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USDA develops experimental shipping fever vaccine
KANSAS CITY (OsterDowJones)--The U.S. Department of Agriculture's Agricultural Research Service has developed an experimental vaccine that should be very effective in cattle against shipping fever, the leading cause of illness and death in U.S. feedlots, according to an ARS release.
The experimental vaccine was created by deleting a large piece of a specific gene from bacteria that cause shipping fever, the release said. When this gene segment is removed, the bacterium no longer causes pneumonia in cattle but does elicit immunity.
Veterinarian Robert Briggs and microbiologist Fred Tatum at the National Animal Disease Center in Ames, Iowa, created the live vaccine without foreign DNA.
The Biotechnology Research and Development Consortium of Peoria, Ill., funded part of the research and applied for several patents on the vaccine. The vaccine has not yet been approved by the USDA's Animal and Plant Health Inspection Service for use in the U.S.
Bovine respiratory disease costs cattle producers more than $1 billion annually. It's also called "shipping fever" because calves develop it about one week after being shipped to feedlots where they finish growing.
Shipping fever results from an interaction of stress, the animal's immune system and infectious pathogens. Bacteria invade the animal's lower respiratory system, causing pneumonia. The respiratory disease reduces the animal's weight gain, adversely affects feed efficiency, increases antibiotic costs, and decreases meat and hide quality, in addition to causing deaths.
In a 1999 study of the top 12 cattle-producing states, the USDA estimated that 97.6 percent of feedlots had at least one animal with shipping fever.
The new ARS-developed vaccine could be administered by a variety of routes, including standard injections or as a novel oral vaccine, the ARS said. The oral vaccine protects the animals within three to four days after being added to feed, instead of the seven- to 10-day wait required with injectable vaccines.
In a field trial with the new experimental vaccine, the mortality rate among vaccinated high-risk calves was 4 percent, compared with 16 percent among unvaccinated ones. The bacterium Mannheimia haemolytica, the leading source of shipping fever, was the culprit in all of the deaths of the unvaccinated animals, but killed none of the vaccinated ones.
During the first 28 days on feed, low-risk calves that received the oral vaccine had a 25 percent higher weight gain on average than untreated cattle.
Additional field trials have confirmed the weight-gain advantage during the first 35 days of feeding.
Date: 12/31/03
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