Existing investors in Advanced Animal Diagnostics have poured another $15 million into the Durham-based company, according to an SEC filing.

The filing, made on Dec. 2, disclosed that AAD raised $14.78 million in exchange for equity in November.

Identities of the investors were not disclosed.

The company was founded in 2001 with a Small Business Innovation Research Grant from the USDA. The North Carolina Biotechnology Center awarded the company a $20,000 company inception loan in 2007, followed by a $100,000 Collaborative Funding Grant for research at North Carolina State University’s College of Veterinary Medicine in 2009.

Intersouth Partners, Novartis and other investors invested $6 million in AAD for launch of two products a year ago.

The 2013 money targeted commercialization of Qscout, an automated on-farm lab system and Qscout MLD, a test for mastitis in dairy cows, as well as development of other tests.

Intersouth, which is based in Durham, and Novartis also were part of a $11 million funding round in 2011.

In February of 2013, AAD said a field trial had demonstrated the effectiveness of its test for diagnosing mastitis in dairy cows, enabling treatment of only cows that were stricken rather than widespread use of antibiotics.

“Selective dry-cow therapy has been shown to have economic benefits, but it hasn’t been a practical option because currently available testing methods are either costly and time-consuming or they lack accuracy,” said Mitchell Hockett, director of technical research for AAD and the principal investigator of the study. “This study shows the MLD reliably diagnoses subclinical mastitis and effectively guides selective treatment decisions at dry-off.”

The Qscout automated reader enables multiple tests to be run on the same machine.

“I understand how frustrating and costly it is to wait for lab results,” said Dr. Ben Shelton , owner of Rocky Creek Dairy, Rocky Creek Veterinary Service and AAD board member, in the funding announcement. “Producers need fast diagnostic information on the farm that’s cost-effective enough to use widely, and that’s what this funding will help ensure.”