Victor Espinoza will ride Whitmore in the May 7 Kentucky Derby, Shagaf will have the comebacking Joel Rosario aboard, and Irad Ortiz Jr. moves to My Man Sam, the trainers of those runners said Wednesday.

Ortiz had ridden Whitmore to a third-place finish in the Arkansas Derby last Saturday. His main client is trainer Chad Brown, so he is sticking with that camp. Ron Moquett, the trainer and co-owner of Whitmore, said Espinoza had the mount.

Espinoza has won five of the last six Triple Crown races aboard California Chrome and American Pharoah.

The backside of Fonner Park in Grand Island, Neb., has been placed under a 21-day quarantine after three horses tested positive for the equine herpesvirus, the highly contagious disease that has affected operations at a handful of racetracks this year.

One of the horses who tested positive died Sunday night, while the other two have been isolated from the rest of the population on the Fonner Park backside, according to the Nebraska Dept. of Agriculture. Racing will be allowed to continue at Fonner while the quarantine is in place.

A horse trained by Ron Dandy at Parx Racing tested positive for the equineherpesvirus on Tuesday, which will extend the quarantine the track has been under since April 1.

Canterbury Park announced Tuesday plans to lower pari-mutuel takeout to North America’s lowest level for its 2016 race meet, which starts May 20.

According to Eric Halstrom, vice president of racing operations at Canterbury, the Shakopee, Minn., track’s blended takeout in 2016 will be 16.5 percent, while win-place-show wagers will have a takeout of just 15 percent, also the lowest rate in North America. The takeout on all exotic wagers will be 18 percent.

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Creator wins Arkansas Derby, targets Kentucky Derby

Ricardo Santana Jr., the leading rider at Oaklawn Park’s just-concluded meet, has asked the Arkansas Racing Commission for approval to serve a portion of a 21-day suspension during the remainder of this year rather than at the start of next year’s Oaklawn meet, according to his agent.

The scoreboard watching as to who’s in and who’s out for the Kentucky Derby on May 7 at Churchill Downs began in earnest on Monday and produced the first significant development when Cupid, who finished 10th as the favorite in the Arkansas Derby, was ruled out of the race by trainer Bob Baffert.

Baffert said Cupid emerged from the Arkansas Derby with an entrapped epiglottis and was to have surgery Monday at Rood and Riddle Equine Hospital in Lexington, Ky.

Fonner Park in Grand Island, Neb., has closed its backstretch as it awaits blood tests on horses who have displayed symptoms consistent with the equine herpesvirus, the highly contagious disease that has led to quarantines at racetracks across the U.S. this year.

Cupid, who finished 10th as the favorite in the Arkansas Derby on Saturday, is out of consideration for the Kentucky Derby after being found to have an entrapped epiglottis, for which he was to have surgery Monday at Rood and Riddle Equine Hospital in Lexington, Ky., trainer Bob Baffert said Monday.

Baffert said Cupid would go to Churchill Downs after the surgery and, assuming he recovers quickly, would be pointed to the Preakness on May 21 at Pimlico.

His defection moves Mo Tom into the top 20 on qualifying points. Fellowship becomes the bubble horse.

A fever will prevent the champion Songbird from starting in the $1 million Kentucky Oaks at Churchill Downs on May 6.

Songbird was diagnosed with a fever in the days after her win in the $400,345 Santa Anita Oaks on April 9. Her condition did not improve over the weekend, owner Rick Porter and trainer Jerry Hollendorfer said on Sunday evening.