Epidemiology


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.

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.

Borana women with sheep and goats at a traditional deep well water source, Garba Tulla, Isiolo, Kenya (photo credit: ILRI/Fiona Flintan).

Brucellosis is an important zoonotic disease that affects wildlife and livestock. People may get exposed to the disease through direct contact with an infected animal or consumption of raw or undercooked animal products. In humans, the disease is characterized by prolonged fever, body aches, joint pains and weakness, while in livestock, it mainly causes abortions and infertility. 

A study carried out in Garissa and Tana River counties of Kenya set out to identify the factors that affect the spread of brucellosis in people and livestock. Livestock and people from randomly selected households were recruited and serum samples were obtained and screened for Brucella antibodies to determine the level of exposure to Brucella spp. 

The study found that the chances of exposure to brucellosis in humans were at least three times higher in households that had at least one Brucella-seropositive animal compared to those that had none. 

This finding can be used to design risk-based surveillance systems for brucellosis, based on the locations of the primary cases of the disease, where each case of Brucella infection identified in livestock could signal potential locations of additional brucellosis cases in humans, and vice versa.

Citation

Kairu-Wanyoike, S., Nyamwaya, D., Wainaina, M., Lindahl, J., Ontiri, E., Bukachi, S., Njeru, I., Karanja, J., Sang, R., Grace, D. and Bett, B. 2019. Positive association between Brucella spp. seroprevalences in livestock and humans from a cross-sectional study in Garissa and Tana River Counties, Kenya. PLOS Neglected Tropical Diseases 13(10): e0007506.

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 Clippings

womanandlivestockatdandoragarbagedump_cropped

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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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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Cow in Kenya

Cow in Kenya. A new Rift Valley fever risk map for Kenya will help develop prevention and control measures to combat the disease in the country (photo credit: ILRI/Stevie Mann).

A new Rift Valley fever risk map for Kenya, based on data from a period spanning over 50 years, will be an important tool for use in developing measures to prevent and control the disease in the country.

Rift Valley fever is a viral disease that affects animals such as cattle, sheep, camels and goats. It is also a zoonotic disease, meaning it can be transmitted from animals to people.

Rift Valley fever epidemics occur every 3 to 10 years in specific regions of the Greater Horn of Africa, southern and western Africa and in the Arabian Peninsula, resulting in high rates of infection and death among people and livestock.

In Kenya, the most recent outbreaks of the disease occurred in 1997-98 and 2006-07. Experts agree that the severity of Rift Valley fever epidemics can be reduced through the use of effective early warning systems followed by rapid implementation of prevention and control measures.

In 2008, international experts and decision-makers from eastern Africa developed a risk-based decision support framework designed to guide responses during various stages of the Rift Valley fever disease cycle.

Now, a team of researchers from Kenya, the Netherlands and the United States of America has added to the arsenal of tools to prevent and control Rift Valley fever by using surveillance data from 1951 to 2007 to develop a Rift Valley fever risk map for Kenya.

The map shows the risk of an outbreak of the disease for each of the 391 administrative divisions in the country (based on the 1999 administrative map), classifying the divisions as high, medium or low risk.

The authors of the study say that the Rift Valley fever risk map will provide the Government of Kenya with an evidence-base from which it can respond to a Rift Valley fever epidemic warning as well as develop long-term prevention and control programs in high-risk areas.

The map is published in an article in the journal PLOS ONE (25 Jan 2016): Predictive factors and risk mapping for Rift Valley fever epidemics in Kenya

Citation
Munyua, P.M., Murithi, R.M., Ithondeka, P., Hightower, A., Thumbi, S.M., Anyangu, S.A., Kiplimo, J., Bett, B., Vrieling, A., Breiman, R.F. and Njenga, M.K. 2016. Predictive factors and risk mapping for Rift Valley fever epidemics in Kenya. PLOS ONE 11(1): e0144570.

ILRI news

High-risk areas in Uganda for possible/potential pig transmission of Ebola

The map above shows high-risk areas due to a spatial overlap of three proposed risk factors for zoonotic Ebola virus transmission in Uganda: modelled zoonotic niche, domestic pig distribution and high numbers of people living in extreme poverty; the map is taken from a paper published in Transboundary and Emerging Diseases, Assessing the potential role of pigs in the epidemiology of Ebola virus in Uganda, by C Atherstone, E Smith, P Ochungo, K Roesel, D Grace, 27 August 2015 (figure credit: ILRI).

This article is written by two of this paper’s authors: Christine Atherstone, an ILRI researcher based in Uganda who leads this work and is lead author, and Delia Grace, who leads ILRI’s Food Safety and Zoonoses research program.

A new risk assessment paper, Assessing the potential role of pigs in the epidemiology of the Ebola virus in Uganda, was published in the science journal

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In April 2010, Miyazaki prefecture in Southwest Japan experienced an outbreak of foot-and-mouth disease, one of the most contagious animal diseases. Although the outbreak was successfully contained in just four months, by July 2010 there were 292 cases and 300,000 cows and pigs had been slaughtered. This resulted in an economic loss of about 2 billion US dollars.

In addition to the economic impact of the epidemic, the mental and psychosocial well-being of individuals and the community at large was also affected. For example, the sudden death of large numbers of animals caused considerable mental stress among farmers as well as the veterinarians and municipal government teams involved in the slaughter and disposal of infected cattle and pigs.

Restrictions on movement were imposed as part of efforts to prevent the disease from spreading; this led to stress-related symptoms among some residents, particularly the elderly. In addition, many farmers experienced depression and anxiety about the future following the loss of their livelihoods.

Recognizing the multiple impacts of the disease epidemic, a coordinated multisectoral approach was adopted, under the One Health concept, to tackle the disease as well as manage the mental health and psychological well-being of the residents of Miyazaki.

In a video titled Responding to an animal disease epidemic: Lessons from Miyazaki, various stakeholders who were involved in responding to the epidemic reflect on the usefulness of a One Health approach in helping to successfully respond to and overcome the challenges of the disease outbreak.

Featured in the video is Kohei Makita, an associate professor of veterinary epidemiology at Rakuno Gakuen University who is on a joint appointment at the International Livestock Research Institute (ILRI). Makita and colleagues had earlier published work on the collaborative response of veterinary and psychiatry experts to the 2010 foot-and-mouth disease outbreak.

The video was produced by the World Bank Tokyo Development Learning Center, the United Nations University International Institute for Global Health, the National Center for Neurology and Psychiatry, Japan and Rakuno Gakuen University.

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