** Shares of animal health company Elanco ELAN.N rise 5% after the bell

** ELAN is set to join the S&P MidCap 400 index next week, replacing Sarepta Therapeutics SRPT.O

** SRPT will replace Brookline Bancorp BRKL.O in the S&P SmallCap 600

** ELAN up 48% YTD, as of Tuesday's close

(Reporting by Juby Babu in Mexico City)

((Juby.Babu@thomsonreuters.com;))