Simulation of Infectious Diarrheal Disease in Philippine Backyard Swine Industry

Infectious diarrheal diseases, such as porcine epidemic diarrhea (PED), have caused significant piglet mortality in many countries, including the Philippines. These diseases remain a persistent threat to the swine industry, necessitating continuous monitoring due to their economic impact. Reports indicate that multiple fecal-oral transmission pathways contribute to the spread of diarrheal pathogens, complicating efforts to predict and control outbreaks. To address this, we developed a mathematical model incorporating various modes of disease transmission to analyze the dynamics of pathogen spread, with a particular focus on backyard farming. Backyard farms account for over 60\% of the swine industry in the Philippines, making them a critical factor in disease management and control. An agent-based simulation was used to examine the spread of the diarrhea-causing pathogen within individual farms and across a network of backyard farms. We considered three farm types based on their operations: farrow-to-finish, farrow-to-wean, and grow-to-finish. Our model predicts the speed of pathogen spread and piglet mortality, with consideration for the amount of pathogen shed by infected pigs. Additionally, we assessed the impact of two key parameters (immunity level and recovery rate) on disease control. Our results indicate that farrow-to-wean and farrow-to-finish operations experienced high mortality rates, primarily due to the heightened susceptibility of piglets to the disease. Moreover, in all farm types considered in the study, farm owners can maintain productivity in their swine operations amid diarrhea epidemics, given effective interventions are implemented. These findings are crucial for predicting the productivity of backyard farms affected by an outbreak.