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Avian flu, H5N1, identified in wild Mongolian birds

Avian flu, H5N1, identified in wild Mongolian birds

Avian flu, H5N1, identified in wild Mongolian birds
August 18, 2005

Background from
H5N1 is a highly pathogenic strain of avian influenza, also known as bird flu. It was first isolated in terns in South Africa in 1961. The first known appearance of this type of flu in humans was in Hong Kong during 1997. The name refers to the subtypes of surface antigens present on the virus, Hemagglutinin type 5, and Neuraminidase type 1.

As of July 21, 2005, one hundred and nine cases of human infection have been confirmed resulting in fifty five deaths outside of China. Thirteen countries across Asia and Europe have been affected. Additionally more than one hundred and twenty million birds have died from infection or been culled.

Usually these flu viruses are carried worldwide by wild bird populations in their intestines and are non-lethal. However this variant has mutated into the most lethal strain of influenza ever recorded. Such occurrences are natural and have happened in the past, as in the 1918 Spanish influenza pandemic.

Wildlife Conservation Society Release – August 18, 2005

NEW YORK, NY (August 18, 2005)–The United States Department of Agriculture (USDA) has positively identified the pathogenic form of avian flu–H5N1–in samples taken from birds last week in Mongolia by field veterinarians from the Wildlife Conservation Society (WCS). It is the first instance of this viral strain occurring in wild migratory birds with no apparent contact to domestic poultry or waterfowl.

Present in Mongolia for a health survey of wild bird populations in the south and north of the country, WCS field vets Drs. William Karesh and Martin Gilbert responded to initial reports of the most recent avian influenza outbreak in Kovsgol Province near the Russian border from the Mongolian Ministry of Food and Agriculture, which conducted preliminary testing of birds that died at Erkhel Lake. Their finding coincided with confirmations of cases of avian influenza in Russia and Kazakhstan. Karesh and Gilbert immediately traveled to the site with a team of Mongolian virologists, veterinarians, and public health officials. Approximately 100 dead birds were found at the site.

The team–including personnel from WCS, the Mongolian National Academy of Sciences, the Mongolian Institute of Veterinary Medicine, the State Central Veterinary Laboratory, Ministry of Food and Agriculture Veterinary Department, and the Ministry of Health Mongolian Center of Communicable Diseases with Natural Foci–collected samples from hundreds of wild birds, both live and dead including, ruddy shelduck, herring gull, black-headed gull, bar-headed goose, whooper swan, and Eurasian wigeon that are all at risk for contracting the virus.

Recent reports of influenza outbreaks in wild birds in China and Russia have failed to put die-offs in perspective with the numbers of unaffected birds, thus there was no way to assess the impact. The WCS team at Erkhel Lake in Mongolia collected this information for the first time. Overall, over 6,500 apparently healthy birds of 55 species were observed on the lake. The percentage of sick or dead birds was miniscule according to Gilbert following the survey, suggesting that either the virus had little effect on the birds or that very few were actually infected by the bug. Early results suggest that it may be the latter.

Supported by the U.N.’s Food and Agriculture Organization (F.A.O.), the team has sent the samples (774 in total) to the U.S.D.A.’s Poultry Research Laboratory in Athens, Georgia, for further testing to determine whether this virus is the H5N1 strain that has killed over 50 people in Southeast Asia and more than 5,000 wild birds in western China. As of today, preliminary tests from one dead whooper swan collected in Mongolia have shown the presence of the H5N1 strain of Avian Influenza using RT-PCR, while results from 30 live whooper swans living at the same site and also a nearby lake were negative for the virus. Samples collected from other live birds at the two sites, including sixty ruddy shelducks, twenty-four bar-headed geese, and twenty-five black-headed gulls, were found to be negative for the virus.

Whereas prior outbreaks in wild birds have happened either in close proximity to infected domestic poultry and waterfowl, or in regions where such contact could not be excluded, Mongolia’s paucity of domestic poultry suggests a new vector of avian flu. Finding the H5N1 strain during this expedition suggests that while the highly pathogenic avian influenza can be carried across long distances, the waterfowl species typically identified in recent outbreaks appear to be victims rather than effective carriers of the disease.

The multidisciplinary, collaborative response to this latest outbreak reflects the WCS One World-One Health approach to making informed, multidisciplinary decisions on global health crises that intersect human, wildlife, and livestock health. WCS experts are warning that to contain this potential epidemic, prevention activities must include better management practices in farms, especially those that are small and open-air, where domestic poultry and waterfowl are allowed to intermingle with wild birds. Officials would also need to monitor wildlife markets, where wild and domesticated species are kept in close proximity, and risk exposure to a wide range of pathogens.

Wildlife and health experts, including the F.A.O., maintain that indiscriminate culling of wild migratory bird populations would be ineffective in preventing the spread of avian flu. “Focusing our limited resources on the hubs and activities where humans, livestock, and wildlife come into close contact,” says Dr. William Karesh, Director of WCS’s Field Veterinary Program, who lead the WCS team in Mongolia, is “the best hope for successfully preventing the spread of avian flu and protecting both people and animals.”

This is a WCS release.

Group questions whether wild birds carry much flu By Maggie Fox, Health and Science Correspondent
Thu Aug 18, 6:38 PM ET

WASHINGTON (Reuters) – An outbreak of avian flu in Mongolia seems to have died out quickly on its own, wildlife experts said on Thursday, raising questions about how easily migrating birds will spread the virus.

They said only about 100 birds seemed to have succumbed to the virus in an outbreak at Erkhel Lake, near where the borders of Russia, China, Kazakhstan and Mongolia meet.

At least some of the birds that died carried an H5 avian influenza virus, said Wildlife Conservation Society veterinarian William Karesh.

But he cautioned that it has not been confirmed as the frightening H5N1 virus that is affecting flocks in China, Japan, Vietnam, Thailand, Russia and perhaps also Kazakhstan.

“We found it was H5 influenza,” Karesh told Reuters in a telephone interview.

But only about 100 of the 6,500 birds on the lake, representing 55 different species, had died, he added.

“So we are talking about a tiny percentage of mortality,” he said.

Avian influenza has decimated flocks of chickens in an outbreak that started in 2003, and has killed about 50 people. Experts fear it will eventually acquire the ability to spread easily from person to person and cause a global pandemic of exceptionally deadly influenza.

No one is sure how it is spreading, but migrating birds are a prime suspect. Officials fear migrating birds could export the virus to Western Europe, Africa and the Middle East over coming months.

In Russia it has spread across Siberia to the Ural mountains, the geographic divide between Asia and Europe.

Karesh led a team to Mongolia because of its position on the borders of countries involved.

While there, they heard birds were dying at a small lake called Lake Erkhel so they went there.


“Sure enough, birds were dying,” Karesh said. They sampled some of the dead swans, geese and gulls, and also collected samples from healthy birds.

“In this situation it had a very low impact,” Karesh said.

“It makes the disease self-limiting in wild birds.”

Karesh said he will wait for full results of tests being done by U.S. Department of Agriculture labs in Georgia on the samples taken from healthy birds at the lake, as well as tests to confirm the dead birds carried H5N1 and not another H5 virus.

Experts say the key to spreading influenza would be healthy birds that are not sickened by the virus. If the virus kills an animal quickly, it is less likely to spread it.

“Currently, all evidence points to domestic ducks as the ones who can shed it and transmit it and not get sick,” Karesh said.

But the jury is out on wild birds as being major spreaders of the virus, Karesh said. “If we have lots of wild birds shedding it and they look healthy, that would be pretty good evidence that they are,” he said.

“The key to this is better security on poultry production,” he added. If farmer use fencing, roofing and clean water to separate ducks and chickens from wild birds, that will likely limit the spread of the disease, he said.

The Dutch Agriculture Ministry has done that, saying on Tuesday it would make farmers keep all poultry indoors to prevent contact with migrating birds. German officials are considering similar measures.

But on Thursday Russian media reported that some Russian regions have opened the hunting season early for wild birds to try to limit the spread.

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