You need to see the vet. Most things aren't safe for a puppy that young and can kill it (as can a bunch of fleas). However you do need to get rid of them because they can make the pup very ill and cause anemia and a bunch of problems. Maybe this is why mom abandoned the pup and you just need to safely get rid of the fleas to put this pup on the road to recovery or maybe not. The only person that can tell you is a veterinarian who has the chance to examine the pup and get the whole story and figure it out from there. Where is the mom?
Fleas are actually insects that live on dogs and suck their blood. Fleas can cause itching and hair loss. Treatment of fleas in dogs includes
- Use of oral anti allergy medicines or use of topical steroids
- Use of insecticides to control fleas
- Use of antibiotics if secondary infection is present