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A virus that causes intestinal disease and death in young pigs has been
found to survive longer than currently used decontamination schedules.
Transmissible gastroenteritis virus (TGEV) costs the U.S. pig industry
more than $100 million a year. Sows infected with TGEV pass the virus on
to their nursing piglets, causing intestinal disorders that can kill the
young pigs. Those that survive require longer to reach market weight.
Typically, pigs are removed from farrowing houses for four weeks while the
houses are decontaminated. Now ARS researchers suspect the virus may
survive longer than four weeks. In laboratory studies, they demonstrated
that some pigs infected with TGEV can shed the virus in their feces up to
18 months. This information is needed by farrowing house managers to
adopt new management practices to eliminate TGEV from farrowing houses.
Pigs with TGEV virus cannot be sold to export markets.
Virology Swine
Research, Ames, IA
Roger D. Woods, (515) 239-8358
A newly recognized bacteria that sickens swine may prove even more
costly to pork producers than its look-alike cousin, the bacterial culprit
behind swine dysentery. ARS researchers recently assisted an
Australian student in describing and naming the new bacterium,
Serpulina pilosicoli. This is the first time it's been
distinguished from S. hyodysenteria, which causes swine
dysentery and an estimated $100 million annually in losses to pork
producers. The new bacterium's name, officially accepted in January 1996,
means "little serpent of the hairy colon." The researchers have developed
diagnostic tests to distinguish the various Serpulina
bacteria known to cause intestinal diarrhea in pigs and humans.
Enteric Diseases and
Food Safety Research, Ames, IA
Thaddeus B. Stanton/Neil S. Jensen, (515) 239-8495
Contrary to conventional wisdom, cold pond water doesn't necessarily
have a chilling effect on a vaccinated fish's ability to retain immunity
against enteric septicemia of catfish (ESC). In field tests, catfish
received a live vaccine against Edwardsiella ictaluri,
the pond-dwelling bacterium that causes ESC. The fish then were grown in
water temperatures of either 66.2 degrees F or 78.8 degrees. The fish
were challenged monthly with exposure to E. ictaluri for four months. The
conclusion: Immunized fish in the colder water were no more likely to
become infected than their counterparts in warmer water. These findings
give catfish farmers a wider window of opportunity in which to vaccinate
their fish against ESC, a costly disease that can kill up to half of
catfish in infected ponds.
Fish Diseases and
Parasites Laboratory, Auburn, AL
Phillip H. Klesius, (334) 887-4526
A new system developed by ARS scientists cleans up fish farming
wastewater and gives greenhouse growers a more efficient and productive
way to produce cash crops from that wastewater. The wastewater is
loaded with nutrients like phosphorus, needed by plants for growth. In
troughs that carry wastewater, researchers placed young plants near the
beginning of the water flow where nutrients are highest, moving the plants
further down the trough as they matured. Young lettuce and basil plants
absorbed and stored more nutrients than they needed--a process called
luxury consumption--at the front end of the troughs. These surpluses
sustained them when they were moved toward the end where the water had
been cleaned of most of the nutrients. Luxury consumption allowed the
plants to be productive even in water that didn't contain enough nutrients
to produce a crop. As mature plants are moved into the cleaner water,
young, new plants take their place at the nutrient-rich end of the trough.
This system allows maximum productivity from expensive greenhouse space.
Also, after the nutrients have been removed from the wastewater by the
plants, the clean water can be used on other crops.
Appalachian Fruit Research
Station, Kearneysville, WV
Paul R. Adler, (304) 725-3451
A viral gene dubbed 23-NL could lead researchers closer to a vaccine
for African swine fever (ASF). Researchers have found that the gene
appears to be a key player in the worst ravages of this often deadly
disease of swine. When the 23-NL gene is removed from highly virulent ASF
strains, the virus can still infect but will no longer kill pigs. Also of
interest: The gene-deleted virus takes longer to make its appearance in
the pig. This suggests the gene is involved in the virus' ability to
reproduce itself in critical target cells, such as the animal's lymph
nodes and spleen. While the United States has never had an outbreak of
ASF, the virus has flared up in Europe, Central and South America and
Cuba, often resulting in the slaughter of all swine in the infected area.
The virus has found its way into many countries via the feeding of
ASF-infected meat products in garbage to pigs. Experiments have shown
viable ASF virus can survive in salted, dried meat products for as long as
10 months.
African Swine Fever Research, Plum Island, NY
Dan Rock, (516) 323-2500
A new diagnostic test uses proteins from the organism Neospora caninum
to reveal whether an animal is infected with this newly discovered, costly
parasite. N. caninum may be the culprit behind up to
half of all cattle abortions. Existing tests to unmask N.
caninum required growing the entire parasite in culture--a
time-consuming and costly procedure. The new test relies on antigens,
proteins produced by the parasite that cause an animal's immune system to
make antibodies. Purified antigens are mixed with blood from animals
thought to be infected. If the blood contains antibodies to N.
caninum--indicating infection--the purified antigens will bind to
the blood sample. Then, a second antibody is added that contains an
enzyme that changes color if the blood is infected. The purified antigens
are mass-produced in fast-growing E. coli bacteria and
the final diagnostic procedure can be automated to check dozens of samples
per minute. Researchers say the new test could be available commercially
within the next two to three years.
Immunology and Disease Resistance Laboratory, Beltsville, MD
Mark C. Jenkins, (301) 504-8054
A new test warns feed processors if poultry meal is contaminated with
gizzerosine, a chemical substance that can sicken poultry by eroding their
gizzards. The condition is known commonly as black vomit disease.
Gizzerosine forms during heat processing in making fish-meal, which is a
protein source for poultry. The new test detects trace amounts of
gizzerosine in fish meal. This is a more precise, less costly procedure
than the current method of testing on live chicks. The test also can
assist scientists in understanding how the toxin affects chickens by
following the metabolism of gizzerosine.
Growth Biology
Laboratory, Beltsville, MD
John McMurtry, (301) 504-8803
Last updated: October 22, 1996
Return to: Quarterly Report
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