I saw a blurb about an article in the Emerging Infectious Diseases Journal that showcases how your pets can transmit diseases to you when you sleep with them next to you in your bed. Diseases mentioned include...
-Bubonic plague - yes, THE plague!
-Cat-scratch fever - apparently you can also get this from being licked by an infected cat, as opposed to being scratched.
-Chagas disease - I've heard of this, but had to look it up. Symptoms include fever, fatigue, body aches, headache, rash, loss of appetite, diarrhea, and vomiting - not good times.
The authors commented that it is rare to get these diseases by sleeping in the same bed as your pet, but it could be a problem for the very young and immuno-compromised people.
In addition to getting sick, sleeping in the same bed as your pet can contribute to insomnia. I recommend to my patients with insomnia to have your pet sleep outside your bedroom if fido or fluffy is disrupting your sleep by sharing your bed.