Anaplasmosis is a disease found mostly in the southern US. It is a bacterial disease; the bacteria are usually passed by ticks. It is also called Ehrlichiosis.
Piroplasmosis is a different and separate disease of horses, is also passed by ticks, but the ticks carry a parasite. I don't think it is common in the US - it's in S. America, Spain, other parts. I think the US is trying very hard to keep it out.
For anaplasmosis horses are treated with doxycycline, often the vaccine is given (once) with the antibiotics. Antibiotics are given daily, usually for a month. If I had to treat it 'again' I would be working very hard with a very good vet.
According to my vet, anaplasmosis was formerly thought of as ehrlichiosis, but they are not the same. As far as working with a vet, I do. "Again" means that indeed they can be reinfected with a new tick bite, as with Lyme disease. He is being treated with doxy,(as per vet instruction) as I always have it on hand due to the prevalence of lyme and anaplasmosis in this area. I can save a farm call visit and speak with my vet over the phone. His first infection was a year ago June(2009). This time it is milder. I was only looking for advice beyond probiotics (he's on them), garlic(he gets that too) and general supportive care. But thanks for the heads up on piroplasmos. I will discuss that with the vet at his next visit!