Animalnet July 8/04 -- II
H5N1 evolved
into a highly pathogenic virus through continued circulation and gene swapping
with other viruses in East Asia
Water-treatment
residues curb phosphorus runoff
Swine manure
fertilizer contributes to reduced soil crusting
Zootechnics
- legislation
how to subscribe
H5N1
evolved into a highly pathogenic virus through continued circulation and gene
swapping with other viruses in East Asia
July 8, 2004
From a press release
MEMPHIS, Tenn. -- An avian influenza virus that has caused three major outbreaks
among poultry and killed several people in East Asia over the past seven years
arose through a series of genetic reassortment events with other viruses. This
study finding, by scientists from St. Jude Children's Research Hospital, the
People's Republic of China, China's Special Administrative Region of Hong Kong,
Thailand, Vietnam and Indonesia, is published in the July 8 online edition of
Nature.
Reassortment is the swapping of genes when two or more viruses infect the same
animal.
The researchers say that their study of the genetic makeup of H5N1 subtypes
collected since 1997 traces the evolution of the virus into a dangerous pathogen
through a series of reassortment events. Results of the study indicate that
domestic ducks in southern China played a key role in the generation of this
virus. The H5N1 virus forced health authorities to slaughter millions of
chickens in order to prevent the spread of the disease, which can quickly wipe
out poultry in open-air markets and farms and spread to other flocks.
The investigators warn that outbreaks of H5N1 in East Asian poultry populations
must be rapidly and effectively controlled to prevent H5N1 from evolving into a
virus that causes a human pandemic, or worldwide epidemic. By cleaning up
open-air markets and regularly slaughtering infected birds, Hong Kong remained
free of H5N1 outbreaks in poultry during the 2004 influenza crisis, according to
Robert Webster, Ph.D., member of Infectious Diseases department and holder of
the Rose Marie Thomas Chair at St. Jude, and Richard Webby, Ph.D., also of the
department of Infectious Diseases at St. Jude.
"In order to reduce the ability of H5N1 to trigger another poultry
epidemic, officials in East Asia must follow Hong Kong's lead," Webster
said. "Otherwise, H5N1 will likely continue to infect birds and other
animals and eventually could evolve into a dangerous human pathogen as
well."
Webster and Webby are co-authors of the Nature report, which details genetic
studies of the evolving H5N1 virus that caused the initial human outbreak in
Hong Kong in 1997. The report traces the origins of the outbreaks of highly
pathogenic H5N1 disease in Asian poultry that occurred in 2003 and 2004.
The researchers collected samples of the virus from poultry in Indonesia,
Thailand and Vietnam, and from humans in Thailand and Vietnam. They then
compared the eight genes carried by these viruses with the eight genes carried
by samples of 253 H5N1 viruses collected from live poultry markets in Hong Kong
and the Chinese provinces of Guangdong, Hunan and Yunnan between 2000 and 2004.
The study found that H5N1 viruses occurred only in ducks during 2000, but from
2001 on, the viruses spread to chickens, too. Furthermore, the various H5N1
viruses isolated over the years all contained two genes (HA and NA) derived from
the same, older virus called Goose/Guangdong/1/96. The other six genes came from
various influenza viruses through reassortment. HA and NA are two proteins on
the surface of flu viruses that permit the virus to infect cells and to spread
from animal to animal or from person to person.
The study also showed that a specific type of H5N1 called the Z genotype,
although widely entrenched in poultry in southern China, is still adapting to
these birds, suggesting that these viruses will continue to evolve through
mutation or reassortment to achieve greater fitness in poultry species.
In addition, the researchers found that genotype Z viruses in Thailand, Vietnam
and Indonesia carried a specific mutation in a protein called M2, known to cause
resistance to a family of antiviral drugs used to treat human influenza. The
mutation also developed in some genotype B, Y and Z+ viruses.
The fact that the M2 resistance mutation is arising in different viruses
suggests that it can be readily acquired, according to the researchers. If this
gene were passed on to a human flu virus during reassortment in an animal
infected with both avian and human influenza viruses, the resulting virus would
be resistant to an important family of drugs.
In fact, the common human influenza H3N2 has been found inside pigs in southern
China, according to the St. Jude researchers. If H5N1 infects a pig harboring
H3N2, these two viruses might swap genes. The resulting "recombinant"
virus might be particularly dangerous to humans, depending on which gene or
genes it acquired.
The report in Nature also notes other indications that H5N1 could evolve into a
worldwide threat to humans: the outbreak of H5N1 in poultry in Asia in 2003 and
2004 was unprecedented in its geographical range, which showed the wide reach
this virus already has.
"The transmission of H5N1 to even just a relatively few people was an
ominous sign that it has the potential to adapt to humans," Webster said.
A key question left unanswered by the present study is whether the highly
pathogenic H5N1 influenza virus is now being spread by wild migratory birds.
"Although these deadly viruses were isolated from dead migrating birds, we
don't know if the birds are actually spreading H5N1," Webby said. "We
must do further research to find out, since migratory birds could conceivably
spread highly pathogenic H5N1 throughout the rest of Asia and into Europe and
the Americas."
The key to preventing a human pandemic of H5N1 is the rapid and effective
control of poultry infections, the St. Jude researchers say. And while this is a
challenging task, the recent success of Hong Kong in avoiding H5N1 poultry
outbreaks due to preventive measures taken demonstrates the wisdom of this
approach.
The culling of hundreds of millions of poultry across East Asia reduced the
threat of transmission of bird flu to humans, and possibly even prevented the
outbreak of a human pandemic, the St. Jude researchers said. But that public
health victory came at a significant cost to poultry farms. The question
remaining is whether such farmers and their governments should bear this
financial burden by themselves.
"If we consider H5N1 to be a global problem that could get much worse,
perhaps the costs should be borne instead by the World Health Organization's
global influenza program," Webster said. "The results of this study
are a wake-up call for the world to provide the resources needed to prevent
future outbreaks of H5N1 among poultry or to prepare for a human pandemic of a
very dangerous virus."
This work was supported in part by the National Institutes of Health, The
Wellcome Trust, the Ellison Foundation, the Li Ka Shing Foundation and the
Research Grants Council of Hong Kong.
Other authors of the report are K. S. Li (Shantou University Medical College;
Guangdon, P.R. China); Y. Guan, J. Wang, K. M. Xu, L. Duan, H. Chen, J.S. M.
Peiris (Shantou University and The University of Hong Kong, Queen Mary Hospital;
Hong Kong SAR P.R. China); G. J.D. Smith, L.L. M. Poon, K.Y. Yuen (The
University of Hong Kong, Queen Mary Hospital; Hong Kong SAR, P.R. China); A. P.
Rahaedjo, A.T. S. Estoepangeste (Universitas Airlangga; Surabaya, Indonesia); P.
Puthavathana, P. Auewarakul (Sriraj Hospital; Bangkok, Thailand); C. Buranathai
and A. Chaisingh (National Institute of Animal Health; Bangkok, Thailand); H.T.
Long and N.T. H. Hanh (National Institute of Hygiene and Epidemiology; Hanoi,
Vietnam); and W. Lim (Department of Health, Hong Kong SAR, P.R. China).
St. Jude Children's Research Hospital
St. Jude Children's Research Hospital is internationally recognized for its
pioneering work in finding cures and saving children with cancer and other
catastrophic diseases. Founded by late entertainer Danny Thomas and based in
Memphis, Tennessee, St. Jude freely shares its discoveries with scientific and
medical communities around the world. No family ever pays for treatments not
covered by insurance, and families without insurance are never asked to pay. St.
Jude is financially supported by ALSAC, its fundraising organization. For more
information, please visit http://www.stjude.org .
SOURCE St. Jude Children's Research Hospital
Water-treatment
residues curb phosphorus runoff
July 8, 2004
ARS News Service
Agricultural Research Service, USDA
Residue from water-treatment plants, often discarded as waste into landfills,
may make good soil treatments for preventing phosphorus runoff from farms.
Agricultural Research Service soil scientist Jeffrey M. Novak at the agency's
Coastal Plains Soil, Water and Plant Research Center in Florence, S.C., is
studying an alum-based water-treatment residual that increases soil's capacity
to bond phosphorus, a vital plant nutrient.
The studies, done in collaboration with Ray Bryant, research leader at the ARS
Pasture Systems and Watershed Management Research Unit in University Park, Pa.,
may benefit states along the nation's mid- to-southern-Atlantic seaboard, where
sandy soils generally take up and hold less phosphorus than finer-textured
soils.
Increased bonding, or adsorption, of phosphorus would curb runoff of this
nutrient that can lower the oxygen content of water bodies and spoil the taste
of drinking water. Phosphorus in manure makes agricultural facilities, such as
large livestock production operations, potential sources of runoff pollution.
According to Novak, chemically binding phosphorus into water-insoluble
complexes using residuals containing iron oxide, aluminum oxide and hydroxide
may become an important management practice. The alum-based water-treatment
residual this research focuses on has a high phosphorus-binding capacity.
A separate study, conducted on wheat by agronomist Eton Codling at the ARS
Animal Manure and Byproducts Laboratory in Beltsville, Md., found that the
treatment has no negative effect on plants' absorption of phosphorus once plant
roots grow beyond the 6-inch-deep layer the treatment creates in soil.
In lab tests with sandy soil, the treatment increased phosphorus-binding
potential four- to fivefold over that of untreated soil. The lab studies will be
repeated, and additional research will be done in the field during the next two
years. If successful, this use for waste from water-treatment processing not
only could get rid of the waste, but would also hold phosphorus on the land
until a crop uses it.
Read more about this research in the June issue of Agricultural Research
magazine, available online at:
http://www.ars.usda.gov/is/AR/archive/jul04/water0704.htm
ARS is the U.S. Department of Agriculture's chief scientific research agency.
Swine
manure fertilizer contributes to reduced soil crusting
July 8, 2004
Farmscape (Episode 1554)
Research conducted by the University of Saskatchewan shows the use of swine
manure fertilizer can actually help reduce the risk of soil crusting. A graduate
student study, conducted as part of the University of Saskatchewan's long term
research into the use of swine manure, looked at the effect of repeated
applications on surface soil crusting and its potential impact on crop
germination and emergence. The project compared barley, flax and canola
fertilized with swine manure to crops grown using commercial fertilizer and
unfertilized crops. Senior Researcher Dr. Jeff Schoenau says manure application
had no significant impact on crusting.
Clip-Dr. Jeff Schoenau-University of Saskatchewan
With swine manure, although it can have a positive impact on organic matter
content of the soil which would improve structure, the swine manure contains
salts particularly sodium salts which may cause dispersion and deterioration of
structure. What we wanted was to determine overall, "what's the net impact
of these counterbalancing influences?" I think what we found in this study,
to sum it up, is that the repeated application of manure for five to seven years
hasn't had any appreciable negative or positive impact on the crusting of the
soil compared to our control and our commercial fertilizer comparisons. I think,
out in the field, we were seeing a real impact there of the increased residue
cover that we get from improved crop growth on the manure treated soils
resulting in higher soil moisture content in the early spring which reduced the
issue of crusting compared to what we saw on our controls with very little
residue. Out in the field under those conditions I think we saw the manure have
a positive impact.
Dr. Schoenau says, while the manure itself had no direct effect on crusting, it
provided an indirect benefit by stimulating crop growth and increasing the
amount of crop residue left on the surface. For Farmscape.Ca, I'm Bruce Cochrane.
*Farmscape is a presentation of Sask Pork and Manitoba Pork Council
Zootechnics
- legislation
July 7, 2004
European Commission- Health and Consumer Protection
The complete document of the following can be viewed from:
http://europa.eu.int/comm/food/animal/zootechnics/legislation_en.htm
Performance testing and genetic evaluation - Commission Decision 90/256/EEC
updated
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