Tick-borne infections

Clinical Manifestations

• Many of the diseases should be suspected in patients with:
  • Flu-like illness that occurs not in flu season
  • ± cytopenias, ± liver enzyme abnormalities
  • Exposure history (outdoors activities, rats)

By Disease

Common Diseases

	Lyme disease	Babesiosis	Anaplasmosis	Ehrlichiosis	RMSF
Pathogen	B. burgdorferi	B. microti	A. phagocytophilum	E. chaffeensis	R. rickettsii
Incubation	2-3 wk	1-4 wk	5-14 d	5-14 d	3-12 d
Tick	Black-legged tick	Black-legged tick	Black-legged tick	Black-legged tick, Lonestar tick	American dog tick
Symptoms	Fever	Fever, headache, nausea/vomiting, diarrhea	Fever, headache	Fever, headache, myalgias, nausea/vomiting	Fever, headache
Cells	Disseminated	Erythrocytes	Granulocytes	Monocytes	Vascular endothelial
Rash	Erythema migrans	Rare	Rare	Maculopapular (30%)	Maculopapular; eschar with R. parkeri
Labs	Uncommon	Hemolytic anemia, thrombocytopenia, liver enzymes	Leukopenia, liver enzymes, thrombocytopenia	Leukopenia ± lymphocytosis, liver enzymes, thrombocytopenia	Thrombocytopenia, liver enzymes, hyponatremia
Complications	Carditis, neurological symptoms, arthritis	DIC, ARDS, CHF, AKI	Opportunistic infections, shock	Seizure, coma, CHF, pericardial effusion, shock	Coma/seizure (30%)
Diagnosis	EM, serology	Microscopy	Serology, ±microscopy	Serology, ±microscopy	Serology, biopsy
Mortality	Rare	3-20%	7-10%	2-5%	8%
Treatment	Doxycycline	Azithromycin, Atovaquone	Doxycycline	Doxycycline	Doxycycline

Other Diseases

Disease	Vector	Clinical Manifestations
African tick-bite fever	Amblyomma	fever with eschar in Africa
Mediterranean spotted fever	Rhipicephalus sanguineus	fever with eschar in the Mediterranean
Powassan virus	Ixodes	encephalitis in North America
Rickettsioses, not otherwise specified	multiple	fever ±rash ±ulcer
Rocky Mountain spotted fever	multiple	fever with cetripetal rash in North America
Southern tick-associated rash illness	Amblyomma americanum	erythema migrans in the southern US
Tick-borne encephalitis	Ixodes	biphasic: flu-like illness followed by meningoencephalitis
Tick-borne relapsing fever	Ornithodorus	relapsing-remitting febrile illness (3 days on, 7 off)
Tick paralysis	Dermacentor	ascending paralysis with preserved sensation
Tularemia	multiple	severe flu-like illness ±ulcer ±lymphadenopathy

By Tick

Tick	Distribution	Transmits	Comments
American dog tick (Dermacentor variabilis)	East of the Rockies, and in limited areas in the Pacific coast	Tularemia and RMSF	Highest risk of bites in spring and summer. Sometimes called wood ticks.
Blacklegged (deer) tick (Ixodes scapularis)	Across the eastern US and in Ontario	Lyme disease, Anaplasma, B. miyamotoi, ehrlichiosis, babesiosis, and Powassan virus	Highest risk in spring through fall, but can be found any time it's above freezing.
Brown dog tick (Rhipicephalus sanguineus)	Worldwide	RMSF (uncommon)	Dogs are the primary host but it can also bite humans.
Gulf Coast tick (Amblyomma maculatum)	Coastal areas along the Guld of Mexico and southern Atlantic	Rickettsia parkeri
Lone Star tick (Amblyomma americanum)	Southeastern and eastern United States	Ehrlichiosis, Heartland virus, tularemia, STARI	Very aggressive tick. Irritation at site does not indicate infection.
Rocky Mountain wood tick (Dermacentor andersoni)	Rocky Mountains and southwestern Canada from elevations of 4,000 to 10,500 feet	RMSF, Colorado tick fever, and tularemia
Western blacklegged tick (Ixodes pacificus)	Pacific coast of the U.S., particularly northern California	Anaplasmosis and Lyme disease
Soft tick (Ornithodoros species)		Tick-borne relapsing fever (non-Lyme Borrelia species)	Short feeds at night, associated with rodents

Further Reading

• TickEncounter tick identification, hosted by the University of Rhode Island