Author
Dries Calus
Bio: Dries Calus is an academic researcher from Ghent University. The author has contributed to research in topics: Mycoplasma hyopneumoniae & Virulence. The author has an hindex of 10, co-authored 17 publications receiving 438 citations.
Papers
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TL;DR: Vaccination with a conventional vaccine could not prevent the establishment of M. hyopneumoniae organisms in the lung and the infectious status of the animals was determined based on results of nPCR performed on bronchoalveolar lavage fluid.
96 citations
TL;DR: It is indicated that vaccination does not significantly reduce the transmission of this respiratory pathogen in nursery pigs under field conditions.
Abstract: This study investigated the effect of vaccination against Mycoplasma hyopneumoniae on its transmission in nursery pigs under field conditions. Seventy-two pigs were randomly allocated at weaning into vaccinated (V) and non-vaccinated (NV) groups. Animals in the V group were vaccinated at 3 weeks of age with a commercial M. hyopneumoniae bacterin vaccine. Broncho-alveolar lavage fluid taken at weaning and at the end of the nursery period was assessed for the presence of M. hyopneumoniae by nested PCR, and the reproduction ratio of infection (Rn) was calculated. The percentage of positive pigs in the V and NV groups was 14% and 36% at weaning, and 31% and 64% at the end of the nursery period, respectively. The Rn-values for the V and NV groups were 0.71 and 0.56, respectively (P > 0.05). The study indicates that vaccination does not significantly reduce the transmission of this respiratory pathogen.
62 citations
TL;DR: An assay based on multiple-locus variable-number tandem-repeat analysis allowed differentiating and studying diversity and persistence of Mycoplasma hyopneumoniae strains in pig herds without prior cultivation.
Abstract: An assay based on multiple-locus variable-number tandem-repeat analysis allowed differentiating and studying diversity and persistence of Mycoplasma hyopneumoniae strains in pig herds without prior cultivation. The test had a discriminatory index of >0.99 and was applied reliably to porcine bronchoalveolar lavage fluid and tracheal swabs.
52 citations
TL;DR: It is demonstrated that pigs inoculated with low virulent isolates of M. hyopneumoniae are not protected against a subsequent infection with a highly virulent isolate 4 weeks later and may even develop more severe disease signs.
50 citations
TL;DR: The present study indicates that the difference in pathogenicity between the highly and low virulent isolates is associated with a faster in vitro growth, a higher capacity to multiply in the lungs and the induction of a more severe inflammation process by the highly virulent isolate.
49 citations
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TL;DR: The main effects of vaccination include less clinical symptoms, lung lesions and medication use, and improved performance, however, bacterins provide only partial protection and do not prevent colonization of the organism.
370 citations
TL;DR: The present paper reviews the current knowledge on M. hyopneumoniae infections, with emphasis on identification and analysis of knowledge gaps for optimizing control of the disease.
Abstract: Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary pathogen of enzootic pneumonia, a chronic respiratory disease in pigs. Infections occur worldwide and cause major economic losses to the pig industry. The present paper reviews the current knowledge on M. hyopneumoniae infections, with emphasis on identification and analysis of knowledge gaps for optimizing control of the disease. Close contact between infected and susceptible pigs is the main route of M. hyopneumoniae transmission. Management and housing conditions predisposing for infection or disease are known, but further research is needed to better understand M. hyopneumoniae transmission patterns in modern pig production systems, and to assess the importance of the breeding population for downstream disease control. The organism is primarily found on the mucosal surface of the trachea, bronchi and bronchioles. Different adhesins and lipoproteins are involved in the adherence process. However, a clear picture of the virulence and pathogenicity of M. hyopneumoniae is still missing. The role of glycerol metabolism, myoinositol metabolism and the Mycoplasma Ig binding protein-Mycoplasma Ig protease system should be further investigated for their contribution to virulence. The destruction of the mucociliary apparatus, together with modulating the immune response, enhances the susceptibility of infected pigs to secondary pathogens. Clinical signs and severity of lesions depend on different factors, such as management, environmental conditions and likely also M. hyopneumoniae strain. The potential impact of strain variability on disease severity is not well defined. Diagnostics could be improved by developing tests that may detect virulent strains, by improving sampling in live animals and by designing ELISAs allowing discrimination between infected and vaccinated pigs. The currently available vaccines are often cost-efficient, but the ongoing research on developing new vaccines that confer protective immunity and reduce transmission should be continued, as well as optimization of protocols to eliminate M. hyopneumoniae from pig herds.
182 citations
TL;DR: The current state of knowledge of the epidemiology of M. hyopneumoniae infection including its transmission, infection and seroconversion dynamics is reviewed and the various epidemiological tools used to monitor EP are compared.
Abstract: Mycoplasma hyopneumoniae is the principal aetiological agent of enzootic pneumonia (EP), a chronic respiratory disease that affects mainly finishing pigs. Although major efforts to control M. hyopneumoniae infection and its detrimental effects have been made, significant economic losses in pig production worldwide due to EP continue. M. hyopneumoniae is typically introduced into pig herds by the purchase of subclinically infected animals or, less frequently, through airborne transmission over short distances. Once in the herd, M. hyopneumoniae may be transmitted by direct contact from infected sows to their offspring or between pen mates. The 'gold standard' technique used to diagnose M. hyopneumoniae infection, bacteriological culture, is laborious and is seldom used routinely. Enzyme-linked immunosorbent assay and polymerase chain reaction detection methods, in addition to post-mortem inspection in the form of abattoir surveillance or field necropsy, are the techniques most frequently used to investigate the potential involvement of M. hyopneumoniae in porcine respiratory disease. Such techniques have been used to monitor the incidence of M. hyopneumoniae infection in herds both clinically and subclinically affected by EP, in vaccinated and non-vaccinated herds and under different production and management conditions. Differences in the clinical course of EP at farm level and in the efficacy of M. hyopneumoniae vaccination suggest that the transmission and virulence characteristics of different field isolates of M. hyopneumoniae may vary. This paper reviews the current state of knowledge of the epidemiology of M. hyopneumoniae infection including its transmission, infection and seroconversion dynamics and also compares the various epidemiological tools used to monitor EP.
177 citations
TL;DR: The findings indicate that M. hyopneumoniae, PRRSV and SIV H1N1 are the major pathogens involved in pneumonia-like gross lesions even though PCV2 may play a role.
140 citations
TL;DR: Results of this study have demonstrated that M. hyopneumoniae infected pigs can be incubatory as well as convalescent carriers of the pathogen and that convalescence carriers can remain infectious for up to 200 days.
95 citations