Dynamic Modeling Of The Transmission And Control In Echinococcosis

Echinococcosis has been recognized as one of the most severe helminth zoono-sis,which can be transmitted among numerous hosts and continually infected in hosts.As the prevention and treatment of echinococcosis still faces great chal-lenges,it is significant to systemically study the transmission mechanism,key processes and effective control measures of the endemic.In this dissertation,de-terministic models are established to investigate the transmission mechanisms of both Cystic echinococcosis and Alveolar echinococcosis,and further to examine the optimal control strategies of Cystic echinococcosis.A dynamic model distinguishing stray dogs from domestic dogs is proposed to explore the special role of stray dogs and potential effects of disposing stray dogs on the transmission of Echinococcosis.The basic reproduction number R₀,which measures the impact of both domestic dogs and stray dogs on the transmission,is determined to characterize the transmission dynamics.Moreover,due to difficul-ties in estimating the parameters involved in R₀with real data and the limitation of R₀in real-world applications,a new risk assessment tool called relative risk index is defined for the control of zoonotic diseases,and the studies of the risk as-sessment for Echinococcosis infection show that it is essential to distinguish stray dogs from domestic dogs in applications.The results identify the stray dog as a key factor in the transmission and control of cystic echinococcosis,which provides reference for improving the surveillance system and setting control strategies for cystic echinococcosis.Based on the study of transmission mechanism on Cystic echinococcosis,a model incorporating health education,sheep vaccination,and treatment for infec-tious dogs,is developed to assess the optimal control measures for minimizing the cost and maximizing the protection of humans as well as livestock.Theoretical analyses of the model,which rely on the theory of asymptotic autonomous sys-tems and direct Lyapunov method,characterize the existence and global stability of equilibria.In addition,sensitive analyses conducted by obtaining PRCCs are used to evaluate the effect of control parameters and key characters on the basic reproduction number as well as epidemic size.The result indicates that food re-sources of stray dog and the invalid sheep vaccinated rate are significant to the cystic echinococcosis transmission and control.Then,numerical simulations of the optimal control problem suggest that,the implementation of optimal control strategies can significantly reduce the infections,meanwhile sheep vaccination and stray dogs disposing should be emphasized ahead of domestic dogs deworming to minimum control cost.The model further explains the transmission mechanism of Cystic echinococcosis and gives the optimal control strategy.It provides an impor-tant theoretical support for the formulation of prevention and control strategies against Cystic echinococcosis.Alveolar echinococcosis,different from Cystic echinococcosis,is always spread in wild animals.Considering foxes and voles as the main definitive and intermedi-ate hosts,an ecoepidemiological model is proposed to quantitatively describe the transmission mechanism of E.multilocularis and determine control strategy.The insightful quantities（demographic and epizootiological reproduction numbers）are determined to characterize the transmission dynamics.Theoretical results reveal that under the effect of predation between foxes and voles,all hosts and the dis-ease can coexist via stable state or cyclic oscillation.Moreover,the assessment of chemical,biological and integrated controls on voles shows that a single use of biological control can not block the transmission of Alveolar echinococcosis,and when the predation rate of foxes on voles is high,it is more advantageous to im-plement integrated controls.This is necessary for the planning of more suitable preventive measures against Alveolar echinococcosis.