Tick-borne disease

Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. Because individual ticks can harbor more than one disease-causing agent, patients can be infected with more than one pathogen at the same time, compounding the difficulty in diagnosis and treatment. 16 tick-borne diseases of humans are known, of which four have been discovered since 2013.

Tick-borne disease
SpecialtyInfectious disease

As the incidence of tick-borne illnesses increases and the geographic areas in which they are found expand, health workers increasingly must be able to distinguish the diverse, and often overlapping, clinical presentations of these diseases. Several high-profile deaths have been caused by the tick–human transmission of disease, including the death of former Senator Kay Hagan in the United States in 2019 at the age of 66.[1]

Diagnosis and treatment

In general, specific laboratory tests are not available to rapidly diagnose tick-borne diseases. Due to their seriousness, antibiotic treatment is often justified based on clinical presentation alone.

Exposure

Ticks tend to be more active during warmer months, though this varies by geographic region and climate. Areas with woods, bushes, high grass, or leaf litter are likely to have more ticks. Those bitten commonly experience symptoms such as body aches, fever, fatigue, joint pain, or rashes. People can limit their exposure to tick bites by wearing light-colored clothing (including pants and long sleeves), using insect repellent with 20%–30% DEET, tucking their pants legs into their socks, checking for ticks frequently, and washing and drying their clothing (in a hot dryer).[2][3]

Assessing risk

For a person or companion animal to acquire a tick-borne disease requires that the individual gets bitten by a tick and that the tick feeds for a sufficient period of time. The feeding time required to transmit pathogens differs for different ticks and different pathogens. Transmission of the bacterium that causes Lyme disease is well understood to require a substantial feeding period.[4]

For an individual to acquire infection, the feeding tick must also be infected. Not all ticks are infected. In most places in the US, 30-50% of deer ticks will be infected with Borrelia burgdorferi (the agent of Lyme disease). Other pathogens are much more rare. Ticks can be tested for infection using a highly specific and sensitive qPCR procedure. Several commercial labs provide this service to individuals for a fee. The Laboratory of Medical Zoology (LMZ), a nonprofit lab at the University of Massachusetts, provides a comprehensive TickReport [5] for a variety of human pathogens and makes the data available to the public.[6] Those wishing to know the incidence of tick-borne diseases in their town or state can search the LMZ surveillance database.[6]

Examples

Major tick-borne diseases include:

Bacterial
  • Lyme disease or borreliosis
  • Relapsing fever (tick-borne relapsing fever, different from Lyme disease due to different Borrelia species and ticks)
    • Organisms: Borrelia species such as B. hermsii, B. parkeri, B. duttoni, B. miyamotoi
    • Vector: Ornithodoros species
    • Regions : Primarily in Africa, Spain, Saudi Arabia, Asia in and certain areas of Canada and the western United States
    • Symptoms: Relapsing fever typically presents as recurring high fevers, flu-like symptoms, headaches, and muscular pain, with less common symptoms including rigors, joint pain, altered mentation, cough, sore throat, painful urination, and rash[9]
    • Treatment: Antibiotics are the treatment for relapsing fever, with doxycycline, tetracycline, or erythromycin being the treatment of choice.[10]
  • Typhus Several diseases caused by Rickettsia bacteria (below)
  • Rocky Mountain spotted fever
  • Helvetica spotted fever
    • Organism: Rickettsia helvetica
    • Region(R. helvetica): Confirmed common in ticks in Sweden, Switzerland, France, and Laos[11]
    • Vector/region(s)#1: Ixodes ricinus is the main European vector.[11]
    • Symptoms: Most often small red spots, other symptoms are fever, muscle pain, headache and respiratory problems[11]
    • Treatment: Broad-spectrum antibiotic therapy is needed, phenoxymethylpenicillin likely is sufficient.[11]
  • Human granulocytic anaplasmosis (formerly human granulocytic ehrlichiosis or HGE)
    • Organism: Anaplasma phagocytophilum (formerly Ehrlichia phagocytophilum or Ehrlichia equi)
    • Vector: Lone star tick (Amblyomma americanum), I. scapularis
    • Region (US): South Atlantic, South-central
  • Bartonella: Bartonella transmission rates to humans via tick bite are not well established [12] but Bartonella is common in ticks. For example: 4.76% of 2100 ticks tested in a study in Germany [13]
  • Tularemia
    • Organism: Francisella tularensis, A. americanum
    • Vector: D. variabilis, D. andersoni
    • Region (US): Southeast, South-central, West, widespread

Viral

Protozoan
  • Babesiosis
    • Organism: Babesia microti, B. equi
    • Vector: Ixodes scapularis, I. pacificus
    • Region (US): Northeast, West Coast
  • Cytauxzoonosis
    • Organism: Cytauxzoon felis
    • Vector: Dermacentor variabilis (American dog tick)
    • Region (US): South, Southeast

Toxin
  • Tick paralysis
    • Cause: Toxin
    • Vector (US): D. andersoni, D. variabilis West
    • Region (US): East
    • Vector (Australia): Ixodes holocyclus[18]
    • Region (Australia): East

Allergies
  • Alpha-gal allergy - Alpha-gal syndrome caused by immune reaction to the Alpha-gal sugar molecule introduced by ticks. The immune reaction can leave people with an allergy to red meat.
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See also

References
  1. Henkel C (October 28, 2019). "North Carolinians remember the life and legacy of U.S. Senator Kay Hagan". The Progressive Pulse. NC Policy Watch.
  2. "Tick-Borne Diseases". cdc.gov. Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Retrieved May 21, 2009.
  3. Rahlenbeck S, Fingerle V, Doggett S (September 2016). "Prevention of tick-borne diseases: an overview". The British Journal of General Practice. 66 (650): 492–4. doi:10.3399/bjgp16X687013. PMC 5198687. PMID 27563139.
  4. "TickEncounter Resource Center". University of Rhode Island.
  5. "TickReport". Laboratory of Medical Zoology. University of Massachusetts.
  6. "Tick-Borne Disease Network". Laboratory of Medical Zoology. University of Massachusetts.
  7. Mayo Clinic Staff. "Lyme disease: Symptoms". MayoClinic.com. Diseases and Conditions. Mayo Clinic.
  8. Mayo Clinic Staff. "Lyme disease: Treatments and drugs". MayoClinic.com. Diseases and Conditions. Mayo Clinic.
  9. Relapsing fever at eMedicine.
  10. Relapsing fever~treatment at eMedicine.
  11. Lindblom A, Wallménius K, Nordberg M, Forsberg P, Eliasson I, Påhlson C, Nilsson K (March 2013). "Seroreactivity for spotted fever rickettsiae and co-infections with other tick-borne agents among habitants in central and southern Sweden". European Journal of Clinical Microbiology & Infectious Diseases. 32 (3): 317–23. doi:10.1007/s10096-012-1742-3. PMC 3569577. PMID 22961007.
  12. Ben Beard C, Nelson CA, Mead PS, Petersen LR (November 2012). "Bartonella spp. Bacteremia and rheumatic symptoms in patients from lyme disease-endemic region". Emerging Infectious Diseases. 18 (11): 1918–9. doi:10.3201/eid1811.120675. PMC 3559143. PMID 23092626.
  13. Janecek E, Mietze A, Goethe R, Schnieder T, Strube C (October 2012). "Bartonella spp. infection rate and B. grahamii in ticks". Emerging Infectious Diseases. 18 (10): 1689–90. doi:10.3201/eid1810.120390. PMC 3471628. PMID 23017501.
  14. Dobler G (January 2010). "Zoonotic tick-borne flaviviruses". Veterinary Microbiology. Zoonoses: Advances and Perspectives. 140 (3–4): 221–8. doi:10.1016/j.vetmic.2009.08.024. PMID 19765917.
  15. "Powassan Virus | Powassan | CDC". www.cdc.gov. Retrieved 2017-06-07.
  16. Pastula DM, Turabelidze G, Yates KF, Jones TF, Lambert AJ, Panella AJ, et al. (March 2014). "Notes from the field: Heartland virus disease - United States, 2012-2013". MMWR. Morbidity and Mortality Weekly Report. 63 (12): 270–1. PMC 5779346. PMID 24670929.
  17. "Chinese researchers highlight new tick-borne disease, Alongshan virus". CIDRAP - Center for Infectious Disease Research and Policy. Minneapolis, MN: University of Minnesota. May 29, 2019.
  18. "Ticks". medent.usyd.edu.au. Department of Entomology, University of Sydney and Westmead Hospital. November 7, 2003.
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