Merck (NYSE:MRK) announced Monday an agreement to acquire Elanco Animal Health’s (NYSE:ELAN) aqua business for $1.3B in cash, a move to expand the pharma giant’s animal health business. Once the deal is finalized in mid-2024, the Rahway, New Jersey-based drugmaker will get access to drugs, vaccines, supplements, and other products Elanco (ELAN) mar…