Study: Poultry most likely to bring H5N1 to Americas

Study: Poultry most likely to bring H5N1 to Americas

Maryn McKenna * Contributing Writer

Dec 5, 2006 (CIDRAP News) – Poultry infected with H5N1 avian influenza pose the greatest risk of bringing the disease to the Americas, according to a new study by British and US researchers that challenges US efforts to detect flu in migratory birds.

Once on this continent, avian flu is likely to spread to migratory birds that will cross US borders—but the greatest risk will be birds from Central and South America that are not sampled in current wild-bird testing, the researchers said.

The study, to be published in Proceedings of the National Academy of Sciences, employs a complex analytical method that compares the migratory routes of wild bird species thought to be the main reservoirs of avian flu with data on legal trade in poultry and wild birds and avian-flu gene sequences deposited in the public database GenBank.

Plotting those pieces of data against each other allowed the researchers to hypothesize whether migratory birds, wild bird trade, or poultry were responsible for H5N1 influenza's past spread across the globe, as well as to model its possible future paths.

Heading their conclusions: The combination of poultry trade and bird migrations allowed the virus to spread much farther than either would have allowed on its own.

Heading their predictions: The greatest threat to the continental United States will be the arrival of avian flu in Central and South America—where poultry trade is less restricted than in North America—via live poultry imports from countries where avian flu has affected either domesticated or wild birds. Strict regulation of poultry trade across US borders will not be adequate protection, they concluded.

"The question is not just who you trade with, but who your neighbors trade with," A. Marm Kilpatrick, PhD, a senior research scientist with the Consortium for Conservation Medicine and the lead author of the study, told CIDRAP News.

The Consortium is a New York-based non-profit supported by six institutions: the Cummings School of Veterinary Medicine at Tufts University, the Johns Hopkins University School of Public Health, the U.S. Geological Survey's National Wildlife Health Center, the University of Pittsburgh School of Public Health, the University of Wisconsin-Madison Nelson Institute for Environmental Studies, and the Wildlife Trust. Other authors came from the Royal Society for Protection of Birds and the Smithsonian Institution.

Kilpatrick said the researchers' analytical method allowed them to theorize about which population—poultry, migratory birds such as ducks and swans, or traded wild birds such as parrots and birds of prey—was responsible for the spread of H5N1 influenza across Asia and into Europe.

Poultry played a greater role than wild birds in distributing H5N1 through Asia, they found, but migratory birds that picked up the virus from poultry carried it westward, introducing it to 20 of the 23 European countries where it has been found. In Africa, they suggested, both poultry and wild birds played a role, along with poultry products such as chicken droppings bought for fertilizer and fish feed.

The findings challenge previous conclusions on the routes by which some countries were infected. For instance, plotting genetic sequences from H5N1 isolates against migratory routes revealed that bird flu arrived in Turkey, the first European-region country to be affected, not through previously blamed poultry imports from Thailand but via migratory birds winging from Russia.

The researchers' method—which combined estimates of "infectious bird days" (the product of the number of birds entering a country, the prevalence of infection in those populations, and the number of days birds are likely to shed virus) with data on trade and migration from U.S. and international agencies—does not consider the possible influence of the illegal trade in poultry and wild birds, an omission that Kilpatrick acknowledged is a weakness.

But the analysis points so strongly to the influence of legal trade in spreading the pathogen that it argues for implementing trade controls, he said.

"Although the risk of H5N1 introduction into the mainland United States by any single pathway is relatively low, the risk of introduction by poultry to other countries in the Americas, particularly Canada, Mexico and Brazil, is substantial unless all imported poultry are tested for H5N1 or trade restrictions on imports from the old world are imposed," the report says.

The argument over the relative roles played by poultry and migratory birds in spreading H5N1 has been bitter, with agricultural interests defending poultry and conservation groups contending that wild birds are victims rather than disease vectors. The researchers' conclusions are likely to find favor with conservation groups, and appear to accord with past observations by avian virologists that migratory-bird importation to the United States is unlikely because flyways and feeding grounds allow relatively little overlap for viral exchange.

But the research implicitly challenges the focus of the $29 million migratory-bird testing effort being conducted in the United States by the departments of Interior and Agriculture. Since April that effort has tested more than 21,000 samples from wild birds in the United States, primarily in Alaska, without finding any high-pathogenic avian flu.

Because the wild birds sampled to date have shown such low prevalence of all avian flu strains—2.6% among Alaskan isolates, according to the National Wildlife Health Center in Madison, Wis.—surveillance should refocus on dead birds, the researchers said.

But scientists at the National Wildlife Health Center—which leads the US sampling effort but is also a coalition partner of the Consortium for Conservation Medicine—said Monday's study lacks enough data to persuade them to shift their efforts. In particular, they said a decision by the authors to exclude shorebirds from their analysis leaves out important information, because shorebirds congregate in large groups that facilitate viral exchange more than individual encounters do.

"A model is only as good as the assumptions you make and the data you put into it," said Leslie Dierauf, VMD, the center's director. "There may be better data we can obtain on trade in domestic fowl. There is certainly in my mind at this point not good enough data for migratory birds."

Nevertheless, Dierauf, who reviewed the paper a year ago when it was in draft form, said the analysis raises questions that are vital for successful avian flu prevention and control.

"I am not certain [the paper] makes a significant advance in knowledge, but I do know it sets a number of scientific matters on the table that we all need to look at, no matter whether we are looking from the wild-bird perspective or the poultry perspective or the trade perspective," she said. "That is very good."

Kilpatrick AM, Chmura AA, Gibbons DW, et al. Predicting the global spread of H5N1 avian influenza. Proc Nat Acad Sci 2006 (published online Dec 7) [Abstract]

See also:

Olsen B, Munster VJ, Wallensten A, et al. Global patterns of influenza A virus in wild birds. Science 2006 Apr 21;313(5772):384-8 [Full text]


Center for Infectious Disease Research & Policy
Academic Health Center -- University of Minnesota
Copyright © 2006 Regents of the University of Minnesota

Bird flu virus 'still smoldering,' U.S. expert says

Bird flu virus 'still smoldering,' U.S. expert says
By Caleb Hellerman
CNN

A year ago, headlines were screaming about a looming disaster: the rapid spread of bird flu across two-thirds of the globe. The H5N1 strain of the virus was killing more than half its human victims. Experts were urging the government to stockpile medicine and experimental vaccines.

Dr. Robert Webster, whose vaccine the U.S. government plans to use in case of an outbreak, told CNN at the time, "If this virus learns to transmit human to human and maintains that level of killing, we've got a global catastrophe."

That worldwide pandemic hasn't yet materialized, and bird flu has been out of the headlines for a while. But we may be in for another round of news.

Last week South Korea announced two new outbreaks in poultry. And Dr. Timothy Uyeki of the U.S. Centers for Disease Control and Prevention said he's bracing for another surge in human infections. "When the temperature drops and the humidity drops, that's when you start seeing more poultry outbreaks. And when you see poultry outbreaks, that's when you see human cases."

"It's still smoldering," said Dr. Anthony Fauci, who heads U.S. scientific efforts to combat bird flu. "What it hasn't done, much to our relief, is to become more virulent or better able to transmit from person to person."
New research

Three recent papers in the New England Journal of Medicine illustrate serious roadblocks to understanding and controlling the virus. The first describes three clusters of cases within families in Indonesia, eight patients in all. In two of the clusters, the authors said it's quite possible one person caught the disease, then passed it to family members.

One of those families was profiled in "Killer Flu," a CNN program last December. Rini Dina, a 37-year-old woman in a Jakarta suburb, died of an H5N1 infection, and her 8-year-old nephew, Firdaus, was hospitalized with fever for 10 days. Indonesian health officials said Rini was probably infected by tainted fertilizer in her garden. Firdaus had no direct contact with birds or the garden, but cuddled with his aunt on a couch while she lay shivering with fever. According to medical detectives, that's probably how he got sick.

"We can't prove it, but it probably happened," said Dr. Uyeki, who helped an Indonesian team with the investigations. Worldwide, about a third of all cases involve family clusters and there are a handful of cases where the virus likely passed from person to person, he said.

As a clinician, Uyeki has also helped to examine bird flu patients in Indonesia and Vietnam, the only U.S. doctor to do so. As the virus evolves, he said, its symptoms are evolving as well. "The clinical features in 1997 were different than what they are now. We're seeing less diarrhea, and in Indonesia, it's been much more fatal." Other, more common symptoms are hard to distinguish from other infections -- fever, aches and coughing, and shortness of breath and pneumonia as the illness progresses.

Simply making a diagnosis can be difficult. A second NEJM paper describes eight human patients in Turkey, all of whom initially tested negative for H5N1. The first samples were taken by swabbing the patients' nasal passages. That's standard for most influenza tests, but Uyeki says the H5N1 virus embeds itself deeper in the throat and lungs.

In Turkey, all the patients had been in contact with sick birds, so doctors were looking for H5N1. But in less-suspicious cases, a delay could be fatal. The only known treatment is the drug oseltamivir, sold as Tamiflu. While data are scarce because of the small number of human cases, most experts believe Tamiflu can lessen the symptoms of bird flu -- as it does with typical influenza - but only if taken in the first two days after symptoms appear.

In a commentary published with the two articles, Webster and another prominent flu expert said efforts to eradicate the virus, through killing infected chicken flocks or by vaccinating poultry, have largely failed. Worse, they said, many vaccines used in Asia are of poor quality and are pushing the virus to mutate faster, in potentially more dangerous directions.

So far, H5N1 hasn't gained the ability to easily infect humans, but eyebrows went up during an outbreak in May, on the Indonesian island of Sumatra. Bird flu infected eight people in a single family, killing seven of them. The World Health Organization concluded the illness had spread among the victims, but said genetic testing did not show major changes in the virus. Fauci said the H5N1 virus is indeed "a moving target," but that the existing vaccine provides at least some protection against the different strains. Work on more advanced vaccines is ongoing, he said. "Our capability is getting better and better, but it's not going to happen overnight."

"It's been a really rare human disease to date," Uyeki cautions, but "who can predict what's going to happen? We better continue to monitor and plan. To ignore this would be insane."

Caleb Hellerman is a producer with CNN Medical News.

Find this article at:
http://www.cnn.com/2006/HEALTH/12/06/bird.flu

Scientists to Review Fight Against Bird Flu at Mali Conference

Scientists to Review Fight Against Bird Flu at Mali Conference
By Phuong Tran
Dakar
05 December 2006


Representatives from more than 100 countries are preparing to attend the fourth international conference on avian influenza, Wednesday in Bamako, Mali. Scientists fear that the rapid spread of this highly contagious virus, combined with the lack of preparation in vulnerable countries, can lead to added economic and human losses. Phuong Tran reports from Dakar.

The participants will include donors, health professionals and representatives from the livestock industry. They will discuss ways to contain the highly contagious H5N1 virus, also known as bird flu.

A conference report prepared by the World Bank says that some of the most rapid promulgation in the past year has happened in Africa, where several countries have reported the avian flu in both poultry and humans.

Vendor prepares chickens for sale in Garki market in Abuja, Nigeria (File photo)
Vendor prepares chickens for sale in Garki market in Abuja, Nigeria (File photo)
This report suggests Africa needs close to a half billion dollars to fight the avian flu. A veterinary consultant to the conference, Faouzi Kechrid, explains Africa's vulnerability.

Kechrid believes that the virus poses a big problem for Africa, given the nature of cattle breeding, the lack of well-developed veterinarian services and what he says is the lack of proper information for people working on non-commercial family farms.

Alex Thiermann is president of the standards committee at the Paris-based World Organization for Animal Health. The committee develops the World Trade Organization's standards for the trade of animals and animal products. Thiermann's concern is that the most vulnerable countries for the spread of avian flu are also the ones that do not have the tools to control the virus.

"The concern that we have is countries that do not have the necessary infrastructure to do an early detection, take rapid action and notify international authorities," he said. " In Africa, we have problems because either the message does not get to the farmer or the message gets to the farmer and the farmer is afraid to report it, because he or she may lose the poultry, and [they think] it may be better to move them to a neighboring village or a neighboring country."

Thiermann and Kechrid identify two conditions for a successful containment strategy. First, Thiermann points to Southeast Asia, where there was an outbreak of the virus in poultry in 2003. He thinks this region's strong veterinary infrastructure helped contain the virus.

Second, Kechrid explains how a compensation system can help encourage farmers to take early action.

Kechrid explains that the ideal situation would be that when a farmer suspects an animal of carrying the virus, he kills it. But this can seriously damage the farm's earnings. Kechrid says that is why a compensation system is needed to ease farmers' losses from killing poultry.

Since 2003, the World Bank reports that avian influenza has killed or forced the killing of 250 million poultry birds, which translates to direct economic losses for people connected to the livestock industry. According to the World Health Organization, most cases have occurred in rural households, where small flocks of poultry are kept.

The World Bank conference report says the international community needs to raise an additional $1.5 billion to control the virus. Some of this money would go to a compensation system for farmers.

Thiermann of the World Organization for Animal Health says that a similar compensation system for livestock farmers in Thailand and Vietnam contributed toward those countries' success in controlling the spread of avian flu.

Thiermann's focus goes beyond the conference, to long-term structural change.

"Tomorrow, we are going to be fighting another emerging disease. We cannot target just avian flu. We need to strengthen each country's infrastructure. Otherwise, not only those countries, but the rest of the world is going to be at risk for these new emerging diseases."

According to the World Health Organization, since the discovery of the virus in a human in 1997, there have been close to 250 laboratory confirmed human cases of avian flu, leading to more than 150 deaths. Health experts have been monitoring the H5N1 strain for almost eight years, aware that there is a chance the virus can cross over to humans and spread rapidly.

New Research Predicts U.S. Entry of H5N1 Avian Influenza

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December 05, 2006 08:00 AM Eastern Time
New Research Predicts U.S. Entry of H5N1 Avian Influenza

Scientists Uncover Disease Pathways and Causes

NEW YORK--(BUSINESS WIRE)--Scientists at the Consortium for Conservation Medicine (CCM), Royal Society for the Protection of Birds, and Smithsonian Institution’s National Zoo report H5N1 avian influenza is most likely to be introduced to countries in the Western Hemisphere through infected poultry trade.

Following initial outbreaks of H5N1 avian influenza in Hong Kong, scientists and government officials worldwide have debated exactly how the virus was being spread and what could be done to stop it.

Dr. Marm Kilpatrick, senior research scientist with CCM, led the team in their efforts to predict the most likely method of introduction to the U.S. Dr. Kilpatrick and colleagues predict that bird flu will most likely be introduced to countries in the Western Hemisphere through infected poultry trade rather than from migrating birds from eastern Siberia, as previously thought. The subsequent movement of infected migrating birds from countries south of the U.S. would be a likely pathway for H5N1 avian influenza to reach the USA.

Avian influenza has reached more than 50 countries, and millions of chickens have been either infected and/or culled to prevent its spread to other poultry farms. Estimated financial losses are in the tens of billions of dollars. In addition, 258 people have been infected and 153 human deaths have occurred, with most cases in Vietnam, Indonesia, Thailand, and China.

This new research set out to identify the pathways for individual H5N1 introductions as the virus spread through Asia, Europe and Africa. The predictive modeling approach used offers substantial promise for understanding past introductions, the pathway for new introductions, and ways to prevent future spread of the deadly virus.

The researchers analyzed the risk of introduction by three different pathways: poultry, wild bird trade, and movement of migratory birds. “To determine the pathway of introduction we gathered global data on country-to-country trade in poultry and wild birds and mapped out the migratory routes of every species of duck, goose, or swan. We then compared our analyses based on these data to the relationships between virus isolates from the different countries,” said Kilpatrick. Dr. Robert Fleischer, a Smithsonian Institution scientist noted, “The rate of genetic change of the virus is extremely fast, which means we can use genetic analysis to trace the geographic and evolutionary pathways the virus has taken.”

The findings showed that migratory bird movements were likely responsible for three introductions in Asia, 20 in Europe, and three in Africa. Dr. David Gibbons, Head of Conservation Science with UK's Royal Society for the Protection of Birds said, “Much of the spread of H5N1 around Europe followed an unusually cold period of weather in central and eastern Europe in January and February 2006, with wild birds moving west through Europe in search of more clement conditions, some carrying H5N1 with them. As part of the UK Government's AI surveillance strategy, RSPB staff will be looking for sick or dead ducks, geese and swans this winter.”

Peter Marra, an avian ecologist with the Smithsonian’s Migratory Bird Center at the National Zoo commented, “In almost all cases in which we have detected H5N1 in wild birds, it has been found in dead birds. It’s critical that dead bird surveillance mechanisms be developed for early detection of H5N1 and other diseases.” In comparison, poultry trade was responsible for two introductions to countries in Africa and nine important introductions in Asia where the disease is still infecting humans and poultry. “The synergistic combination of poultry trade and migratory bird movements spread H5N1 much further than it would have gone by either of these pathways alone,” said Dr. Kilpatrick.

Dr. Peter Daszak, Executive Director of CCM stated, “This study shows how trade between continents opens the door for pathogens to move effortlessly along those routes.” Daszak added, “The study of Conservation Medicine strives to understand how human activities drive disease spread and proposes critical action steps on preventing future pandemics.” Donald Burke, Dean of the University of Pittsburgh Graduate School of Public Health, and an advisor to the group said, “This report shows how we can move beyond the conventional surveillance and response mode to one of prediction and prevention.” Dr. Mary Pearl, President of Wildlife Trust and co-founder of CCM noted, “Fully three-quarters of new diseases have an animal origin. By researching the links among wildlife, livestock, and humans, we can preempt the movement of many new disease-causing agents to people.” Dr. Leslie A. Dierauf, Director of USGS National Wildlife Health Center, a Federal laboratory that conducts influenza surveillance, commented, “This research is integral to our preparedness for the anticipated arrival of HPAI in North America.”

About The Consortium for Conservation Medicine

The Consortium for Conservation Medicine is a coalition of six scientific organizations that enables scientists from multiple disciplines to collaborate on key issues of human, animal, and environmental health and conservation. The CCM is a think-tank for the origin, prediction, and prevention of emerging diseases. www.conservationmedicine.org
Contacts

For The Consortium for Conservation Medicine
Anthony Ramos, 212-380-4469
ramos@wildlifetrust.org