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Cecilia H, Arnoux S, Picault S, Dicko A, Seck MT, Sall B, Bassène M, Vreysen M, Pagabeleguem S, Bancé A, Bouyer J, Ezanno P. Dispersal in heterogeneous environments drives population dynamics and control of tsetse flies. Proc Biol Sci 2021; 288:20202810. [PMID: 33529565 PMCID: PMC7893214 DOI: 10.1098/rspb.2020.2810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Spatio-temporally heterogeneous environments may lead to unexpected population dynamics. Knowledge is needed on local properties favouring population resilience at large scale. For pathogen vectors, such as tsetse flies transmitting human and animal African trypanosomosis, this is crucial to target management strategies. We developed a mechanistic spatio-temporal model of the age-structured population dynamics of tsetse flies, parametrized with field and laboratory data. It accounts for density- and temperature-dependence. The studied environment is heterogeneous, fragmented and dispersal is suitability-driven. We confirmed that temperature and adult mortality have a strong impact on tsetse populations. When homogeneously increasing adult mortality, control was less effective and induced faster population recovery in the coldest and temperature-stable locations, creating refuges. To optimally select locations to control, we assessed the potential impact of treating them and their contribution to the whole population. This heterogeneous control induced a similar population decrease, with more dispersed individuals. Control efficacy was no longer related to temperature. Dispersal was responsible for refuges at the interface between controlled and uncontrolled zones, where resurgence after control was very high. The early identification of refuges, which could jeopardize control efforts, is crucial. We recommend baseline data collection to characterize the ecosystem before implementing any measures.
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Affiliation(s)
| | | | | | - Ahmadou Dicko
- Cirad, INRAE, ASTRE, University of Montpellier, Montpellier, France
| | - Momar Talla Seck
- Institut Sénégalais de Recherches Agricoles, Laboratoire National d'Elevage et de Recherches Vétérinaires, Dakar-Hann, Senegal
| | - Baba Sall
- Direction des Services vétérinaires, Ministère de l'Elevage et des Productions animales, Sphères ministérielles de Diamniadio, Bât. C, 3ème étage, Senegal
| | - Mireille Bassène
- Institut Sénégalais de Recherches Agricoles, Laboratoire National d'Elevage et de Recherches Vétérinaires, Dakar-Hann, Senegal
| | - Marc Vreysen
- Insect Pest Control Laboratory, Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, 1400 Vienna, Austria
| | - Soumaïla Pagabeleguem
- Insectarium de Bobo-Dioulasso - Campagne d'Eradication des Tsé-tsé et Trypanosomoses (IBD-CETT), Bobo-Dioulasso 01, BP 1087, Burkina Faso.,Université de Dédougou (UDDG), BP 176, Burkina Faso
| | - Augustin Bancé
- Centre International de Recherche-Développement sur l'Elevage en Zone Subhumide (CIRDES), Bobo-Dioulasso 01 01 BP 454, Burkina Faso
| | - Jérémy Bouyer
- Cirad, INRAE, ASTRE, University of Montpellier, Montpellier, France.,Insect Pest Control Laboratory, Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture, 1400 Vienna, Austria.,UMR 'Interactions hôtes-vecteurs-parasites-environnement dans les maladies tropicales négligées dues aux trypanosomatides', Cirad, Montpellier, France
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Mulenga GM, Henning L, Chilongo K, Mubamba C, Namangala B, Gummow B. Insights into the Control and Management of Human and Bovine African Trypanosomiasis in Zambia between 2009 and 2019-A Review. Trop Med Infect Dis 2020; 5:E115. [PMID: 32664551 PMCID: PMC7559803 DOI: 10.3390/tropicalmed5030115] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/18/2020] [Accepted: 07/08/2020] [Indexed: 12/02/2022] Open
Abstract
Tsetse transmitted trypanosomiasis is a fatal disease commonly known as Nagana in cattle and sleeping sickness in humans. The disease threatens food security and has severe economic impact in Africa including most parts of Zambia. The level of effectiveness of commonly used African trypanosomiasis control methods has been reported in several studies. However, there have been no review studies on African trypanosomiasis control and management conducted in the context of One Health. This paper therefore seeks to fill this knowledge gap. A review of studies that have been conducted on African trypanosomiasis in Zambia between 2009 and 2019, with a focus on the control and management of trypanosomiasis was conducted. A total of 2238 articles were screened, with application of the search engines PubMed, PubMed Central and One Search. Out of these articles, 18 matched the required criteria and constituted the basis for the paper. An in-depth analysis of the 18 articles was conducted to identify knowledge gaps and evidence for best practices. Findings from this review provide stakeholders and health workers with a basis for prioritisation of African trypanosomiasis as an important neglected disease in Zambia and for formulation of One Health strategies for better control and/or management of the disease.
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Affiliation(s)
- Gloria M. Mulenga
- Department of Veterinary Services, Kakumbi Tsetse and Trypanosomiasis Research Station, P.O Box 70, Mfuwe 10101, Zambia
- Ministry of Fisheries and Livestock, Department of Veterinary Services, Lusaka 10101, Zambia; (K.C.); (C.M.)
- College of Public Health Medical and Veterinary Services, James Cook University, Townsville, Queensland 4814, Australia; (L.H.); (B.G.)
| | - Lars Henning
- College of Public Health Medical and Veterinary Services, James Cook University, Townsville, Queensland 4814, Australia; (L.H.); (B.G.)
| | - Kalinga Chilongo
- Ministry of Fisheries and Livestock, Department of Veterinary Services, Lusaka 10101, Zambia; (K.C.); (C.M.)
| | - Chrisborn Mubamba
- Ministry of Fisheries and Livestock, Department of Veterinary Services, Lusaka 10101, Zambia; (K.C.); (C.M.)
| | - Boniface Namangala
- Institute of distance learning, The University of Zambia, Lusaka 10101, Zambia;
| | - Bruce Gummow
- College of Public Health Medical and Veterinary Services, James Cook University, Townsville, Queensland 4814, Australia; (L.H.); (B.G.)
- Faculty of Veterinary Science, University of Pretoria, 0028 Pretoria, South Africa
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Hargrove JW, Vale GA. Models for the rates of pupal development, fat consumption and mortality in tsetse ( Glossina spp). BULLETIN OF ENTOMOLOGICAL RESEARCH 2020; 110:44-56. [PMID: 31190649 DOI: 10.1017/s0007485319000233] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Environmental temperature is an important driver of the population dynamics of tsetse (Glossina spp) because the fly's immature stages are particularly vulnerable to temperatures (T) outside the range T = 16-32°C. Laboratory experiments carried out 50 years ago provide extensive measures of temperature-dependent rates of development, fat consumption and mortality in tsetse pupae. We improve on the models originally fitted to these data, providing better parameter estimates for use in population modelling. A composite function accurately models rates of pupal development for T = 8-32°C. Pupal duration can be estimated by summing the temperature-dependent daily percentage of development completed. Fat consumption is modelled as a logistic function of temperature; the total fat consumed during pupal development takes a minimum for T ≈ 25°C. Pupae experiencing constant temperatures <16°C exhaust their fat reserves before they complete development. At high temperatures, direct effects kill the pupae before fat stores are exhausted. The relationship between pupal mortality and temperature is well described by the sum of two exponential functions. Summing daily mortality rates over the whole pupal period does not reliably predict overall mortality. Mortality is more strongly correlated with the mean temperature experienced over pupal life or, for T ≤ 30°C, the fat consumption during this period. The new results will be particularly useful in the construction of various models for tsetse population dynamics, and will have particular relevance for agent-based models where the lives of individual tsetse are simulated using a daily time step.
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Affiliation(s)
- J W Hargrove
- SACEMA, University of Stellenbosch, Stellenbosch, South Africa
| | - G A Vale
- SACEMA, University of Stellenbosch, Stellenbosch, South Africa
- Natural Resources Institute, University of Greenwich, London, UK
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Alderton S, Macleod ET, Anderson NE, Machila N, Simuunza M, Welburn SC, Atkinson PM. Exploring the effect of human and animal population growth on vector-borne disease transmission with an agent-based model of Rhodesian human African trypanosomiasis in eastern province, Zambia. PLoS Negl Trop Dis 2018; 12:e0006905. [PMID: 30408045 PMCID: PMC6224050 DOI: 10.1371/journal.pntd.0006905] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 10/05/2018] [Indexed: 11/19/2022] Open
Abstract
This paper presents the development of an agent-based model (ABM) to investigate Trypanosoma brucei rhodesiense human African trypanosomiasis (rHAT) disease transmission. The ABM model, fitted at a fine spatial scale, was used to explore the impact of a growing host population on the spread of disease along a 75 km transect in the Luangwa Valley, Zambia. The model was used to gain a greater understanding of how increases in human and domestic animal population could impact the contact network between vector and host, the subsequent transmission patterns, and disease incidence outcomes in the region. Modelled incidence rates showed increases in rHAT transmission in both humans and cattle. The primary demographic attribution of infection switched dramatically from young children of both sexes attending school, to adult women performing activities with shorter but more frequent trips, such as water and firewood collection, with men more protected due to the presence of cattle in their routines. The interpretation of model output provides a plausible insight into both population development and disease transmission in the near future in the region and such techniques could aid well-targeted mitigation strategies in the future. African trypanosomiasis is a parasitic disease which affects humans and other animals in 36 sub-Saharan African countries. The disease is transmitted by the tsetse fly, and the human form of the disease is known as sleeping sickness. With human and animal populations growing across Africa, demand for space to settle is on the rise, and people are being forced to occupy increasingly marginal spaces. This behaviour has the potential to increase exposure to pre-existing biological hazards, including vector-borne diseases. This investigation utilises agent-based modelling techniques to investigate the implications of a growing and spreading human and animal population in a region affected by Rhodesian human African trypanosomiasis. The model incorporates previously developed spatial data for the Luangwa Valley case study in Zambia, along with demographic data for its current inhabitants, and a detailed, seasonally-driven tsetse lifecycle. Tsetse and potential human and animal hosts are modelled at the individual level, allowing each contact and infection to be recorded through time. By modelling at a fine-scale, we can incorporate detailed mechanisms for tsetse birth, feeding, reproduction and death, as well as a realistic theoretical human and domestic animal population increase, before considering the possible spatial and demographic impact.
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Affiliation(s)
- Simon Alderton
- Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom
- Centre for Health Informatics, Computing and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
- Geography and Environment, Faculty of Social and Human Sciences, University of Southampton, Southampton, United Kingdom
- * E-mail:
| | - Ewan T. Macleod
- Division of Infection and Pathway Medicine, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, 1 George Square, Edinburgh, United Kingdom
| | - Neil E. Anderson
- The Royal (Dick) School of Veterinary Studies and the Roslin Institute, University of Edinburgh, Roslin, United Kingdom
| | - Noreen Machila
- Division of Infection and Pathway Medicine, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, 1 George Square, Edinburgh, United Kingdom
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Martin Simuunza
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Susan C. Welburn
- Division of Infection and Pathway Medicine, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, 1 George Square, Edinburgh, United Kingdom
| | - Peter M. Atkinson
- Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom
- Centre for Health Informatics, Computing and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
- Geography and Environment, Faculty of Social and Human Sciences, University of Southampton, Southampton, United Kingdom
- School of Geography, Archaeology and Palaeoecology, Queen's University Belfast, Northern Ireland, United Kingdom
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
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Alderton S, Macleod ET, Anderson NE, Palmer G, Machila N, Simuunza M, Welburn SC, Atkinson PM. An agent-based model of tsetse fly response to seasonal climatic drivers: Assessing the impact on sleeping sickness transmission rates. PLoS Negl Trop Dis 2018; 12:e0006188. [PMID: 29425200 PMCID: PMC5806852 DOI: 10.1371/journal.pntd.0006188] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 12/22/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND This paper presents the development of an agent-based model (ABM) to incorporate climatic drivers which affect tsetse fly (G. m. morsitans) population dynamics, and ultimately disease transmission. The model was used to gain a greater understanding of how tsetse populations fluctuate seasonally, and investigate any response observed in Trypanosoma brucei rhodesiense human African trypanosomiasis (rHAT) disease transmission, with a view to gaining a greater understanding of disease dynamics. Such an understanding is essential for the development of appropriate, well-targeted mitigation strategies in the future. METHODS The ABM was developed to model rHAT incidence at a fine spatial scale along a 75 km transect in the Luangwa Valley, Zambia. The model incorporates climatic factors that affect pupal mortality, pupal development, birth rate, and death rate. In combination with fine scale demographic data such as ethnicity, age and gender for the human population in the region, as well as an animal census and a sample of daily routines, we create a detailed, plausible simulation model to explore tsetse population and disease transmission dynamics. RESULTS The seasonally-driven model suggests that the number of infections reported annually in the simulation is likely to be a reasonable representation of reality, taking into account the high levels of under-detection observed. Similar infection rates were observed in human (0.355 per 1000 person-years (SE = 0.013)), and cattle (0.281 per 1000 cattle-years (SE = 0.025)) populations, likely due to the sparsity of cattle close to the tsetse interface. The model suggests that immigrant tribes and school children are at greatest risk of infection, a result that derives from the bottom-up nature of the ABM and conditioning on multiple constraints. This result could not be inferred using alternative population-level modelling approaches. CONCLUSIONS In producing a model which models the tsetse population at a very fine resolution, we were able to analyse and evaluate specific elements of the output, such as pupal development and the progression of the teneral population, allowing the development of our understanding of the tsetse population as a whole. This is an important step in the production of a more accurate transmission model for rHAT which can, in turn, help us to gain a greater understanding of the transmission system as a whole.
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Affiliation(s)
- Simon Alderton
- Geography and Environment, Faculty of Social and Human Sciences, University of Southampton, Southampton, United Kingdom
- Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom
- Centre for Health Informatics, Computing and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
- * E-mail:
| | - Ewan T. Macleod
- Division of Infection and Pathway Medicine, Biomedical Sciences, Edinburgh Medical School, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
| | - Neil E. Anderson
- The Royal (Dick) School of Veterinary Studies and the Roslin Institute, University of Edinburgh, Roslin, United Kingdom
| | - Gwen Palmer
- Independent Researcher, Leyland, Lancashire, United Kingdom
| | - Noreen Machila
- Division of Infection and Pathway Medicine, Biomedical Sciences, Edinburgh Medical School, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Martin Simuunza
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Susan C. Welburn
- Division of Infection and Pathway Medicine, Biomedical Sciences, Edinburgh Medical School, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
| | - Peter M. Atkinson
- Geography and Environment, Faculty of Social and Human Sciences, University of Southampton, Southampton, United Kingdom
- Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom
- Centre for Health Informatics, Computing and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
- School of Geography, Archaeology and Palaeoecology, Queen's University Belfast, Northern Ireland, United Kingdom
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
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