Abstract
Brucellosis is a zoonotic infection caused by Gram-negative bacteria of genus Brucella. The disease is of public health, veterinary, and economic significance in most of the developed and developing countries. Direct contact between susceptible and infective animals or their contaminated products are the two major routes of the disease transmission. In this paper, we investigate the impacts of controls of livestock vaccination, gradual culling through slaughter of seropositive cattle and small ruminants, environmental hygiene and sanitation, and personal protection in humans on the transmission dynamics of Brucellosis. The necessary conditions for an optimal control problem are rigorously analyzed using Pontryagin’s maximum principle. The main ambition is to minimize the spread of brucellosis disease in the community as well as the costs of control strategies. Findings showed that the effective use of livestock vaccination, gradual culling through slaughter of seropositive cattle and small ruminants, environmental hygiene and sanitation, and personal protection in humans have a significant impact in minimizing the disease spread in livestock and human populations. Moreover, cost-effectiveness analysis of the controls showed that the combination of livestock vaccination, gradual culling through slaughter, environmental sanitation, and personal protection in humans has high impact and lower cost of prevention.
Highlights
Brucellosis is a zoonotic infection caused by Gram-negative bacteria of genus Brucella which includes; B. abortus primarly from cattle, B. melitensis from small ruminants, B. suis from swine, and B. canis from dogs [1,2,3,4]
It is considered by the Food and Agriculture Organisation (FAO), the World Health Organisation (WHO), and World Organization for Animal Health (Office International des Epizooties (OIE)) as one of the most widespread zoonoses in the world alongside bovine tuberculosis and rabies [5]. e disease is an ancient one that was described more than 2000 years ago by the Romans [6] and has been known by various names, including Mediterranean fever, Malta fever, gastric remittent fever, Bang’s disease, Crimean fever, Gibraltar fever, rock fever, lazybones disease, and undulant fever [7]
Formulation of the optimal control model is guided by the following assumptions: (i) e mixing of individuals in each population is homogeneous (ii) ere is no direct transmission between cattle and small ruminants (iii) Infected animals shed Brucella pathogens in the environment (iv) Livestock seropositivity is life-long lasting (v) Immunized individuals cannot be infected unless they are resistant to infection wanes (vi) ere is a constant natural mortality rate in each of the species (vii) e birth rate for each population is greater than the natural mortality rate e compartmental diagram with the time-dependent control strategies is shown in Figure 1, whereas the variables and parameters used in this model are, respectively, summarized in Tables 1 and 2
Summary
Brucellosis is a zoonotic infection caused by Gram-negative bacteria of genus Brucella which includes; B. abortus primarly from cattle, B. melitensis from small ruminants, B. suis from swine, and B. canis from dogs [1,2,3,4]. Few studies [10, 26,27,28,29,30,31,32,33] have been developed to analyze dynamics and spread of brucellosis in homogeneous/heterogeneous populations None of these studies had considered the mathematical approach for optimal control and cost effectiveness in reducing or eradicating the disease in cattle, small ruminants, and human populations. The dynamics and cost effectiveness of the control strategies for brucellosis using mathematical models are rigorously studied
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