Browsing by Author "Lusekelo, Eva"

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Dynamic modelling and optimal control analysis of a fractional order chikungunya disease model with temperature effects
(Elsevier, 2023-01-19) Lusekelo, Eva; Helikumi, Mlyashimbi; Kuznetsov, Dmitry; Mushayabasa, Steady
Approximately 1.3 billion inhabitants in 94 countries are estimated to be at risk of chikungunya virus infection. A mechanistic compartmental model based on fractional calculus, the Caputo derivative has been proposed to evaluate the effects of temperature and multiple disease control measures (larvicides use, insecticides and physical barriers) during an outbreak. The proposed model was calibrated based on data from literature and validated with daily chikungunya fever cases reported at Kadmat primary health centre, India. The transmission potential of the disease was examined. Sensitive analyses were conducted through computing partial rank correlation coefficients. Memory effects which are often neglected when mechanistic models are used to model the transmission dynamics of infectious diseases, were found to have a significant effect on the dynamics of chikungunya.
Mathematical Models for Chikungunya Virus: Effects of Heterogeneity and Periodic Environmental Variations
(NM-AIST, 2024-08) Lusekelo, Eva
In recent years, chikungunya, a mosquito-borne viral disease has spread globally and invaded new habitats and, as such, it is now regarded as one of the global threats to humanity because of its highly debilitating nature and unprecedented magnitude of its spread. Precisely, there is inadequate mechanistic understanding of how environmental factors, socioeconomic factors and disease intervention strategies, combined, affects epidemic magnitude and duration. In this study, we developed four mechanistic models for Aedes aegypti mosquitoes and chikungunya virus transmission that incorporates relevant ecological and biological factors, socio-economic factors and disease intervention strategies. The first model quantifies the effects of biological control and temperature on the growth of Aedes aegypti mosquito population in the environment. Utilising empirically derived temperature functions in literature, we observed that temperature ranges from 29^0 C to 35^0 C supports maximum egg hatching as well as development of larva and pupa. We also computed the vector reproduction number and examined the influence of entomological parameters on its magnitude. In addition, results also revealed that the attack rate of aquatic predators has higher impact to reduce mosquito population compared to the size of the predator population in the environment. In the second model, we developed a mathematical model to determine optimum timing of rolling out intervention strategies during a chikungunya virus outbreak. The proposed model incorporates three intervention strategies, physical barriers, larvicide and insecticide. Making use of optimal control theory, parameter sensitivity analysis, and numerical simulations, we performed a cost-effective analysis of the aforementioned intervention strategies. Findings from the proposed model offer a framework for designing cost-effective strategies for chikungunya with multiple intervention methods. Temperature and heterogeneous biting exposure are known to be integral factor capable of altering the spread of chikungunya during an outbreak. To quantify the role of these factors, we developed two mechanistic models, an autonomous and a non-autonomous. In a non-autonomous model temperature varies with time while in the autonomous it is regarded to be constant. In all scenarios, analysis of the model showed that both temperature and heterogeneous biting exposure have a substantial influence on shaping the transmission of the disease during an outbreak. Besides, temperature and heterogeneous biting exposure, the non-autonomous model incorporated mass media campaigns. Upon evaluating the implications of mass media campaigns during chikungunya outbreak, we observed that if 20% of infections are detected and reported, with mass media campaigns at 90% efficient, then the new infections produced may decrease by 68.8% over a four-year period. Overall, our results showed that temperature, predation, heterogeneous biting exposure and mass media campaigns play an essential component in determining both the short and long chikungunya virus dynamics.
Modeling the effects of temperature and heterogeneous biting exposure on chikungunya virus disease dynamics
(Elsevier, 2022-07-06) Lusekelo, Eva; Helikumi, Mlyashimbi; Kuznetsov, Dmitry; Mushayabasa, Steady
Within the last decades, chikungunya virus (CHIKV), a mosquito-borne arboviral disease transmitted by Aedes species mosquitoes has been a growing public health burden. Approximately 1.3 billion inhabitants in 94 countries are estimated to be at risk of chikungunya virus infection. Prior studies suggest that temperature and heterogeneous biting exposure are some of the key determinant factors in transmission dynamics of vector-borne diseases. In order to direct preparedness for future outbreaks, it is imperative to evaluate the effects of heterogeneous biting exposure and temperature variations on transmission dynamics of CHIKV. In this paper, a mathematical model that incorporates heterogeneous biting exposure and temperature effects has been developed and analyzed. The basic reproduction number, an important metric for infectious disease models has been determined. Data from literature has been used to calibrate the model and observed CHIKV data for Kadmat primary health centre, India (2 July to 7 September 2007) has been used to validate the model. Results from the study suggest that disease prevention strategies which are effective at stopping transmission of CHIKV more than 80% of the time, will be highly effective minimizing disease burden during outbreaks. The proposed model can be used to inform policy makers on effective ways of managing CHIKV during outbreaks.
Quantifying the effects of temperature and predation on the growth of Aedes mosquito population
(Springer Nature, 2023-01-10) Lusekelo, Eva; Helikumi, Mlyashimbi; Kuznetsov, Dmitry; Mushayabasa, Steady
Despite having been tested in multiple settings, the quantitative impact of predatory aquatic insects to reduce mosquito population remains unclear. To address this question, an ecological model of Aedes mosquito population incorporating temperature-dependent entomological parameters and predation is developed. The vector reproduction number is derived and entomological parameters that strongly influence it have been identified. Implications of predation on mosquito growth are examined. Results show that predators with high daily attack rate can significantly reduce vector reproduction to extremely low values close to zero. The study provides a framework for more detailed, predator specific studies that are essential to develop an improved understanding on the relationship between predatory aquatic insects and Aedes mosquitoes.