Recurrent viruses in a Singapore intensive pig farming estate

The Ponggol intensive pig farming estate was conceived approximately 10 years ago to accommodate pig farms resettled from water catchment areas. Initially stocking density of the estate was 1300-1500 pigs per hectare (ha) and the total pig population in the estate was 200,000. Over the past 10 years the numbers of pigs have increased to 400,000 and the stocking density of the big commercial units have increased to 1500-2500 per ha. With such intensive methods of husbandry environmental problems of waste disposal and recurrent viral diseases have emerged as the most important factors influencing the viability of the industry and the efficiency of productivity. The highly infectious viruses most frequently identified were the Aujeszky's disease virus (herpesviridae), swine fever virus (togaviridae) and transmissible gastroenteritis virus (coronaviridae). The incidence of these diseases have affected the health status of the pigs over the past years. It is also significant that swine influenza and Japanese encephalitis which are diseases of public health importance have not been found to be recurring clinical entities within the estate. The knowledge of these viral diseases within a closely knit pig population could throw some light as to the impact these representative families of viruses might have under conditions of widespread viral persistence within a dense population of susceptible hosts.