Iris Villarreal

Bio: Iris Villarreal is an academic researcher from Ghent University. The author has contributed to research in topics: Mycoplasma hyopneumoniae & Bacterial vaccine. The author has an hindex of 7, co-authored 10 publications receiving 286 citations.

The effect of vaccination on the transmission of Mycoplasma hyopneumoniae in 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.

Multiple-Locus Variable-Number Tandem-Repeat Analysis Is a Suitable Tool for Differentiation of Mycoplasma hyopneumoniae Strains without 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.

Effect of challenge of pigs previously immunised with inactivated vaccines containing homologous and heterologous Mycoplasma hyopneumoniae strains

Abstract: Mycoplasma hyopneumoniae is the primary cause of enzootic pneumonia in pigs. Although vaccination is an important control tool, the results observed under field conditions are variable. This may be due to antigenic differences between the strains circulating in pig herds and the vaccine strain. This study compared the protective efficacy of four bacterins against challenge infection with a highly virulent field strain of M. hyopneumoniae. Seventy eight, one-week old piglets were randomly assigned to five treatment groups (A, B, C, D, E), 14 piglets each, and a negative control group (F) consisting of 8 piglets. All pigs were injected at 1 (D7) and 4 weeks of age (D28), with 2 ml of either a placebo or a bacterin based on selected M. hyopneumoniae strains, namely A (F7.2C), B (F20.1L), C (B2V1W20 1A-F), D (J strain), E (placebo; positive control), F (placebo; negative control). At D56, all pigs except those of group F were challenged intratracheally with 7 ml culture medium containing 107 CCU/ml of M. hyopneumoniae strain F7.2C. All pigs were euthanized and necropsied at D84. The severity of coughing and pneumonia lesions were the main parameters. Immunofluorescence (IF) testing, nested PCR testing of bronchoalveolar lavage (BAL) fluid and serology for M. hyopneumoniae were also performed. The different bacterins only slightly improved clinical symptoms (average 0.38 in vaccinated groups vs. 0.45 in group E) and histopathological lung lesions (average 3.20 in vaccinated groups vs. 3.45 in group E), but did not improve macroscopic lung lesions (score 4.30 vs. 4.03 in group E). None of the vaccines was significantly and/or consistently better or worse than the other ones. All bacterins evoked a serological response in the vaccinated animals. All pigs, except those from group F, were positive with nPCR in BAL fluid at D84. The bacterins did not induce a clear overall protection against challenge infection, and there were no significant differences in protective efficacy between bacterins containing homologous and heterologous M. hyopneumoniae strains. Further research is necessary to better characterize the antigens involved in protection and to elucidate the protective immunity responses following M. hyopneumoniae vaccination and/or infection.

Update on Mycoplasma hyopneumoniae infections in pigs: Knowledge gaps for improved disease control.

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.

The REFLECT statement: reporting guidelines for Randomized Controlled Trials in livestock and food safety: explanation and elaboration.

Abstract: Concerns about the completeness and accuracy of reporting of randomized clinical trials (RCTs) and the impact of poor reporting on decision making have been documented in the medical field over the past several decades. Experience from RCTs in human medicine would suggest that failure to report critical trial features can be associated with biased estimated effect measures, and there is evidence to suggest that similar biases occur in RCTs conducted in livestock populations. In response to these concerns, standardized guidelines for reporting RCTs were developed and implemented in human medicine. The Consolidated Standards of Reporting Trials (CONSORT) statement was first published in 1996, with a revised edition published in 2001. The CONSORT statement consists of a 22-item checklist for reporting a RCT and a flow diagram to follow the number of participants at each stage of a trial. An explanation and elaboration document not only defines and discusses the importance of each of the items, but also provides examples of how this information could be supplied in a publication. Differences between human and livestock populations necessitate modifications to the CONSORT statement to maximize its usefulness for RCTs involving livestock. These have been addressed in an extension of the CONSORT statement titled the REFLECT statement: Methods and processes of creating reporting guidelines for randomized control trials for livestock and food safety. The modifications made for livestock trials specifically addressed the common use of group housing and group allocation to intervention in livestock studies; the use of deliberate challenge models in some trials and the common use of non-clinical outcomes, such as contamination with a foodborne pathogen. In addition, the REFLECT statement for RCTs in livestock populations proposed specific terms or further clarified terms as they pertained to livestock studies.