Mosquito larvae in dogs water bowl?

We found LOTS of mosquito larvae swimming around the dogs water dish when we got home today. Based on the internet it would have taken 2 - 4 days for them to hatch and get to the stage we found them so the dogs must have ingested some of the larvae while drinking their water the past couple of days. Vet says to watch the dogs to make sure the don't get sick. What could this do to my dogs?