The 158 elk were known to have had contact with an infected herd.

One of the worst mistakes made was when an infected herd was released from quarantine because of insuffi-cient funds.

Pigs in an infected herd become immune to re-infection after a few weeks.

In spite of regular and frequent TB testing of cattle herds, the number of infected herds snowballed and continued to increase until 1994.

Mortality was high, nearing 100% in the infected herd.

"We do not want an animal from an infected herd in the state of Montana," for quarantine or other purposes, Mr. Petersen said.

The current proposal, still awaiting approval, is to create a 25-mile wide "dynamic corridor" across the park well north of the infected herds.

Public ignorance was preferable to the only expedient response, which was to slaughter all the infected herds, test the remaining cattle and publicize the known risks.

Protothecal mastitis is endemic worldwide, although most cases of infected herds have been reported in Germany, the United States, and Brazil.

In another scenario, incomplete depopulation of an infected herd could result in a dual infection during a subsequent outbreak.