HM18

HM18: Tick-borne illnesses


 

Presenter

Andrew J. Hale, MD
University of Vermont Medical Center, Burlington

Session summary

With rising temperatures from climate change, tick territory – and therefore tick-borne illnesses – are being seen with increasing frequency.

Dr. James Kim of Emory University, Atlanta

Dr. James S. Kim

Lyme disease manifests as early-localized, early-disseminated, and late disease. The diagnosis of Lyme can be challenging and the pretest probability is key (geographic distribution, time of year, consistent symptoms). Do not send serologies unless the pretest probability is high, since the sensitivity of the test is generally low.

Concerning early-localized disease, 20% of patients will not develop the classic “bullseye” erythema migrans rash. Only 25% of patients recall even getting a tick bite. Not everyone with a rash will have a classic appearance (prepare for heterogeneity).

Neurologic symptoms can appear early or late in Lyme disease (usually weeks to months, but sometimes in days). The manifestations can include lymphocytic meningitis (which can be hard to separate from viral meningitis), radiculopathies, and cranial nerve palsies.

Lyme carditis happens early in the disseminated phase with a variety of disease (palpitations, conduction abnormalities, pericarditis, myocarditis, left ventricular failure). For those who develop a high-grade atrioventricular block, a temporary pacer may be needed; a permanent pacemaker is unnecessary because patients often do well with a course of antibiotics.

Late Lyme develops months to years after infection. It often presents as arthritis of the knee, although other large joints such as the shoulders, ankles, and elbows can also be affected. Chronic neurologic effects such as peripheral neuropathy and encephalitis can also occur.

Treatment depends on how the disease manifests. If one has arthritis or mild carditis, 28 days of doxycycline is appropriate; for neurologic disease or “bad” carditis, give ceftriaxone for 28 days; for everything else, 14-21 days of doxycycline. Amoxicillin can be used for patients who cannot tolerate doxycycline.

Borrelia miyamotoi and B. mayonii are emerging infections. Compared with Lyme, B. miyamotoi will present with more joint pain and less rash. B. mayonii has a more diffuse rash, but is otherwise similar to Lyme. Serologies for Lyme for both will be negative, but they are treated the same as Lyme disease.

Anaplasma presents as a flu-like illness and can be difficult to distinguish from Lyme. Ehrlichia is similar, but has more headache and CNS findings. Diagnosis during the first week is best with a blood smear (looking for morulae) and polymerase chain reaction; in week 2, serology is a bit better; after 3 weeks, serologies are very sensitive. Treatment for both is doxycycline for 7-14 days. Rifampin is second-line treatment, but does not treat Lyme (both can happen simultaneously).

Babesia is found in the same distribution as Lyme disease. Incubation is 1-12 weeks. Mild disease consists of parasitemia of less than 4% while severe disease is greater than 4%. Being asplenic, having HIV, receiving tumor necrosis factor alpha blockers or rituximab increases risk for severe disease. A blood smear is sufficient to diagnose Babesia, but polymerase chain reaction is also available. Treatment is atovaquone and azithromycin for 7 days for mild disease; clindamycin and quinine for 7-10 days for severe. Exchange transfusion can also be done especially for those with high parasitemia or severe symptoms.

Powassan virus is seen in the northeastern United States and the Minnesota/Wisconsin region. It has a fatality rate of 10%. About 50% of patients have long-term neurologic sequelae. Heartland virus has symptoms similar to other tick-borne illnesses, but can be associated with nausea, headache, diarrhea, myalgias, arthralgias, and renal failure. Bourbon virus also behaves like most tick-borne illnesses, but patients can develop a rapid sepsis picture.

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