiques suggestives de la Pneumonia Enzootica (PE) a nivell de casos clinics i nivell danimals de camp.Del estudi de la dinamica de infeccio en vam concloure que caracteristiques inherents de cada granja tenien un efecte molt important en el patro de circulacio de M.hyopneumoniae. Fins i tot dins duna mateixa granja, es podien trobar dinamiques de infeccio diferents entre diferents lots danimals, repercutint en diferents graus i moments daparicio de les lesions. A mes a mes, el tipus de produccio utilitzat (1-2 llocs versus 3 llocs) tambe influenciava la dinamica de infeccio del patogen. Els resultats obtinguts en les granges en 3 llocs, clarament donen suport a la caracteristica tardana aparicio del complex respiratori porci en els sistemes de produccio en multiples fases. De fet, la colonitzacio en transicio era menor i mes tardana en els sistemes en 3 llocs comparats amb en 1-2 llocs. A mes a mes, en els sistemes de produccio en multiples fases, sobservava un increment molt brusc de la proporcio danimals infectats associat a brot respiratoris tardans.Malgrat que la infeccio per M.hyopneumoniae es va detectar en totes les granges, aquest patogen no estava sempre involucrat en els problemes respiratoris observats. De fet, es van observar garnges infectades clinica i subclinicament per M.hyopneumoniae Aquest fet pot ser important en el moment de prendre decisions sobre les estrategies de prevencio i control de malalties. Els seroperfils no van resultar ser discriminatius per determinar el paper del agent en els problemes respiratoris observats. Els bacterioperfils van ser mes utils per determinar el paper del patogen, ja que laparicio de la simptomatologia clinica estava estretament lligada a un increment de la proporcio danimals infectats (basat en la deteccio de M.hyopneumoniae en hisops nasals). Tot i no ser discriminatiu, la proporcio danimals seropositius va ser major tambe en les granges afectades clinicament que en les subclinicament.La seroconversio en front a aquest agent ha estat descrita com lenta, retardada i molt variable. Ens els estudis de camp presentats en aquesta Tesis, la seroconversio tambe va ser variable. Sembla ser, que la seroconversio estava mes relacionada amb la deteccio de M.hyopneumoniae en els hisops bronquials que en els nasal o tonsil.lars, i a la vegada amb el percentatge danimals amb els hisops bronquials positius.Tal i com sesperava, lhisop bronquial va ser el millor en predir la presencia de lesions macroscopiques i microscopiques de PE coincidint amb els treball previament publicats. Sorprenentment, la proporcio relativa de deteccio de M.hyopneumoniae en hisops nasals va ser menor en lestudi de camp que en lestudi on les mostres de diagnostic. La major proporcio dhisops positius en els animals de diagnostic es podria explicar per: un increment de lexcrecio de M. hyopneumoniae degut a situacions estressants (tal com el transport) o el increment de la multiplicacio de les bacteries despres dunes hores de la mort de lanimal.Els resultats daquesta Tesis, han demostrat que M. hyopneumoniae es pot detectar en tonsil.la, on no hi ha cellules epitelials. Malgrat el mostreig dhisops tonsil.lar en animals vius es possible pero molt laborios, pot esdevenir un lloc de mostreig mes adequat per monitorejar la infeccio per M.hyopneumoniae a nivell de granja.Per altre banda, el resultats obtinguts, demostren que quan lhisop bronchial es positiu, la probabilitat de tenir lesions macroscopiqes i microscopiques compatibles amb PE es alta. Tanmateix, la presencia daquestes lesions no sempre implica la deteccio de M.hyopneumoniae en bronqui, ja que poden ser causades per altres patogens com pot ser SIV._________________________________________________The research presented in this Thesis assessed 1) the dynamics of infection of M. hyopneumoniae at a herd level and its relationship with production systems and 2) its detection in three respiratory levels (nasal cavities, tonsil and bronchi), taking into account the presence of seroconversion and macroscopic and microscopic lung lesions suggestive of Enzootic Pneumonia (EP)The studies on infection dynamics showed that the factor with greatest effect on M. hyopneumoniae circulation pattern was the farm. Even within a farm, significant differences in the dynamics of infection between different batches were observed, which were also related with different degrees and timings of M. hyopneumoniae related lesions appearance.Moreover, the type of production system (1/2-site versus 3-site herds) was another factor that influenced M.hyopneumoniae infection dynamics. Results of our field trial in regards M.hyopneumoniae, involving 12 Spanish herds clearly support the characteristic late appearance of Porcine Respiratory Disease Complex (PRDC) in multisite production systems. M. hyopneumoniae colonization in nurseries was lower and occurred later in time in 3-site versus in 1/2-site production systems. Moreover, an abrupt increase in the proportion of infected animals, associated with late respiratory outbreaks was seen in the multisite production systems.Although M. hyopneumoniae infection was detected in all farms, it was not always involved in the respiratory disease. An important contribution of this work is that, although seroconversion and M. hyopneumoniae infection were detected in all herds, clinical and subclinical infections were described. This is important for decision making on the control strategies to implement at the farm. Serumprofiles were not discriminative to determine the involvement of M. hyopneumoniae in a clinical outbreak. Bacteriumprofiles were more useful in determining M. hyopneumoniae involvement in respiratory disease, since an increase of the proportion of infected pigs (based on detection of M. hyopneumoniae in nasal swabs) was clearly related with appearance of the clinical outbreak. Although not discriminative, the proportion of seropositive pigs was also greater in clinically than in subclinically infected herds.Dynamics of serocoversion against M. hyopneumoniae was another issue addressed in both, transversal and longitudinal field trials. Several authors have described the time of seroconversion under field conditions as slow, delayed and vaery variable. In field studies presented here time of seroconversion was also variable. Seroconversion was more related to detection of M. hyopneumoniae in bronchial swabs rather than in nasal or tonsillar swabs, and to the detection of a higher percentage of pigs with a positive nPCR bronchial swab.As expected, bronchial swabs were the best predictors of presence of microscopic and gross EP lesions coinciding with previously published studies. However, to sample bronchial swabs from live animals is not possible. Surprisingly, the relative proportion of nasal detection was lower in the field study than in the study using pigs received at the diagnostic laboratory. An increase of M.hyopneumoniae shedding in nasal cavities due to stressful situations (such as transport) or due to increase multiplication of bacteria after the animals death have been proposed as potential explanations for a larger proportion nPCR positive nasal samples obtained in diagnostic samples.Results of this study demonstrated that detection of M.hyopneumoniae in tonsil where no ciliated epithelial cells exists, is possible. Although tonsillar sampling in live animals is more laborious than nasal samplings, it is possibly more adequate to monitor M. hyopneumoniae detection at a farm level.Results obtained in this Thesis and from previous works, showed that when bronchial swabs are positive the probability to show EP-compatible microscopic lesions in the animal is high. However, presence of EP-compatible lesions does not always imply M. hyopneumoniae detection in bronchi, and that may be caused by other pathogens such as SIV." @default.
• W2128819125 created "2016-06-24" @default.
• W2128819125 creator A5018318649 @default.
• W2128819125 date "2006-01-01" @default.
• W2128819125 modified "2023-09-23" @default.
• W2128819125 title "Epidemiological Features of natural Mycoplasma hyopneumoniae infection in pigs in Spain" @default.
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