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Advanced epidemiological analysis of Mycoplasma hyopneumoniae infection in pigs

Final Report Summary - EPIDEMIOLOGY OF MHYO (Advanced epidemiological analysis of Mycoplasma hyopneumoniae infection in pigs)

Mycoplasma (M.) hyopneumoniae is the causative agent of porcine enzootic pneumonia (EP), which is leading to reduced weight gain, increased feed conversion, impaired health in pigs and increasing use of antibiotics, thus being one of the major health problems in pig production throughout Europe. The epidemiology of EP and within herd transmission of the pathogen is influenced by several factors including management, hygiene, etc. Over the last years Dr. Nathues conducted studies investigating various aspects of M. hyopneumoniae infection, but mainly descriptive analysis of these data has been carried out. Based on this background the objectives of the funded project were:
1) to improve the understanding of the epidemiology of EP in pigs by analysing existing data collected by projects of Dr. Nathues using a multivariable approach, and
2) to develop a compartmental mathematical model of the within herd transmission of M. hyopneumoniae which will allow assessing the impact of different husbandry system and potential control measures.
The first objective has been achieved in cooperation with Dr. Barbara Wieland and Ruby Chang, both very experienced in multivariable analysis of comprehensive data sets. Dr. Nathues acquired in-depth knowledge about the risk factor analysis and increased his technical skills in statistics. The outcome of this research has been published in Open Access journals. It was shown that the prevalence of M. hyopneumoniae infection in suckling pigs as well as seroprevalence and occurrence of clinical symptoms of EP in fattening pigs were influenced by purchase of gilts and the way of organizing their acclimatisation. Additionally, co-infections, a non-cyclic batch farrowing rhythm, large farrowing units, too high temperatures in piglets’ creep areas and an increase in piglets´ age at the time of weaning have been identified being a risk factor for M. hyopneumoniae infection. Moreover, the contact between pigs of different age and the age of the interior of compartments has been shown to influence the occurrence of EP.
The second objective included the outline of a concept of a stochastic, time discrete compartment model describing the within-herd transmission of M. hyopneumoniae. Subsequently, the mathematical backbone has been developed in R® and a baseline model has been established considering various input parameters and the risk factors identified in the first part of this project. Following this attempt, the model has been validated and a sensitivity analysis as well as several scenarios analyses considering known risk factors have been performed in order to identify and to better understand control measures minimizing or preventing the within-herd transmission of M. hyopneumoniae. The outcome of the model informs the process of setting up prevention programmes and strategies of controlling EP in endemically infected pig herds. Emphasis must be placed on an optimized pig flow, including sufficient acclimatisation of breeding pigs, and the implementation of strict hygiene and biosecurity measures, which might also increase the productivity of the herd by reducing morbidity and mortality in different age groups of pigs. These intervention measures facilitate the prevention of clinical disease, the reduction of pain and suffering of animals, and in refraining from the use of antibiotics. Thus, the outcome can be utilized for a considerable increase of the animals' health and welfare as well as a considerable reduction of the use of antimicrobial drugs in pig production, which in its turn will lead to a reduction of the risk of bacterial resistance in general and the amount of resistant bacteria in the food chain.
Beside his work on the project Dr. Nathues attended project-relevant modules of the MSc in Veterinary Epidemiology at the RVC and was able to improve his skills in scientific and financial management of a research project, to develop leadership and project management skills and to enhance communication skills and networking opportunities. At the end of the project period, Dr. Nathues was able to compile findings of this research project and former studies into his habilitation and he was successful with his application for a professorship for Pig Medicine at the VetSuisse Faculty, University of Berne, Switzerland. Today he is responsible for education and research in porcine health management and he is heading the Clinic for Swine of the VetSuisse in Berne.