Using systems thinking to understand the drivers of brucellosis in Jordan

Abstract

Background: Brucellosis is a contagious widely spread disease distributed worldwide. In Jordan, there is a high burden of brucellosis in livestock (mainly sheep) and humans with the incidence noticeably increased in recent years. Conventional modelling methodologies have not been extensively applied to brucellosis and are limited in their capacity to capture broader drivers of transmission.Methods and Aim: System dynamics has been employed to understand the dynamic drivers of brucellosis transmission in Jordan and suggest new interventions to aid in its control. Semi-structured in-depth interviews with relevant stakeholders were conducted to gain an understanding of the structures of the system and a quantitative systems dynamic simulation model (Stock and Flow) was created. Several scenarios to control brucellosis transmission were assessed.Results and Discussion: The causal loop diagram and the dynamic model showed that Brucella transmission among sheep and between sheep farms and sheep markets (Local markets) are the main drivers of human brucellosis incidence. Farmers’ visits to veterinary clinics are a critical intervention point for the control of brucellosis because they are the focal point for the contact between sheep owners and veterinary services regarding access to vaccination, advice and services on testing and culling. The newly adopted vaccination strategy using conjunctival administration by itself might not be sufficient to control brucellosis in animals and prevent human infection. Vaccination of sheep alone did not achieve the expected level of reduction in sheep and human incidence in the model. The simulation results of the model suggest testing and culling of sheep is the most efficient brucellosis control strategy. However, to maximise the potential of testing and culling a thorough assessment of economic implications, prevalence, reliable diagnostic tests and cooperation of farmers. The model also suggests a strong synergy between sectors, emphasising the benefits of a multi-sectoral approach for better disease control.