| Cross-species transmission has led to the emergence of
various infectious diseases such as H5N1/H1N1, monkeypox, Lyme disease, West
Nile virus, HIV/AIDS, severe acute respiratory syndrome and Creutzfeldt-Jakob
disease.
James Hughes, MD, past president of the
Infectious Diseases Society of America, professor of medicine and public health
at Emory University, and an Infectious Disease News Editorial Board
member, said these diseases are a significant global health threat, and with
re-emergence of novel pathogens, more work is needed on predicting and
preventing their emergence.
James Hughes, MD
For this reason, researchers for the PREDICT project
developed a strategic framework for identifying and responding to zoonotic
pathogens of pandemic potential that have not yet emerged. The international
project, funded by the US Agency for International Development, is currently
active in Africa, Southeast Asia, Asia and Latin America. ADVERTISEMENT
Zoonotic pathogens
The core of the project is centered on the concept of
the One Health Initiative — to unite physicians and veterinarians to
recognize the importance of the interface of humans, animals and the
environment in the development of infectious diseases.
“We can improve our surveillance, diagnostics and
response to disease by including animal health specialists in infectious
disease training, planning and surveillance,” Jonna A.K. Mazet, DVM,
MPVM, PhD, of the Davis School of Veterinary Medicine at the University of
California, said in an interview with Infectious Disease News.
Mazet presented preliminary findings of the PREDICT
project during a symposium at the recent IDSA Annual Meeting in Boston.
Since 2009, researchers led by Mazet have trained more
than 900 field personnel across 20 countries in safety and surveillance
measures. Approximately 16,000 samples have been obtained from bats, rodents,
birds, primates and ungulates. Pyrosequencing and polymerase chain reaction
testing were used to target pathogens in an efficient and timely manner. The
researchers discovered various novel viruses, including corona, boca, herpes,
retro, adeno and rhabdo.
Jonna A.K. Mazet, DVM, MPVM, PhD
“We’re discovering new viruses all the
time,” Mazet said. “We’re also finding what we think of as human
viruses in animals, and what we think of as animal viruses in humans. Right
now, we’re working to characterize which ones are important and should be
included in new surveillance systems, and which ones we should know about and
be ready to recognize.”
According to Mazet, early detection offers the key to
control of zoonotic pathogens, by reducing post-transfer host adaptation,
potentially lowering transmissibility and allowing sequencing to improve
quality and speed of diagnostics.
Future research efforts will entail the determination of
which pathogens have the highest potential for consequences. “Including
pathogens of potential pandemic significance of animal origin in surveillance
plans before they spill over into humans can help us prepare for epidemics and
keep them from becoming pandemics,” she said.
Targeting surveillance
Another team of researchers for the PREDICT project are
targeting hotspots where wildlife host species have significant interaction
with domestic animals and high-density human populations.
For this portion of the study, researchers led by
Peter Daszak, PhD, president of the EcoHealth Alliance, pooled data from
the International Committee on Taxonomy of Viruses database to identify host
species associations for each virus from 1940 to 2010.
Results yielded 1,239 unique host species-virus pairs,
333 host species (including 222 genera, 68 families and 17 orders) and 305
unique viruses (including 222 RNA and 81 DNA viruses). Strategic selection of
both species and geographic locations for surveillance were conducted.
Surveillance measures led to the identification of
independent factors driving emerging infectious disease events, including human
population density and growth, rainfall, latitude and mammal diversity.
Further, the researchers discovered 195 mammal genera with one or more viruses
shared with humans, indicating that “phylogenetic distance from humans was
a strong predictor for the number of shared viruses.”
Peter Daszak, PhD
Daszak said this information will be used to test
hotspot model assumptions, and future changes in climate change, increases in
human population density, livestock production and trade changes and economic
modeling will determine the trade-off between the cost of global surveillance
and the cost of emerging infectious diseases.
“If we spend time analyzing the causes of emerging
diseases, we can use this to predict future disease emergence — ultimately
the next pandemic,” Daszak said. “My contention is that to fully
understand the viral threat to human health, we need to bring the best minds
together who understand microbes, human demography and environmental change.
The One Health Initiative does just that.”
Human, animal health infrastructure
Although the PREDICT project is a major stepping stone
toward the One Health Initiative, more efforts are needed, according to Hughes,
as the impetus for this initiative comes primarily from veterinarians, and it
has not been adequately funded.
“There are several reasons for infectious disease
physicians to support this initiative and to more enthusiastically embrace the
communication and collaboration with their veterinary colleagues,” Hughes
said. “Infectious disease physicians are often on the front line and in an
excellent position to recognize new and emerging diseases, which has happened
in the past with AIDS, SARS and the West Nile virus.”
Hughes said infectious disease physicians can learn from
their veterinary colleagues when a new disease appears. “What we learned
in 2003, when SARS was recognized, was that the veterinarians knew a lot more
about coronavirus infections than infectious disease physicians did.”
He said physicians should be more involved because most
bioterrorism threat agents of highest concern are zoonotic diseases such as
anthrax, plague, tularemia and Ebola. The biggest issue is cross-species
transmission, according to Hughes.
“That’s where the new diseases come from,
that’s the way HIV arose, and that’s how the next influenza pandemic
will arise. There are more disasters in our future, and the more we have a
collaborative interdisciplinary context to work in, clinically, in the public
health arena and in the research arena, the better prepared we’re going to
be.”
More collaboration, including joint research efforts and
training, are needed, according to Lonnie J. King, DVM, of the College
of Veterinary Medicine at Ohio State University.
“Because of the advent of specialization in
medicine, we now have increased our fragmentation and don’t appreciate our
interconnections and integrated approaches to problem-solving,” King said.
“Our training is biased toward a specialization while the One Health
Initiative is more of a holistic approach requiring collaborative work across
disciplines and professions. We have to overcome our training and education
bias.” – by Ashley DeNyse
For more information:
- Daszak P. #746.
- Mazet J. #748. Both presented at: IDSA 49th Annual Meeting; Oct.
20-23, 2011; Boston.
- One Health Initiative. Available at:
www.onehealthinitiative.com. Accessed: Nov. 7, 2011.
Disclosure: Drs. Hughes, Mazet, Daszak, and King
report no relevant financial disclosures.
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