Thirty-Six Hours: The Number That Governs Tick Risk, and the Four Pathogens It Was Not Written For

1. Introduction: one number doing all the work

Almost every practical question about a tick bite resolves to one quantity, which is how long the tick was attached. Whether preventive treatment is offered, how worried a person should be, and what the bite is likely to have transmitted all turn on it.

Manitoba publishes the threshold explicitly, which is more than many jurisdictions do.

1.1 What this paper adds

The threshold concerns Lyme disease. The same tick is tested by the provincial programme for four different pathogens, one of which can be transmitted by a life stage the rule does not contemplate. That gap is the subject of §11 to §16.

2. The four conditions

The published criteria for preventive treatment after a bite.

The conditions are that the tick can be reliably identified as a blacklegged tick (Ixodes scapularis), and the tick was attached for a minimum of 36 hours, or engorged, and the tick was picked up from a location in southern Manitoba, south of the 53rd parallel, or another known risk area outside of Manitoba, and there are no known allergies to the antibiotic, doxycycline.¹

2.1 The structure is conjunctive

All four must hold. A tick that was attached for two days but cannot be identified does not meet the criteria, and neither does an identified tick removed after four hours.

That is a demanding standard, and it is demanding in a specific direction: it requires information that is frequently unavailable at the moment a person notices a tick.

3. Why identification comes first

The species condition is not a formality.

Lyme disease is caused by a bacterium transmitted in North America by the bite of an infected blacklegged tick or western blacklegged tick.¹ Other tick species are common and are not vectors of it.

3.1 The practical difficulty

Blacklegged ticks are much smaller than the wood ticks most people recognise and, in their immature stages, can be no larger than a poppy seed.¹⁰

Identification of a small arthropod by a non-specialist is exactly the problem this journal set out at length in the spider article, where physicians correctly identified a recluse under two per cent of the time. The same caution applies: a person looking at a tick they have just removed is not in a good position to classify it.

3.2 The implication

Retaining the tick matters, because the criterion is written around a tick that can be examined. A tick that has been destroyed cannot satisfy condition one regardless of what it was.

It also feeds the surveillance system. The passive programme described in §19 is built from ticks that members of the public submitted after finding them, so a retained tick contributes to the risk maps that condition the geographic criterion for everyone else.⁴⁹

4. The attachment threshold

The central number.

The provincial criterion is a minimum of 36 hours attached.¹ Other guidance describes transmission as becoming likely after typically at least 24 to 36 hours, with prompt removal of a blacklegged tick described as one of the most effective ways to reduce risk.¹⁰

4.1 The underlying literature

The provincial guidance for health professionals cites work specifically on pathogen transmission in relation to duration of attachment by Ixodes scapularis ticks.²³

This is therefore a threshold derived from transmission studies rather than an administrative convenience, which is worth knowing when it is being applied to an individual case that falls just short of it.

4.2 What it implies for behaviour

If transmission requires prolonged attachment, then the interval between exposure and removal is the variable a person controls. A daily check after outdoor activity puts removal inside the window in most cases; a weekly one does not.

That is the entire practical content of tick prevention beyond avoiding bites, and it follows directly from the number.

4.3 A threshold is not a guarantee

The published wording is careful in both directions. The provincial criterion is a minimum for offering treatment,¹ and the general description is that transmission becomes likely after the stated period.¹⁰

Neither says transmission cannot occur earlier. A threshold used to allocate a prescription is answering the question of when treatment is justified, which is not the same question as when risk begins, and the two get conflated whenever the number is repeated without its wording.

4.4 Why the distinction is practical

A person who removed a tick at twenty hours has not been told they are safe. They have been told they fall outside the criteria for preventive antibiotics, which is why §8 matters to them as much as to someone who met the threshold.

5. Or engorged

The alternative limb of the second condition, which deserves separate attention.

The criterion is 36 hours attached or engorged.¹

5.1 Why the alternative exists

Most people do not know when a tick attached. The bite is painless and frequently unnoticed, so the duration is an estimate at best.

Engorgement is a physical state that can be observed at the time of removal, and it is evidence that feeding has been prolonged. The criterion therefore offers an observable proxy for an unobservable history, which is a sensible piece of drafting.

5.2 The limitation of the proxy

Assessing engorgement in a tick the size of a poppy seed is not trivial, and we would expect it to be assessed by the clinician rather than the patient. This again argues for retaining the tick rather than describing it.

6. The geography condition

The third condition locates the exposure.

The tick must have been picked up from a location in southern Manitoba, south of the 53rd parallel, or another known risk area outside of Manitoba, with a map of Lyme disease risk areas in Canada referenced.¹

6.1 Why a parallel of latitude

The 53rd parallel is an administrative simplification of an ecological boundary. Tick establishment depends on climate, host availability and habitat, and those vary continuously rather than at a line.

A simple boundary is nonetheless usable at the point of care, and the alternative is a clinician consulting a risk map for every bite.

6.2 The trade-off in drawing it

Any threshold of this kind produces two error types. Some people inside the boundary will be offered treatment after a bite that carried no risk, and some outside it will be refused after a bite that did.

Choosing where to draw it is a decision about which error to prefer, and that is a policy question rather than a scientific one. This journal made the same observation about the commonly accepted methods standard in rental housing: an administrable rule and an accurate one are different objects.

7. Why the map understates it

The qualification that the provincial guidance itself supplies, and it is important.

The risk of exposure is not uniform within, nor solely confined to, these risk areas, as ticks can be transported great distances by migrating birds and deer. Consequently, tick-borne diseases can potentially be acquired anywhere in the southern part of the province.²

7.1 The two directions of error

Risk is not uniform inside a risk area, so being inside one does not mean a given site is hazardous. And risk is not confined to risk areas, so being outside one does not mean a site is safe.

A map of established populations is a map of where surveillance has found them, which is a different thing from where ticks are. Birds moving ticks long distances mean the leading edge is always ahead of the documentation.

7.2 The tension with the criterion

The geographic condition for preventive treatment uses risk areas, while the guidance states disease can potentially be acquired anywhere in the southern part of the province.¹²

We would not call that inconsistent. A treatment threshold has to be drawn somewhere, and drawing it at documented risk areas is defensible. But a person outside one should not read the criterion as a statement that they were not exposed.

8. The instruction that follows treatment

The sentence at the end of the criteria, which we think is the most easily missed.

Individuals should continue to monitor themselves for symptoms in the months following their tick bite, even if they receive preventative treatment.¹

8.1 What that tells you

Preventive treatment reduces risk; it does not close the matter. The monitoring period is months, not days.

This also means that failing to meet the four conditions and failing to receive treatment does not end the question either. Symptom monitoring is the common element in both paths, and it is the part that does not depend on any threshold.

9. What Lyme disease looks like

The clinical picture as published.

Symptoms typically appear 3 to 30 days following the bite of an infected blacklegged tick. Other early symptoms are non-specific and may include headache, fatigue, chills, fever, muscle aches, joint pain, stiff neck or swollen lymph nodes.¹

If left untreated, infection can cause joint, heart and nervous system complications, and the disease can be successfully treated with antibiotics, particularly when diagnosed early.¹

9.1 The window is why monitoring matters

A three to thirty day onset means a person who feels fine a week after a bite has learned very little. The non-specific symptom list overlaps with ordinary summer illness, which is what makes the next section useful.

9.2 Diagnosis is clinical

The guidance to health professionals states that treatment should be initiated based on clinical suspicion of disease, and that depending on symptoms and timing of diagnosis, some cases may require a longer or repeat course of treatment.²

9.3 Why that phrasing matters

Treatment initiated on clinical suspicion means a clinician is not required to wait for a laboratory result before acting. Serological testing has its own positivity criteria and its own timing constraints, and the guidance references those separately.²

For a patient this reframes the encounter. What is being brought to a clinician is a history and a set of symptoms, and the tick, if retained, is part of that history rather than the test that decides it.

10. The rash detail

One specific and unusually useful piece of published guidance.

Many people develop a characteristic expanding rash, erythema migrans, which is neither itchy, nor tender.¹

10.1 Why that qualifier is worth knowing

Most skin reactions people notice are itchy or sore, and those sensations are what draw attention to them. A rash that does neither is easy to miss and easy to dismiss.

The absence of itch and tenderness is therefore a discriminating feature rather than a reassuring one. This journal made the same argument about spider bite lesions: the intuition that a serious skin finding should hurt is wrong often enough to be dangerous.

11. The four pathogens

The complication the threshold does not address.

Ticks submitted to the national passive tick surveillance programme from Manitoba have been tested by PCR for Borrelia burgdorferi since 1995, Anaplasma phagocytophilum since 2006, and Babesia microti and Borrelia miyamotoi since 2013.⁹

The study determined the geographic distribution and the minimum infection rate of ticks infected with each, on the basis that the expanding geographical range of blacklegged ticks and their ability to transmit these agents poses an emerging public health risk.⁹

11.1 What the testing history shows

The list has grown over three decades. A bite in 1995 was understood as a Lyme exposure; the same bite today is an exposure to four agents that the programme considers worth testing for.

The 36 hour criterion, and the doxycycline it gates, are about the first of them.

11.2 What a minimum infection rate is

The Manitoba study reports the minimum infection rate of ticks infected with each pathogen, using regression models to test the association of that rate by year for each agent.⁹

The term is worth understanding because it sets a floor rather than an estimate. A minimum infection rate is the lowest proportion consistent with the testing performed, so the true proportion of infected ticks is at least that figure and may be higher.

11.3 Why a floor is the right statistic here

It is conservative in the protective direction, which is the correct bias for a public health indicator. It also means a reported infection rate should not be read as the chance that a given tick is carrying something, and we have deliberately not quoted specific rates for that reason.

The study's purpose was distribution and trend by year rather than individual risk assessment.⁹

12. Anaplasmosis

The second agent, and the one with a reported trend.

Since 2013 the incidence has been steadily rising in Manitoba, with the reported figure 1.54 per 100,000 in 2018, twice as high as the incidence in 2017 at 0.66 per 100,000.⁸

There is a risk of anaplasmosis infection in any community with an established population of blacklegged ticks, and areas with a greater risk of Lyme disease also carry a higher risk of anaplasmosis.⁸

12.1 Reading the doubling carefully

A rate doubling between two consecutive years at these absolute levels can reflect genuine increase, improved recognition, expanded testing, or all three. Two data points do not establish a trend, although the source describes the rise as steady since 2013.

We would treat it as consistent with the range expansion evidence in §17 rather than as independent proof of it.

The qualifier in the source is worth keeping too: the figures are for Manitoba where surveillance is available, while surveillance data is limited across the rest of Canada.⁸ A province that measures something will report more of it than one that does not, and comparisons between jurisdictions carry that distortion before any biology enters.

12.2 The co-location finding

That Lyme risk areas are also anaplasmosis risk areas⁸ is operationally useful. The same avoidance and checking behaviour addresses both, which means the prevention advice does not fragment by pathogen even though the treatment criteria do.

13. Babesiosis

The third agent.

Babesiosis is primarily transmitted by the parasite Babesia microti through Ixodes scapularis, although infection is also possible by Babesia duncani and Babesia divergens. Infection is usually mild to moderate with flu-like symptoms; however, complications and death are possible among susceptible populations, being immunocompromised persons and older adults.⁸

13.1 Why the susceptible-population framing matters

An agent that is usually mild but dangerous to a subset changes how advice should be given. The same bite carries materially different risk depending on who received it.

General advice pitched at a healthy adult is not adequate for an immunocompromised or older person, and the threshold in §2 does not vary by patient characteristics as published.

14. The relapsing fever spirochete

The fourth agent, and the one that breaks the model most directly.

Borrelia miyamotoi has been the subject of a Manitoba human seroprevalence study covering 2011 to 2014,² and is included in provincial tick testing from 2013.⁹

The provincial guidance cites work on transmission of the relapsing fever spirochete, Borrelia miyamotoi, by single transovarially-infected larval Ixodes scapularis ticks.²

14.1 What transovarial means here

The pathogen passes from an infected female tick into her eggs, so the larvae that hatch are already infected. They do not need to feed on an infected host first.

For Lyme disease, a larval tick is generally not a concern because it has not yet fed on a reservoir host. For this agent, that reasoning does not hold.

15. Why the larval route matters

The consequence for risk assessment.

Tick risk messaging concentrates on nymphs and adults because those are the stages that have fed before and can therefore be carrying something. A transovarially transmitted agent makes the smallest and most numerous stage a potential source.

15.1 The detection problem this creates

If a nymph is the size of a poppy seed,¹⁰ a larva is smaller. The stage most likely to go unnoticed is the one the standard reasoning excludes.

We would flag this as our inference from two sourced facts rather than a claim either source makes. Neither the provincial criteria nor the general advice we read addresses larval exposure.

15.2 Proportion unknown

We have no figure for what share of infections arise this way, and the single-tick transmission study demonstrates that it can occur rather than how often it does. This is a mechanism, not an epidemiological estimate.

16. What the threshold does not settle

Setting §11 to §15 against §4: the 36 hour criterion concerns Lyme disease, and gates a specific antibiotic.¹ The tick that delivered the bite is tested by the surveillance programme for four agents.⁹

16.1 What we are and are not saying

We are not saying the criterion is wrong. It is a Lyme criterion and it does what it says.

We are saying that a person who is told they do not meet it should not conclude that a tick bite carried no risk, and that the published advice to monitor for symptoms for months¹ is the part that covers the gap. That instruction is doing more work than its placement suggests.

17. The range expansion

Why this is a growing problem rather than a stable one.

A speed of spread model for Ixodes scapularis estimated that the tick's range was expanding northward at 46 km per year.⁵

The tick has undergone extensive range expansion, with reforestation of large areas of the United States creating suitable habitat for the tick and for the primary host of the adult stage, the white-tailed deer, re-emerging from two foci in the northeastern United States and the Midwest, with the northern extent of the range currently expanding into Canada.⁵

17.1 The local driver

Historically Manitoba's harsh winters reduced tick populations, while milder winters in recent years have allowed more ticks to survive until spring, increasing the number of active ticks searching for hosts, and ticks require moist environments to survive.¹⁰

That source is a commercial one and we treat the climate attribution as its characterisation rather than as a finding we have verified.

17.2 The deer link

The peer-reviewed account gives the ecological mechanism. Reforestation created suitable habitat for the tick and for the primary host of the adult life stage, the white-tailed deer.⁵

That is the part of this story that is not about climate. A tick population needs a host for its adult stage, and the distribution of that host is shaped by land use over decades. Where deer go, the adult stage can complete its cycle.

17.3 Why this matters for a property owner

It identifies what makes a site hospitable rather than merely what the weather has been. Vegetation structure, moisture and host presence are properties of a place, and they are the reason risk varies between two sites at the same latitude.

We would flag the application to residential properties as our inference. The sources describe landscape-scale ecology and do not offer yard-level guidance.

18. The Ontario sequence

The pattern to expect, documented next door.

Analysis of surveillance data for 2010 to 2016 in eastern Ontario demonstrates the rapid northward spread of Ixodes scapularis ticks and Borrelia burgdorferi, followed by increasing human Lyme disease incidence, with most spread occurring during 2011 to 2013.⁶

18.1 The order of events

Ticks arrive, the pathogen arrives, and human cases follow. That sequence has a lag, which means present case counts describe a tick distribution from some years earlier.

The practical consequence is that human case data is the slowest of the available signals. A jurisdiction waiting for cases to accumulate before designating a risk area is designating it several years after the exposure began, which is the argument for the acarological indicators in §19 rather than epidemiological ones.⁴

Field sampling detected ticks and the pathogen at sites across southern, eastern and central Ontario, and a later revisit found ticks at 17 of 36 sites including five new ones.⁵ Site-specific density in an Ottawa assessment ranged from 0 to 16.3 ticks per person-hour.⁷

19. Passive surveillance as an indicator

How the risk areas in §6 are determined.

A study found that passive blacklegged tick surveillance data is specific and sensitive for detecting census subdivisions in Ontario and Manitoba where human cases of Lyme disease are most expected, with a strong positive relationship between tick submissions and cases.⁴

The analysis used five adults and nymphs as the optimal cut-off point as a predictor of human Lyme disease risk, distinguishing areas of emerging risk with one to two human cases from endemic areas where three or more cases were acquired.⁴

19.1 What passive means

Passive surveillance depends on members of the public submitting ticks they found. It is therefore shaped by awareness, by access, and by how many people are looking.

That it performs well as a predictor is a genuinely useful finding, and the same caution this journal applied to trap counts applies here: the signal is real and the sampling process is not neutral.

19.2 The active alternative

The other approach sends people out to look. Active surveillance uses tick dragging, in which a cloth is pulled over vegetation and questing ticks attach to it.⁵

The Ottawa assessment used active surveillance at 28 sites and applied a field indicator tool to determine the risk of establishment for each tick cohort at each site, then assigned each site an ecological classification describing the pattern of tick colonisation over two successive cohorts.⁷

19.3 What each method is good for

Active sampling measures density at a chosen site and can establish whether a population is becoming established there. Passive submission covers a far larger area at no field cost and reflects where people and ticks actually meet.

Neither is a substitute for the other, and the risk maps that condition §6 rest on both. We would note that this is the same complementarity this journal described between monitoring and inspection in structural work, arrived at independently by a different discipline.

20. Why the bite goes unnoticed

The reason the attachment clock is usually unknown.

Blacklegged ticks are much smaller than wood ticks and often go unnoticed, being no larger than a poppy seed during immature stages.¹⁰

20.1 The consequence for the criterion

Condition two asks how long the tick was attached. For a nymph found during a body check, the honest answer is usually that nobody knows, which is why the engorgement alternative in §5 carries so much of the load.

It also means the practical intervention is the check itself. A tick found is a tick removed; a tick not looked for continues feeding.

20.2 The size difference across stages

The stage matters for detection as much as for infection. Adults are large enough to be noticed; nymphs are described as no larger than a poppy seed; larvae are smaller again.¹⁰

So the probability that a bite is noticed falls as the stage gets smaller, which runs opposite to what a risk assessment would want. The bites most likely to exceed the attachment threshold are the ones least likely to be found in time.

20.3 What this implies about advice

Telling people to check for ticks is not the same as telling them what they are checking for. A person scanning for something the size of a sesame seed will not find a nymph, and the published description exists precisely because the intuitive mental image is wrong.

We would rank communicating the size ahead of communicating the threshold, since a person who cannot find the tick never reaches the question of how long it was attached. That ranking is ours rather than a sourced recommendation.

21. What actually reduces risk

Check daily after exposure. The threshold is 36 hours, so a daily check puts removal inside it in most cases.¹

Remove promptly. Prompt removal is described as one of the most effective ways to reduce risk.¹⁰

Keep the tick. Identification is the first condition and cannot be met from a description.¹

Do not treat a negative on the criteria as an all-clear. Monitoring for months is advised even where treatment is given.¹

Know the rash is not itchy or tender. That absence is a feature, not reassurance.¹

Do not rely on being outside a risk area. Birds and deer move ticks long distances.²

There is no vaccine for general use in Canada. Prevention rests on avoiding bites, repellents, clothing and checks.¹⁰

Know what size you are looking for. A nymph is described as no larger than a poppy seed.¹⁰

Risk of infection can be lowered by preventing tick bites. That is the province's own summary of the whole subject.¹

22. Limitations and open questions

This is not medical advice and contains no removal instructions. We have deliberately not described removal technique, because that is clinical guidance and the published sources should be used directly.

The criteria are as published and may change. Treatment criteria are set by health authorities and revised.¹ Anyone relying on specifics should consult the current provincial source.

Two transmission studies are cited through provincial guidance. The attachment-duration work and the transovarial transmission work reach us through a reference list rather than being read in the original.²³

One source is a commercial clinic blog. The poppy seed comparison, the climate attribution, the 24 to 36 hour framing and the vaccine statement come from it.¹⁰ We flag it and note it is consistent with the provincial material on the points where they overlap.

The anaplasmosis figures are two years. Stated in §12.1.

Much of the expansion evidence is Ontario. The speed of spread estimate, the emergence sequence and the density figures are from Ontario work.⁵⁶⁷

Sections 3.1, 7.1, 13.1, 15 and 16.1 are our reasoning. The identification difficulty comparison, the two-directions-of-error argument, the susceptible-population point, the larval detection argument and the reading of the criterion's scope are ours rather than sourced positions.

Our commercial position. This company offers tick treatments, so tick-borne disease is a subject we have a commercial interest in. The article's central point, that attachment time governs transmission and that post-bite medical advice is what covers the gap, does not argue for any property treatment we sell. An earlier version of this paragraph stated that we did not treat ticks, which was wrong. We publish it because it is the vector question our clients ask about after mosquitoes and because the one number that governs it is not widely known.

23. Conclusion

Manitoba offers preventive treatment after a blacklegged tick bite only where the tick is reliably identified, was attached at least 36 hours or is engorged, came from southern Manitoba or another known risk area, and there is no allergy to the antibiotic, and it advises monitoring for symptoms for months afterwards even where treatment is given.¹ That is a clear, published, defensible standard, and almost everything a person can do about ticks follows from the second condition.

What the standard does not do is cover the bite. The surveillance programme has tested these ticks for Borrelia burgdorferi since 1995, Anaplasma phagocytophilum since 2006, and Babesia microti and Borrelia miyamotoi since 2013,⁹ reported anaplasmosis incidence roughly doubled between 2017 and 2018,⁸ and one of those agents passes through the egg so that a larval tick can carry it.² The threshold is a Lyme threshold, and the bite is no longer only a Lyme exposure.

Which leaves the least memorable sentence in the provincial guidance doing the most work: keep watching for months, whatever the criteria said. The number is what determines the prescription. The instruction that follows it is what covers everything the number was not written for, and it is the part that gets left out when the advice is repeated.

References

1. Lyme Disease. Public Health, Manitoba Health, Province of Manitoba. Primary provincial source. Used for the statement that Lyme disease is caused by a bacterium transmitted in North America by the bite of an infected blacklegged tick (Ixodes scapularis) or western blacklegged tick (Ixodes pacificus); that symptoms typically appear 3 to 30 days following the bite with many people developing a characteristic expanding rash, erythema migrans, which is neither itchy nor tender; that other early symptoms are non-specific and may include headache, fatigue, chills, fever, muscle aches, joint pain, stiff neck or swollen lymph nodes; that untreated infection can cause joint, heart and nervous system complications and that the disease can be successfully treated with antibiotics particularly when diagnosed early; for the four published conditions for preventive treatment, being that the tick can be reliably identified as a blacklegged tick, that the tick was attached for a minimum of 36 hours or engorged, that the tick was picked up from a location in southern Manitoba south of the 53rd parallel or another known risk area outside Manitoba, and that there are no known allergies to doxycycline; and for the advice that individuals should continue to monitor themselves for symptoms in the months following their tick bite even if they receive preventative treatment. https://www.gov.mb.ca/health/publichealth/diseases/lyme.html
2. Tickborne Infections in Manitoba. Manitoba Health communication to health care providers, 2019. Primary provincial source. Used for the statement that the risk of exposure is not uniform within, nor solely confined to, the identified risk areas, as ticks can be transported great distances by migrating birds and deer, so that tick-borne diseases can potentially be acquired anywhere in the southern part of the province; for the reference to surveillance having revealed established blacklegged tick populations with a current surveillance map; for its citation of Eisen, Pathogen Transmission in Relation to Duration of Attachment by Ixodes scapularis Ticks, Ticks and Tick-borne Diseases 2018, 9(3), 535 to 542; for its citation of Breuner and colleagues on transmission of the relapsing fever spirochete Borrelia miyamotoi by single transovarially-infected larval Ixodes scapularis ticks, Ticks and Tick-Borne Diseases 2018, 9(6), 1464 to 1467; for its citation of Kadkhoda and colleagues on human seroprevalence of Borrelia miyamotoi in Manitoba in 2011 to 2014, CMAJ Open 2017, 5(3), E690 to E693; and for the guidance that treatment should be initiated based on clinical suspicion of disease. https://manitoba.ca/health/publichealth/cdc/docs/hcp/2019/061119.pdf
3. Eisen, L. (2018). Pathogen Transmission in Relation to Duration of Attachment by Ixodes scapularis Ticks. Ticks and Tick-borne Diseases, 9(3), 535 to 542. doi:10.1016/j.ttbdis.2018.01.002. Cited for identification as the attachment-duration literature underlying the provincial criterion; it reaches us through the reference list at reference 2 and we have not read the original. https://doi.org/10.1016/j.ttbdis.2018.01.002
4. Detection of municipalities at-risk of Lyme disease using passive surveillance of Ixodes scapularis as an early signal: A province-specific indicator in Canada. PLOS One. doi:10.1371/journal.pone.0212637. Used for the finding that passive blacklegged tick surveillance data is specific and sensitive for detecting census subdivisions in Ontario and Manitoba where human cases of Lyme disease are most expected, with a strong positive relationship between tick submissions and cases; and for the use of five adults and nymphs as the optimal cut-off point as a predictor of human Lyme disease risk, distinguishing areas of emerging risk with one to two human cases from endemic areas where three or more cases were acquired. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0212637
5. Northward range expansion of Ixodes scapularis evident over a short timescale in Ontario, Canada. PubMed Central PMC5744917. Used for the estimate from a speed of spread model developed by Leighton and colleagues (2012) that the tick's range was expanding northward at 46 km per year; for the account that the blacklegged tick has undergone extensive range expansion, that reforestation of large areas of the United States created suitable habitat for the tick and for the white-tailed deer as primary host of the adult stage, that the tick re-emerged from two foci in the northeastern United States and the Midwest, and that the northern extent of its range is currently expanding into Canada; and for the field results that baseline sampling detected the tick and Borrelia burgdorferi at sites across southern, eastern and central Ontario and that a revisit collected ticks at 17 of 36 sites, five of which were new. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5744917/
6. Kulkarni, M.A., Narula, I., Slatculescu, A.M. and Russell, C. (2019). Lyme Disease Emergence after Invasion of the Blacklegged Tick, Ixodes scapularis, Ontario, Canada, 2010 to 2016. Emerging Infectious Diseases. doi:10.3201/eid2502.180771. Used for the finding that analysis of surveillance data for 2010 to 2016 in eastern Ontario demonstrates the rapid northward spread of Ixodes scapularis ticks and Borrelia burgdorferi, followed by increasing human Lyme disease incidence, with most spread occurring during 2011 to 2013, and that continued monitoring is essential to identify emerging risk areas. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6346472/
7. A multi-year assessment of blacklegged tick (Ixodes scapularis) population establishment and Lyme disease risk areas in Ottawa, Canada, 2017 to 2019. PubMed Central PMC7861446. Used for the statement that Canadians face an emerging threat of Lyme disease due to the northward expansion of the tick vector, for the use of active surveillance at 28 sites with a field indicator tool to determine establishment risk for each tick cohort, and for the reported total annual site-specific density ranging from 0 to 16.3 ticks per person-hour. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7861446/
8. A review of ticks in Canada and health risks from exposure. National Collaborating Centre for Environmental Health. Evidence review. Used for the statement that since 2013 anaplasmosis incidence has been steadily rising in Manitoba where surveillance is available, with an incidence of 1.54 per 100,000 in 2018, twice as high as the 0.66 per 100,000 recorded in 2017; that there is a risk of anaplasmosis infection in any community with an established population of blacklegged ticks and that areas with greater Lyme disease risk also carry higher anaplasmosis risk; and that babesiosis is primarily transmitted by Babesia microti through Ixodes scapularis although infection is also possible by Babesia duncani and Babesia divergens, with infection usually mild to moderate with flu-like symptoms but complications and death possible among immunocompromised persons and older adults. https://ncceh.ca/resources/evidence-reviews/review-ticks-canada-and-health-risks-exposure
9. Geographic range and minimum infection rate of Borrelia burgdorferi, Anaplasma phagocytophilum, Babesia microti, and Borrelia miyamotoi in Ixodes scapularis ticks in Manitoba, Canada from 1995 to 2017. PubMed record 38807283. Used for the statement that the expanding geographical range of blacklegged ticks and their ability to transmit these four agents poses an emerging public health risk; for the study determining the geographic distribution and minimum infection rate of ticks infected with each, submitted to the Public Health Agency of Canada's passive tick surveillance programme from 1995 to 2017; and for the testing history, in which ticks were tested by PCR for B. burgdorferi since 1995, A. phagocytophilum since 2006, and Ba. microti and B. miyamotoi since 2013. https://pubmed.ncbi.nlm.nih.gov/38807283/
10. Fast Tick Bite Treatment to Prevent Lyme Disease as Cases Rise in Manitoba. Commercial medical clinic blog. Commercial source with an interest in treatment services, cited as attributed material. Used for the statements that in most cases the tick must remain attached for a prolonged period, typically at least 24 to 36 hours, before Lyme disease transmission becomes likely, and that promptly removing a blacklegged tick is one of the most effective ways to reduce risk; that blacklegged ticks are much smaller than wood ticks and often go unnoticed, being no larger than a poppy seed during immature stages; that Manitoba's historically harsh winters naturally reduced tick populations while milder winters in recent years have allowed more ticks to survive until spring, and that ticks require moist environments; and that there is currently no approved Lyme disease vaccine available for the general public in Canada, with prevention relying on avoiding tick bites, repellents, protective clothing and routine tick checks. https://emcare.ca/blog/fast-tick-bite-treatment-to-prevent-lyme-disease/