You can not catch it from your dog or from fleas, but you can catch it from deer ticks (Ixodes scapularis). Other ticks are non-carriers and are a lot bigger than deer ticks, who are are very small (about the size of a freckle). The one that got me was even smaller and a male. I did not get Lyme Di ease.
Good news, "Not all ticks are infected, and studies of infected deer ticks have shown that they begin transmitting Lyme disease an average of 36 to 48 hours after attachment.Therefore, your chances of contracting LD are greatly reduced if you remove a tick within the first 48 hours."
You should get educated about the tick and about Lyme disease.
The Iowa State's Deer Tick Home Page allows you to see what the tick looks like
You can learn about Lyme Disease in humans at the American Lyme Disease Foundation's web site:
http://www.aldf.com/
See also (for dog and human):
http://www.vetmed.wsu.edu/clientED/lyme.asp
http://www.2ndchance.info/lyme.htm
http://www.cs.cmu.edu/afs/cs.cmu.edu/user/jake/mosaic/lyme.html