An interesting report found that the blood of the Western fence lizard contains a chemical that destroys B. burgdorferi, the Lyme disease spirochete. The presence of this lizard may help explain the low incidence of Lyme disease in the West. The Lyme disease organism is also common in Europe, particularly the Netherlands, Switzerland, Croatia, and parts of Italy. Both forms have now been reported in Europe and HME has been reported in Africa. A Swedish study reported an almost equal prevalence of ehrlichiosis and Lyme disease in one population group.
Many experts believe ehrlichiosis is much more prevalent than official reports indicate.
For example, groups in Connecticut and New York reported an increase from about 50 cases of ehrlichiosis in 1995 to 163 cases two years later. Some studies indicate that it may have been around much longer than originally thought and have been underdiagnosed or mistakenly diagnosed as Lyme disease. In the northeastern and north central U.S., most cases of Lyme disease and HGE are reported from May through August, with Lyme disease peaking in July and HGE peaking in June and July. This same climate also creates the wet green environment that increases the risk. In the noncoastal western U.S., the diseases most often occur between January and May and on the West Coast between November and April.