Environment health and infectious diseases Hélène M De Nys CIRAD COHESA Workshop on integrating environment and ecosystem health and its practitioners into One Health Hwange, Zimbabwe, 19-23 February 2024 Presenter Notes Presentation Notes Present, researcher vet and disease ecologist The link between Health of the environment and infectious diseases. Given my background I will focus on animal/human diseases but applicable to plants. Healthy Environment Stable climate Balanced and clean water systems High Biodiversity Clean air Persistant vegetation, habitat connectivity Presenter Notes Presentation Notes - It is important to note that infectious diseases arise from a combination of ecological, social and economic pressures that combine to amplify disease risk, - So what I will present is only part of the PICTURE, but what I want to show is the fact that the health of the environment is CENTRAL and that Environment ACTORS play a central role in prevention. - So let me start from the beginning: - A healthy environnent can be reflected through different indicators such as stable climate …. - Human caused pressures through mining, industrialisation, wood explotation, intensive agriculture…can lead to a Unhealthy enviroment with accelerated climate change, habitat fragmentation and degradation, loss of biodiversity… (non exhaustive, but to give some examples of mechanisms ) - This in turn will impact infectious diseases, with complex mechanisms,. Let me give you some practical examples in order to illustrate some of the main ones. - I tried to select well illustrated/described examples not always on the african contient, but the same concepts are applicable Healthy Environment Stable climate Balanced and clean water systems Unhealthy Environment High Biodiversity Unbalanced and polluted water systems Accelerated climate change Clean airAir pollution Biodiversity loss Persistant vegetation, habitat connectivity Deforestation, habitat fragmentation, land degradation, … Presenter Notes Presentation Notes - It is important to note that infectious diseases arise from a combination of ecological, social and economic pressures that combine to amplify disease risk, - So what I will present is only part of the PICTURE, but what I want to show is the fact that the health of the environment is CENTRAL and that Environment ACTORS play a central role in prevention. - So let me start from the beginning: - A healthy environnent can be reflected through different indicators such as stable climate …. - Human caused pressures through mining, industrialisation, wood explotation, intensive agriculture…can lead to a Unhealthy enviroment with accelerated climate change, habitat fragmentation and degradation, loss of biodiversity… (non exhaustive, but to give some examples of mechanisms ) - This in turn will impact infectious diseases, with complex mechanisms,. Let me give you some practical examples in order to illustrate some of the main ones. - I tried to select well illustrated/described examples not always on the african contient, but the same concepts are applicable Effect of HABITAT LOSS on risks of pathogen spill-over from animal reservoir host to other species Long-term study - Environnemental drivers - Effect on reservoir host ecology • Paramyxovirus • Bats (flying foxes) are reservoir host in Australia • Horses act as bridge hosts between bats and humans • severe and often fa ta l disea se in both horses and humans Viral shedding in droppings increases + Land-use change/forest clearance Food shortage -> new winter roost in urban and agricultural areas suboptimal food Cumulative stress Increased virus spillover risk Habitat change impact animal host behaviour, distribution, abundance, physiology & wildife/domestic animals/humans interface On the African continent, bats harbour Henipah-like viruses, and similar dynamics are suspected for Ebola viruses (habitat fragmentation) Changing interfaces Example of Hendra virus in Australia Plowright et al. 2015 Presenter Notes Presentation Notes - If we look at habitat loss (land-use change, deforestation…) and how it impacts … - I ‘m taking the example of Hendra virus - Hendra virus are maintained adn transmitted by bats. Shedding in guano and urine,horses get infected…. - I thook this example as an austrlian team ran a long term study and analysed 25 years of data to understand environmebtal drivers. when you want to look at ecological Envrionmental drivers, longterm and large spatila scalestudies needed - Bats feed in forested areas, especially during winter but forests are cleared for agriculture and urbanisation (winter flowering trees dissapeared) - Food shortage and Bats move in smaller groups to urban and agricultural areas with constant non native food + Climate change - Cumulative stress and immunosupression thus obserevd increased viral shedding in droppings - also interfaces changed -> more outbreaks in horses and increased risks for humans I they show habitat change can impact behaviour of animal hosts of a pathogen, their distribution and abundace, thier immune response and their interactoions with other species, and thus risks of transmissions to other species or human Hendra like virsues in african abts, same mechanisms suspected for Ebolavirus 1994 firs toutbreak, 90 horses, 7 humans, respi and neurological Long term AND SPATIAL Env drivers of interspecies tranmsissions and emergence, and Pteropus spp. Roosts depends on resources (nomadic, feed in forests, especially during winter but forsts are cleared for agriculture and urbanisation Bats move in smaller groups to urban and agricultural areas with constant non native food Stress changes dynamics of invfection, reactivation of infection through immunosupression Across eastern Australia, habitats for the winter-flowering lants that drive flying fox nomadism have been reduced through land clearance, in turn driving nutritionally stressed bats into novel urban and agricultural environments outside their typical overwintering Range could be driven by immunosuppression, such that cumulative stressors may impair HeV tolerance and facilitate replication or allow latent infections to reactivate Flying foxes that have gone without food or have moved into a new location are more likely to have the deadly Hendra virus in their droppings. Bats often act as a bridge via which viruses can switch species. The ease at which transfer to humans occurs is thought to depend on the ecological conditions of bats, but it has been challenging to determine the ecological factors that facilitate this transfer. Now, a team with two researchers from Griffith University in Australia has studied the Hendra virus — which is fatal to both horses and humans — in nine flying fox roosts over three years. By comparing the ecological conditions of the bats with the amount of droppings contained the Hendra virus, they found that excrement of the virus peaked after food shortages and when flying foxes moved to a new location. This information will be valuable for better estimating the risk of viruses spilling over to humans. �Changes in land-use (e.g. land conversion, oil extraction, mining, deforestation, wetland drainage, etc.) and food production practices)) Effect of habitat loss/fragmentation on animal host behaviour, physiology & wildife/domestic animals/humans interface Example of Ebola virus? Forest fragmentation in Central (and West Africa in 2000 and 2014. Most of the centers of first infection (are located in areas affected by increasing forest fragmentation, Rulli et al. 2017. Foraging and mating behaviors of Hypsignathus monstrosus at the bat-human interface in a central African rainforest, Schloesing et al. 2023 Presenter Notes Presentation Notes - It s not the best examples as still a lot of uncertainties regarding its ecology. Bats are suspected to maintain and transmit direclty to people or via other species like duikers and primates - A Study Shows outbreak more likley to start in highly disturbed forested areas, relatively populated, and forested, but with increasing deforestation. - Impact on abundance and and behaviour of fruit bats (more abundant as adapt, stress, biodiv loss, feed on human agricultural resouces: Hammer headed bats) - Actually one of our studetns collared Hammer headed fruit bast and showed to prefer foraging in agricultural areas rather than in the forest. . So habitat change can affect risk of transmission ((Sites of first infection on average exhibit significantly higher population density (Table 2), average forest cover (Tables 2 and S1), fragmentation and increase in fragmentation (Tables 2 and S3, S4) than the rest of the reg preferentially occur in areas that are relatively populated and forested, yet where deforestation is reshaping the forest boundaries by increasing forest fragmentation29. Some studies show edge effect on increasing frugivorous Changes in land-use with forest fragmentation -> natural resources -> changes of animal behaviours, migrations +increased interfaces (some species do better and adapt, and also humans encroach -> change of interfaces + stress -> increased spillover + loss of biodiversity)) At a global scale: high biodiversity ->hotspots for infectious disease emergence? What happens at the local scale? Effect of BIODIVERSITY LOSS (land-use change, habitat destruction …) on infectious disease risk GLOBAL d r ive r s o f h u m a n p a t h oge n r ich n e ss a n d p re va le n ce Dunn et al. 2010 Presenter Notes Presentation Notes What about Biodiversity? Biodiversity is key for food security, development, well-being, health ….,. So we really need to preserve it. When it comes to the link between biodiversity and pathogens it is complex Why 1/ At a GLOBAL scale: The number of pathogen speices increases with the number of species of birds and mammals, hence also the risk of one of these pathogens to jumpt to people. Hence high biodiversity regions are hotspots for disease emergence. 2/What happens at a smaller scale: ((Global scale: Alternatively, regions with greater host richness probably have a higher total richness of pathogens, such that the species pool of pathogens capable of jumping to humans may be higher  Dun et al show : We find that most of the variation in pathogen richness from one political region to the next is explained by mammal and bird richness, health spending and total human population. In itself, mammal plus bird richness explained most (72%) of the variation in pathogen richness. By contrast, pathogen prevalence is influenced by pathogen richness and disease control efforts, as well as the direct effects of climate and total human population. Hypothsis on the mechanisms (several are cited) A second possibility is that regions with high bird and mammal richness have higher total pathogen richness, and hence a higher probability of the origin or host switch of a pathogen that also or newly affects humans. In this model, much like the model recently offered to explain correlations between consumer and producer richness (Jetz et al. 2009), diversity begets diversity.  geographical variation in human pathogen richness (a: darker red indicates greater richness; maximum 249) ) Biodiversity loss - > dilution effect -> WNV, Malaria, Hantavirus Dilution effect : Increased pathogen prevalence and disease risk with decreasing biodiversity – higher biodiversity often results in lower disease risk Controversial as it is a complex mechanisms Occurs in specific host –pathogen systems, under specific conditions:  where species vary in reservoir competency  Generalist vector species -> depending on the host-pathogen system (ecology of the pathogen, the type of hosts, host competence, …) LOCAL SCALE Presenter Notes Presentation Notes 2/At a smaller local scale, there is a mechanisms called dilution effect, according to which Higher biodiversity results in lower disaes risk . - But still complex and not applicable everywhere. It is just an example to sho effects of biodiv on disaese. It depends on specific conditons . Biodiversity can decrease prevaelnce of pathogens as less competent hosts (variation in suceptibility, in ability of transmissions, i attractiveness for vectors) and thus reduce infectious disease risk. Give figure to explain Controversial as complex Give examples: Used for long in disease management: plants but also humans: ex Malaria: when mosquitioes prefer animals, and need to estimate the right distance livestock/people Occurs naturally : Khalil et al on bank voles in Sweden but many other studies in north and central America (Panama, Europe, on rodents and hantavirus: encounter reduction (aggressive behaviour between rodents), competition which decreases competent host density Shown for lyme disease: rodetns and deers, some rodents are not competent and reduce encounters between competent hosts and also are bitten by the ticks Dilution effect : higher diversity often results in lower disease risk LOCAL SCALE Example of Natural dilution effect: Hantavirus in small mammals (Khalil et al 2016: Puumala hantavirus in bank voles, haemorrhagic fever with renal syndrome in humans) Encounter reduction Susceptible host regulation Presenter Notes Presentation Notes To explian this I wiull use the example of Hanatviruses in small mammals.�Hanatviruses are zoonotic and transmitted by reodents in seevral continents like Amreics, Europe… hantaviruses have also bee found on rodents in Guinea and people a dnew strains are detected in shrews and bats. Caiauses Pulmonary syndrome and hermorrrhagic syndrome This is in Sweden, transmitted by bank voles Low biodiversity Add NON COMPETENT HOSTS: common shrew, distrubs and field vol: competitor Khalil et al on bank voles in Sweden but many other studies in north and central America (Panama, Europe, Wherelow biodiversity with bank voles = reservoir versus higher diversity with other non competent hosts on rodents and hantavirus: encounter reduction (aggressive behaviour between rodents), competition which decreases competent host density Bank vole , common shrew and field vole Used for long in disease management: plants but also humans: ex Malaria: when ùosquotos prefer animals, and need to estimate the right distance livestock/people ((Shown for lyme disease: rodetns and deers, some rodents are not compteentet adn reduce encounters between competent hosts and also are bitten by the ticks)) Altizer et al. 2013 Effect of CLIMATE CHANGE on distribution and prevalence of infectious diseases  Effect on immunity/physiology  Effect on habitat/landscape, biodiversity, ….  Effect on water systems  Effect on spatiotemporal occurrence and abundance of VECTORS and the pathogens they transmit. Example of Malaria Anopheles mosquitoes & parasite dependent on rainfall and temperature Increasing risk in tropical highland regions, in particular the East African highlands Areas where malaria is predicted to disappear (in red) or invade ( (in green) by the 2050s in relation to the present situation (Rogers et al. 2000) Presenter Notes Presentation Notes Climate change affetcs infectious diseases in different ways Can directly impact immunology/physiology of host and pathogen see paper Water systesm: cholera but no time here/; Effect obvious for Vector borne diseases as transmitted by mosquitoes, flies and ticsk which are sensitive to rainfall and temp Example of malaria, risk is predicted to increase in tropical highlands. Some areas will be lessa t risk in the future Changing weather patterns can shift the geographic range, seasonality, and intensity of transmission of some climate-sensitive diseases, particularly vector-borne diseases. Global temperature rise Malaria, Dengue fever, Increased number and Chikungunya, Yellow range of vector mosquitos fever, Zika , RVF MALARIA: Caminade 2018: Many studies: The number of reported human infections with P. falciparum is increasing in tropical highland regions across the globe, for example, in Eastern Africa,24, 25, 43-46Nepal,47-50 and Colombia.43 Competent malaria vectors have also recently been found at higher altitudes.49, 51-54, 47This has serious implications for indigenous highland human populations that usually lack protective immunity and are more vulnerable to severe malaria morbidity and mortality. Models show risk in East african highlands, and going south. Dengue: Dengue fever is the most important viral vector-borne disease in the world.3 The disease affects hundreds of millions of people every year, and is transmitted predominantly by one species of mosquito, Aedes aegypti, which has adapted to living near areas of human habitation. It feeds during the day and prefers human beings to other animals. Globalization and introductions of invasive species, for example translocation of disease vectors like Aedes aegypti and A. albopictus mosquitoes, the most important vectors of Dengue, Chikunguna, and Zika viruses (Gloria-Soria et al. 2016; Musso and Gubler 2015),  The prevalence of malaria (Pascual et al. 2006; Chaves et al. 2008), plague (Snall et al. 2009) and dengue (Cazelles et al. 2005) are affected both by climate and changes in climate. Example of arboviruses (dengue, zika, chikungunya, yellow fever, West Nile virus …) Aedes mosquito – Culex (WNV) & viral replication dependent on rainfall and temperature DENGUE: Estimated baseline population at risk in 1990 (A) and estimated population at risk in 2085 (B) Hales et al 2002 The current and future predicted probability of occurrence values of R. appendiculatus, Olwoch et al 2008 East Coast fever future risk map, Olwoch et al 2008 Example of Tick-borne diseases (Theileriosis, ehrlichiosis, …) Presenter Notes Presentation Notes - Other examples are arboviruses - Transmitted by Mosquitoes: mosq and the virus replication ios dependent on rainfall and on temp Dengue: - Dengue fever is the most important viral vector-borne disease in the world (Aedes aegypti and albopictus). - Predictions show that pop at risk will increase , model based on humidity. Already in France - Also tick borne disaeses such as theileriosis and Ehrlichiosis - Theileria depends on Ripic. Append and its distribution is predicted to change - Areas willl become more suitable for transmission and others less - Zimbabwe: incrase all year round and more districts of Jan disease, distr change of r appendiculati - Can go in both directions buyt bottom line is there will be important changes and we need to be ready The disease affects hundreds of millions of people every year, and is transmitted predominantly by one species of mosquito, Aedes aegypti, which has adapted to living near areas of human habitation. It feeds during the day and prefers human beings to other animals. mosquitoes require standing water to breed, and a warm ambient temperature is critical to adult feeding behaviour and mortality, the rate of larval development, and speed of virus replication.4, Humidity is very important. Model based on vapour pressure:climate change is likely to increase the area of land with a climate suitable for dengue fever transmission. Now: autochthonous transmission ofboth dengue and chikungunya reported in southernFrance in 2010 and 2014. Other factors alos play. Important urban vector Theileriosis. R appendicaltus 3 host tick. changes in botw ways. But expanding in southern and DRC, + also increase in density and parasite cycles (one/year in SA can change to more) . Angola, Namibia, southern DRC become climatically unsuitable for R. appendiculatus infestation. However, the northern and eastern Cape provinces of South Africa as well as Botswana, Zambia and eastern DRC, that are currently unsuitable, are rendered climatically suitable for R. appendiculatus under future climate scenarios. This may be because of enhanced rainfall in these areas. Rises in temperature (especially the minima) as predicted over most of tropical Africa and southern Africa may contribute to the increases in suitability of R. appendiculatus in these regions. These effects would shorten generation time and may allow po Zimbabwe: incrase all year round and more districts of Jan disease, distr change of r appendiculatis Globalization and introductions of invasive species, for example translocation of disease vectors like Aedes aegypti and A. albopictus mosquitoes, the most important vectors of Dengue, Chikunguna, and Zika viruses (Gloria-Soria et al. 2016; Musso and Gubler 2015),  The prevalence of malaria (Pascual et al. 2006; Chaves et al. 2008), plague (Snall et al. 2009) and dengue (Cazelles et al. 2005) are affected both by climate and changes in climate. Epidemics Pandemics Mortality Morbidity Poverty … Epidemics Pandemics Mortality Morbidity Poverty … Epidemics Pandemics Mortality Morbidity Poverty … Epidemics Pandemics Mortality Morbidity Poverty … Healthy Environment Stable climate Balanced and clean water systems Unhealthy Environment High Biodivers ity Unbalanced and polluted water systems Accelerated climate change Clean airAir pollution High Biodiversity Persistant vegetation, habitat connectivity Deforestation, habitat fragmentation, land degradation, … Presenter Notes Presentation Notes As you can see Environmental health is central, starting point. With unhealthy env leading to epidemics… We want to prevent this, through keeping a healthy environment and to do so we need to work hand in habd with specialists, environment actors, government, research, NGO’s... We need to work together for preventive measures through available policies, strategies, interventions, technologies and knowledge ((Multiple factors, multiple mechanisms, will illustrate with examples with some of main mechanisms. At the end to show that it alls tarts with unhealthy environment. And that this is central. We need envrionmental experts/actions etc. preventive measures through available policies, strategies, interventions, technologies and knowledge Actors: )) Bibliography Becker DJ, Eby P, Madden W, Peel AJ, Plowright RK. Ecological conditions predict the intensity of Hendra virus excretion over space and time from bat reservoir hosts. Ecol Lett. 2023 Jan;26(1):23-36. doi: 10.1111/ele.14007. Epub 2022 Oct 30. PMID: 36310377. Eby, P., Peel, A.J., Hoegh, A. et al. Pathogen spillover driven by rapid changes in bat ecology. Nature 613, 340–344 (2023). https://doi.org/10.1038/s41586-022-05506-2 Plowright et al. 2015. Ecological dynamics of emerging bat virus spillover. 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Erasmus, Climate change and the tick-borne disease, Theileriosis (East Coast fever) in sub-Saharan Africa, Journal of Arid Environments, Volume 72, Issue 2, 2008, Pages 108-120, ISSN 0140-1963,https://doi.org/10.1016/j.jaridenv.2007.04.003 Carlson, C.J., Albery, G.F., Merow, C. et al. Climate change increases cross-species viral transmission risk. Nature 607, 555–562 (2022). https://doi.org/10.1038/s41586-022-04788-w https://doi.org/10.1038/s41586-022-05506-2 http://doi.org/10.1098/rspb.2014.2124 https://doi.org/10.1038/srep41613 https://doi.org/10.1038/srep31314 https://doi.org/10.1186/s12936-015-0822-0 https://doi.org/10.1111/nyas.13950 https://doi.org/10.1126/science.289.5485.1763 The project ‘Capacitating One Health in Eastern and Southern Africa’ (COHESA) is co-funded by the OACPS Research and Innovation Programme, a programme implemented by the Organization of African, Caribbean and Pacific states (OACPS) with the financial support of the European Union Acknowledgements Slide Number 1 Slide Number 2 Slide Number 3 Slide Number 4 Slide Number 5 Slide Number 6 Slide Number 7 Slide Number 8 Slide Number 9 Slide Number 10 Slide Number 11 Slide Number 12 Acknowledgements Slide Number 14