African Trypanosomiasis Dynamics: Modelling the Effects of Treatment, Education, and Vector Trapping

African trypanosomiasis is a vector-borne disease that is mainly transmitted by infected tsetse flies. A deterministic model of tsetse fly vector, human, and cattle hosts is formulated and analyzed to gain insights into the disease dynamics. The roles of public health education, treatment, and tsetse fly traps are studied. The effective reproduction number, a threshold used to determine whether the disease persists or dies out in the population, is determined. The sensitivity analysis of the model parameters is performed to determine their relationship with the effective reproduction number. The results show that the tsetse fly biting rate is the most sensitive parameter to the effective reproduction number. Furthermore, the model’s numerical simulation shows that a combination of all three interventions has the most significant impact on the control of African trypanosomiasis. Thus, we recommend that these control measures be put concurrently in endemic areas for effective control of the disease transmission.

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Livestock, pathogens, vectors, and their environment: a causal inference-based approach to estimating the pathway-specific effect of livestock on human African trypanosomiasis risk

10.1101/2022.01.13.22268994 ◽

2022 ◽

Author(s):

Julianne Meisner ◽

Agapitus Kato ◽

Marshall Lemerani ◽

Erick Mwamba Miaka ◽

Acaga Ismail Taban ◽

...

Keyword(s):

Environmental Change ◽

Causal Inference ◽

Disease Transmission ◽

Human African Trypanosomiasis ◽

Spatial Epidemiology ◽

Specific Effect ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Change Effect

Livestock are important reservoirs for many diseases, and investigation of such zoonoses has long been the focus of One Health research. However, the effects of livestock on human and environmental health extend well beyond direct disease transmission. In this retrospective ecological cohort study we use pre-existing data and methods derived from causal inference and spatial epidemiology to estimate three hypothesized mechanisms by which livestock can come to bear on human African trypanosomiasis (HAT) risk: the reservoir effect, by which infected cattle and pigs are a source of infection to humans; the zooprophylactic effect, by which preference for livestock hosts exhibited by the tsetse fly vector of HAT means that their presence protects humans from infection; and the environmental change effect, by which livestock keeping activities modify the environment in such a way that habitat suitability for tsetse flies, and in turn human infection risk, is reduced. We conducted this study in four high burden countries: at the point level in Uganda, Malawi, and Democratic Republic of Congo (DRC), and at the county-level in South Sudan. Our results indicate cattle and pigs play an important reservoir role for the rhodesiense form (rHAT) in Uganda, however zooprophylaxis outweighs this effect for rHAT in Malawi. For the gambiense form (gHAT) we found evidence that pigs may be a competent reservoir, however dominance of the reservoir versus zooprophylactic pathway for cattle varied across countries. We did not find compelling evidence of an environmental change effect.

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China’s effective control and other countries’ uncharted challenge against COVID-19: an epidemiological and modelling study

10.1101/2020.04.28.20083899 ◽

2020 ◽

Author(s):

Lingling Zheng ◽

Qin Kang ◽

Weiyao Liao ◽

Xiujuan Chen ◽

Shuai Huang ◽

...

Keyword(s):

Disease Transmission ◽

Reproduction Number ◽

Case Reports ◽

Epidemiological Data ◽

Control Measures ◽

Time Dependent ◽

Effective Control ◽

List Type ◽

Global Epidemic ◽

Serial Interval

AbstractBackgroundOn the present trajectory, COVID is inevitably becoming a global epidemic, leading to concerns regarding the pandemic potential in China and other countries.ObjectiveIn this study, we use the time-dependent reproduction number (Rt) to comprise the COVID transmissibility across different countries.MethodsWe used data from Jan 20, 2019, to Feb 29, 2020, on the number of newly confirmed cases, obtained from the reports published by the CDC, to infer the incidence of infectious over time. A two-step procedure was used to estimate the Rt. The first step used data on known index-secondary cases pairs, from publicly available case reports, to estimate the serial interval distribution. The second step estimated the Rt jointly from the incidence data and the information data in the first step. Rt was then used to simulate the epidemics across all major cities in China and typical countries worldwide.ResultsBased on a total of 126 index-secondary cases pairs from 4 international regions, we estimated that the serial interval for SARS-2-CoV was 4.18 (IQR 1.92 – 6.65) days. Domestically, Rt of China, Hubei province, Wuhan had fallen below 1.0 on 9 Feb, 10 Feb and 13 Feb (Rt were 0.99±0.02, 0.99±0.02 and 0.96±0.02), respectively. Internationally, as of 26 Feb, statistically significant periods of COVID spread (Rt >1) were identified for most regions, except for Singapore (Rt was 0.92±0.17).ConclusionsThe epidemic in China has been well controlled, but the worldwide pandemic has not been well controlled. Worldwide preparedness and vulnerability against COVID-19 should be regarded with more care.What is already known on this subject?The basic reproduction number (R0) and the-time-dependent reproduction number (Rt) are two important indicators of infectious disease transmission. In addition, Rt as a derivative of R0 could be used to assess the epidemiological development of the disease and effectiveness of control measures. Most current researches used data from earlier periods in Wuhan and refer to the epidemiological features of SARS, which are possibly biased. Meanwhile, there are fewer studies discussed the Rt of COVID-19. Current clinical and epidemiological data are insufficient to help us understand the full view of the potential transmission of this disease.What this study adds?We use up-to-data observation of the serial interval and cases arising from local transmission to calculate the Rt in different outbreak level area and every province in China as well as five-top sever outbreak countries and other overseas. By comparing the Rt, we discussed the situation of outbreak around the world.

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Tsetse Flies (Glossina) as Vectors of Human African Trypanosomiasis: A Review

BioMed Research International ◽

10.1155/2016/6201350 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 18

Author(s):

Florence Njeri Wamwiri ◽

Robert Emojong Changasi

Keyword(s):

Disease Transmission ◽

Human African Trypanosomiasis ◽

Tsetse Fly ◽

Public Health Issue ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Land Use Patterns ◽

Transmission Cycle ◽

Use Patterns ◽

Abundance And Distribution

Human African Trypanosomiasis (HAT) transmitted by the tsetse fly continues to be a public health issue, despite more than a century of research. There are two types of the disease, the chronicgambienseand the acuterhodesiense-HAT. Fly abundance and distribution have been affected by changes in land-use patterns and climate. However, disease transmission still continues. Here, we review some aspects of HAT ecoepidemiology in the context of altered infestation patterns and maintenance of the transmission cycle as well as emerging options in disease and vector control.

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Mixing in regional-structure model about the influence of floating population and optimal control about TB in Guangdong province of China

International Journal of Biomathematics ◽

10.1142/s1793524517501066 ◽

2017 ◽

Vol 10 (08) ◽

pp. 1750106 ◽

Cited By ~ 1

Author(s):

Chuanqing Xu ◽

Xiaoxiao Wei ◽

Jingan Cui ◽

Xiaojing Wang ◽

Dashun Xu

Keyword(s):

Deterministic Model ◽

Reproduction Number ◽

Programming Model ◽

Vaccine Coverage ◽

Local Population ◽

Guangdong Province ◽

Control Measures ◽

Floating Population ◽

Effective Control ◽

Prevention Measures

In the last 60 years, great progress has been made in controlling and preventing tuberculosis in China. However, the number of tuberculosis cases has increased dramatically in the last 25 years, mainly due to the lack of effective control measures of immigrating populations with tuberculosis. In order to explore the effective control and prevention measures we propose a deterministic model to study the transmission dynamics of tuberculosis in Guangdong province of China in this paper. The model consists of susceptible, exposed and infectious recovered subpopulations of immigrating populations from other provinces and the local population of Guangdong. We obtain the effective reproduction number. Based on the analysis, we also establish an optimal immune programming model, and get the optimal proportion of vaccine coverage with control of the effective reproduction number. Simulation is used to determine the validation and reliability. Our study demonstrates that the immigrating population from different provinces needs to be vaccinated according to the incidence rate of TB in their original provinces, and it is an effective way to prevent the outbreak of tuberculosis in Guangdong.

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Mathematical Modelling of Human African Trypanosomiasis Using Control Measures

Computational and Mathematical Methods in Medicine ◽

10.1155/2018/5293568 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 4

Author(s):

Hamenyimana Emanuel Gervas ◽

Nicholas Kwasi-Do Ohene Opoku ◽

Shamsuddeen Ibrahim

Keyword(s):

Human African Trypanosomiasis ◽

Reproduction Number ◽

Tsetse Fly ◽

Control Measures ◽

Asymptotically Stable ◽

African Trypanosomiasis ◽

Globally Asymptotically Stable ◽

Vector Borne ◽

Next Generation Matrix ◽

Disease Free

Human African trypanosomiasis (HAT), commonly known as sleeping sickness, is a neglected tropical vector-borne disease caused by trypanosome protozoa. It is transmitted by bites of infected tsetse fly. In this paper, we first present the vector-host model which describes the general transmission dynamics of HAT. In the tsetse fly population, the HAT is modelled by three compartments, while in the human population, the HAT is modelled by four compartments. The next-generation matrix approach is used to derive the basic reproduction number, R0, and it is also proved that if R0≤1, the disease-free equilibrium is globally asymptotically stable, which means the disease dies out. The disease persists in the population if the value of R0>1. Furthermore, the optimal control model is determined by using the Pontryagin’s maximum principle, with control measures such as education, treatment, and insecticides used to optimize the objective function. The model simulations confirm that the use of the three control measures is very efficient and effective to eliminate HAT in Africa.

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Mathematical Modelling of Human African Trypanosomiasis Using Control Measures

10.20944/preprints201810.0561.v1 ◽

2018 ◽

Author(s):

Hamenyimana Emanuel Gervas ◽

Nicholas Kwasi-Do Ohene Opoku ◽

Shamsuddeen Ibrahim

Keyword(s):

Human Population ◽

Human African Trypanosomiasis ◽

Reproduction Number ◽

Tsetse Fly ◽

Control Measures ◽

Asymptotically Stable ◽

African Trypanosomiasis ◽

Globally Asymptotically Stable ◽

Next Generation Matrix ◽

Disease Free

Human African Trypanosomiasis (HAT) commonly known as sleeping sickness, is a neglected tropical vector borne disease caused by trypanosome protozoa. It is transmitted by bites of infected tsetse fly. In this paper we first present the vector-host model which describes the general transmission dynamics of HAT. In the tsetse fly population, the HAT is modelled by three compartments while in the human population, the HAT is modelled by four compartments. The next generation matrix approach is used to derive the basic reproduction number, R0, and also it is proved that if R0 ≤ 1 the disease free equilibrium is globally asymptotically stable, which means the disease dies out. The disease persist in the population if the value of R0 > 1. Furthermore, the optimal control model is determined by using the Pontryagin’s maximum principle with control measures such as education, treatment and insecticides used to optimize the objective function. The model simulations confirm that the use of the three control measures are very efficient and effective to eliminate HAT in Africa.

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MODELING THE IMPACT OF VOLUNTARY TESTING AND TREATMENT ON TUBERCULOSIS TRANSMISSION DYNAMICS

International Journal of Biomathematics ◽

10.1142/s1793524511001726 ◽

2012 ◽

Vol 05 (04) ◽

pp. 1250029 ◽

Cited By ~ 3

Author(s):

S. MUSHAYABASA ◽

C. P. BHUNU

Keyword(s):

Deterministic Model ◽

Reproduction Number ◽

Positive Impact ◽

Transmission Dynamics ◽

Effective Control ◽

Reproductive Number ◽

Voluntary Testing ◽

Manifold Theory ◽

The Impact ◽

Disease Free

A deterministic model for evaluating the impact of voluntary testing and treatment on the transmission dynamics of tuberculosis is formulated and analyzed. The epidemiological threshold, known as the reproduction number is derived and qualitatively used to investigate the existence and stability of the associated equilibrium of the model system. The disease-free equilibrium is shown to be locally-asymptotically stable when the reproductive number is less than unity, and unstable if this threshold parameter exceeds unity. It is shown, using the Centre Manifold theory, that the model undergoes the phenomenon of backward bifurcation where the stable disease-free equilibrium co-exists with a stable endemic equilibrium when the associated reproduction number is less than unity. The analysis of the reproduction number suggests that voluntary tuberculosis testing and treatment may lead to effective control of tuberculosis. Furthermore, numerical simulations support the fact that an increase voluntary tuberculosis testing and treatment have a positive impact in controlling the spread of tuberculosis in the community.

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Global Stability and Optimal Control of Dengue with Two Coexisting Virus Serotypes

MATEMATIKA ◽

10.11113/matematika.v35.n4.1269 ◽

2019 ◽

Vol 35 (4) ◽

pp. 149-170

Author(s):

Afeez Abidemi ◽

Rohanin Ahmad ◽

Nur Arina Bazilah Aziz

Keyword(s):

Optimal Control ◽

Global Stability ◽

Disease Transmission ◽

Deterministic Model ◽

Control Strategies ◽

Equilibrium Points ◽

Effective Control ◽

Asymptotically Stable ◽

Globally Asymptotically Stable ◽

Boundary Equilibrium

This study presents a two-strain deterministic model which incorporates Dengvaxia vaccine and insecticide (adulticide) control strategies to forecast the dynamics of transmission and control of dengue in Madeira Island if there is a new outbreak with a different virus serotypes after the first outbreak in 2012. We construct suitable Lyapunov functions to investigate the global stability of the disease-free and boundary equilibrium points. Qualitative analysis of the model which incorporates time-varying controls with the specific goal of minimizing dengue disease transmission and the costs related to the control implementation by employing the optimal control theory is carried out. Three strategies, namely the use of Dengvaxia vaccine only, application of adulticide only, and the combination of Dengvaxia vaccine and adulticide are considered for the controls implementation. The necessary conditions are derived for the optimal control of dengue. We examine the impacts of the control strategies on the dynamics of infected humans and mosquito population by simulating the optimality system. The disease-freeequilibrium is found to be globally asymptotically stable whenever the basic reproduction numbers associated with virus serotypes 1 and j (j 2 {2, 3, 4}), respectively, satisfy R01,R0j 1, and the boundary equilibrium is globally asymptotically stable when the related R0i (i = 1, j) is above one. It is shown that the strategy based on the combination of Dengvaxia vaccine and adulticide helps in an effective control of dengue spread in the Island.

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Potential impacts of climate change on geographical distribution of three primary vectors of African Trypanosomiasis in Tanzania’s Maasai Steppe: G. m. morsitans, G. pallidipes and G. swynnertoni

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0009081 ◽

2021 ◽

Vol 15 (2) ◽

pp. e0009081

Author(s):

Happiness Jackson Nnko ◽

Paul Simon Gwakisa ◽

Anibariki Ngonyoka ◽

Calvin Sindato ◽

Anna Bond Estes

Keyword(s):

Public Health ◽

Climate Change ◽

Ecological Niche Modeling ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Modeling Tools ◽

Distribution Maps ◽

Current Climate ◽

Maasai Steppe

In the Maasai Steppe, public health and economy are threatened by African Trypanosomiasis, a debilitating and fatal disease to livestock (African Animal Trypanosomiasis -AAT) and humans (Human African Trypanosomiasis—HAT), if not treated. The tsetse fly is the primary vector for both HAT and AAT and climate is an important predictor of their occurrence and the parasites they carry. While understanding tsetse fly distribution is essential for informing vector and disease control strategies, existing distribution maps are old and were based on coarse spatial resolution data, consequently, inaccurately representing vector and disease dynamics necessary to design and implement fit-for-purpose mitigation strategies. Also, the assertion that climate change is altering tsetse fly distribution in Tanzania lacks empirical evidence. Despite tsetse flies posing public health risks and economic hardship, no study has modelled their distributions at a scale needed for local planning. This study used MaxEnt species distribution modelling (SDM) and ecological niche modeling tools to predict potential distribution of three tsetse fly species in Tanzania’s Maasai Steppe from current climate information, and project their distributions to midcentury climatic conditions under representative concentration pathways (RCP) 4.5 scenarios. Current climate results predicted that G. m. morsitans, G. pallidipes and G swynnertoni cover 19,225 km2, 7,113 km2 and 32,335 km2 and future prediction indicated that by the year 2050, the habitable area may decrease by up to 23.13%, 12.9% and 22.8% of current habitable area, respectively. This information can serve as a useful predictor of potential HAT and AAT hotspots and inform surveillance strategies. Distribution maps generated by this study can be useful in guiding tsetse fly control managers, and health, livestock and wildlife officers when setting surveys and surveillance programs. The maps can also inform protected area managers of potential encroachment into the protected areas (PAs) due to shrinkage of tsetse fly habitats outside PAs.

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Human African trypanosomiasis

Oxford Textbook of Medicine ◽

10.1093/med/9780198746690.003.0169 ◽

2020 ◽

pp. 1451-1459

Author(s):

Reto Brun ◽

Johannes Blum

Keyword(s):

Trypanosoma Brucei ◽

Human African Trypanosomiasis ◽

Specific Treatment ◽

Protozoan Parasite ◽

Control Measures ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Control Programmes ◽

The 1960S ◽

Stage 1

Human African trypanosomiasis (sleeping sickness) is caused by subspecies of the protozoan parasite Trypanosoma brucei. The disease is restricted to tropical Africa where it is transmitted by the bite of infected tsetse flies (Glossina spp.). Control programmes in the 1960s were very effective, but subsequent relaxation of control measures led to recurrence of epidemic proportions in the 1980s and 1990s. Control is now being regained. Untreated human African trypanosomiasis is almost invariably fatal. Specific treatment depends on the trypanosome subspecies and the stage of the disease. Drugs used for stage 1 include pentamidine and suramin, and for stage 2 include melarsoprol, eflornithine, and nifurtimox, but regimens are not standardized, and treatment is difficult and dangerous; all of the drugs used have many side effects, some potentially lethal.

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