The Full Story
Ticks are vectors, or vehicles, for the passing of pathogens. The two other important vectors of disease are fleas and mosquitoes. Vectors feed on blood and carry pathogens like bacteria, viruses, and parasites from one host to another. During 2004-2016, over half a million cases of 16 bacterial, viral, and parasitic diseases transmitted by the bites of these vectors were reported to the Centers of Disease Control and Prevention (CDC). Diseases transmitted by ticks accounted for over three-fourths of these cases.
Previous issues of The Poison Post have already covered the general approach to tick bites, and one specific tickborne disease: Lyme disease, which accounts for the about 82% of tick-borne illnesses in the US. Here we will review some other important tick-borne diseases found in the US.
The microorganism behind this tick-borne disease is the bacterium Anaplasma phagocytophilum. It's transmitted to humans through the bite of an infected black-legged tick or deer tick, which is the same tick that transmits Lyme disease. A. phagocytophilum attacks red and white blood cells and platelets leading to lower-than-normal counts of all of these. The incubation period is about 1-2 weeks, and symptoms can mimic many other infectious diseases—fever, chills, muscle aches, nausea, vomiting, and diarrhea. There were approximately 5,700 cases of anaplasmosis in the US reported in 2017, almost all of which were in the upper Midwest and Northeast. Diagnosis is made based on signs and symptoms and laboratory findings. Anaplasmosis is usually not serious or life-threatening when diagnosed early and is treatable with antibiotics.
Ehrlichiosis is very similar to anaplasmosis in that red and white blood cells and platelets are attacked and that antibiotics are effective. It differs in that it is caused by a different organism (bacteria in the Ehrlichia family) and is transmitted by the Lone Star tick instead of the black-legged tick. It is also found in a different region of the US–mostly in the southeastern and south-central states. There were approximately 1,600 cases of ehrlichiosis reported to the CDC in 2017.
Rocky Mountain Spotted Fever
Rocky Mountain spotted fever (RMSF) is a tick-borne disease caused by Rickettsia rickettsii bacteria that invade, damage, and multiply in the blood vessels and capillaries. This leads to small, pink spots that appear initially on the wrists, forearms, and ankles. This rash, along with high fever and severe headache, are initial signs of the disease. RMSF can be fatal if not treated early, but it is treatable with antibiotics. Despite its name, RMSF is most common in the southeastern US rather than the Rocky Mountain region. A little over 6,200 cases of RMSF were reported in 2017.
Babesiosis is caused by the Babesia family of parasites. It's transmitted to humans via the bite of an infected black-legged or deer tick, usually in its young stage when it's about the size of a poppy seed. This makes the tick quite difficult to detect. The parasites invade and destroy the red blood cells leading to anemia. It occurs primarily in the northeast and upper Midwest of the US. Most infected people have mild flu-like symptoms or no symptoms at all and might not require any treatment. The illness can be severe in the elderly, those with weakened immune systems, and those with other serious health conditions such as liver disease. It is treatable with a combination of antibiotics and antiparasitic medications.
Colorado Tick Fever
Colorado tick fever (CTF) is a rare viral illness transmitted by the bite of an infected Rocky Mountain wood tick and occurs in the western US. The most common symptoms of infection are nonspecific and mimic many other infectious illnesses—fever, chills, body aches, and lethargy. About half of all people infected feel better after a few days and then develop a second bout of fever and illness. There is no specific treatment for CTF. Care is directed towards supporting the patient and treating the symptoms (medicating for fever and pain or providing fluids, for example) until the illness resolves.
There are several other tick-borne diseases reported in the US and around the world, and tick-borne diseases might be on the rise.
Ticks are experts at feeding on your blood and, in return for your generosity, transmitting disease to you. Prevention is key. Do what you can to prevent them from having access to you. Use an effective insect repellent, wear long sleeves and pants treated with insect repellent, avoid wooded areas or areas with tall grass, and shower immediately and perform a thorough check for ticks after spending time outdoors.
If you have any questions about tick-borne pathogens or if someone has been bitten by a tick, check the webPOISONCONTROL® online tool or call Poison Control at 1-800-222-1222 for guidance.
Serkalem Mekonnen, RN, BSN, MPH
Certified Specialist in Poison Information
Krause, JP, Corrow CL, Bakken JS. Successful treatment of human granulocytic ehrlichiosis in children using rifampin. Pediatrics. Sep 2003;112(3 Pt 1):e252-3.
Rosenberg R, Lindsey NP, Fischer M, Gregory CJ, Hinckley AF, Mead PS, Paz-Bailey G, et al., Vital signs: trends in reported vectorborne disease cases - United States and territories, 2004–2016. MMWR Morb Mortal Wkly Rep. 2018 May 4;67(17):496-501.
Selected tickborne diseases reported to CDC, US, 2016. Atlanta: Centers for Disease Control and Prevention; [last reviewed 10 Jan 2019; cited 13 May 2019].
Tick-borne diseases. Atlanta: Centers for Disease Control and Prevention; [last reviewed 22 Sep 2011; cited 13 May 2019].
- Use an effective insect repellent and wear long sleeves and pants when outdoors.
- Wear clothing treated with insect repellent.
- Avoid wooded areas or areas with tall grass.
- Shower immediately and perform thorough checks for ticks after spending time outdoors.
This Really Happened
A 4-year-old girl was brought to her pediatrician because of fever as high as 105.1°F (40.6°C), chills, shaking, sore throat, muscle aches, and fatigue for the previous 9 days. She lived in a wooded area of Connecticut and had recently experienced three bites from ticks. Laboratory tests did not point to a specific cause, but doctors were able to rule out Lyme disease and Epstein Barr, a common human virus. The girl was diagnosed with a nonspecific viral illness.
The girl's symptoms worsened and she was brought back 3 days later. She was admitted to the hospital because her fever continued and she developed new symptoms: abdominal pain, loose stools, and vomiting. She also had elevated heart and respiratory rates along with a rash on her neck and back.
The doctors ordered additional tests. One that detected human granulocytic ehrlichiosis, a bacterial tick-borne disease, came back positive.
The girl received treatment with an antibiotic and her fever resolved 6 hours after the first dose. A day later, she had more appetite, increased energy and alertness, and fewer muscle aches. All of her symptoms resolved and she was sent home 2 days after the first antibiotic dose.
From Krause et al., 2003