| Sampling efforts by state | |||
| State | Total Samples | Earliest Collection Date | Last Collection Date |
| Idaho | 3050 | October 11, 1997 | January 30, 2005 |
| Maryland | 884 | February 4, 2005 | February 4, 2005 |
| Nebraska | 983 | September 16, 2003 | December 31, 2003 |
| Oregon | 3314 | October 1, 1959 | April 15, 2005 |
| Washington | 4065 | January 1, 2001 | March 23, 2005 |
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