Infectious Disease

Extreme precipitation events and water quality in California: Implications for human health in a varying and changing climate

Authors: Alexander Gershunov1, Tarik Benmarhnia1,2, Rosana Aguilera1
Author Affiliations: 1Scripps Institution of Oceanography, University of California San Diego; 2Department of Family Medicine and Public Health, University of California San Diego

Most pathogens and pollutants collect on the land surface or in infrastructure between strong rainfall episodes, and are then mobilized and delivered via storm runoff to areas of human exposure, such as coastal recreational waters, as a consequence of sewage or water treatment systems overflow. In California, USA, precipitation events are projected to become more extreme, and at the same time decrease in frequency as storm tracks move poleward due to polar-amplified global warming. Precipitation extremes in California are dominated by atmospheric rivers (ARs), which carry more moisture in a warmer climate. Thus, the physical driver of extreme precipitation events in this region is expected to grow stronger with climate change, and pollutant accumulation and runoff-generated exposure to those pollutants are expected to increase, particularly after prolonged dry spells. Extreme precipitation effects on water quality and associated human health impacts have been related to waterborne disease outbreaks in the conterminous USA and associated with beach closings in coastal areas due to the flushing of fecal contaminants through storm drains. In southern California, microbiological contamination of water during winter storms exposes human populations to elevated concentrations of microorganisms in bathing waters at beaches, which could cause gastrointestinal and ear infections, and lead to exposure to pathogens causing life-threatening conditions, e.g. hepatitis A. For this purpose, we use a recently published catalog of ARs, in combination with historical daily precipitation and fecal pollution indicators such as total and fecal coliforms in coastal waters to explore associations between extreme events related to ARs and the variability in coastal water quality in California. These associations will be used to identify mechanisms of fecal pollutant delivery to coastal recreational waters via storm runoff and to track sources of pollution common in the region, such as sewage outfalls and homeless encampments near rivers and streams. Overall, this work aims to quantitatively assess the influence of precipitation regime changes on human health via exposure to recreational coastal waters in California, with the ultimate goal of reducing vulnerability to extreme weather, as well as to delineate measures, such as an early warning system, that improve the response and resilience of human populations and ecosystems to a varying and changing climate.

Revitalising Informal Settlements and their Environment (RISE) in Fiji – an RCT study

Authors: Amelia Turagabeci1, Karin Leder2, Rebekah Brown2, Tony Wong3, Bruce Cahan4, Thomas Clasen5, Stephen Luby4, David McCarthy2, Diego Ramirez-Lovering2, Joanne O’Toole2, Paul Jagals1
Author Affiliations: 1Fiji National University; 2Monash University, Australia; 3Cooperative Research Centre for Water Sensitive Cities Limited; 4Stanford University; 5Emory University

Fiji is the center of the South Pacific, an island vulnerable to many natural disasters and one that recently, in 2016, witnessed a Category 5 tropical cyclone Winston which left many challenges and opened new opportunities at re-looking at how environmental health services are delivered.

The RISE (Revitalising Informal Settlements and their Environment) study is a collaborative research led by Monash University in collaboration with Standford University and Emory University, with local university at implementation sites, Fiji National University and Hassanudin University in Indonesia. Urbanisation is a major demographic trend globally with Informal settlements accounting for much urban growth, exacerbating the inextricably linked challenges of sanitation, water provision, and public health. The team have pioneered an alternative, water-sensitive approach that integrates sustainable design with the management of the water-cycle, benefiting human health and urban ecosystems.

The project has five specific objectives:
-To develop novel urban design, architecture, and infrastructure models in partnership with local communities to implement water-sensitive revitalisations. These models will incorporate ongoing feedback between communities, team members, and other stakeholders.
-To measure, analyse, and interpret the impact of the interventions on environmental contamination and ecology.
-To assess the impacts on human health.
-To determine the broader impacts on residents’ wellbeing.
-To enable priority setting for the sustainable revitalisation of informal settlements and drive policy and investment decisions.

RISE will use a parallel-cluster RCT design with stratified randomisation by tidal/non-tidal sites (i.e. settlements). 6 settlements in each of Suva and Makassar will be randomly assigned to the intervention group, and 6 to controls. Monitoring and assessment will be conducted for all settlements during years 2–5. In year 6, the ADB will implement the intervention in all control settings following the conclusion of the study. In Fiji, the (12) selected communities have formed a Community Engagement Councils and have also agreed to participate in the study. These communities have past problems of water inundation following heavy rain, flooding or coastal events.

This decentralised, climate-change sensitive approach provides financial flexibility for multistage developments and adaptability to future technologies. It promises a solution to the water services challenges of informal settlements, yet has only been demonstrated in developed world settings. It is anticipated that this project will deliver the first public health and environmental data on the benefits and risks of water-sensitive approaches. Our scientific, economic and implementation findings will provide the basis for profound changes to infrastructure policies, investments, loan strategies, and their sustainability across the Asia-Pacific and the developing world.

The Ecological, Socioeconomic and Spatial Mechanisms Behind Malaria Transmission in Rural Madagascar in the Face of Land Use Change

Authors: Nicholas Arisco1, Christopher D. Golden1,2, Benjamin L. Rice3, Luciano M. Tantely, Romain Girod4, Hervet J. Randriamady5,6
Author Affiliations: 1Department of Environmental Health, Harvard T.H. Chan School of Public Health; 2Planetary Health Alliance, Australia; 3Department of Organismic and Evolutionary Biology, Harvard University; 4Institut Pasteur de Madagascar; 5Madagascar Health and Environmental Research (MAHERY); 6MAHERY Health Program, Catholic Relief Services, Madagascar

Background Large-scale deforestation and subsequent land use change is widespread in Madagascar. This disruption of natural systems causes shifting patterns of species distribution, diversity, and abundance in Madagascar’s ecosystems. Humans inhabiting rural Madagascar intimately and frequently interact with their natural environments, and this interface predicates their health status. Limited data exist to explore the mechanistic pathways behind Madagascar’s chronic and acute disease burden. Here we will specifically explore the ecological, socioeconomic, and spatial mechanisms underpinning malaria prevalence across five ecoregions in Madagascar.

Methods We studied 31 communities across five ecoregions in Madagascar. We collected data on the ecology and spatial distribution of mosquito species composition and malaria infections through larval collection and geospatial mapping of larval habitats. These data were spatially linked to socioeconomic and health data. We will build Bayesian regression models followed by piecewise structural equation models to determine hierarchal paths for malaria risk linking land use change to malaria infection risk in a semi-causal framework.

Findings Our empirical collection of mosquito larvae confirmed the presence of Anopheles larvae in 16 of the 31 communities. Species present were A. squamosus, A. coustani, A. mascarensis, and A. gambiae s.l. Anopheles larvae were primarily found in rice fields, though there were Anopheles positive human-made pools of water in arid regions. Preliminary data indicate clustering of malaria cases within households and among household groupings. Clustering seems random at the household level with respect to nearby Anopheles habitats. Further statistical analyses will explore the link between variables such as occupation, proximity to rice fields, local larval habitat abundance, and regional climate variables and individual/household malaria prevalence.

Interpretation Anopheles larvae were commonly present in human-made ponds for livestock and rice paddies, indicating that livestock raising and agriculture could present risk of malaria transmission. Preliminary findings also show possible local transmission in arid regions not expected to exhibit transmission, although these sites could be easily controlled with spraying and active prevention. Malaria cases exist in sites with no positive larval breeding habitats, indicating migration of cases into these communities or preserved infections from past periods when local transmission was possible. Rapid land-use change may open opportunities for Anopheles sp. to colonize in new regions. Introduction of vectors coupled with low human population immunity will lead to more severe cases in these previously unaffected regions. Understanding mechanistic pathways for malaria transmission in these communities will inform control programs on the most efficient, targeted intervention points.

Global effects of land use on zoonotic host communities

Authors: Rory Gibb1, David W. Redding1, Kai Chin1, Tim Blackburn1, Tim Newbold1, Kate E. Jones1
Author Affiliations: 1Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London;

Background: Environmental trade-offs associated with land use, for example between food security and biodiversity conservation, represent critical dimensions of planetary health. Land use-driven biodiversity losses may predictably affect disease risk if reservoir host species are consistently more likely to persist under human disturbance (i.e. if ecological communities in modified habitats generally have a higher zoonotic potential). Such a phenomenon has been observed in specific disease systems, but with high rates of global land use change projected for this century, assessing its global and taxonomic generality would shed light on an important hypothesised driver of environmental synergies or trade-offs between conservation and public health.

Methods: We combine data on hosts of human-shared parasites and pathogens (‘hosts’) with a global database of local ecological communities and associated land use data (originally collated from published studies). We analyse the effects of land use on host diversity metrics across over 9000 sites globally, controlling for disease-related research effort and differences in survey methods.

Findings: Ecological communities in anthropogenic land uses (managed ecosystems and urban) contain a consistently higher richness and abundance of host species than communities in nearby primary land sites. However, among mammal hosts of zoonotic pathogens, we find considerable taxonomic variation in host responses to land use, with rodent and bat host abundances generally increasing and primate and carnivore hosts declining in modified landscapes.

Interpretation: Our results suggest that future global land use change has potential to drive increasing contact between people and ecological communities with increased shared pathogen potential (i.e. more potential hosts and possible opportunities for transmission). However, the variability among mammals, for example with rodent hosts most abundant in modified habitats and primate hosts most abundant in intact communities, highlights that these changes are unlikely to affect all zoonotic diseases consistently. This result supports arguments that, rather than expecting a consistent biodiversity-disease relationship, in practice policies aiming to both conserve biodiversity and reduce human disease (for example through establishment of protected areas) must be disease- and context-specific.

The combined responses of major African zoonoses to environmental and socio-economic change

Authors: David Redding1, Kate Jones1
Author Affiliations: 1University College London

Background
Understanding the global environmental context of human health is of key current concern (e.g. The Rockefeller Foundation–Lancet Commission on planetary health, The Wellcome Trusts’ priority area Our Planet, Our Health). While there is an increasing discussion regarding the need to consider the interplay between poverty, human health, land-use conversion and climate change, there are few tools available to undertake system dynamic analyses of disease burden. Improving the understanding of how zoonotic diseases will respond, as a whole, to global change represents a vital component of setting future, sustainable global development policies.

Methods
Here, we use recently developed techniques, at a continental scale, to understand the expected responses of a wide set of zoonotic diseases to major drivers of change. Using a novel, grid-cell based, environmental-mechanistic model, we combine a correlative distribution model of host niche suitability, with a mathematical model of pathogen spill-over and a compartment model of zoonotic disease infections in humans. These models are parameterised across space using remote-sensed input data, while also incorporating poverty-health relationships and simulating human behaviour across empirically-based human contact and transportation networks. We apply these models to historical, present day and future conditions, validate against case data, and, finally, combine burden estimates across all diseases to calculate a net response for each time period in each grid cell.

Findings
Zoonotic diseases display a varied response to different drivers of environmental change. Some animal-borne diseases show a low sensitivity e.g. to climate change (Rabies), while others show a stronger response e.g. to land-use change, with both increases in prevalence (Lassa) and some reductions (e.g. Ebola). The patterns are spatially heterogeneous, with many disease seeing both increases and decreases across their endemic areas.

Interpretation
Recent outbreaks of Zika, Ebola and SARS have cause widespread public concern by emerging into novel geographic areas. Our results allow a better understanding of the conditions that precipitated such changes and then allow us to predict, in the future, how ongoing climate, land-use and socio-economic changes will likely alter these risks.

A scoping review to understand the relationship between climate change and schistosomiasis

Author: Dominic Dee1
Author Affiliation: 1Barts and the London School of Medicine, Queen Mary, University of London

Background
Climate change will increasingly have widespread effects on human health, including transmission of vector-borne diseases such as schistosomiasis. Schistosoma trematodes have snails as intermediate hosts and transmission is closely linked to climatic factors such as temperature and rainfall. However, it remains difficult to predict the effect of climate change on schistosomiasis. This scoping review aims to collate research findings to understand the complex relationship between climate change and schistosomiasis.

Methods
A comprehensive literature search was performed using PubMed and Web of Science databases. In total, 266 results were screened and 28 original research papers were included and analysed in this scoping review.

Findings
Most studies (N=25) looked at the effect of temperature, whilst some assessed rainfall (N=8) or drought (N=2). Temperature has a non-linear effect on most stages of the parasite life cycle. There is variation in the effect of temperature between intermediate host snail species. Seven studies used laboratory experiments and fourteen used modelling to predict future distribution. Studies have either predicted a local decrease in schistosomiasis due to climate change (N=7), an increase or range shift (N=9), or that changes would be dependent on location (N=5). This scoping review presents an overview of the current literature, offers an evidence-based conceptual framework for the consequences of climate change on schistosomiasis and aims to identify future research needs.

Interpretation
The effects of global climate change on schistosomiasis are complex and heterogeneous. Some cool, wet areas may experience an increase in cases, whilst hotter areas may become less suitable for transmission due to increased snail and parasite mortality. Overall, transmission in sub-Saharan Africa, where schistosomiasis is most common, is predicted to decrease although areas in the east and south of the continent may experience increases. In China, suitable snail habitats could increase in area due to a north-shifting freezing line. Worldwide, there will be some range shift into non-endemic areas at the edge of transmission and at altitude. Most studies have evaluated temperature alone, whereas changes to precipitation and extreme weather events are also likely to be important drivers of epidemiological change. Furthermore, indirect consequences of climate change such as human migration and shifts in land use should be considered. Climate change will impact global control initiatives and it is essential that programmes are responsive to future variation in disease patterns.

Impact of global change on future Ebola emergence and epidemic potential in Africa

Author: Kate Jones1, David Redding1
Author Affiliations: 1University College London

Animal-borne or zoonotic human diseases (e.g., SARS, Rabies) represent major health and economic burdens throughout the world, disproportionately impacting poor communities. In 2013-2016, an outbreak of the Ebola virus disease (EVD), a zoonotic disease spread from animal reservoirs caused by the Zaire Ebola virus (EBOV), infected approximately 30,000 people, causing considerable negative social and economic impacts in an unexpected geographical location (Sierra Leone, Guinea, and Liberia). It is not known whether the spatial distribution of this outbreak and unprecedented severity was precipitated by environmental changes and, if so, which areas might be at risk in the future. To better address the major health and economic impacts of zoonotic diseases we develop a system-dynamics approach to capture the impact of future climate, land use and human population change on Ebola (EVD). We create future risk maps for affected areas and predict between a 1.75 and 3.2-fold increase in EVD outbreaks per year by 2070. While the best case future scenarios we test saw a reduction in the likelihood of epidemics, other future scenarios with high human population growth and low rates of socioeconomic development saw a fourfold increase in the risk of epidemics occurring and almost 50% increase in the risk of catastrophic epidemics. As well as helping to target where health infrastructure might be further developed or vaccines best deployed, our modelling framework can be used to target global interventions and forecast risk for many other zoonotic diseases.

Genetic characterization of the airborne resistomes (multidrug resistant organisms) in the outdoor environment of Bangladesh with their temporospatial diversity and clinical significance

Author: Muhammad Asaduzzaman1
Author Affiliation: 1International Centre for Diarrheal Disease Research, Bangladesh

Background
Antibiotic resistance (AMR) has been widely recognised as a global threat to human health which costs for significant annual deaths worldwide. Along with use in human therapy, antibiotics are used in an extensive way in animal farming specially food animal and agricultural field and eventually, a large amount of antibiotic and their residues are disseminated in the environment both air and water. So, the environment is recognised as an important reservoir of antibiotic resistant bacteria, enhancing the horizontal transfer of resistant genes. But, there is no comprehensive information of airborne resistant organism (resistomes) in Bangladesh that carry genes conferring resistance to antibiotics. Even, the capacity to carry and propagate resistance of these resistomes is poorly studied worldwide. Again, the environmental risks of AMR transmission are likely to change dramatically with seasonal and rainfall variability. So, the quantity of organisms and diversity of antimicrobial resistance genes (ARGs) will vary in air of different environments in different seasons. This study addresses not only the presence and characterization of resistant organisms in air using different phenotypic and genotypic methods but also the clonal distribution of those organisms with seasonal variation. Therefore, the risky environments can be identified effectively including humans and animals.

Methods
This cross sectional study is being conducted at four distinct outdoor environments – i)urban live poultry markets and ii) commercial poultry farms in peri-urban sites iii) peri-urban households and iv) Urban residential area in Dhaka metropolitan area and Mirzapur Upazilla of Tangail district for which Environmental systematic and grid sampling are used. To identify the temporal diversity, air samples are collected in both wet (August- October’2017) and dry (January-March’18) seasons by active microbial air sampler through multiple culture media to obtain both gram positive and gram negative resistant organisms.

Findings
The study is ongoing and the results will be presented at the annual meeting. A large number of 3rd generation cephalosporin (3GC) and Carbapenem as well as Oxacillin and Vancomycin resistant organisms have been found which will be further analysed by qPCR and metagenomics.

Interpretation
Geospatial mapping of the concentrations of AMR bacteria in environmental compartments will help to identify the hotspots of resistant bacteria and their clonal relationship will be used to inform scientific community a new planetary health insight regarding the spread of antibiotic resistance to human.

Tungiasis in Madagascar: A Neglected Tropical Parasite Exacerbated by Climate Change?

Author: Nina Finley1, Jussi Eronen2, Sarah Zohdy3
Author Affiliation: 1Centre ValBio; 2University of Helsinki; 3Auburn University

Background: Tungiasis, a parasitic zoonosis of impoverished tropical communities, occurs when a female sand flea (Tunga penetrans or T. trimamillata) burrows into the skin. The disease can cause inflammation, altered gait, secondary infections, and death. Nonsterile sand-flea removal has been hypothesized as a driver of blood-borne illnesses among African children. In Brazil, tungiasis peaks during the dry season and decreases sharply with onset of rains. The mechanism linking precipitation to disease is unknown, but previous studies have hypothesized that humid soils hamper larval development or that rains wash away free-living fleas. Here, we combine human surveys and climate data to investigate the relationship between climate conditions and tungiasis in Madagascar.

Methods: We interviewed 58 households in three rural villages of eastern Madagascar and collected data on weather patterns associated with tungiasis. Focusing on the same region, we used present-day and model climate data based on four IPCC Representative Concentration Scenarios (RCPs) to predict climate and tungiasis prevalence in the years 2050 and 2070.

Findings: Our interviews reveal that rural Malagasy, particularly children and elders, currently experience a high sand-flea burden. All interviewees experienced tungiasis at least once, and 12% were actively infected. Of the households interviewed, 93% remove fleas with shared, unsterilized needles, and 39% reported secondary infections following removal. As a preventative treatment, 52% of respondents rub feet with toxic substances such as kerosene or insecticide. Tungiasis was reported to occur most often in the dry-season months of September to December, particularly on hot, dry days. Our climate results from all four RCPs predict a shortening of the wet season (precipitation >250 mm), while the dry (<80 mm) and very-dry (<50 mm) seasons are predicted to lengthen.

Interpretation: The impact of tungiasis in rural Madagascar is significant and likely to increase with climate change due to a lengthening dry season. We argue that tungiasis is a neglected tropical disease that should be given higher priority for planetary-health research and control, as incidence is likely to increase due to the climate change. Our method of pairing disease seasonality with climate projections can also be expanded to endemic regions globally.

Public health and solid waste management in Sub-Saharan African cities: a study of Johannesburg, South Africa

Author: Nzalalemba Serge Kubanza1
Author Affiliation: 1School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand

This paper discusses the impacts of solid waste on human health and environmental wellbeing in Johannesburg, South Africa. Using both secondary and primary data collected through semi-structured interviews with members of a local community of Windsor, municipal officials and other stakeholders involved in solid waste management in Johannesburg, it finds that mismanagement of solid waste negatively affects the urban environment and human health, leading to reduced productivity and economic growth. Further, it is argued that ineffective solid waste management must be seen as a consequence both of institutionalized failure to implement and enforce urban policies and regulations and a parallel failure to recognize the importance of private agents and community participation in urban development and management. Developing an effective and sustainable solid waste management system in Johannesburg requires city authorities to devolve resources and authority to local along with clear guidelines and strategies to strengthen local management processes.

Landscape and climate determinants of Ae. albopictus abundance at the northern limits of the species’ range, United States

Authors: Pallavi Kache1, Kaitlin Collins-Palmer1, Richard Falco2, Bryon Backenson2, Maria Diuk-Wasser1
Author Affiliations: 1Department of Ecology, Evolution, and Environmental Biology, Columbia University; 2New York State Department of Health

Background: The Aedes albopictus mosquito is a vector of arboviruses associated with high rates of global morbidity and mortality. The northern extent of Ae. albopictus in the United States runs through the southern counties of New York State (NYS). During 2016, there were 1,499 imported cases of human Dengue, Zika, and Chikungunya in NYS. Given the geographic overlap of a potentially competent vector and infectious human hosts, the NYS Department of Health (NYSDOH) enhanced Ae. albopictus trapping and testing during the 2016–2017 summer seasons. The objective of this research is to understand the landscape and climate determinants of the spatiotemporal variation in Ae. albopictus abundance at the northern limit of the species’ range.

Methods: Here we present a landscape-level analysis of mosquito abundance as measured by daily counts of Ae. albopictus across 53 trap sites in three counties during 2016–2017. Using a negative binomial model, we evaluate the effect of variables such as land cover classification, elevation, distance to roads, precipitation, and temperature on Ae. albopictus abundance.

Findings: During 2016–2017 the number of Ae. albopictus caught per night of trapping ranged from zero to 98 across all sites, with an average of three Ae. albopictus mosquitoes per night of trapping. Preliminary analyses demonstrated that the percent of low-intensity and medium-intensity development within a 200 meter buffer of mosquito traps were associated with higher abundance, while controlling for other climatic and landscape factors. The percent of high-intensity development was associated with lower mosquito abundance when controlling for other factors. Daily mean temperature was positively associated with mosquito abundance, while elevation and distance to highway were negatively associated.

Interpretation: Findings are supported by previous evidence that Ae. albopictus experience lower growth and survival rates within urban sites compared to non-urban sites. Additionally, heterogeneities may be explained by differential accumulation of artificial breeding containers and pesticide treatment across land development gradients. Continued investigation over a broader geographic area is required. However, in collaboration with the NYSDOH, this project will aid in implementing and evaluating mosquito surveillance and control. In the long-term, information from this study can be used to mitigate the northward invasion of Ae. albopictus, and in turn risk of disease introduction, under changing landscape and climate conditions.

Multinational patterns of seasonal asymmetry in human movement influence infectious disease dynamics and access to healthcare

Authors: Amy Wesolowski1Elisabeth zu Erbach-Schoenberg2Andrew J. Tatem2, Keitly Mensah3, Jean Michel Heraud, Christopher Lourenco2, Cecile Viboud5, Vivek Charu5, Nathan Eagle, Kenth Engø-Monsen7, Taimur Qureshi7, Caroline O. Buckee6, C.J.E. Metcalf3
Author Affiliations: 1Johns Hopkins Bloomberg School of Public Health; 2University of Southampton; 3Princeton University;  4Institut Pasteur – Madagascar, 5Fogarty International Center NIH; 6Harvard TH Chan School of Public Health; 7Telenor Research

Seasonal variation in human mobility is globally ubiquitous and affects the spatial spread of infectious diseases, but knowledge of seasonality in human movement has been limited by data availability. Here, we use mobile phone data to quantify seasonal travel and directional asymmetries in Kenya, Namibia, and Pakistan, across a spectrum from rural nomadic populations to highly urbanized communities. We test the importance of climatic versus social drivers in seasonal differences in mobility patterns. We then model how the geographic spread of several acute pathogens with varying life histories could depend on country-wide connectivity fluctuations through the year. In all three countries, major national holidays are associated with shifts in the scope of travel. Within this broader pattern, the relative importance of particular routes also fluctuates over the course of the year, with increased travel from rural to urban communities after national holidays, for example. These changes in travel impact how fast communities are likely to be reached by an introduced pathogen. We then extend this work to analyze the possible implications for how access to healthcare and vaccination may be impacted by season.

Exploring extended human-chicken interaction and associated public health risks and risk mitigation strategies in rural Tanzania

Authors: Elpidius Rukambile1Vitali Sintchenko2, Gary Muscatello1, Wende Maulaga3, Robyn Alders4
Author Affiliations: 1School of Life and Environmental Sciences, University of Sydney; 2Centre for Infectious Diseases and Microbiology – Public Health, Sydney Medical School, University of Sydney; 3Tanzania Veterinary Laboratory Agency; 4Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney

Poultry keeping, particularly scavenging village chickens, is one of the main agricultural activities in rural Tanzania. There are 4.7 million agricultural households in Tanzania of which 78 percent (3.7 million) raise chickens. Scavenging village chickens are frequently the only source of poultry meat and eggs in rural areas and contribute 20 percent of these products consumed in urban areas. Promoting village chicken production is a key option for achieving an adequate supply of animal- source protein and micronutrients as they are readily accessible to a majority of households. Village chickens are highly adaptable and are expected to be one of the agricultural commodities less affected by climate change. Therefore, several initiatives have been made to enable increased production in support of sustainable nutritional diversity and income generation in the village context. Keeping chickens under scavenging systems increases human-chicken interaction whereby chickens freely gain access to every part of the human house including the kitchen and children’s play areas which increases the risk of humans acquiring chicken-associated infections. Chickens colonised by enteric pathogens of public health importance shed pathogens in the environment through faeces which increases the risk of human chicken-origin environmental enteropathy, which may contribute to undernutrition and stunting in children. The study site is in a semi-arid area of Central Tanzania where households are already suffering increased water shortages and crop failures due to weather variability and lower and erratic rainfall. Hygiene practices associated with risks which may lead to chicken-associated pathogens entering the human food chain were investigated using mixed methodology: a questionnaire (84 households within 718 enrolled in a larger study), key informant interviews (10), focus group discussions (8) and two-weekly reports of the incidence of diarrhoea in enrolled households (84 of 718 households) across three wards in Central Tanzania. Of all risk factors analysed, only two were positively associated with diarrhoeal incidence in enrolled children: i) access of chickens to unwashed utensils (p<0.001); and ii) access of chickens to washed utensils (p<0.001). Options for addressing potential enteric bacterial infection risks associated with raising chickens under extensive systems are discussed. Implementation of feasible and culturally acceptable risk mitigation strategies are important if sustainable village scavenging chicken production and improved public health in rural areas are to be achieved in the face of a changing climate.

Quantifying the health benefits of limiting global warming to 1.5°C above pre-industrial levels: dengue fever in the Americas

Authors: Felipe Colon-Gonzalez1Iain R Lake1
Author Affiliations:1University of East Anglia

Background: The Climate Agreement signed in Paris aims to limit rises in global-mean temperature to below 2°C. It also aims to pursue efforts to limit temperature rises to 1.5°C in comparison to preindustrial levels. Although there are benefits for human health in limiting global warming to 1.5°C, the magnitude with which those societal benefits will be accrued remains fundamentally unknown. Crucial to public health preparedness and response is understanding and quantifying the impacts at different levels of warming. Dengue is a rapidly spreading vector-borne viral disease that is endemic to over 100 countries. It is estimated to cause ~390 million cases each year, 54 million of which occur in Latin America and the Caribbean.

Method: Monthly counts of laboratory confirmed dengue cases were obtained from the Mexican, Brazilian and Colombian Ministries of Health for the period January 2001 to December 2012. Generalized additive mixed model were used to model associations with current weather. A multi-GCM, multi-scenario approach was then used to investigate and quantify the risks avoided by limiting global mean temperature to 1.5°C above pre-industrial compared to those occurring at 2°C or 3.7°C. Using the ClimGen pattern-scaling tool, we generated climate projections from five CMIP5 climate models by scaling their simulated patterns of climate change by time-series of global temperature rise obtained using the IMAGE modeling framework which identifies socioeconomic pathways and projects the climatic implications of different climate and energy policy scenarios.

Findings and interpretation: Policies to limit global warming to 1.5°C could reduce dengue cases by up to 5.2 (1.7–13.8) million cases per year by the end of the century compared with a no-policy scenario that warms by 3.7°C. This number is comparable to ~50% of the estimated burden for the region in 2010. Furthermore, we found that by limiting global warming we can limit the expansion of the disease towards areas where incidence is currently low. Our results demonstrate that although future climate change may amplify dengue transmission in the region, some impacts could be avoided by constraining the level of warming.

Modelling the impact of global environmental change on vector-borne disease risk

Authors: Rachel Lowe1
Author Affiliations: 1London School of Hygiene & Tropical Medicine

Background: Vector-borne diseases, such as dengue, Zika and malaria, are highly sensitive to environmental changes, including variations in climate and land-surface characteristics. For example, changes in temperature and moisture impact developmental rates and survival of both the vector and pathogen, and the availability of vector breeding sites. Vector-borne disease emergence and spread is also exacerbated by anthropogenic activities, such as deforestation, mining, urbanisation and human mobility, which alter the natural habitats of vectors and increase vector-host interactions.

Innovative epidemiological modelling tools can help understand how environmental conditions interact with socio-economic risk factors to determine the risk of disease transmission and spread. In recent years, disease modelling has benefited from computational advances in fitting complex mathematical models and the increasing availability of environmental, socio-economic and disease surveillance datasets. At the same time, the ability to understand and model the climate system has steadily improved. Climate forecasts at sub-seasonal to seasonal time scales tend to be more skilful during El Niño-Southern Oscillation events in certain regions of the tropics. Thus, climate forecasts provide an opportunity to anticipate potential outbreaks of vector-borne diseases from several months to a year in advance.

Method: A Bayesian spatio-temporal model framework, which quantifies the extent to which environmental and socio-economic indicators can explain variations in disease risk, is presented. The framework is designed to disentangle the impacts of climate from other risk factors, using multi-source data and random effects, which account for unknown and unmeasured sources of spatial, seasonal and inter-annual variation. The model provides probabilistic predictions of monthly dengue incidence and the probability of exceeding outbreak thresholds, which are determined in consultation with public health stakeholders.

Findings: This disease model framework, combined with seasonal climate forecasts, has been successfully applied to produce real-time probabilistic dengue early warnings ahead of a mass gathering event in Brazil and following a major El Niño event in southern coastal Ecuador. Forecasts from the new model framework performed better than benchmark models, based on historical seasonal dengue averages.

Interpretation: This flexible model framework can be adapted to predict any climate-sensitive disease at various spatio-temporal scales and in diverse ecological settings. Incorporating sub-seasonal and seasonal climate forecasts in disease prediction models could support public health decision-makers in targeting timely disease control and prevention strategies months in advance, to mitigate the risk of imminent disease epidemics and emerging disease threats.

Global effects of land use on zoonotic host communities

Author: Rory Gibb1David W. Redding1Kai Chin1, Tim Blackburn1, Tim Newbold1, Kate E. Jones1
Author Affiliations: 1Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London

Background: Environmental trade-offs associated with land use, for example between food security and biodiversity conservation, represent critical dimensions of planetary health. Land use-driven biodiversity losses may predictably affect disease risk if reservoir host species are consistently more likely to persist under human disturbance (i.e. if ecological communities in modified habitats generally have a higher zoonotic potential). Such a phenomenon has been observed in specific disease systems, but with high rates of global land use change projected for this century, assessing its global and taxonomic generality would shed light on an important hypothesised driver of environmental synergies or trade-offs between conservation and public health.

Methods: We combine data on hosts of human-shared parasites and pathogens (‘hosts’) with a global database of local ecological communities and associated land use data (originally collated from published studies). We analyse the effects of land use on host diversity metrics across over 9000 sites globally, controlling for disease-related research effort and differences in survey methods.

Findings: Ecological communities in anthropogenic land uses (managed ecosystems and urban) contain a consistently higher richness and abundance of host species than communities in nearby primary land sites. However, among mammal hosts of zoonotic pathogens, we find considerable taxonomic variation in host responses to land use, with rodent and bat host abundances generally increasing and primate and carnivore hosts declining in modified landscapes.

Interpretation: Our results suggest that future global land use change has potential to drive increasing contact between people and ecological communities with increased shared pathogen potential (i.e. more potential hosts and possible opportunities for transmission). However, the variability among mammals, for example with rodent hosts most abundant in modified habitats and primate hosts most abundant in intact communities, highlights that these changes are unlikely to affect all zoonotic diseases consistently. This result supports arguments that, rather than expecting a consistent biodiversity-disease relationship, in practice policies aiming to both conserve biodiversity and reduce human disease (for example through establishment of protected areas) must be disease- and context-specific.

Extreme precipitation events and water quality in California: Implications for human health in a varying and changing climate

Authors: Alexander Gershunov1Tarik Benmarhnia1,2, Rosana Aguilera1
Author Affiliations: 1Scripps Institution of Oceanography, University of California San Diego; 2Department of Family Medicine and Public Health, University of California San Diego

Most pathogens and pollutants collect on the land surface or in infrastructure between strong rainfall episodes, and are then mobilized and delivered via storm runoff to areas of human exposure, such as coastal recreational waters, as a consequence of sewage or water treatment systems overflow. In California, USA, precipitation events are projected to become more extreme, and at the same time decrease in frequency as storm tracks move poleward due to polar-amplified global warming. Precipitation extremes in California are dominated by atmospheric rivers (ARs), which carry more moisture in a warmer climate. Thus, the physical driver of extreme precipitation events in this region is expected to grow stronger with climate change, and pollutant accumulation and runoff-generated exposure to those pollutants are expected to increase, particularly after prolonged dry spells. Extreme precipitation effects on water quality and associated human health impacts have been related to waterborne disease outbreaks in the conterminous USA and associated with beach closings in coastal areas due to the flushing of fecal contaminants through storm drains. In southern California, microbiological contamination of water during winter storms exposes human populations to elevated concentrations of microorganisms in bathing waters at beaches, which could cause gastrointestinal and ear infections, and lead to exposure to pathogens causing life-threatening conditions, e.g. hepatitis A. For this purpose, we use a recently published catalog of ARs, in combination with historical daily precipitation and fecal pollution indicators such as total and fecal coliforms in coastal waters to explore associations between extreme events related to ARs and the variability in coastal water quality in California. These associations will be used to identify mechanisms of fecal pollutant delivery to coastal recreational waters via storm runoff and to track sources of pollution common in the region, such as sewage outfalls and homeless encampments near rivers and streams. Overall, this work aims to quantitatively assess the influence of precipitation regime changes on human health via exposure to recreational coastal waters in California, with the ultimate goal of reducing vulnerability to extreme weather, as well as to delineate measures, such as an early warning system, that improve the response and resilience of human populations and ecosystems to a varying and changing climate.

The impact of precipitation on clinic-diagnosed enteric infections in Rusizi District, Rwanda

Authors: Miles Kirby1Phillip Okull2, Jean Aime Nsabimana2, Chris Uejio3, James Habyarimana4, Thomas Clasen1
Author Affiliations: 1Emory Rollins School of Public Health2Innovations for Poverty Action, Research – Rwanda; 3Florida State University; 4Georgetown University 


Background
Enteric infections are a major cause of morbidity and mortality, particularly among children less than 5 years of age. Climate change projections for Rwanda predict increases in average temperature, along with increases in total precipitation and frequency of heavy events. Previous research in Rwanda has found that heavy rainfall events increase the risk of contaminated drinking water, a substantial contributor to diarrhea in this setting. Relatively little is known about the impact of precipitation on more severe clinic-diagnosed infections in rural, low-income settings such as Rwanda.

Methods
In the context of a randomized controlled trial to assess the impact of a national environmental health campaign in Rwanda, we collected data from all government health facilities in Rusizi District, Western Province for calendar year 2015. Patient data for children under 5 from all 150 study villages were extracted from paper-based registers. Gridded daily precipitation data were downloaded from Climate Hazards Group InfraRed Precipitation with Station data and NASA’s Tropical Rainfall Measurement Mission, supplemented by local weather station data. Using both time-series and case-crossover designs, we examined the effect of extreme precipitation (95th percentile) on visits for enteric symptoms (i.e, diarrhea, gastroenteritis, vomiting controlling for intervention status and village distance to primary health facility. We also investigated the association between temperature and humidity for enteric symptoms, as well as respiratory symptoms, diagnosed pneumonia, and diagnosed malaria.

Findings
Data were extracted from 50 facilities, with a study catchment area of approximately 13230 children under 5. Preliminary results indicate there were 3736 cases of clinic-reported enteric symptoms in 2015, with an estimated annual incidence of 282 cases per 1000. Incidence was lowest in dry season months and increased in both rainy season periods. This trend was evident for all children and those less than 2 years of age, an age group with high rotavirus vaccination rates. Results of extreme precipitation impacts will be presented.

Interpretation
Clinic data from low-income settings is a rich and under-utilized resource which could have broad applications for improving planetary health at household, community, and regional levels. They add objectivity over self-reported conditions and capture the more serious outcomes that impact health care systems. Our results are consistent with others showing increased risk from rainfall events, likely due to flushed contaminants and water supply vulnerabilities. Understanding the impacts and mechanisms of precipitation on infectious diseases can help inform the design of locally-relevant intervention and adaptation strategies.

Assessing the effect of irrigated agriculture on the risk of Japanese encephalitis transmission in Asia

Author: Lydia Franklinos1Kate Jones1David Redding1, Ibrahim Abubakar1
Author Affiliations: 1University College London

BACKGROUND: Humanity has traded off many of the Earth’s supportive and regulating processes to feed human population growth and development, often with negative consequences for global human health. The use of irrigated agriculture for global food production has more than doubled since the 1960s and is mainly focused in developing countries in Africa and Asia, with future expansion expected in the same regions. Despite the benefits of enhanced global food production and economic development that have come with irrigated agriculture, it has also been associated with an increased risk of mosquito-borne disease. This is due to the dramatic expansion in vector breeding sites that are provided by irrigation, which may extend disease transmission seasons, alter seasonal transmission dynamics in endemic areas and introduce pathogens into non-endemic areas. However, the effects of expanding irrigated agriculture on the seasonality and geographic distribution of mosquito-borne disease risk remains poorly understood.

METHODS: We used a Bayesian spatial model using Integrated Laplace Approximations (INLA), to investigate environmental drivers of Culex tritaeniorhynchus occurrence; the main vector for Japanese encephalitis (JE). The model was used to create a novel dataset of spatio-temporal predictions for Culex tritaeniorhynchus retrospectively at time points over the last 20 years, and then summarised to give 12 monthly spatial predictions at a continental scale.

FINDINGS: The new data resource can be used to determine how environmental drivers vary spatially and temporally and how they may affect the transmission risk of JE, the most significant cause of viral encephalitis in Asia. This enables the identification of areas that are vulnerable to JE transmission risk under current and future levels of global change.

INTERPRETATION: This study contributes towards efforts determining the importance of underlying environmental drivers for JE transmission risk, and can be used to predict the impact of irrigation schemes and identify key areas where interventions should be prioritised within a changing planet.

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