Everyone who spends time in the woods (or the garden, park or anywhere else) would do well to check the CDCs website on
Lyme Disease and check out the link to 'other tick borne diseases' as well. Ticks aren't the only problems either.
Lyme disease is caused by a specific bacteria that can be carried by blacklegged ticks. These ticks are in their highest concentrations where the most cases are reported, but can be found in nearly all of the US. The rest of the country has other types of ticks that carry different bacteria that cause a bunch of other nasty problems.
Not every tick carries the bacteria and not every bite results in an infection. Though Lyme Disease is caused by a specific type of bateria, there are a number of different strains, each with it's own little quirks (same with E.coli outbreaks too... ever wonder how the CDC tracks down where the E.coli originated from? Each strain is slightly different genetically).
The damn bloodsuckers can carry a bunch of other little 'bugs' that can cause serious problems and present many of the same symptoms as Lyme Disease.
A blood test is only reliable in the later stages of an infection, and by then your chances of comlications goes up.
As Rob unfortunately has found out, some people have problems for years after the bacterial infection has cleared up. The exact cause is unknown, but the chances of it happening go up dramatically the longer you have the infection! Antibiotics are the best way to get rid of a bacterial infection quickly. Your body can do it alone - and does on a daily basis - but when something comes along that really challenges it (and this bug does) your immune system starts to act a little funny. There's credible data that suggests the lingering effects are autoimmune in nature.
When your body has a bad infection (like the late stages of Lyme disease) your immune system is really cranking, trying to find some antigen it can make antibodies against so it can fight the infection. Unfortunately, when your immune system is stressed that bad, it starts making mistakes, and can start making antibodies against things that aren't a problem, or worst case, part of your own body.
After that response has died down - either on it's own, using steriods or natural remedies (some of which resemble steriods) - the cells that caused the problem don't go away. They are there waiting to see something they recognize so they can start the process all over again. Allergies work the same way (this is also the basis for how vaccines work). These cells can stick around for years or even a lifetime.