scholarly journals Effects of complexity and seasonality on backward bifurcation in vector–host models

2018 ◽  
Vol 5 (2) ◽  
pp. 171971 ◽  
Author(s):  
Shakir Bilal ◽  
Edwin Michael
Keyword(s):  
Disease Transmission ◽  
Backward Bifurcation ◽  
Epidemiological Models ◽  
Seasonal Fluctuations ◽  
Complex Vector ◽  
Vector Borne Disease ◽  
Force Of Infection ◽  
Vector Borne ◽  
The Stability ◽  
Disease Free

We study implications of complexity and seasonality in vector–host epidemiological models exhibiting backward bifurcation. Vector–host diseases represent complex infection systems that can vary in the transmission processes and population stages involved in disease progression. Seasonal fluctuations in external forcing factors can also interact in a complex way with internal host factors to govern the transmission dynamics. In backward bifurcation, the insufficiency of R 0  < 1 for predicting the stability of the disease-free equilibrium (DFE) state arises due to existence of bistability (coexisting DFE and endemic equilibria) for a range of R 0 values below one. Here we report that this region of bistability decreases with increasing complexity of vector-borne disease transmission as well as with increasing seasonality strength. The decreases in the bistability region are accompanied by a reduced force of infection acting on primary hosts. As a consequence, we show counterintuitively that a more complex vector-borne disease may be easier to control in settings of high seasonality.

scholarly journals Understanding mosquito host-choice behaviour: a new and low-cost method of identifying the sex of human hosts from mosquito blood meals

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Fiona Teltscher ◽  
Sophie Bouvaine ◽  
Gabriella Gibson ◽  
Paul Dyer ◽  
Jennifer Guest ◽  
...  
Keyword(s):  
Blood Meal ◽  
Host Species ◽  
Disease Transmission ◽  
Low Cost ◽  
Host Choice ◽  
Epidemiological Models ◽  
Choice Behaviour ◽  
Vector Borne ◽  
Transmission Models ◽  
Blood Meals

Abstract Background Mosquito-borne diseases are a global health problem, causing hundreds of thousands of deaths per year. Pathogens are transmitted by mosquitoes feeding on the blood of an infected host and then feeding on a new host. Monitoring mosquito host-choice behaviour can help in many aspects of vector-borne disease control. Currently, it is possible to determine the host species and an individual human host from the blood meal of a mosquito by using genotyping to match the blood profile of local inhabitants. Epidemiological models generally assume that mosquito biting behaviour is random; however, numerous studies have shown that certain characteristics, e.g. genetic makeup and skin microbiota, make some individuals more attractive to mosquitoes than others. Analysing blood meals and illuminating host-choice behaviour will help re-evaluate and optimise disease transmission models. Methods We describe a new blood meal assay that identifies the sex of the person that a mosquito has bitten. The amelogenin locus (AMEL), a sex marker located on both X and Y chromosomes, was amplified by polymerase chain reaction in DNA extracted from blood-fed Aedes aegypti and Anopheles coluzzii. Results AMEL could be successfully amplified up to 24 h after a blood meal in 100% of An. coluzzii and 96.6% of Ae. aegypti, revealing the sex of humans that were fed on by individual mosquitoes. Conclusions The method described here, developed using mosquitoes fed on volunteers, can be applied to field-caught mosquitoes to determine the host species and the biological sex of human hosts on which they have blood fed. Two important vector species were tested successfully in our laboratory experiments, demonstrating the potential of this technique to improve epidemiological models of vector-borne diseases. This viable and low-cost approach has the capacity to improve our understanding of vector-borne disease transmission, specifically gender differences in exposure and attractiveness to mosquitoes. The data gathered from field studies using our method can be used to shape new transmission models and aid in the implementation of more effective and targeted vector control strategies by enabling a better understanding of the drivers of vector-host interactions.

scholarly journals Stability and Hopf Bifurcation of a Vector-Borne Disease Model with Saturated Infection Rate and Reinfection

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Zhixing Hu ◽  
Shanshan Yin ◽  
Hui Wang
Keyword(s):  
Hopf Bifurcation ◽  
Infection Rate ◽  
Disease Model ◽  
Endemic Equilibrium ◽  
Basic Reproductive Number ◽  
Reproductive Number ◽  
Cure Rate ◽  
Vector Borne Disease ◽  
Vector Borne ◽  
The Stability

This paper established a delayed vector-borne disease model with saturated infection rate and cure rate. First of all, according to the basic reproductive number R0, we determined the disease-free equilibrium E0 and the endemic equilibrium E1. Through the analysis of the characteristic equation, we consider the stability of two equilibriums. Furthermore, the effect on the stability of the endemic equilibrium E1 by delay was studied, the existence of Hopf bifurcations of this system in E1 was analyzed, and the length of delay to preserve stability was estimated. The direction and stability of the Hopf bifurcation were also been determined. Finally, we performed some numerical simulation to illustrate our main results.

The effectiveness of pre-impregnated permethrin in military clothing in the prevention of insect bites

2018 ◽  
Vol 104 (2) ◽  
pp. 80-83
Author(s):  
D Biggs
Keyword(s):  
Disease Transmission ◽  
Integrated Approach ◽  
Negative Control ◽  
Vector Borne Disease ◽  
Volunteer Study ◽  
Significant Difference ◽  
Insect Mortality ◽  
Alternative Means ◽  
Vector Borne ◽  
Insect Bites

AbstractIntroductionWhen on operational deployment, or where a vector-borne disease threat has been identified, military personnel wear uniform that has been pre-impregnated with permethrin insecticide to prevent insect bites, as part of an integrated approach to bite avoidance in order to reduce disease non-battle injury. This article reports a study that was carried out to investigate whether the clothing treatments currently in use are effective at preventing insect bites.MethodsA human volunteer study was conducted using two different species of mosquito and clothing subjected to different washing schedules. The number of landing events and probing events, and insect mortality, were recorded.ResultsThere was a marked increase in mosquito activity as the amount of viable permethrin was reduced through washing. There was a statistically significant difference between 50 washes and the negative control, and between 50 and 5 washes. As clothing is increasingly washed, its effectiveness is reduced.ConclusionThe use of pre-impregnated uniform does not provide complete protection against biting insects throughout the life of the garment. No single means of protection will prevent personnel from being bitten, and a suite of personal and communal measures should be employed to reduce the risk of vector-borne disease, including the use of insect repellent, mosquito nets, anti-malarial chemoprophylaxis and re-treatment of clothing against biting insects in order to reduce the risk of disease transmission. Since this study, alternative means of clothing treatment have been sought to reinforce the pre-treated uniforms issued. Advice and direction is available, specific to the environment personnel are deploying to, based upon risk.

scholarly journals Stability Analysis of a Vector-Borne Disease with Variable Human Population

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Muhammad Ozair ◽  
Abid Ali Lashari ◽  
Il Hyo Jung ◽  
Young Il Seo ◽  
Byul Nim Kim
Keyword(s):  
Mathematical Model ◽  
Human Population ◽  
Feasible Region ◽  
Asymptotically Stable ◽  
Globally Asymptotically Stable ◽  
Vector Borne Disease ◽  
Vector Borne ◽  
Theoretical Results ◽  
Disease Free ◽  
Varying Population

A mathematical model of a vector-borne disease involving variable human population is analyzed. The varying population size includes a term for disease-related deaths. Equilibria and stability are determined for the system of ordinary differential equations. IfR0≤1, the disease-“free” equilibrium is globally asymptotically stable and the disease always dies out. IfR0>1, a unique “endemic” equilibrium is globally asymptotically stable in the interior of feasible region and the disease persists at the “endemic” level. Our theoretical results are sustained by numerical simulations.

scholarly journals The effect of resource limitation on the temperature dependence of mosquito population fitness

2021 ◽  
Vol 288 (1949) ◽  
Author(s):  
Paul J. Huxley ◽  
Kris A. Murray ◽  
Samraat Pawar ◽  
Lauren J. Cator
Keyword(s):  
Disease Transmission ◽  
Resource Limitation ◽  
Adult Size ◽  
Population Modelling ◽  
Juvenile Mortality ◽  
Low Resource ◽  
Vector Borne Disease ◽  
High Resource ◽  
Optimal Resource ◽  
Vector Borne

Laboratory-derived temperature dependencies of life-history traits are increasingly being used to make mechanistic predictions for how climatic warming will affect vector-borne disease dynamics, partially by affecting abundance dynamics of the vector population. These temperature–trait relationships are typically estimated from juvenile populations reared on optimal resource supply, even though natural populations of vectors are expected to experience variation in resource supply, including intermittent resource limitation. Using laboratory experiments on the mosquito Aedes aegypti , a principal arbovirus vector, combined with stage-structured population modelling, we show that low-resource supply in the juvenile life stages significantly depresses the vector's maximal population growth rate across the entire temperature range (22–32°C) and causes it to peak at a lower temperature than at high-resource supply. This effect is primarily driven by an increase in juvenile mortality and development time, combined with a decrease in adult size with temperature at low-resource supply. Our study suggests that most projections of temperature-dependent vector abundance and disease transmission are likely to be biased because they are based on traits measured under optimal resource supply. Our results provide compelling evidence for future studies to consider resource supply when predicting the effects of climate and habitat change on vector-borne disease transmission, disease vectors and other arthropods.

Immune response in HIV epidemics for distinct transmission rates and for saturated CTL response

2019 ◽  
Vol 14 (3) ◽  
pp. 307 ◽  
Author(s):  
Ana R.M. Carvalho ◽  
Carla M.A. Pinto
Keyword(s):  
Immune Response ◽  
Disease Transmission ◽  
Cytotoxic T Lymphocyte ◽  
Point Of View ◽  
Ctl Response ◽  
Transmission Rates ◽  
Distinct Disease ◽  
The Stability ◽  
Disease Free

In this paper, we study the immune response in a fractional order model for HIV dynamics, for distinct disease transmission rates and saturated cytotoxic T-lymphocyte (CTL) response. Our goal is twofold: (i) to analyze the role of the order of the fractional derivative, α, on the efficacy of the immune response, (ii) to examine the immune response for distinct transmission functions, in the presence of saturated CTL response. We compute the reproduction number of the model and state the stability of the disease-free equilibrium. We discuss the results of the model from an epidemiological point of view.

scholarly journals Assessing the Potential Impact of Immunity Waning on the Dynamics of COVID-19: An Endemic Model of COVID-19

2021 ◽  
Author(s):  
MUSA RABIU ◽  
Sarafa A. Iyaniwura
Keyword(s):  
Disease Transmission ◽  
Reproduction Number ◽  
Transmission Rate ◽  
Backward Bifurcation ◽  
Disease Dynamics ◽  
Potential Impact ◽  
The Impact ◽  
Induced Immunity ◽  
Disease Free ◽  
Pharmaceutical Interventions

Abstract We developed an endemic model of COVID-19 to assess the impact of vaccination and immunity waning on the dynamics of the disease. Our model exhibits the phenomenon of backward bifurcation and bi-stability, where a stable disease-free equilibrium co-exists with a stable endemic equilibrium. The epidemiological implication of this is that the control reproduction number being less than unity is no longer sufficient to guarantee disease eradication. We showed that this phenomenon could be eliminated by either increasing the vaccine efficacy or by reducing the disease transmission rate (adhering to non-pharmaceutical interventions). Furthermore, we numerically investigated the impacts of vaccination and waning of both vaccine-induced immunity and post-recovery immunity on the disease dynamics. Our simulation results show that the waning of vaccine-induced immunity has more effect on the disease dynamics relative to post-recovery immunity waning, and suggests that more emphasis should be on reducing the waning of vaccine-induced immunity to eradicate COVID-19.

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