Lyme disease is endemic across the Delaware Valley and Philadelphia. Acute Lyme is simple to recognize and treat with doxycycline when the erythema migrans rash is present or when there is clear early disseminated disease. Late and post-treatment Lyme is more complicated: serology has interpretation pitfalls, persistent symptoms after treatment occur in 5-20% of patients, and the differential includes other tick-borne infections (anaplasmosis, babesiosis, Powassan), and post-treatment Lyme disease syndrome. Fishtown Medicine evaluates Lyme thoughtfully and is honest about the limits of current testing and treatment.
Philadelphia and the Delaware Valley have been Lyme country for decades. The black-legged tick (Ixodes scapularis) that carries Lyme is established across most of the suburbs, throughout Bucks, Chester, Montgomery, and Delaware counties, into Camden and Burlington, and increasingly into the Wissahickon and other green spaces in the city itself.
This page is how Fishtown Medicine in Philadelphia approaches tick bites, acute Lyme, late Lyme, post-treatment syndromes, and the broader tick-borne picture.
Acute Lyme
The classic acute presentation is the erythema migrans (EM) rash: a spreading, often (but not always) bull's-eye rash at the site of a tick bite, appearing 3-30 days after the bite. The rash is typically larger than 5 cm, expands over days, and is usually painless and non-pruritic.
In the right epidemiologic context (Lyme-endemic area, recent tick exposure), the EM rash is diagnostic. Serology is not required. We treat empirically with doxycycline 100 mg twice daily for 10-14 days (longer for early disseminated disease). For pregnant patients, children under 8, or doxycycline allergy, amoxicillin or cefuroxime is used.
Other acute presentations include flu-like illness without rash, often with fever and arthralgias, in someone with recent tick exposure. Empirical treatment is appropriate when the picture fits even without EM rash.
For asymptomatic patients with a known tick bite that is identified as Ixodes scapularis and has been attached for over 36 hours, single-dose doxycycline 200 mg (200 mg in adults) within 72 hours of removal is prophylaxis with reasonable evidence.
Lyme testing and the interpretation pitfalls
Standard testing is two-tiered: an ELISA or immunoassay followed by a confirmatory Western blot if the first test is positive or equivocal.
Important interpretation points:
- Early Lyme (first 4-6 weeks) often tests negative because antibodies have not yet developed. Treat the EM rash without testing.
- Antibodies persist for years after successful treatment. A positive test years after a treated episode does not mean ongoing infection.
- False positives occur, particularly with EBV, certain autoimmune conditions, and other infections.
- The "alternative" Lyme tests (CD57, certain IgG band-only criteria, urine antigen tests) sold by some clinics have not been validated and frequently lead to overdiagnosis.
We use FDA-approved two-tiered testing and interpret results within the clinical picture.
Co-infections
Co-infection with other tick-borne pathogens occurs in a meaningful fraction of Philadelphia Lyme cases. The major ones:
- Anaplasmosis (Anaplasma phagocytophilum). Fever, headache, leukopenia. Treated with doxycycline.
- Babesiosis (Babesia microti). Hemolysis, fever, can be severe in immunocompromised patients. Treated with atovaquone plus azithromycin.
- Powassan virus. Rare but serious. Supportive care.
- Borrelia miyamotoi. Increasingly recognized. Treated similarly to Lyme.
- Alpha-gal syndrome. Tick-induced red meat allergy. See Alpha-Gal playbook.
For patients with severe acute Lyme or persistent symptoms, screening for co-infection is appropriate.
Late and chronic Lyme
Late Lyme disease (months after untreated infection) can present with arthritis (particularly large joints), neurologic symptoms (facial palsy, radiculopathy, encephalitis), or cardiac (carditis with heart block). These are typically responsive to longer courses of doxycycline or, for severe cases, IV ceftriaxone.
"Chronic Lyme disease" is a more contested term, often used for patients with persistent multi-system symptoms attributed to ongoing Borrelia infection. The mainstream medical position is that persistent Borrelia infection after appropriate treatment is rare; the alternative-medicine position is that it is common and requires prolonged antibiotic therapy.
Fishtown Medicine
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The evidence on long-course antibiotics for persistent symptoms is mixed and the major guidelines do not recommend extended antibiotic therapy beyond 4-8 weeks because the trials have not shown durable benefit and the risks (line infections, C. diff, antibiotic resistance) are real.
We are honest about this: we treat acute and late Lyme with evidence-based regimens, we do not prescribe prolonged antibiotic courses for unvalidated indications, and we work hard to identify and treat alternative or contributing diagnoses in patients with persistent symptoms.
Post-treatment Lyme disease syndrome
A subset of patients (5-20% in studies) have persistent symptoms - fatigue, musculoskeletal pain, cognitive symptoms - after treatment for acute Lyme. The mechanisms are debated and probably multiple: immune dysregulation, autonomic dysfunction, central sensitization, co-infection, comorbid conditions.
We manage these patients with the same thoughtful approach we use for long COVID and other post-infectious syndromes: structured workup, treatment of treatable comorbidities (sleep, thyroid, iron, mood, autonomic), and supportive care. We do not prescribe prolonged IV antibiotics for unvalidated indications.
How Lyme care works at Fishtown Medicine
For acute tick bites and possible EM rash, we offer same-day evaluation and treatment. For evaluation of chronic symptoms attributed to Lyme, the first visit is 90 minutes; we build the history, decide on the workup, and have an honest conversation about what evidence-based treatment looks like.
We coordinate with infectious disease at Penn, Jefferson, Temple, Main Line Health, or other Philadelphia programs for complex or treatment-refractory cases.
What it costs
Membership at Fishtown Medicine covers all visits and ongoing management; see pricing for current rates. All visits and ongoing management are included. Antibiotics and labs are billed separately at the cheapest of insurance or cash. Doxycycline is inexpensive at most Philadelphia pharmacies.
Key Takeaways
- Lyme is endemic across the Philadelphia region and the Delaware Valley.
- Acute Lyme with EM rash is diagnostic and responsive to doxycycline.
- Lyme testing has interpretation pitfalls; FDA-approved two-tiered testing is the standard.
- "Chronic Lyme" is contested; persistent post-treatment symptoms are real and managed with supportive care.
- Fishtown Medicine treats Lyme with honesty within the evidence base.
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