Issue 8, April 2001
About this Newsletter

Anaplasmosis to Viral Diarrhea--
A Look at ARS Vaccine Research

From the first whole-cell vaccine for hog cholera in 1886 through the first effective subunit vaccine-- for foot-and-mouth disease--created nearly a century later, USDA scientists have long been at the forefront of vaccine research and development. Today, Agricultural Research Service scientists at 12 locations are working on new or improved vaccines for all major U.S. agricultural animals.

Although it is nearly always more desirable to vaccinate and prevent diseases rather than treat existing ones, vaccine development produces unique challenges. Scientists must learn the identity and characteristics of the disease-causing agent (e.g. virus, bacterium), how the agent stimulates an immune response in the animal host, and how the agent avoids that response. The disease agent survives by overcoming the ongoing evolutionary development of the animal as it attempts to resist disease. Some of the larger viruses have even taken on genes from their host and modified them to help evade an animal’s immune response.

Researchers at ARS’ laboratory on Plum Island, for example, are working on two of the world’s most difficult vaccine challenges: African swine fever and foot-and-mouth disease.

The virus that causes African swine fever has both direct and tickborne life cycles. It has a large, complicated genetic structure with some genes similar to those that govern the host’s immune response. Foot-and-mouth virus has 7 serotypes with at least 62 subtypes, each requiring a specific vaccine. Similar to influenza viruses, foot-and-mouth evolves rapidly to develop new ways of getting around vaccine strategies.

Social and political factors also enter into vaccine development. In some cases, the disease may not be widespread enough to make vaccine development and production cost-effective. In others, a vaccine may make it difficult to determine whether an animal has naturally contracted the disease of concern or merely received vaccine. Diagnostic complications can have serious impacts on trade.

The key to overcoming these challenges is to gain increasingly detailed knowledge about disease agents and the animals they affect. During the last decade, researchers worldwide have shifted their focus to understanding and manipulating specific proteins rather than entire disease organisms.

At ARS' National Animal Disease Center, for example, scientists have been able to use biotechnology to remove virulence proteins from the bacterium, Pasteurella haemolytica, which is involved in causing shipping fever of calves. Injecting the modified P. haemolytica into cattle induces an immune response and prevents the disease.

At the Southeastern Poultry Research Laboratory, researchers have developed a vaccine using only the hemagglutinin protein from avian influenza virus rather than the whole virus. These recombinant vaccines provide excellent protection from avian influenza. These approaches will also allow development of diagnostics tests to differentiate between vaccinated and infected animals.

ARS is well-suited to conduct vaccine research. Long-term projects allow scientists to spend the years necessary to develop the best control strategies for each disease. And animal-care and housing facilities allow researchers to better understand animal immune systems by direct study.

Recent accomplishments include vaccines or significant research progress on vaccines for brucellosis, mastitis, and shipping fever in cattle; coccidiosis in chickens; and Streptococcus iniae in fish and the first licensed modified live fish vaccine against enteric septicemia of catfish.

Current research includes developing new or improved vaccines for the following:

• Livestock: anaplasmosis, brucellosis, bovine viral diarrhea, bovine leptospirosis, E. coli, foot- and-mouth disease, porcine reproductive and respiratory syndrome (PRRS), Salmonella, swine fever, and swine parasites.
  Contacts: Keith Murray, (515) 663-7200; Daniel Rock, (631) 323-2500
• Poultry: avian influenza, avian leukosis virus J, avian pneumovirus, coccidiosis, enteric viruses, fowl cholera, Marek’s disease, mycoplasmosis, Newscastle disease, Salmonella enteridis, and turkey coryza.
  Contact: David Swayne, (706) 546-3433
• Fish: Enterococcus and Streptococcus in striped bass, Flexibacter columnaris infections in tilapia and catfish, and parasitic diseases.
  Contact: Phillip Klesius, (334) 887-3741

For more information, contact the researchers listed above or ARS’ National Program Staff:

William Laegreid , (301) 504-5774

Caird Rexroad, Jr., (301) 504-7050

Research Briefs

An ARS-produced clone of a pure-bred jersey cow may offer genetic resistance to mastitis. The cow, named "Annie," has genetically engineered cells that secrete a protein called lysostaphin. In trials with transgenic mice, lysostaphin killed mastitis-causing bacteria in mammary glands and milk.
Kevin Wells
Robert Wall
(301) 504-8342

When fed to pigs and cows in low doses, sodium chlorate selectively killed Salmonella typhimurium and E. coli O157:H7, ARS researchers found.
David Nisbet
(979) 260-9368
Robin Anderson
(979) 260-9317

Oxbow lake fisheries can be improvedby cultural practices established by ARS scientists. Plankton growth, water quality and bass populations were all increased in two lakes where best management practices were applied.
Scott Knight
(662) 232-2935

A new CD-ROM on screwworm eradication, published by the National Agricultural Library, presents the story of the sterile insect technique and other technologies that made possible the pest's elimination from the United States, Mexico and much of Central America.
Susan Fugate
(301) 504-7593

Faster-growing catfish should result from a new catfish breeding line, released by ARS scientists.
William Wolters
Brian Bosworth
(662) 686-3596

Awards

These ARS researchers have been honored recently for their achievements:

ARS Scientist of the Year Awards:

Mohammad Koohmaraie , Meat Animal Research Center, for innovative research to enhance meat quality and safety.
Craig Shoemaker, Aquatic Animal Health Research Laboratory, for co-development of the first modified live vaccine licensed for fish in the United States.
Hong Li, Animal Disease Research Unit, for discovery of methods for detection and control of malignant catarrhal fever virus.

ARS Technology Transfer Awards:

Victor Raboy, Small Grains and Potato Germplasm Research Unit, Aberdeen, Idaho, for developing a technique that lowers the amount of phytate in grains, thereby improving the amount of phosphorus that pigs, poultry and fish can absorb from feed.
Thomas Jenkins and Charles Williams, Meat Animal Research Center, for developing an easy-to-use, science-based computer program that helps cattle producers make breeding, feeding and management decisions for their herds.
A team of eight researchers led by H. Duane Norman, Animal Improvement Programs Laboratory, for initiating a project that speeds up the rate of genetic improvement of milk yield in dairy cows.

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