Abstract
In this study, an optimal control theory was applied to a nonautonomous model for Newcastle disease transmission in the village chicken population. A notable feature of this model is the inclusion of environment contamination and wild birds, which act as reservoirs of the disease virus. Vaccination, culling, and environmental hygiene and sanitation time dependent control strategies were adopted in the proposed model. This study proved the existence of an optimal control solution, and the necessary conditions for optimality were determined using Pontryagin’s Maximum Principle. The numerical simulations of the optimal control problem were performed using the forward–backward sweep method. The results showed that the use of only the environmental hygiene and sanitation control strategy has no significant effect on the transmission dynamics of the Newcastle disease. Additionally, the combination of vaccination and environmental hygiene and sanitation strategies reduces more number of infected chickens and the concentration of the Newcastle disease virus in the environment than any other combination of control strategies. Furthermore, a cost-effective analysis was performed using the incremental cost-effectiveness ratio method, and the results showed that the use of vaccination alone as the control measure is less costly compared to other control strategies. Hence, the most effective way to minimize the transmission rate of the Newcastle disease and the operational costs is concluded to be the timely vaccination of the entire population of the village chicken, improvement in the sanitation of facilities, and the maintenance of a hygienically clean environment.
Highlights
Newcastle disease (ND) is a contagious viral disease that affects domestic and other wild avian species [1,2,3,4]
The results showed that the use of only the environmental hygiene and sanitation control strategy has no significant effect on the transmission dynamics of the Newcastle disease
This work presented a mathematical model describing the dynamics of ND in the village chicken population
Summary
Newcastle disease (ND) is a contagious viral disease that affects domestic and other wild avian species [1,2,3,4]. The transmission routes of ND in village chicken include air, direct contact with infected chicken, and contaminated water, food, droppings or discharges of the infected chicken, and other equipment in the flock [4, 7] Another topic of interest is the interaction of domestic chicken with other wild birds as the second transmission route of the ND among the avian species [7, 10, 11]. Environmental hygiene and sanitation can be applied by safely disposing the manure from the infected chickens, avoiding contaminated feeds, and improving sanitation for the caretakers of chickens Application of these three control measures helps in the reduction and possibly eradication of the ND in the village chicken but has economic implications. Owing to the scarcity of resources for most village chicken growers, the design of a control strategy that is economically viable and reduces the adverse effects of the ND in chicken flocks is of paramount importance
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