Decision tree risk analysis for FMD outbreak prevention in Egyptian feedlots

Abstract

Foot and Mouth Disease (FMD) is one of the most contagious and economically influential viral diseases on animal health and productivity. Introduction of newly purchased animals to beef farms constitutes a greater risk for the FMD outbreaks in endemic countries. Physical examination of newly purchased animals in live animal markets and/or at the receiving farm, and the timing of preventative FMD vaccination may reduce the risk of FMD outbreaks under endemic conditions. Small (< 50 animals) and medium (50-500 animals) sized beef farms in Egypt constitute more than 60% of the country's beef industry where protocols for receiving newly purchased animals vary widely between farms. The current risk analysis aimed to build a decision tree model to reduce FMD outbreaks associated with introduction of replacement cattle on Egypt's medium sized beef farms. Management practices explored were the use of physical examinations and FMD vaccination and their timing for replacements with the goal of reducing losses due to FMD outbreaks. A producer survey revealed that more than 50% of the study herds relied on live animal markets as a source for replacements and reported more FMD outbreaks (P-value=0.09), FMD herd morbidity > 50% (p-value=0.05), and weight loss > 15 kg/animal in FMD clinical cases (P-value=0.01) in comparison to herds that received replacements from other farms, imported, or purchased from small stakeholders. More than 70% of the surveyed farms received replacements ≤ 1year old and reported significantly higher FMD outbreaks (P-value=0.02) in comparison to farms that received older animals. More than 80% of the surveyed farms performed physical examination of newly purchased animals before arrival at their premises. Of the surveyed farms, 73% reported FMD outbreaks with 67% of the outbreaks being reported during the Fall and Winter seasons. The decision tree identified physical examination of newly purchased animals prior to arrival and mixing with a premises beef herd followed by vaccination against FMD upon arrival as the intervention resulting in the lowest probability of FMD outbreak (8.9%). In contrast, herds that did not perform physical examination and delay the FMD vaccination for two or more weeks had the highest probability of FMD outbreaks (33.5%).

Keywords: Animal replacements; FMD; FMD vaccination; Live animal markets; Physical examination.