Now that our month of point of care ultrasound (POCUS) is over, it is time to talk about other clinically relevant topics. Michelle Perkins is back again this time to help us cover tickborne illnesses in the United States.
- Ticks can transmit all sorts of badness—viruses, bacteria, and parasites. The ones we care about the most are the rickettsial diseases.
- Our focus today will be the “major” tickborne illnesses in the US—the ones that the CDC tracks and reports on—anaplasmosis, ehrlichiosis, babesiosis, Lyme disease, Rocky Mountain Spotted Fever, and tularemia.
- What makes tickborne illness so vexing is that the presentations can be all over the map. Patients can be with or without fever, rash, or neurological symptoms. They may not even know they were bit by a tick and the manifestations of the disease can be divergent, even within the same disease entity.
- There are approximately 80 species in the US, and most belong to the Ixodidae family.
- Most common vector isn the US: the deer tick or black legged tick–> Ixodes scapularis.
- Endemic in the northeast, south, and midwest. The season is basically any time above freezing.
- They can transmit Lyme, anaplasmosis, and babesiosis.
- The Lone Star Tick is also a player and becoming more widespread.
- These are found in ever-widening zones, especially in the southeastern and eastern US.
- They can transmit ehrlichiosis and tularemia.
- Dog ticks are less often a problem, but can transmit tularemia and RMSF.
General Workup and Diagnosis
- History and physical are going to be the most helpful—if you aren’t thinking about tickborne illness, you’re not going to diagnose it.
- Labwork is typically not very helpful. CBC, CMP, and tick panel/serology are going to be your mainstay. PCR is becoming more available and can further aid the diagnosis.
- DON’T DELAY TREATMENT FOR SEROLOGIC CONFIRMATION! This could be deadly.
- Transmitted by the same ticks as Lyme and babesiosis, so the same geographic distribution–>upper midwestern and northeastern US.
- Presents as flu-like symptoms: fever, headache, malaise, nausea/vomiting, and cough.
- Generally NO rash.
- Labwork potentially anemia, thrombocytopenia, maybe a small bump in the LFTs.
- Peripheral smear may show neutrophils with intracytoplasmic inclusions (morulae), but do NOT rely on this finding to rule in or rule out anaplasmosis.
- Treatment: Doxycycline 100 mg twice daily for 7-14 days.
- Sidebar: dogma is to avoid doxycycline in kids younger than 8 years of age due to the risk of tooth staining.This has not been shown in the literature and was more an issue with tetracycline. Both the CDC and the AAP Committee on Infectious Disease say just use doxy.
- Acts very similar to anaplasmosis, just a different bug in a different geographic distribution—more southeast and south central US.
- Again, presents with fever, headache, malaise, GI symptoms.
- Generally no rash.
- Labs may show abnormal CBC—with leukopenia and/or thrombocytopenia. Also may have mildly elevated LFTs.
- Peripheral smear MAY show morulae—but, again, don’t hang your hat on that finding either way.
- Treatment again is doxycycline.
- America’s malaria!
- This used to be called “Nantucket Fever”—geographic distribution again is northeastern and upper Midwest US.
- Diagnosis is further challenged by the long incubation—can be anywhere from one week to months.
- Illness can range from asymptomatic to potentially life-threatening.
- The presentation is very similar to malaria ,with fever, chills, malaise, headache, possibly dark urine and hepatosplenomegaly.
- Severe cases can manifest with DIC and hepatorenal failure. These tend to occur in the elderly or immunocompromised (including the surgically immunocompromised—splenectomy patients!). 5-9% of cases are fatal!
- Bloodwork is generally consistent with hemolytic anemia and thrombocytopenia. Peripheral smear MAY show “Maltese cross” patterns inside red blood cells—similar to malaria.
- Treatment is based on severity:
- Atovaquone and azithromycin together for 7-10 days for symptomatic but not severe presentations.
- Clindamycin and quinine together for severe presentations.
- The most common tickborne illness in the US—upwards of 30,000 cases per year.
- Also, the tickborne illness with the most hype, hysteria, and woo surrounding it.
- Again, endemic in the northeast and upper Midwest US.
- How these cases present depends upon how disseminated it is.
Early/localized illness: erythema migrans, a characteristic, isolated bulls-eye lesion that is -pathognomonic for Lyme. BUT, it is only present in 70-80% of patients. But if they have it, BOOM—diagnosis made. They can also have concominant flu-like symptoms +/- fever.
all bets are off. This is where you see the weird stuff. You can see multiple bullseyes, flu symptoms, and rheumatologic manifestations like migratory joint pain, muscle pain, and bone pain. You can see cardiac manifestations, like AV nodal block, myocarditis, and pericarditis. And the neuro stuff can be deceptive—you can see meningitis or even encephalitis, you can see neuropathy, Bell’s palsy, and/or cognitive issues. As far as labwork, you may see an elevated ESR/WBC, but generally not much acutely. Lyme serology is negative for the first few weeks, so not helpful in that window. You also can’t distinguish between active and past infection with serology. So you can’t use testing to measure treatment response. RANT TIME
- While Lyme can cause chronic problems, such as rheumatologic or neurologic issues, “Chronic Lyme” is Not A Thing.
- There is this notion that a vague constellation of symptoms that patients report are due to active, ongoing Lyme disease that requires prolonged antibiotic treatment, sometimes even parenterally, for months to years.
- Many of these patients are “treated” based on symptoms alone, despite not even ever having proven Lyme.
- ”Lyme literate” clinicians have set up shop, offering testing through dubious labs, some of which have an over 50% false positive rate.
- Ethics of this aside, this practice is not without potential, serious harm to patients in the long-run.
Rocky Mountain Spotted Fever
- This can occur anywhere, but just five states account for over 60% of the cases: North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri.
- Acts similar to other tick borne illnesses, with the fever, chills, malaise, severe HA, sometimes GI stuff, focal neurological deficits, and photophobia.
- The rash with RMSF starts as an erythematous maculopapular rash that appears 2-5 days after the fever.
- This transitions to a petechial rash. This is a sign of severe, progressive disease—the horse is out of the barn at this point.
- Roughly 10% of people NEVER develop a rash.
- The key with RMSF is early treatment. Antibiotics are less likely to prevent fatalities after 5 days.
- Fatalities are more common in the very young and very old, as well as immunocompromised patients. Mortality comes from multi-system involvement in most cases.
- Lab findings are non-specific—you can see hyponatremia, thrombocytopenia, and possibly a mild elevation of LFTs.
- Treatment is doxycycline for at least a week and for at least 3 days after fever subsides.
- Can be found in every state except Hawaii.
- Dog tick and Lone Star tick transmission generally, but can be transmitted via sick animals.
- Can run the gamut from mild to life-threatening.
- Can have differing manifestations depending on the site of inoculation:
- The most common presentation you’ll see, from a tick bite. Manifests with an ulcer but NOT ALWAYS, as well as localized adenopathy, fever, chills and malaise.
- When the bacteria enters through the eye (like when touching the eye after handling a sick animal)—this will manifest with photophobia, tearing, and conjunctivitis.
- Comes from eating or drinking contaminated food or water—this will manifest with pharyngitis and lymphadenitis.
- The most concerning—manifests with non-productive cough, fever, and chest pain. Untreated ulceroglandular disease can progress to this!
- This subset is when the patient has a hodge podge of the symptoms above—non-localized.
- Lab findings are non-specific. Will sometimes see elevated WBC and ESR, thrombocytopenia, hyponatremia, elevated LFTs, and possibly elevated CPK.
- Treatment is with streptomycin or gentamicin for severe disease, cipro or doxy for more mild cases
- Started out in Southeast, but has been spreading geographically as the Lone Star tick has spread.
- Manifests as a sudden, severe allergy to red meat.
- This occurs when the tick bites and transmits the alpha-gal molecule. The body then mounts an immune response that manifests as an allergic reaction to red meat.
- Treatment is as with any severe allergy.
- Tickborne illness can be vexing to diagnose, but failing to do so can have serious consequences for the patient.
- These can manifest in a variety of ways across the spectrum of severity.
- Much can be gleaned from the history and physical. Labwork and serology not really all that helpful in the moment.
- Never delay antibiotics for definitive diagnosis!
- Chronic Lyme isn’t a thing. But be aware that your patient may be under treatment for such and what that might mean for their risk for serious infection and antibiotic resistance.
- Know what’s in your area, and be suspicious for those diagnoses. But be aware that all of these illnesses can present anywhere.
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