Tick-Borne Diseases of Public Health Significance

Disease Transmission

• The risk of human infection increases with the time a tick is attached to a person. Lyme disease usually requires the tick to be attached for 24 hours or more. However, it may take as little as 15 minutes for Powassan virus to be acquired from a blood-feeding tick.
• Ticks can attach to any part of the human body but may be in hard-to-see areas such as the armpits, groin and scalp.
• Most humans are infected through the bites of immature ticks called nymphs, which are tiny (less than two mm) and difficult to see.
• Adult ticks are larger (five mm) and therefore more likely to be discovered and removed before they have had time to transmit pathogens.
• Early detection and removal of ticks is important in the prevention of tick-borne diseases.

Epidemiology/Surveillance

For the most up-to-date trends in human cases for TBDoPHS see PHO’s Ontario Vector-Borne Disease Tool. This tool is updated weekly for all human cases.

For information about TPH’s blacklegged tick surveillance program and the latest tick dragging results, visit TPH’s Blacklegged Tick Surveillance.

Clinical Signs & Symptoms

TBDoPHS can have similar and non-specific signs and symptoms, which may include:

• Fever/chills
• Rash
• Headache, fatigue, muscle aches

The combination of symptoms varies greatly from person to person. Refer to the individual TBDoPHS pages for specific signs and symptoms.

The following summary table from Public Health Ontario may assist in distinguishing between TBDoPHS symptoms:

Criteria	Lyme Disease	Anaplasmosis	Babesiosis	Powassan virus
Tick Bite Risk	≥ 24-36 hours	≥ 12-24 hours	≥ 36-48 hours*	≤ 15 minutes
Incubation	3 to 30 days	5 to 21 days	1 to 3 weeks (tick bite) or 1 to 24 weeks (transfusion)	1 to 5 weeks
Skin Lesions	Erythema migrans (70%)	Maculopapular (≤10%)	Petechiae (rare, if severe)	Morbiliform (rare)
Other Differential Symptoms	Arthralgia, headache, lymphadenopathy, subacute or late manifestations	Arthralgia, headache, occasionally multi-organ failure	High fever, dark urine, severe if low immunity or low splenic function	Encephalitis after short prodrome (1-3 days) and 50% have sequelae
Routine Blood Work	Usually normal in early localized cases	Leukopenia (>45%), thrombocytopenia (>70%), high transaminases (>50%)	Hemolytic anemia (>90%), thrombocytopenia (>60%), high transaminases (>70%)	Usually normal (<15% thrombocytopenia)

Note:*May be at least 24 hours (MOH)

Sources:Sanchez E, Vannier E, Wormser GP, Hu LT. Diagnosis, Treatment, and Prevention of Lyme Disease, Human Granulocytic Anaplasmosis and Babesiosis. JAMA. 2016;315(16):1767-1777. Available from: https://doi.org/10.1001/jama.2016.2884Dumic I, Jevtic D, Veselinovic M, Norstrom CW, Jovanovic M, Mogulla V, et al. Human Granulocytic Anaplasmosis—A Systematic Review of Published Cases. Microorganisms. 2022;10(7):1433. Available from: https://doi.org/10.3390/microorganisms10071433White DJ, Talarico J, Chang HG, Birkhead GS, Heimberger T, Morse DL. Human Babesiosis in New York State. Review of 139 Hospitalized Cases and Analysis of Prognostic Factors. Arch Intern Med. 1998;158(19):2149-2154. Available from: https://doi.org/10.1001/archinte.158.19.2149Piantadosi A, Rubin DB, McQuillen DP, Hsu L, Leder PA, Ashbaugh CD et al. Emerging Cases of Powassan Virus Encephalitis in New England: Clinical Presentation, Imaging, and Review of the Literature. Clin Infect Dis. 2016;62(6):707-713. Available from: https://doi.org/10.1093/cid/civ1005

Diagnosis, Testing & Treatment

Knowledge of a patient’s exposure to blacklegged ticks is an important parameter for tick-borne disease diagnosis.

• Tick populations continue to expand, and it is possible that tick-borne diseases can be acquired outside currently identified areas.
• Ticks can travel or migrate on the bodies of animals such as birds and therefore can be sporadically present in very low numbers over an even broader area.

Diagnosis, testing and treatment varies by TBDoPHS. Testing is generally not indicated for asymptomatic patients. For specific recommendations, see:

• Lyme Disease
• Anaplasmosis
• Babesiosis
• Powassan Virus Infection

The following summary table from Public Health Ontario may assist in distinguishing between testing and treatment options:

Criteria	Lyme Disease	Anaplasmosis	Babesiosis	Powassan virus
Routine Core Lab Tests	Usually normal in early localized cases	Leukopenia (>45%), thrombocytopenia (>70%), high transaminases (>50%)	Hemolytic anemia (>90%), thrombocytopenia (>60%), high transaminases (>70%)	Usually normal (<15% thrombocytopenia)
Main Diagnostic Tests	Early localized: Clinical Other stages: Serology (paired)	Acute illness: PCR Subacute illness: Serology (paired)	Acute, prolonged, or relapsing illness: Smears +/- PCR	Prodrome: PCR Encephalitis stage: Serology (paired)
Main Treatment Options	Doxycycline, amoxicillin, cefuroxime, or ceftriaxone	Doxycycline	Atovaquone plus azithromycin, or clindamycin plus quinine	None (supportive)

Source: Rodino KG, Theel ES, Pritt BS. Tick-Borne Diseases in the United States. Clin Chem. 2020;66(4):537-548. Available from: https://doi.org/10.1093/clinchem/hvaa040

Infection Prevention and Control

Prevention of tick bites will reduce the risk of all TBDoPHS. Visit Toronto Public Health’s Environmental Health Lyme disease prevention page for information and how to prevent tick bites.

Tick Identification

An electronic tick identification platform eTick, is available in Ontario, where anyone can submit a photo of a tick and receive species identification results within 48 hours. This free publicly available tick identification platform can be used for ticks found on a person, pet or in the environment.

Tick Submission

There is no longer an added benefit to continue passive tick surveillance because all of Toronto is considered an estimated risk area. Toronto Public Health continues to perform selective active surveillance activities. It is not recommended to submit ticks to Public Health Ontario (PHO) for clinical purposes.

If you wish to submit a tick to the PHO labs, please visit their website for more information.

More information:

• Public Health Ontario’s Tick submission and testing FAQ 
• TPH’s Information for patients on tick removal and identification
• Blacklegged tick surveillance in Toronto
• Surveillance Form for Tick Identification (PHO) 

Reporting

Report all suspect or confirmed cases of Lyme Disease, Anaplasmosis, Babesiosis or Powassan Virus to TPH at 416-392-7411 during business hours (8:30 am to 4:30 pm, Monday to Friday) or 311 after hours.

Resources for Patients

• Tick-Borne Diseases (TPH)
• Lyme Disease (TPH)
• Anaplasmosis Fact Sheet (TPH)
• Babesiosis Fact Sheet (TPH)
• Powassan Virus Infection Fact Sheet (TPH)