The U.S. District Court for the Northern District of Mississippi has recently denied plaintiffs bid for class certification of a putative nationwide class of pet owners that had purchased Heartgard medication for their dogs – Haley v. Merial. Ltd.,Case No. 4:09-CV-0094-GHD. Plaintiffs’ contended that Merial engaged in false marketing of Heartgard in violation of RICO. Despite the fact that the FDA requires all manufacturers of heartworm preventives to demonstrate that their medications are 100% effective in eliminating the tissue larval stage of heartworm infections, plaintiffs claimed that previous product advertisements for Heartgard that promoted 100% efficacy were false and misleading. With respect to Rule 23(b)(3) assessment of plaintiffs’ monetary claims, the court held that “there are individualized issues present in this case that predominate over any common issues, making Rule 23(b)(3) class certification untenable.” The district court also rejected plaintiffs’ request for certification of an injunctive class under Rule 23(b)(2).