A former exec with the American Humane Assn. has filed a wrongful termination lawsuit, claiming she was fired after urging the org to report the mistreatment of horses on the HBO drama “Luck.”

Barbara Casey filed suit against the AHA, HBO and Stewart Prods. in Los Angeles Superior Court on Monday, alleging that there was “ongoing, systematic and unlawful animal abuse and cruelty toward horses on the set of ‘Luck.’ ”

HBO had renewed “Luck” for a second season, but wound up cancelling the series shortly before the end of its first season, in March 2012, after three horses died during production.

Casey claims she was terminated by the AHA, the org tasked with monitoring safety and treatment of animals in film and TV productions, after 13 years in January 2012 because she pressed officials to take action over the alleged violations on the “Luck” set.

The suit maintains that the AHA bowed to “political and financial” pressure from “Luck” producers in order to meet the demands of the show’s production sked. The AHA also engaged in efforts to “conceal and cover-up” criminal violations on the set, according to the suit.

Casey’s suit alleges that horses were drugged in order to perform and that animal handlers “intentionally misidentified horses” to prevent AHA reps from tracking their medical histories, among other abuses.

The Washington, D.C.-based AHA said it could not comment on pending litigation. In a statement, HBO reiterated that the network “took every precaution to ensure that our horses were treated humanely and with the utmost care, exceeding every safeguard of all protocols and guidelines required of the production.” The statement added that questions about Casey’s employment “should be directed to the AHA.”

The non-profit AHA, funded largely by an annual grant from SAG-AFTRA, has been monitoring animal safety on film and TV sets since the early 1940s. The org recently called on the industry to convene a summit to discuss expanding its jurisdiction in the wake of the deaths of animals involved in the production of “Luck” as well as “The Hobbit” (Daily Variety, Dec. 13).

Casey’s suit seeks unspecified damages.