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New Thinking on New
Human and Livestock Disease Threats
As the world's governments raced to deal with a looming flu
pandemic in late April 2009, World Health Organization (WHO)
officials confirmed that the world is better prepared than ever
before to deal with a pandemic, thanks largely to 6 years of
research and preparations to battle bird flu and Severe Acute
Respiratory Syndrome (SARS).
Although it contains animal genetic components, the current
influenza A(H1N1) virus has not been diagnosed in animals before
and has spread from person to person, threatening a pandemic. Three
serious influenza pandemics occurred in the 20th century, with each
new virus eventually infecting up to a third of the world over the
course of 1 to 2 years: the 1918 "Spanish flu"
responsible for more than 40 million deaths, followed by the 1957
"Asian" and 1968 "Hong Kong flu," which killed
between 1 and 3 million people worldwide.
The history of flu epidemics and pandemics, which can be traced
back with some accuracy for the past 300 years, tells us that
outbreaks occur somewhere in the world in most years and pandemics,
which are epidemics that spread worldwide, at 10- to 50-year
intervals. Despite influenza and its causative organism being the
most studied of viral diseases and pathogens until the advent of
HIV/AIDS two decades ago, little has been done in the past century
to change the pattern of influenza infections.
 The role of livestock scientists in the developing
world
Livestock scientists have a vital role to play in helping to
predict, prevent and control zoonotic diseases, which are all those
transmitted between animals and people. Remarkably, zoonoses make
up more than 60 percent of all human infectious diseases and more
than 70 percent of all emerging infectious diseases. These diseases
occur most frequently in Asia and Africa, where people tend to live
in close proximity to their livestock and limited resources hinder
both surveillance and response.
The growing threat of emerging diseases such as Nipah and SARS,
and re-emerging diseases such as Rift Valley Fever and avian
influenza, has served as a wake-up call to animal health and public
health services that their cross-border collaboration is necessary
if these threats are to be minimized. There is increasing
recognition that, for a number of zoonotic diseases, the most
effective way to protect the health of the public is to control
disease in the animal host.
The work of livestock scientists working in and for developing
countries has special relevance in tackling these animal-human
diseases, because within developing countries today, fast changes
in food systems wrought by skyrocketing demand for, and production
of, livestock foods is creating new niches and transmission
pathways for pathogens, with unprecedented numbers of diseases
emerging and re-emerging in recent decades. New tools and
approaches for managing diseases in developing countries are
urgently needed.
Researchers at the International Livestock Research Institute
(ILRI) have been working at the livestock-human disease interface
for three decades, supporting better integration of veterinary and
public health surveillance programs. ILRI's particular
interests are aspects of zoonotic diseases that impact the
world's poorest communities, where animal husbandry is a way of
life and a central means of livelihood for more than half a billion
people. ILRI and its partners, for example, make evidence-based
assessments of the different impacts on the poor of employing
different disease-control methods, thereby helping policymakers
determine optimal pro-poor strategies for different regions and
agricultural production systems of the developing world.
ILRI works with many research institutions within developing
countries to better control zoonotic diseases at local, national
and regional levels. It works with WHO and its international
network of institutions to bolster disease surveillance. It works
with the World Organisation for Animal Health (OIE) and the Food
and Agriculture Organization (FAO) of the United Nations on
participatory epidemiology, a grassroots approach to disease
surveillance and control that is being successfully applied in the
battle against bird flu in Indonesia. And it works with regional
agencies such as the Africa Union / Inter-African Bureau for Animal
Resources to improve laboratory testing and diagnosis of bird flu
and other infectious livestock diseases.
ILRI and its partners are also investigating risk-based
approaches that focus on key hazards and maximize benefits with
available resources. With case studies in Africa and Asia, and
concepts derived from "one medicine" and "one
health," ILRI scientists argue that a "risk-analysis
framework" can and should be extended to integrate risks to
animal, human and environmental health.
The role of policy
ILRI also works with the International Food Policy Research
Institute (IFPRI) and other institutions on providing
evidenced-based policy support, so that we don't fall into the
trap of doing more harm than good in our efforts to control
infections, particularly in poor countries, which can least afford
such mistakes.
Some of the most profound consequences of disease threats are
economic rather than medical, with inappropriate policies
devastating local and national economies. Egypt's on-going
culling of its entire population of some 300,000 pigs, for example,
is reported to be reigniting religious and economic tensions, and
may end up doing more harm than good. The pigs are kept not by
Egypt's majority Muslim population, which views the animals as
unclean, but by Egypt's Coptic Christians, many of whom
maintain pigs on the rubbish heaps of shantytowns, where entire
families pick out organic waste to feed their pigs. On the other
hand, Egyptian authorities may be trying to prevent a repeat of
events 2 years ago, when they were criticized for not responding
swiftly enough to an outbreak of bird flu, which killed 26 people
in the country, three in just the last month.
"Misconceptions and inappropriate responses can spread
quickly during the early stages of a new disease outbreak,"
says John McDermott, a veterinary epidemiologist and ILRI's
director of research. "This 'swine flu' is spread by
people, not by pigs," he adds. "So, most authorities are
appropriately focusing their current attention on stopping the
spread of swine flu among people." (Bird flu, in contrast, is
spread by birds, so authorities focus on controlling that disease
within poultry rather than human populations.) This new swine flu
virus, and our reactions to it, like the more lethal bird flu and
SARS before it, should provide us with many lessons for the
future.
Research gaps
We still know little about the nature of this new influenza virus
strain, except that its genetic makeup is a "mashup" of
human, bird and pig elements (making the name "swine flu"
something of a misnomer). We don't know yet when it first made
the jump from pig to person, why it has been so deadly in Mexico
but not elsewhere or how virulent it will eventually prove to be.
The pathogenicity of a virus can become milder or more severe over
time. Until now, the influenza A(H1N1) virus thankfully has proven
relatively mild, with most of those infected responding well to
usual flu treatments and recovering.
Our ignorance of this new strain of swine flu virus is partly
due to our neglect of animal health matters. In rich as well as
poor countries, veterinary health care and research remains
chronically underfunded. And there is increasing need for disease
control policymakers, agents and researchers to collaborate at the
interface of the human- and animal-health sectors, exchanging
up-to-date information on disease outbreaks and transmission.
Controlling emerging infectious
diseases
"To get serious about preventing new zoonotic infections from
spreading," says ILRI director general Carlos Seré, "we
need to get serious about veterinary resources. We need new ways to
look for new pathogens infecting animals, new ways to assess those
which may be most dangerous and new ways to determine how they may
be transmitted to people. We have just had a demonstration as to
the danger of waiting for a new flu to emerge and begin spreading
among people before trying to contain it."
The influenza A(H1N1) virus is spreading rapidly because in our
ever-shrinking, ever-globalizing world, pathogens are crossing
species and borders with increasing ease. In such a world, says
Seré, "we ignore veterinary health problems in developing
countries at our peril." With high-quality collaboration among
countries (rich and poor alike), scientific disciplines (e.g.,
economics as well as genetics), and sectors (e.g., medical,
veterinary, agricultural, environmental and wildlife), Seré argues,
we can manage today's emerging disease threats.
Because animals are the origin of most emerging diseases, they
could play the same role that canaries did in the mines, in that
case, alerting the coal workers to the presence of noxious gases or
too little oxygen.
"We should be spotting many infectious disease threats not
in people, as we did in the case of this new flu virus," says
Seré, "but rather in animal populations." That should
give authorities more time to design and implement interventions to
protect people from becoming infected. "But as we've seen
in recent outbreaks of bird flu and Rift Valley fever, all too
often it is people rather than animals that serve as our sentinels,
sickening and dying after the disease has begun circulating in
local livestock populations." That's largely because in
poor countries, livestock diseases tend to go unreported (it's
hard to tell one livestock disease from another in countries with
spotty veterinary coverage) and/or underappreciated (people facing
serious human health problems have little time to spare worrying
about animal diseases), and/or ignored (it may be considered
political suicide to report a disease outbreak that might have
large economic consequences).
"To find better ways of controlling human diseases,"
Seré concludes, "we're going to have to find better ways
of understanding and controlling diseases in both domesticated and
wild animal populations. And we're all going to have to work
together, breaking down traditional barriers between organizations
and scientific disciplines in the process. We need new thinking to
tackle these new threats. And bringing diverse expertise together
is the best way of staying on top of fast-evolving situations that
threaten our global public health - as well as the well being of
the world's poorer livestock keeping communities."
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