Modelling the distribution of pig production and diseases in Thailand

This thesis, entitled “Modelling the distribution of pig production and diseases in Thailand”, presents many aspects of pig production in Thailand including the characteristics of pig farming system, distribution of pig population and pig farms, spatio-temporal distribution and risk of most important diseases in pig at present, and the suitability area for pig farming. Spatial distribution and characteristics of pig farming in Thailand were studied using time-series pig population data to describe the trend of pig productions in relation to pig numbers, holder numbers, and number of pigs per holder. In more detailed analyses, pig census data in 2010 were used to describe farming systems including type of pig (native, breeding, and fattening pigs), farm scales (extensive and intensive farming systems), type of farming systems (farrow-to-finish, nursery, and finishing systems) and to quantify the association between the geographical distribution of those and several predictor variables by using Random Forest models. The results show that over the last decades, the pig population has gradually increased over time, with a marked cyclical pattern corresponding to what has been termed the “pork cycle”. The spatial distribution of large-scale pig farms corresponds with that of commercial pig breeds, which are concentrated in lowland urban or peri-urban areas, and are close to means of transportation, facilitating supply to major markets such as provincial capitals and the Bangkok Metropolitan region. Conversely the smallholders are distributed throughout the country, with higher densities located in highland, remote, and rural areas, whence they supply local, rural markets. It is proposed that intensive pig production should be integrated with crop farming within a specific “pig zone”, designated for establishment of intensive farming, which includes the necessary input and output facilities and enhanced bio-security. For smallholder pig farmers, integration of pig-farming with crop production should be promoted and combined with capacity development for farm management, including enhancing the bio-security. Spatial epidemiology of porcine reproductive and respiratory syndrome (PRRS) in Thailand was studied by providing a first description of the spatio-temporal pattern of PRRS in Thailand and to quantify the statistical relationship between the presence of PRRS at the sub-district level and a set of risk factors using two modelling approaches: autologistic multiple regression and boosted regression trees. An atypical and more virulent PRRS (HP-PRRS) emerged in China and spread to many countries, including Thailand, causing a lot of damage to pig production. The results indicated that farms with breeding sows may be an important group for targeted surveillance and control. However, these findings obtained at the sub-district level should be complemented by farm-level epidemiological investigations in order to obtain a more comprehensive view of the factors affecting PRRS presence. In this study, the outbreaks of PRRS could not be differentiated from the potential novel HP-PPRS form, which was recently discovered in the country.Spatial characterization of colonies of the flying fox bat, a carrier of Nipah Virus in Thailand was studied. We conducted field observation, remote sensing, and ecological niche modelling to characterize flying fox colonies and their ecological neighbourhoods. A Potential Surface Analysis was applied to map contact zones among local epizootic actors. Results showed that flying fox colonies were found mainly on Thailand’s Central Plain, particularly in locations surrounded by bodies of water, vegetation, and safe havens such as Buddhist temples. High-risk areas for Nipah zoonosis in pigs include the agricultural ring around the Bangkok metropolitan region where the density of pig farms is high. It is suggested that passive and active surveillance programs should be prioritized around Bangkok, particularly on farms with low biosecurity, close to water, and/or on which orchards are concomitantly grown. Integration of human and animal health surveillance should be pursued in these same areas. Such proactive planning would help conserve flying fox colonies and should help prevent zoonotic transmission of Nipah and other pathogens.Using Spatial Multi-Criteria Decision Analysis to identify suitability of pig farming in Thailand was studied. The suitability maps were generated according to the three objectives obtained from decision making process including; i) pig producers’ profit is maximized, ii) public and environmental health are protected, and iii) pig health is protected and rural areas are developed. The maps showed that the areas surrounding the major consuming centres (Bangkok) were highly suitable for objective 1, the large areas in the Northeast were highly suitable for objective 2, and the areas with rather isolation including in the East and the South were highly suitable for objective 3. The final suitability maps were presented in 6 scenarios based on the level of trade-off and risk, which these can be applied for the appropriate situations. It is suggested that establishment of pig zoning, policy makers should take all aspects into consideration in order for sustainable development in all farm levels. The cost effectiveness should be further analyzed to evaluate the zoning plan before they are developed. Additionally, the plans to scale-up support to sustainable smallholder farmers and environmental management such as manure action plan should be developed.Bringing all these results together, this thesis are discussed into three parts, namely, 1) situation and distribution of pig farming, 2) epidemiology of major pig diseases, and 3) sustainable development of pig farming.Doctorat en Sciences agronomiques et ingénierie biologique