Big problem!
We never saw that salad served. BB would have told Mikkayla to dump the salad, otherwise why would he have pointed it out to her? It would have been irresponsible of BB not to have stopped her serving it.
That salad was the only thing that Ben could have eaten that night. BB would have provided a replacement meal for Ben at least.
By rights, Ben should have been told about the contamination of the salad. This is a major incident, and should not be covered up.
Mikkayla does not have proper control of the dog, and it remains a health hazard to the HMs, especially Ben.
Also shame on Tahan for not caring about the incident either.