story to find out more.
Technician David Michael (left) and veterinary
medical officer Ron Wesley vaccinate a weaned pig with the help of recombinant
adenoviruses. Click the image for more information about it.
Getting Livestock Vaccines Past a Maternal Block
By Luis Pons
November 15, 2006
Use of a virus linked to the common
cold is among the novel approaches Agricultural Research Service (ARS) scientists in Iowa are using to bypass
maternal defenses that thwart vaccination of very young livestock.
Maternal antibodies are crucial to the offspring of animals such as cattle
and swine, which are born with no protective antibodies of their own. These
young get their immunity to disease from suckling colostrum, a protective
substance in their mother's milk, during the first 24 to 36 hours after birth.
But these maternal antibodies also fight off virus strains that are placed
in vaccines to initiate immunity against disease.
In one study, veterinary medical officers
Lager of the ARS National Animal Disease Center (NADC)
in Ames immunizedagainst swine flurecently born piglets that had
suckled maternal influenza-fighting antibodies. They did this by getting the
flu strain past the antibodies piggybacked aboard a genetically engineered
virus made with weakened adenoviruses.
The ability of adenoviruses to infect cells makes them good conduits for
carrying genetic material into animals. And since adenoviruses originate from
humansthey can cause respiratory ailments such as the common cold,
pneumonia and bronchitis in peoplelivestock have no maternal antibody
resistance to them.
This is a potentially major breakthrough that may close a window of
vulnerability during which the maternal antibodies' waning powers still repel
vaccines but leave young animals open to contracting diseases.
In another project, testing led by NADC virologists
Neill indicated that exposing suckling calves to bovine viral diarrhea
virus (BVDV) generates a T-cell, or immune, response that will repel that
virus. BVDV costs U.S. cattle producers millions of dollars in losses each year
and induces diseases affecting animal reproduction and nutrition, milk output
and digestive and respiratory function.
more about this research in the November/December 2006 issue of
Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's principal scientific research agency.