July 7, 2004 Via Facsimile 858-646-8028 and Certified Mail Return Receipt Requested Quidel Corporation 10165 McKellar Court San Diego, CA 92121 Attention: Mark Paiz, Vice President

Exhibit 10.30

July 7, 2004

Via Facsimile 000-000-0000

and Certified Mail

Return Receipt Requested

Quidel Corporation

10165 XxXxxxxx Court

San Diego, CA 92121

Attention:  Xxxx Xxxx, Vice President

RE: Product Supply Agreement dated as of July 3, 1997 by and between Quidel Corporation (“Quidel”) and Heska Corporation (“Heska”) (the  “Supply Agreement”)

Dear Xx. Xxxx:

This letter will confirm the agreement of Heska and Quidel to amend Section 10.1 of the Supply Agreement by adding the following proviso at the end of such Section 10.1:

“provided, however, that Xxxxx may deliver written notice to Quidel on or before March 31, 2005, that it does not wish to renew this Agreement for any additional renewal term following expiration of the renewal term that expires in July 2005.”

Please confirm Quidel’s agreement that this letter constitutes an amendment to the Supply Agreement pursuant to Section 14.1 thereof.

Very truly yours,

  /s/  Xxxxx Xxxxxxxxxx Xxxxxx

Xxxxx Xxxxxxxxxx Xxxxxx, Ph.D.

Executive Vice President

Intellectual Property and Business Development

ACCEPTED AND AGREED:

QUIDEL CORPORATION

By:	/s/  Xxxx X. Xxxx
Its:	COO