International project focuses on cross- species transmission of infectious diseases

Continued collaborative efforts needed for research and training between physicians and veterinarians.

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.

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.

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.

“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.”

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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