A slight update.  DNA of a filarial helminth, a worm that causes symptoms of river blindess or elephantiasis in humans, has been found in ticks in the NE US.  This species inhabits rodents, groudhogs, squirrels and such.  It has been know in them since at least the 1930s. Some of the research specimens came from a Canadian groundhog back then.  It would be safe to say that they are likely in all the US.  Ticks that are carrying them are averaging around 30% of those tested.  The microfilaria are very tiny, .007"long x .0001"wide!  If you have a white ring around your iris, on your cornea, and your OD tries to tell you that it's harmless cholesterol, don't believe them!  I have this white ring, my dad had it too, and he's dead now! I have an area on the back of my neck, where I remember mom pulling the first ticks off me when I was around four years old that is getting better!  I remember the bell's palsy that caused when I was in my teens!  Oh, the species name!  Monanema martini.  In squirrels they make the pleural cavity their home, guess how many times I had my fingers in there during my younger days!  Recent research in Africa shows that the species causes onchocerciasis in humans, just like the better known wuchereria bancrofti and brugia malayi.  Biggest difference is that m. martini doesn't yet appear to be associated with wolbachia, an endosymbiotic bacteria that the big two do have.  M. martini is resistant to Ivermectin and Moxidectin.  In infections with b. malayi and w. bancrofti, killing the endosymbiot with antibiotics sterilizes and sometimes kills the worms.  Probably not so m. martini.