Lyme Disease Prevalence: Connecticut vs. California and Texas
Connecticut has dramatically higher Lyme disease prevalence than both California and Texas, with Connecticut reporting the highest state incidence in the United States at 70 cases per 100,000 population in 1997, while both California and Texas are classified as low-incidence states with minimal case burden. 1
Geographic Distribution and Prevalence Data
Connecticut (High-Endemic State)
- Connecticut represents one of the highest-risk states in the nation, with approximately 90% of all U.S. Lyme disease cases concentrated in roughly 140 counties along the northeastern and mid-Atlantic seaboard, where Connecticut is centrally located 1
- The state reported the highest state-level incidence at 70 per 100,000 persons in 1997 1
- Connecticut is classified as a "high incidence" state (≥10 confirmed cases per 100,000 population annually) 2
- In highly endemic northeastern areas like Connecticut, 15-30% of Ixodes scapularis (blacklegged tick) nymphs carry Borrelia burgdorferi 1, 3
California (Low-Endemic State)
- California is classified as a low-incidence state with minimal Lyme disease burden 2
- The western blacklegged tick (Ixodes pacificus) transmits the disease in California, but only up to 14% of nymphs are infected with B. burgdorferi in endemic pockets—substantially lower than northeastern states 1
- California experiences geographically focal disease primarily in northwest coastal regions, not statewide distribution 4
Texas (Low-Endemic State)
- Texas reports extremely low Lyme disease prevalence, with only 582 confirmed cases reported between 2005-2014 (approximately 58 cases per year across the entire state) 5
- In southern states like Texas, the prevalence of infection in I. scapularis ticks is generally 0-3%—dramatically lower than the 15-30% seen in Connecticut 1
- Texas is classified as a low-incidence state with no significant endemic transmission 2
Key Epidemiologic Differences
Vector Ecology
- Connecticut benefits (or suffers) from optimal tick vector conditions: the explosive repopulation of white-tailed deer in the eastern United States has been directly linked to the spread of I. scapularis ticks and Lyme disease in this region 1
- The northeastern tick vector (I. scapularis) is far more efficient at disease transmission than the western vector (I. pacificus) found in California 1
- Southern states like Texas have tick populations with infection rates of 0-3%, making transmission events rare 1
Clinical Implications
- In Connecticut, clinicians should maintain high clinical suspicion for Lyme disease in patients with compatible symptoms and tick exposure, as the pre-test probability is substantially elevated 2
- In California and Texas, Lyme disease should be considered only in patients with clear exposure history to endemic areas (either local pockets in California or travel to northeastern states) 2
- A rash similar to erythema migrans but NOT caused by B. burgdorferi has been described in southern states like Texas, associated with Amblyomma americanum tick bites—this can lead to misdiagnosis 1
Common Pitfalls
Avoid assuming all tick bites carry equal Lyme disease risk—the geographic variation is profound, with Connecticut having 20-30 times higher risk than Texas based on available data 1, 5. Clinicians in low-incidence states should not reflexively test for or treat Lyme disease without appropriate exposure history, as this leads to overdiagnosis and unnecessary antibiotic use 1.