Hundreds of trees have been felled along Nairobi’s Uhuru and Waiyaki highways to make space for a new expressway. CELINE CLERY/AFP via Getty Images

Eric Fèvre, University of Liverpool and James Hassell, Yale University

There’s been widespread concern in Kenya over the shrinking of green spaces in Nairobi, the capital city. Most recently, there was uproar over the construction of a raised highway. This resulted in the felling of hundreds of trees, though protests managed to save the life of one 100-year-old fig tree.

It was also proposed that part of the highway run through Uhuru park – one of the city’s few recreational parks. Protests successfully diverted the highway to the park’s outskirts, but development still threatens the city’s few undeveloped spaces.

To give an idea of how much green space has already been lost, between 1976 and 2000, Nairobi’s forest cover went from 14% to 3%. Bushland cover, over the same period, was also reduced from 22% to 13%.

This will have an impact on the city’s wildlife and livestock. Nairobi, like other urban environments in the tropics, has an ecosystem that includes wildlife – such as birds, rodents, primates – and livestock such as cattle, goats, sheep and pigs. As green spaces are lost, native wildlife and bird species can dwindle and non-native species proliferate.

But very few studies explore how development affects wildlife and livestock in tropical cities. Recognising this gap, we explored the impact of a growing and changing urban environment on the wildlife and livestock that live with people in Nairobi from 2013 to 2018.

We found that, as land use in Nairobi transformed, there have been significant changes.

Competition between invasive and endemic species has grown, to the detriment of native biodiversity. Species – many of which play important roles in ecosystems such as fruit bats, primates and pollinators – are lost. And as the ecological landscape becomes less diverse, wildlife species that co-exist with humans – such as rats, scavenging and seed-eating birds (collectively known as synanthropes) – thrive, particularly in the poorer, most densely populated areas of Nairobi.

This is troubling because evidence suggests that synanthropes host more germs and could pass diseases on to people and make them sick. These are called “zoonotic diseases” and range from minor short-term illness to major life-changing illness and even death.

We could not assess the risk posed by zoonoses in Nairobi in our study. What we do know is that the city (and likely most other biodiverse, tropical cities) harbours all the ingredients for zoonotic spillover to occur between animals and people, particularly in the most densely populated areas.

Urban development policymakers must recognise that by shrinking green spaces, they increase the likelihood that people will catch zoonotic diseases. This is because species such as rodents proliferate.

Which species dominate, and where

We studied 99 household compounds – people’s houses and private land – across the city. These were selected to represent the different ways in which people interact with livestock and wildlife across the city. Households were stratified by people’s wealth, the types of livestock they kept and the ecological habitats in which they live.

Our data show that synanthropic species – like rats and insectivorous bats – dominate lower income, densely populated areas of the city. Here the synanthropes live in close quarters with poultry, pigs and small ruminants, such as goats and sheep.

We found that the decline in biodiversity – and subsequent colonisation by synanthropes – was driven by urban development. Trees and other forms of vegetation were replaced by man-made structures, removing the natural resources that most wildlife require to survive. Meanwhile, the resources (such as waste) on which synanthropes thrive increased.

As we argue in our paper, this kind of restructuring has important implications for the emergence of novel diseases at urban interfaces, which is why we used our research results to generate a set of testable hypotheses that explore the influence of urban change on microbial communities.

By testing the hypotheses we provide insights into how rapid urbanisation can generate interfaces for pathogen emergence, which should be targeted for surveillance.

Research done elsewhere shows that synanthropes – which thrive in disturbed environments with lower biodiversity – host more pathogens. And synanthropes seek resources provided by humans and their livestock, such as waste, which brings them into closer contact and increases opportunities for pathogens to cross between them.

For instance, our work in Nairobi shows that, as densities of humans and livestock increase, there is more sharing of antimicrobial resistance with wild birds.

Policy recommendations

Our findings have important implications for the public health and the sustainable planning and management of cities, particularly rapidly developing, biodiverse cities.

The high levels of competent disease carriers near humans is a huge risk to public health. The current response to COVID-19 has shown that the ability to limit the spread of a disease depends upon good public health infrastructure. Developing this infrastructure, while more studies are conducted to assess the risk of zoonotic disease transmission, is crucial.

Mitigating steps can be taken. One would be to maintain areas of forests, grasslands and clean waterways throughout the city. This would preserve and increase the wildlife biodiversity that competes with synanthropes, while also improving biosecurity within households, which could help moderate the presence of synanthropic species in urban centres.

It is, however, worth noting that some synanthropes, like insectivorous bats, help to control mosquito populations and agricultural pests in heavily urbanised environments. Eradicating them would not be advisable. Managing people’s interactions with synanthropes through smart urban planning – for example by removing resources on which synanthropes rely such as manure and rubbish from households – is best.

Our findings also raise important concerns about the social equality of urban development. The benefits of urban biodiversity and risks posed by human exposure to animal-borne diseases are not equally distributed. Currently equitable access to green spaces is restricted in many cities due to socioeconomic barriers, such as land ownership, proximity or lack of transportation. Reconfiguring the distribution of green space from the peri-urban fringe of the city to densely populated areas would build a more equitable society, allowing more city dwellers to have access to recreational space.

David Aronson, Senior Communications Advisor with ILRI, and Timothy Offei-Addo, a Princeton-in-Africa fellow with ILRI, contributed to the writing of this article.

Eric Fèvre, Professor of Veterinary Infectious Diseases, University of Liverpool and International Livestock Research Institute, Kenya, University of Liverpool and James Hassell, Wildlife Veterinarian with Smithsonian’s Global Health Program, and adjunct Assistant Professor, Yale University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cattle coming in from the fields in the evening in Lhate Village, Chokwe, Mozambique (photo credit: ILRI/Stevie Mann).

The current coronavirus disease (COVID-19) pandemic has brought into sharp focus the interconnectedness of people, animals and the environment and how this can contribute to the spread of disease.

One Health is a concept that recognizes that the health and well-being of people is intricately linked to the health of animals and the environment. For this reason, disease outbreaks are best tackled through a One Health approach that harnesses the collaborative efforts of multiple disciplines and sectors. This is especially so for zoonotic diseases that are spread between animals and people. One Health is also useful for addressing other public health issues such as antimicrobial resistance and food safety. 

One Health is not a new concept, but it has become more important in recent years. This is because many factors have changed interactions between people, animals and the environment. These changes have led to the emergence and re-emergence of zoonotic diseases.

The International Livestock Research Institute (ILRI) has an established record of collaborative One Health research in Africa and Southeast Asia. To mark One Health Day coming up next week on 3 November, we bring you highlights of some One Health research initiatives by ILRI and partners.

Ecosystem approaches to the better management of zoonotic emerging infectious diseases in Southeast Asia

This project worked directly with over 100 actors involved in managing zoonotic emerging infectious diseases across eight multi-disciplinary teams in Cambodia, China, Indonesia, Laos, Thailand and Vietnam. The project increased the capacity of researchers and policy implementers to use One Health approaches for better control of zoonotic diseases. The project also produced various research outputs and increased understanding of the teams’ knowledge, attitudes and practice in relation to One Health and how this approach could lead to better health outcomes for people, animals and the environment.

One Health Regional Network for the Horn of Africa

This project aims to improve the health and wealth of the people of the Horn of Africa by developing a regional network of individuals and organizations that can undertake high quality research into the link between people’s health and that of livestock and the environment. The project builds capacity to undertake basic and applied research in One Health through training programs and research placements for both research and non-research staff from participating institutions.

One Health Research, Education and Outreach Centre in Africa

The One Health Research, Education and Outreach Centre in Africa was launched barely a week ago (on 22 October 2020) and is hosted at ILRI’s Nairobi campus. Its goal is to improve the health of humans, animals and ecosystems through capacity building, strengthening of local, regional and global networks and provision of evidence-based policy advice on One Health in sub-Saharan Africa. It has four research themes: control of neglected tropical zoonotic diseases; emerging infectious diseases; food safety and informal markets; and prevention and control of antimicrobial resistance. The centre is currently supporting the Government of Kenya’s national response to the COVID-19 pandemic through COVID-19 testing in ILRI’s bioscience laboratories.

One Health Units for Humans, Environment, Animals and Livelihoods

This project applies a One Health approach to enhance the well-being and resilience of vulnerable communities in pastoralist and agro-pastoralist areas of Ethiopia, Kenya and Somalia. The project brings together professionals in human and animal health and the environment to achieve better access to human and veterinary health services and sustainable natural resource management.

Photo credit: Cattle coming in from the fields in the evening in Lhate Village, Chokwe, Mozambique (ILRI/Stevie Mann)

Crop-livestock systems in Vietnam (photo credit: ILRI/Hung Nguyen-Viet).

Dengue fever is a mosquito-borne viral disease that commonly occurs in warm, tropical climates. It is characterized by high fever and flu-like symptoms that can last for up to one week. In a small proportion of cases, severe dengue may occur, leading to bleeding and low blood pressure. There is no specific treatment for infection but medication can be taken to control symptoms.

Climate change and rapid unplanned urbanization are among the factors that have brought people into more frequent contact with the vectors, thus contributing to further spread of disease.

According to the World Health Organization, the global incidence of dengue has risen dramatically in recent decades, with an estimated 390 million dengue infections annually.

Vietnam is one of at least 100 countries where the disease is now endemic. Dengue infection in Vietnam is unstable but peaks from June to October annually.

As part of efforts to curb the spread of dengue in Vietnam, research efforts are being undertaken to develop tools that will enable timely detection and control of the disease. One such research study recently examined seasonal trends of dengue in Vietnam and used the data to develop a statistical model to forecast the incidence of the disease.

The study, published in PLOS ONE (27 Nov 2019), was carried out by a team of researchers from the International Livestock Research Institute and Vietnamese partners from Hanoi University of Public Health, the Institute of Meteorology, Hydrology and Climate Change, the Ministry of Health and the National Institute of Hygiene and Epidemiology.

To develop the statistical risk forecasting model, the researchers used dengue surveillance data that had been collected by health centres in Vietnam’s 63 provinces between 2001 and 2012. In addition, they obtained monthly meteorological data from the Institute of Meteorology and Hydrology and Climate Change. Land cover data were obtained from the Moderate Resolution Imaging Spectroradiometer website of the United States National Aeronautics and Space Administration.

The data were also used to develop risk maps of dengue incidence showing the distribution of the incidence of infection in the wet and dry seasons. The researchers are optimistic that with these new risk-based forecasting tools, policymakers and planners in Vietnam will be better able to predict dengue incidence in the country and thus respond in a timely manner to effectively control the disease.

Citation
Bett, B., Grace, D., Hu Suk Lee, Lindahl, J., Hung Nguyen-Viet, Phuc Pham-Duc, Nguyen Huu Quyen, Tran Anh Tu, Tran Dac Phu, Dang Quang Tan and Vu Sinh Nam. 2019. Spatiotemporal analysis of historical records (2001–2012) on dengue fever in Vietnam and development of a statistical model for forecasting risk. PLOS ONE 14(11): e0224353.

Photo credit: Crop-livestock systems in Vietnam (ILRI/Hung Nguyen)

Delia Grace presents on zoonotic diseases, UNEP Nairobi, 20 May 2016
ILRI veterinary epidemiologist Delia Grace presenting at the United Nations Environment Programme (UNEP) Science-Policy Forum that preceded the second session of the United Nations Environment Assembly (UNEA-2), on 20 May 2016 (photo credit: ILRI).

The United Nations Environment Programme (UNEP) held its first global Science-Policy Forum in Nairobi, Kenya on 19-20 May 2016 as part of the overall programme of the second session of the United Nations Environment Assembly (UNEA-2) held on 23-27 May 2016.

The forum offered a platform to the science community to engage with policymakers and civil society stakeholders on the science and knowledge needed to support informed decision-making to deliver on the environmental dimension of the 2030 Agenda for Sustainable Development.

Delia Grace, a veterinary epidemiologist at the International Livestock Research Institute (ILRI), took part in the forum as a panellist for the launch of the UNEP Frontiers 2016 report on emerging issues of environmental concern.

Her presentation on zoonotic and emerging infectious diseases focused on the global burden of zoonotic diseases (diseases that can be transmitted between animals and people), the drivers of disease (among them, land use change, environmental degradation and climate change) and how the multidisciplinary One Health approach can be used to support timely response to the threat of zoonotic diseases.

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Zoonotic diseases are also featured in a chapter in the UNEP Frontiers 2016 report, Zoonoses: Blurred lines of emergent disease and ecosystem health by Delia Grace and ILRI colleagues Bernard Bett, Hu Suk Lee and Susan MacMillan.

Cover of special issue of Vietnam Journal of Preventive Medicine on risk assessment

The Vietnamese Journal of Preventive Medicine has published a special edition on risk assessment for health research in Vietnam. The June 2013 special edition is a compilation of over 10 original research papers on the application of risk analysis to the management of animal, human and environmental health in Vietnam. The subject of training and capacity development in health risk assessment in Vietnam is also featured.

Risk analysis is a scientific, risk-based approach to assessing the health effects and economic impacts of various hazards (for example, disease-causing microorganisms in food or chemical pollutants in water) in order to develop appropriate interventions to mitigate the health risks posed by the hazards, thus ensuring that people, animals and the environment are safe.

Risk analysis comprises three components: risk assessment, risk management and risk communication. In the developed world, risk assessment is widely applied and used as a tool for risk management, thanks to the availability and accessibility of large databases of diseases.

However, many developing countries – including Vietnam – do not have the research data and risk analysis expertise needed to be able to adequately inform policymaking on risk-based approaches to health management.

The research papers featured in the special issue provide insights into the current status of research on risk analysis in Vietnam, specifically, risk assessment of the health impacts of Salmonella, E. coli and Listeria monocytogenes in the pork value chain in Hanoi, arsenic contamination in drinking water in Hanam Province, dioxin contamination in food in Da Nang and pesticide residues in farms in Thai Binh.

The work is a result of the collaborative efforts of the Vietnamese Journal of Preventive Medicine and the Center for Public Health and Ecosystem Research (CENPHER) at the Hanoi School of Public Health (HSPH).

Among the co-authors of the research papers are Delia Grace and Lucy Lapar, scientists at the International Livestock Research Institute (ILRI), and Hung Nguyen-Viet who leads research at CENPHER-HSPH and is a joint appointee of the Swiss Tropical and Public Health Institute and ILRI.

The papers are in Vietnamese with abstracts available in English. Listed below are the titles of the papers.

  • Risk assessment and health research in Vietnam (editorial)
  • Risk assessment of Salmonella in pork in Hanoi, Vietnam
  • Food-borne hazards in a transforming pork value chain in Hanoi: Basis for future risk assessments
  • Health risk due to exposure to chlorpyrifos for farmers in Thai Binh: Probabilistic risk assessment
  • Risk assessment of arsenic contamination in tube-well drinking water in Hanam Province
  • Environmental health risk assessment of dioxin in foods in Da Nang dioxin hot spot
  • Prevalence of Salmonella contamination in pig and pork at farms and slaughterhouses in the northern provinces of Vietnam
  • Air pollution as a health issue in Hanoi, Vietnam: An opportunity for intensified research to inform public policy
  • Environmental health risk communication: Concept, principles and challenges
  • Training and research programs in health risk assessment in Vietnam
  • Task force of risk assessment for food safety in Vietnam: Linking science to policy to increase food safety and livelihood generation of the poor farmer
  • Research projects on health risk assessment implemented by the Hanoi School of Public Health

The special edition also includes news on risk assessment training in Vietnam and reviews of two books on risk assessment.

For more information on this special edition, please contact Hung Nguyen-Viet (hung.nguyen @ unibas.ch).