Thanks to some genetically engineered cattle, researchers think they may have the tools to better understand how prions cause disease like bovine spongiform encephalopathy (BSE). And the research may eventually help understand brain-wasting diseases in humans.

According to the scientific journal, Nature Biotechnology, USDA-Agricultural Research Service scientists recently evaluated cattle that have been genetically modified so they do not produce prions. The researchers determined that there were no observable adverse effects on the animals' health.

These cattle can help in the exploration and improved understanding of how prions function and cause disease, especially with relation to BSE, says Edward B. Knipling, administrator of ARS. "In particular, cattle lacking the gene that produces prions can help scientists test the resistance to prion propagation, not only in the laboratory, but in live animals as well."

Prions are proteins that are naturally produced in animals. An abnormal form of a prion is believed to cause the devastating illnesses called transmissible spongiform encephalopathies (TSEs), the best known of which is BSE.    

ARS studied eight Holstein males that were developed by Hematech Inc., a pharmaceutical research company based in Sioux Falls, S.D. Veterinary medical officer Juergen Richt, of ARS’ National Animal Disease Center (NADC) in Ames, Iowa, led the evaluation of the prion-free cattle. The evaluation revealed no apparent developmental abnormalities in the prion-free cattle.

Richt says, "The cattle were monitored for growth and general health status from birth up to 19 months of age. Mean birth and daily gain were both within the normal range for Holsteins. General physical examinations, done at monthly intervals by licensed veterinarians, revealed no unusual health problems."

ARS, with assistance from researchers at Hematech and the University of Texas, evaluated the cattle using careful observation, post-mortem examination of two of the animals, and a technology that amplifies abnormal proteins to make them easier to detect. Further testing will take at least three years to complete.

The evaluation was reported in the online version of the scientific journal Nature Biotechnology. To access it, go to: