Emerging Diseases


One Health is a concept that recognizes that the health of people is linked to the health of animals and their shared environment. A One Health approach in preventing and controlling diseases therefore involves the collaborative efforts of multiple disciplines and sectors. This approach is especially useful for managing zoonoses, diseases that are transmitted between animals and people.

According to the World Health Organization, at least 61% of all human pathogens are zoonotic and have represented 75% of all emerging pathogens during the past decade. There are more than 200 known zoonotic diseases. The health and economic cost of these diseases falls largely on poorer countries which bear 98% of the global burden of zoonoses.

Additionally, in poorer countries, zoonoses comprise 25% of the human burden of infectious diseases. Just 13 of over 200 zoonotic diseases cause 2.4 billion cases of illness and 2.2 million deaths annually (not including COVID-19).

Most zoonotic diseases are endemic in nature. Apart from emerging zoonoses like severe acute respiratory syndrome, highly pathogenic avian influenza and now COVID-19, many endemic zoonoses such as brucellosis and cysticercosis are not prioritized by national and international health systems and are therefore termed neglected zoonoses.

The impact of neglected zoonoses is most severe on poor households in low-resource settings as most people living in rural areas depend on livestock for food, transport and farm work. People living in urban slums are also affected as the rise in urban livestock agriculture brings people and animals into closer contact.

The ongoing COVID-19 pandemic has brought into sharp focus the interconnectedness of people, animals and the environment, and the need for multi-disciplinary approaches such as One Health to tackle the challenge. Preventing and controlling zoonoses in domestic and wild animal populations is a cost-effective way to ensure such diseases do not spread to human populations.

The International Livestock Research Institute (ILRI) has a wealth of research expertise on zoonoses and One Health. The institute recently launched a set of seven research briefs that highlight the benefits of One Health in sustainable livestock production towards improving the health of people, animals and the environment.

The brief Preventing and controlling human diseases transmitted by animals saves millions of lives and livelihoods gives an overview of the burdens and risks of endemic zoonoses and highlights what can be done to reduce the burden of neglected zoonoses and prevent the spread of emerging zoonotic diseases.

For example, innovative community disease surveillance programs can help health experts to detect disease outbreaks rapidly and identify the specific disease hotspots for more timely and targeted interventions.

A research study on the business case for One Health shows that every one dollar invested in One Health generates five dollars’ worth of benefits. Now is the time for governments, investors and policymakers to increase investment in One Health to prevent and control neglected zoonoses and safeguard the health of millions of people and animals and their shared ecosystem.

Citation

ILRI (International Livestock Research Institute). 2021. Preventing and controlling human diseases transmitted by animals saves millions of lives and livelihoods. Livestock pathways to 2030: One Health Brief 2. Nairobi: International Livestock Research Institute.

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ILRI’s expertise on One Health

ILRI’s expertise on zoonoses

One Health Research, Education and Outreach Centre in Africa

Photo credit: Camels drinking at a water pan in Wajir county in Kenya (ILRI/George Wamwere-Njoroge)

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)

Cows walk along an irrigation canal in Niolo, Mali (photo credit: ILRI/Stevie Mann).

As part of a special COVID-19 series by the International Food Policy Research Institute (IFPRI), Bernard Bett and Delia Randolph of the International Livestock Research Institute (ILRI) and John McDermott of IFPRI write on the growing risk in Africa of pathogens that spread from animals to people and how we can learn from past epidemics to improve preparedness and response.

In their article, the scientists discuss the evolving patterns of emergence and spread of zoonotic pathogens, factors that might influence the spread of emerging zoonotic pathogens and the opportunities for controlling emerging infectious diseases in Africa. 

They write: “The record thus far on COVID-19 and on past disease outbreaks shows that early, effective and sustained response is essential to winning the battle over these diseases. Innovative use of information and communication tools and platforms and engagement of local communities are crucial to improved disease surveillance and effective response. Building these systems requires demand from the public and commitment from policymakers and investors.” 

Read the full article, Africa’s growing risk of diseases that spread from animals to people, originally posted on the IFPRI website.

Bernard Bett is a senior scientist with ILRI’s Animal and Human Health program, Delia Randolph is the co-leader of ILRI’s Animal and Human Health program and John McDermott is the director of the CGIAR Research Program on Agriculture for Nutrition and Health. The analysis and opinions expressed in the article are of the authors alone.

Photo credit: Cows walk along an irrigation canal in Niolo, Mali (ILRI/Mann)

Researchers entering sampling data (photo credit: Zoonoses and Emerging Diseases).

In the cities of developing nations, where unregulated antibiotic use is common and livestock jostle with people amid often unsanitary conditions, scientists have found a potentially troubling vector for the dissemination of antimicrobial resistant bacteria: wildlife.

The epidemiological study published in the June 2019 issue of the journal Lancet Planetary Health shows that urban wildlife in Nairobi carry a high burden of clinically relevant antimicrobial resistant bacteria. The research team included scientists from the International Livestock Research Institute (ILRI), the University of Liverpool and the Kenya Medical Research Institute, among other research institutions.

Antimicrobial resistance is an increasingly serious threat to public health. Through misuse and overuse of antibacterial medication, more and more of the bacterial diseases that were once easily treated with antibiotics have become drug-resistant; these new strains of old germs require expensive and prolonged treatment at best and at worst can be lethal.

The study deployed teams of veterinary, medical, environmental and wildlife personnel to sample 99 households randomly chosen from Nairobi’s socio-economically diverse neighbourhoods.

The study found higher diversity of antimicrobial resistance in livestock and the environment than humans and wildlife. Rodents and birds were significantly more likely to carry resistance to multiple drugs when exposed to human and livestock waste through poor management practices, a common feature of lower-income neighbourhoods.

“This paper shows that contamination of urban environments with antimicrobial resistance is a serious issue. This is not just specific to Nairobi but findings can be extrapolated to other cities in Africa,” said Eric Fèvre, a joint appointed scientist at ILRI and professor of veterinary infectious diseases at the University of Liverpool.

“We tend to think of antimicrobial resistance in primarily medical terms, of developing new drugs and better using old ones. But we need to take an ecological approach to addressing this threat. Urban cities can address this by better urban planning, better waste disposal, better livestock husbandry practices. This can go far toward disrupting antimicrobial resistance exchange between wildlife, livestock and humans,” said Fèvre.

The lead author of the study, James Hassell, said, “Although we found no evidence to suggest that antimicrobial resistance carried by urban wildlife poses a direct threat to human health, that these animals harbour high levels of resistance to drugs used in human and animal medicine is particularly worrisome. Since wildlife are not treated with antibiotics, this is indicative of how pervasive antimicrobial resistance is in urban environments. Species that move freely across cities and further afield could disseminate resistance acquired in urban areas more widely.”

“We cannot address the rise of antimicrobial resistance without focusing on the environmental, ecological and social settings in which humans exist,” said Hassell.

Citation

Hassell, J.M., Ward, M.J., Muloi, D., Bettridge, J.M., Robinson, T.P., Kariuki, S., Ogendo, A., Kiiru, J., Imboma, T., Kang’ethe, E.K., Öghren, E.M., Williams, N.J., Begon, M., Woolhouse, M.E.J. and Fèvre, E.M. 2019. Clinically relevant antimicrobial resistance at the wildlife–livestock–human interface in Nairobi: An epidemiological study. Lancet Planetary Health 3(6): e259–e269.

ILRI Asia

Nobody likes getting sick. However, climate change, like higher temperatures, heavier rainfall and higher humidity, is already a given, and diseases highly sensitive to such changes would likely increase over time.

Climate change might also make the environment more suitable for diseases to spread, not only among individuals of the same species, but also across species (known as zoonotic diseases). In fact, 70% of the emerging diseases today, like ebola, A(H1N1) (‘swine flu’) and avian influenza (‘bird flu’), have been transferred from animals to humans. Such diseases threaten not only agricultural and food production, but also human lives as well.

A better understanding of how diseases are linked to climate change is needed. “We need more information on climate-sensitive zoonotic diseases to improve healthcare,” said Dr Hu Suk Lee of the International Livestock Research Institute (ILRI).

A team of researchers from ILRI and national climate, agricultural and…

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ILRI Clippings

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A woman sorts through a heap of garbage at the Dandora dumping site among other people, cattle, pigs and storks, in Nairobi (photo credit: Simon Maina / AFP / Getty Images).

Written by Eric Fèvre

‘There are fears that Africa’s next major modern disease crisis will emerge from its cities. Like Ebola, it may well originate from animals. Understanding where it would come from and how this could happen is critical to monitoring and control.

‘Growth and migration are driving huge increases in the number of people living in Africa’s urban zones. More than half of Africa’s people are expected to live in cities by 2030, up from about a third in 2007.

‘The impact of this high rate of urbanisation on issues like planning, economics, food production and human welfare has received considerable attention. But there hasn’t been a substantive effort to address the effects on the transmission of the organisms—pathogens—that…

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An Ethiopian woman breeds sheep for a living (photo credit: ILRI/Zerihun Sewunet).

On the matter of global health and tackling the looming threat of emerging infectious disease pandemics, Delia Grace, a veterinary epidemiologist at the International Livestock Research Institute (ILRI) shares her views in a recent blog post, Pandemic proofing the world, published by How We Get To Next.

The post argues the case for greater attention to diseases that can be transmitted to people through livestock, better incentive structures for reporting of livestock disease outbreaks so that timely disease reporting is rewarded rather than punished, and the need to tackle the root causes and not just the symptoms of emerging zoonotic diseases.

Read the post, Pandemic proofing the world by Delia Grace, How We Get To Next, 29 June 2016

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.

ILRI news

MERS-Coronavirus_NIADTransmission electron micrograph of Middle East Respiratory Syndrome coronavirus, MERS-CoV (image credit: NIAID). MERS-CoV belongs to the coronavirus family. Human coronaviruses were first identified in the mid-1960s; MERS-CoV was first reported in 2012 in Saudi Arabia. Coronaviruses can also infect animals. Named for the crown-like spikes on their surface, coronaviruses are common in people, usually causing mild to moderate upper-respiratory tract illnesses. Two exceptions are the MERS-CoV and the SARS (Severe Acute Respiratory Syndrome)-CoV.

A new study published in the science journal Emerging Infectious Diseases reports that two individuals in Kenya have tested positive for the presence of antibodies to Middle East Respiratory Syndrome coronavirus (MERS-CoV). Neither person is ill or recalls having any symptoms associated with MERS.

There is no evidence of a public health threat and scientists concluded that the infections caused little or no clinical signs of illness. But they plan follow-up studies, as this is the…

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