There’s more to worry about with the summer nuisance than corona and Lyme disease.
You are just starting your shift when a 74-year-old female shows up on the board. She reports three- to four-days of non-bloody diarrhea, malaise, fevers and confusion. She doesn’t appear that well, and vitals are notable for temperature 38.3oC (100.9oF), heart rate 106, blood pressure 126/80, respirations 32 and spo2 98%. Clinical examination reveals dehydration but no other significant findings. Suspecting sepsis – acetaminophen, lactated ringers, cefepime and vancomycin are ordered. Laboratory evaluation reveals WBC 5.2, HGB 14.2, platelets 74, lactate 2.4, sodium 129, AST 65 and ALT 47. Urinalysis is negative. Chest X-ray and a CT of the abdomen/pelvis are also unrevealing.
On the cusp of an unsatisfying admission for sepsis of unknown origin, a key piece of information drops into your lap. The patient is a garden landscaper. A tick-borne disease panel is added and empiric doxycycline started. The next day, Anaplasmosis is confirmed.
Refresher
Now that summer is here and COVID-19 is becoming more of a distant nightmare, it’s time we remember other causes for fever. Tick-borne illness is a problem that is growing in both frequency and geographic range. While most EPs are familiar with the predominant diseases like Lyme Disease and Rocky Mountain Spotted Fever (RMSF), there are several others that we need to be familiar with as well.
There are two easy ways to identify tick-borne illness. The easiest, by far, is the presence of a tick or a history of having been bitten. However, this is absent more often than you would think. Ticks generally feed for a period of 3 to 10 days before detaching spontaneously. It is not uncommon for the tick to fall off before symptoms start and the patient is none the wiser. Disease transmission also occurs during the nymph stage of the life cycle, in which the ticks are vanishingly small. Additionally, many exposures occur around a patient’s house or via their pets, making travel or recreation history less reliable.
Identifying the problem
Since you can’t count on finding a tick, the need for a careful and full skin exam is crucial in patients with illnesses of unclear etiology. This is most notable in tick paralysis, an acute ascending flaccid paralysis that can mimic Guillain-Barré syndrome and is treated with simple tick removal and supportive care.
The second easy way to diagnose these diseases is through their characteristic rashes. Erythema migrans is pathognomonic for lyme disease and few clinicians would miss the palms and soles involvement in RMSF. A newer infection spreading throughout the southeast states and eastern seaboard presents with a rash similar to erythema migrans, but often without the central clearing. Termed Southern Tick Associated Rash Illness (STARI), it is a non-Borrelia non-Rickettsia infection caused by the Lone Star Tick (Amblyomma americanum).
Distribution of tick-borne diseases in the United State, 2012. Each dot represents a single case. [Source: CDC]
Fever. Malaise. GI symptoms. Myalgias. Anaplasmosis and Ehrlichiosis are bacterial diseases with closely overlapping, but non-specific, clinical syndromes that present up to several weeks after a tick bite. The vector for anaplasmosis is the blacklegged tick (Ixodes scapularis and Ixodes pacificus), while ehrlichiosis is transmitted by I. scapularis or A. americanum. Left untreated, these diseases can progress to meningoencephalitis, renal failure, hepatic failure, DIC and death. Diagnosis is aided by a characteristic lab pattern including thrombocytopenia and transaminitis. A mild leukopenia and hyponatremia can be seen. As with most tick-borne diseases, treatment is with doxycycline, even in children.
Babesiosis is unique among tick-borne infections. It presents several weeks after a bite from the blacklegged tick. The causative organism, Babesia microti, is a protozoan parasite that lives and replicates inside red blood cells. Its life cycle in humans leads to the periodic rupture of erythrocytes resulting in cyclic fevers and hemolytic anemia — very similar to malaria.
Initial presentation is with several days of flu-like symptoms followed by hemolytic anemia and jaundice. Babesiosis is a disease with a high rate of serious complications, particularly in elderly, immunocompromised, or asplenic individuals. Diagnosis is primarily by thin-film blood smear demonstrating intraerythrocytic parasites (classic Maltese cross), although PCR is available. Laboratory abnormalities similar to the other tick-borne diseases may be present. Treatment is with azithromycin and the antiparasitic medication atovaquone.
Tick infections
Several emerging tick-borne viral infections have been in the news recently, including Colorado tick fever (Rocky Mountain states), Powassan virus (Northeast, Great Lake states), Bourbon virus (Midwest, Southern) and the Heartland virus (Midwest, Southern) among others. As a group, these infections are notable for high fevers, encephalitis and lab abnormalities including thrombocytopenia and elevated transaminases. Treatment is supportive.
Prevention
Tick-borne disease prevention includes proper clothing, insecticides and daily tick checks. Light colored, long sleeved clothing makes identifying ticks easier and sealing pant legs into socks can limit access to skin. Permethrin impregnated fabrics are safe and highly toxic to ticks. DEET-based bug spray is also effective. Most diseases take several hours to days for transmission, so post-activity or daily tick checks are good preventions.
Removal of an embedded tick is best done by grasping the tick with forceps as close as possible to the skin and removing with gentle traction. Commercial devices can be convenient, but do not provide substantial improvement over forceps. The myriad of folk remedies, including alcohol, matches and fingernail polish are more likely to traumatize the tick and cause increased regurgitation of infected fluids into the host, as well as risk injury to the patient. The site can then be cleaned and disinfected in standard fashion.
Conclusion
Ticks are well-known for a few specific diseases isolated to specific areas. However, they are capable of spreading a much broader group of diseases over a wider area than historically thought. Keep this vector in mind for patients with vague infectious symptoms.
Consider adding LFTs into your workup of febrile patients as abnormalities here lead you to follow up with PCR or other specialized testing. Outside of babesiosis, doxycycline is the kryptonite for most tick-borne diseases (even in children!) and can be started empirically while waiting on the lab results.
The next time you see a febrile patient in the spring-fall, remember your tick-borne diseases.
References:
- Cummins G.A. and Traub S.J Tick-Borne Diseases in Auerbach’s Wilderness Medicine. Chapter 42 pp 968-993. Elsevier, Inc 2017.
- Mikhail Menis, Barbee I Whitaker, Michael Wernecke, Yixin Jiao, Anne Eder, Sanjai Kumar, Wenjie Xu, Jiemin Liao, Yuqin Wei, Thomas E MaCurdy, Jeffrey A Kelman, Steven A Anderson, Richard A Forshee, Babesiosis Occurrence Among United States Medicare Beneficiaries, Ages 65 and Older, During 2006–2017: Overall and by State and County of Residence, Open Forum Infectious Diseases, Volume 8, Issue 2, February 2021, aa608.
- Molaei G, Little EAH, Williams SC, Stafford KC. Bracing for the Worst – Range Expansion of the Lone Star Tick in the Northeastern United States. N Engl J Med. 2019 Dec 5;381(23):2189-2192.
- Tickborne Diseases of the United States: A Reference Manual for Healthcare Providers. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Fifth Edition, 2018.