The word "titer" is a laboratory term that simply refers to amount or concentration of something in blood, such as antibodies against specific germs. A titer can be high or low, of no significance, indicative of exposure in the past to a germ, or evidence of active infection.
Toxoplasmosis is an infection caused by a single-celled parasite, Toxoplasma gondii, which you can pick up from eating contaminated raw or undercooked meat, especially pork, lamb, or venison or by touching your hands to your mouth after handling such meat. Most people know you can also get toxoplasmosis by cleaning kitty litter boxes – cats shed the organism in their feces. The fact that you have a "titer" to toxoplasmosis could mean that you once had the infection or that you have it now. The difference is in the numbers: a titer of 1:16 – 1:256 means that you probably once had an infection that your body has thrown off. However, a titer higher than 1:1,024 suggests an active toxoplasmosis infection. If so, it’s not surprising that you’re unaware of it.
According to the U.S. Centers for Disease Control and Prevention more that 60 million men, women, and children in the U.S. carry the Toxoplasma parasite, but because the immune system usually keeps the bug from causing illness, very few ever develop symptoms. Most healthy people recover from the infection without treatment.
Ringworm is a fungal infection that usually makes itself pretty obvious, but it is also possible to be a carrier without having obvious signs of the infection (typically a ring-shaped, red rash, with a wavy, worm-like border). If a site is identified, treatment with topical anti-fungal agents is usually effective.
You can get a tapeworm from eating raw or undercooked meat from infected animals, and can host this parasite and not know it. The antibodies that showed up in your lab tests will tell the tale. Treatment depends on the type of tapeworm and the site of the infection.
Andrew Weil, M.D.