Browsing by Author "Damian, Kajunguri"

Now showing 1 - 7 of 7
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    Conservation of forest biomass and forest–dependent wildlife population: Uncertainty quantification of the model parameters
    (Heliyon, 2023-07-06) Ibrahim, M. Fanuel; Silas, Mirau; Damian, Kajunguri; Francis, Moyo
    The ecosystem is confronted with numerous challenges as a consequence of the escalating human population and its corresponding activities. Among these challenges lies the degradation of forest biomass, which directly contributes to a reduction in forested areas and poses a significant threat to the survival of wildlife species through the intensification of intraspecific competition. In this paper, a non–linear mathematical model to study the conservation of forest and wildlife species that are reliant on forest ecosystem within the framework of human population dynamics and its related activities is developed and analysed. The study assessed the impacts of economic measures in the form of incentives on reducing population pressure on forest resources as well as the potential benefits of technological efforts to accelerate the rate of reforestation. Qualitative and quantitative analyses reveals that economic and technological factors have the potential to contribute to resource conservation efforts. However, these efforts can only be used to a limited extent, and contrary to that, the system will be destabilised. Sensitivity analysis identified the parameters pertaining to human population, human activities, economic measures, and technological efforts as the most influential factors in the model.
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    Improved estimates for extinction probabilities and times to extinction for populations of tsetse (Glossina spp)
    (PLOS, 2019) Damian, Kajunguri; Elisha B., Are; John W., Hargrove
    A published study used a stochastic branching process to derive equations for the mean and variance of the probability of, and time to, extinction in population of tsetse flies (Glossina spp) as a function of adult and pupal mortality, and the probabilities that a female is inseminated by a fertile male. The original derivation was partially heuristic and provided no proofs for inductive results. We provide these proofs, together with a more compact way of reaching the same results. We also show that, while the published equations hold good for the case where tsetse produce male and female offspring in equal proportion, a different solution is required for the more general case where the probability (β) that an offspring is female lies anywhere in the interval (0, 1). We confirm previous results obtained for the special case whereβ= 0.5 and show that extinction probability is at a minimum for β>0.5 by an amount that increases with increasing adult female mortality. Sensitivity analysis showed that the extinction probability was affected most by changes in adult female mortality, followed by the rate of production of pupae. Because females only produce a single offspring approximately every 10 days, imposing a death rate of greater than about 3.5% per day will ensure the eradication of any tsetse population. These mortality levels can be achieved for some species using insecticide-treated targets or cattle— providing thereby a simple, effective and cost-effective method of controlling and eradicating tsetse, and also human and animal trypanosomiasis. Our results are of further interest in the modern situation where increases in temperature are seeing the real possibility that tsetse will go extinct in some areas, without the need for intervention, but have an increased chance of surviving in other areas where they were previously unsustainable due to low temperatures.
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    Mass transfer approach and the designing of horizontal subsurface flow constructed wetland systems treating waste stabilisation pond effluent
    (IWA Publishing, 2018) Anita M., Rugaika; Damian, Kajunguri; Rob, Van Deun; Bart Van der, Bruggen; Karoli N., Njau
    Pilot-scale constructed wetlands (CWs) that allowed wastewater to flow with high interstitial velocities in a controlled environment were used to evaluate the possibility of using mass transfer approach to design horizontal subsurface flow constructed wetlands (HSSF-CWs) treating waste stabilisation ponds (WSPs) effluent. Since CW design considers temperature which is irrelevant in tropics, mass transfer approach could improve the design. HSSF-CWs were operated in batch recycle mode as continuous stirred tank reactors (CSTR) at different interstitial velocities. The overall removal rate constants of chemical oxygen demand (COD) at various interstitial velocities were evaluated in mesocosms that received pretreated domestic wastewater. The mean overall removal rate constants were 0.43, 0.69, 0.74 and 0.73 d 1 corresponding to interstitial velocities of 15.43, 36, 56.57 and 72 md 1, respectively. Results showed that the interstitial velocities up to 36 md 1 represented a range where mass transfer effect was significant and, above it, insignificant to the COD removal process. Since WSPs effluent has high flow rates and low organic load, it is possible to induce high interstitial velocities in a HSSF-CW treating this effluent, without clogging and overflow. The performance of these HSSF for tertiary treatment in tropical areas could be improved by considering flow velocity when designing.
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    Modeling and analysis of taeniasis and cysticercosis transmission dynamics in humans, pigs and cattle
    (Springer, 2021) Joshua, A. Mwasunda; Jacob I, Irunde; Damian, Kajunguri; Dmitry, Kuznetsov
    Taeniasis and cysticercosis pose a significant challenge to food safety and public health. Cysticercosis reduces the market value for pigs and cattle by making pork and beef unsafe for consumption. In this paper, a mathematical model for the transmission dynamics of taeniasis and cysticercosis in humans, pigs and cattle is formulated and analyzed. The analysis shows that both the disease free equilibrium (DFE) and the endemic equilibrium (EE) exist. To study the dynamics of the diseases, we derived the basic reproduction number R0 by next generation matrix method. When R0 < 1, the DFE is globally asymptotically stable whereas when R0 > 1 the EE is globally asymptotically stable. The normalized forward sensitivity index was used to determine sensitive parameters to the diseases. Humans’ recruitment rate, probability of humans’ infection with taeniasis and the defecation rate of taenia eggs by humans with taeniasis are the most positive sensitive parameters to diseases’ transmission whereas the human natural death rate is the most negative sensitive parameter. However, it is biologically unethical and not practical to increase human natural mortality rate for disease control. In this case, other parameters with negative sensitivity indices such as death rate of taenia eggs and proportions of unconsumed infected beef and pork can be considered for disease control. Generally, to control the diseases, more efforts should be made directed to reducing the number of humans who have taeniasis and defecate in the open environment. Also meat inspection and indoor keeping of cattle and pigs should be emphasized.
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    Modeling The Role Of Wild Birds and Environment in the Dynamics of Newcastle Disease in Village Chicken.
    (Science Asia, 2018) Furaha, Chuma; Gasper G., Mwanga; Damian, Kajunguri
    Newcastle disease is common viral poultry disease which leads to a massive killing of chicken if preventive measures are not well taken. In this paper, we develop and analyze a deterministic model to investigate the role of wild birds and environment on the transmission dynamics of Newcastle disease in village chicken. We compute the basic reproduction number (R0), a threshold that tells the presence of the disease in a population. Finally, we performed the sensitivity analysis of parameters to see their relationship with the basic reproduction number (R0). The numerical results show that the basic reproduction number (R0) is more sensitive to the contact rate between the susceptible village chicken, wild birds and contaminated environment. This implies that, more contamination of the Newcastle virus into the environment increase the chance for the repeatedly occurrence of the disease. The results also shows that increasing the clearance rate of Newcastle disease virus in the environment reduces the rate of spread of the disease in chicken population. Therefore, contaminated environment plays a crucial role in the transmission of Newcastle diseases in the village chicken population.
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    Optimal control analysis of Taenia saginata bovine cysticercosis and human taeniasis
    (Elsevier, 2022) Damian, Kajunguri; Joshua, A. Mwasunda; Jacob I, Irunde
    Bovine cysticercosis and human taeniasis are neglected food-borne diseases that pose challenge to food safety, human health and livelihood of rural livestock farmers. In this paper, we have formulated and analyzed a deterministic model for transmission dynamics and control of taeniasis and cysticercosis in humans and cattle respectively. The analysis shows that both the disease free equilibrium (DFE) and endemic equilibrium (EE) exist. To study the dynamics of the diseases, we derived the basic reproduction number R0 by next generation matrix method which shows whether the diseases die or persist in humans and cattle. The diseases clear if R0 < 1 and persist when R0 > 1. The normalized forward sensitivity index is used to derive sensitive indices of model parameters. Sensitivity analysis results indicate that human’s and cattle’s recruitment rates, infection rate of cattle from contaminated environment, probability of humans to acquire taeniasis due to consumption of infected meat, defecation rate of humans with taeniasis and the consumption rate of raw or undercooked infected meat are the most positive sensitive parameters whereas the natural death rates for humans, cattle, Taenia saginata eggs and the proportion of unconsumed infected meat are the most negative sensitive parameters in diseases’ transmission. These results suggest that control measures such as improving meat cooking, meat inspection and treatment of infected humans will be effective for controlling taeniasis and cysticercosis in humans and cattle respectively. The optimal control theory is applied by considering three time dependent controls which are improved meat cooking, vaccination of cattle, and treatment of humans with taeniasis when they are implemented in combination. The Pontryagin’s maximum principle is adopted to find the necessary conditions for existence of the optimal controls. The Runge Kutta order four forward-backward sweep method is implemented in Matlab to solve the optimal control problem. The results indicate that a strategy which focuses on improving meat cooking and treatment of humans with taeniasis is the optimal strategy for diseases’ control.
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    Optimal control and Cost-Effectiveness Analysis of Taeniasis and Cysticercois in Humans, Pigs and Cattle.
    (Commun. Math. Biol. Neurosci, 2021) Joshua, A. Mwasunda; Jacob I, Irunde; Damian, Kajunguri; Dmitry, Kuznetsov
    Taeniasis and cysticercosis are neglected food-borne diseases that pose challenge to food safety, human health and livelihood of rural livestock farmers. In this paper, an optimal control problem for the dynamics and control of taeniasis and cysticercosis in humans, pigs and cattle with its cost-effectiveness analysis is presented and analysed to determine the optimal and cost-effective strategy for disease control. A combination of two or more time dependent controls involving vaccination of pigs and cattle, meat inspection, environmental hygiene and sanitation, and the treatment of humans who are infected with taeniasis is carried out to study their impacts on disease control. The Pontryagin’s maximum principle is adopted to find the necessary conditions for existence of the optimal controls. The Runge Kutta order four forward-backward sweep method is implemented to solve the optimal control problem. The incremental cost-effectiveness ratio (ICER) is applied to determine the most cost-effective strategy for disease control. The optimal control results indicate that the strategy which focus on the combination of all interventions or that exclude vaccination of pigs and cattle is the most effective optimal control strategy in disease control. However, cost-effectiveness analysis results show that a strategy which excludes vaccination of pigs and cattle is the most cost-effective strategy for disease control. Based on these results, we recommend that interventions which focus on meat inspection, treatment of humans who are infected with taeniasis and improvement in hygiene and sanitation should be considered to control the transmission of taeniasis and cysticercosis in humans, pigs and cattle at a minimal cost.