Fewer Ticks, No Fewer Infections: What the Masked Trials of Yard Tick Control Found

1. Introduction: the outcome a buyer actually wants

Nobody pays to have ticks killed for their own sake. They pay not to get sick. Those are different outcomes, and for most of the history of yard tick treatment only the first was measured.

1.0b The trials were run by public health researchers

A federal disease agency, state health departments and academic ecologists, none of whom sell tick treatment, which is unusual among the studies this journal cites.⁶

1.1 And the first trial found the same

The authors of the second describe their result as consistent with the first.³

1.1b Which is the rarest kind of evidence in this trade

A masked, placebo-controlled test of whether a pest control service changes the outcome people buy it for, as opposed to whether it kills the pest.

1.2 What this article argues

That tick reduction is a surrogate that failed to predict the outcome, that the likeliest explanations all point away from the yard as the unit of protection, and that a company selling tick treatment should describe it accordingly. Sections 14, 17 and 23 are the case.

2. What was already known

That the products work.

In controlled studies, a single springtime application of acaricide has been shown to kill 68%–100% of ticks.¹ Field trials more generally show chemical or biological acaricides reducing tick numbers by 50 to 90 per cent.³

2.1 Which nobody disputes

Neither trial questions that the products kill ticks, and both confirm it on the treated properties.¹⁴

2.1b And the range is wide

Sixty-eight to a hundred per cent in controlled studies and fifty to ninety in field trials, which is what one would expect from differences in product, habitat and timing.¹³

2.2 The question was always the next step

Whether ticks killed in a yard translate into bites avoided by the people living there.

3. And what was assumed

That killing ticks prevents disease.

Although public health authorities recommend use of acaricides to control tick populations in yards, the effectiveness of these pesticides to prevent tick bites or human tick-borne diseases is unknown.¹

3.0a The reasoning behind the advice was sound

Fewer ticks should mean fewer bites, and fewer bites should mean less disease. Each step is plausible, which is why the chain went untested for so long.

3.0b And the expectation is still the default

Later research papers continue to describe acaricides as expected to reduce exposure by reducing tick abundance, citing these trials as the exceptions to that expectation.²

3.1 Recommended before it was tested

Which is the sequence the household trial was designed to correct.¹

3.1b Which is an ordinary sequence in public health

Advice is given on the best available reasoning and tested later, and the test sometimes finds the reasoning incomplete.

3.2 And earlier integrated studies could not settle it

They were described as limited by a lack of masking, a lack of placebo controls, small scale, unbalanced designs and low statistical power, and generally did not include human health outcomes.³

4. The household trial

The first test.

A 2-year, randomized, double-blinded, placebo-controlled trial among 2727 households in 3 northeastern states.¹

4.1 The first to ask the question properly

One later paper describes it as, to the authors' knowledge, the first to test whether experimentally reducing tick abundance reduced human encounters with ticks or tick-borne disease in people.⁸

4.2 After the recommendation was already in place

Which means the advice to treat yards rested on the surrogate alone until this test, for however long it had been given.

5. How it was designed

To look like ordinary practice.

Households received a single springtime barrier application of bifenthrin or water according to recommended practices. Tick drags were conducted three to four weeks after treatment on a tenth of properties, encounters and illness were collected through monthly surveys, and reports of illness were validated by medical record review.¹

5.0b Three states, two years

Enough geography and time that a local quirk or a single unusual season is unlikely to explain the result.¹

5.1 According to recommended practices

Which matters, because it means the trial tested the treatment as commonly delivered rather than an unusually intensive version of it.¹

5.1b A single application

Once in spring, according to what the trial describes as recommended practice, rather than a programme of repeated visits.¹

5.1c Which leaves one question open

Whether repeated applications through a season would do better, which this design did not test and which a company offering more visits would want answered.

5.2 And water as the placebo

Sprayed the same way, so neither the residents nor the people assessing them could tell which yards were treated.¹

6. What it found

Treatment was associated with a 63% reduction in abundance of questing nymphal blacklegged ticks, but the trial did not find concomitant effects on tick encounters or disease incidence.⁴

6.1 Nearly two thirds fewer ticks

A reduction any customer would notice in a tick drag, and the one a treatment would ordinarily be judged by.⁴

6.1b Measured weeks after treatment

Tick drags three to four weeks after the spring application, when the product's effect should be near its strongest, which makes the tick result a fair test of the product.¹

6.2 And no detectable difference in what happened to people

Validated against medical records in the illness reports.¹

7. The neighbourhood trial

Designed to answer the obvious objection.

One possible reason for the first result was that people meet ticks outside their own yards, so a second study asked whether tick control applied throughout a residential neighbourhood, using more than one method, could reduce risk.³

7.0b And a large enrolment

More than 2,380 people and 849 pets took part, with households completing surveys every two weeks about tick encounters.⁷

7.1 Twenty-four neighbourhoods

In a county with some of the highest rates of tick-borne disease, with six replicate neighbourhoods in each of four treatment groups, sized for 80 per cent power to detect an effect of 60 per cent.³

8. Two methods, alone and together

Both chosen as environmentally modest.

Bait boxes attract small mammals and apply fipronil to them, killing ticks feeding on the mice and chipmunks that infect ticks with the Lyme bacterium. A fungal spray, containing spores of a Metarhizium strain, is applied to low vegetation to kill questing ticks.⁶⁴

8.0b Aimed at different stages

Bait boxes kill larval ticks on rodents in summer and autumn, so their effect should appear as fewer nymphs the following spring; the spray kills questing nymphs directly, within days to weeks.⁴

8.1 With matching placebos

Water sprayed from identical trucks and placebo boxes placed around properties, with assignments masked from participants and from the people collecting data.³⁵

8.2 Fully crossed

Neighbourhoods received bait boxes alone, spray alone, both, or neither, so each method and their combination could be tested against placebo in one design.³

8.3 And the spray reached into woodland edges

For properties with extensive forest, spraying extended twelve metres into it, applied twice a year before and during the nymphal peak.³

9. What it found

The same pattern.

Questing ticks and ticks attached to small mammals were reduced by about half in neighbourhoods with active bait boxes, while the fungal spray had a more modest effect, and despite this reduction in abundance of blacklegged ticks, we found no significant effects of either intervention or of both together on incidence of tick-borne diseases in people.⁴

9.0b Over several years

The trial ran from 2017 to 2020, long enough for bait boxes aimed at the next year's nymphs to have shown any cumulative effect.⁴

9.1 Nor on encounters

No effect of either treatment or both together on reported encounters of human or outdoor-pet residents with ticks.⁵

9.1b Encounters were reported in quantity

The trial received 1,664 reports of encounters between ticks and human participants, so the null result on encounters is not for want of data.³

9.2 Aggregated across three years of deployments

The follow-up analysis pooled the 2017 to 2019 seasons, so the null result is not a single bad year.⁴

10. The pet result

The one positive human-adjacent finding.

A significantly reduced incidence of tick-borne disease in outdoor pets was observed in neighbourhoods treated with bait boxes.⁵

10.1 Pets are a different exposure

An outdoor pet spends more of its time inside the treated area than a person does, which is the condition under which a yard treatment should have its best chance.

10.2 So the contrast is informative either way

If real, it fits the idea that exposure away from the treated area is what defeated the human result.

Sections 10.1 and 10.2 are ours.

11. Which the authors handle carefully

More carefully than a marketer would.

The pet effect should be interpreted cautiously: there was no corresponding effect on tick encounters among pets, pet diagnoses were not confirmed with veterinarians, and pet disease was the only outcome for which the fungal spray also showed a significant effect.³

11.0b Which is exactly what a careful author does

Reports the favourable subgroup and then lists every reason not to lean on it, which our earlier articles found commercial sources almost never do.

11.1 That last point is the telling one

A spray that barely reduced ticks appearing to reduce pet disease suggests the pet result may not be measuring what it seems to.

That reading is ours.

12. Two trials, one pattern

The neighbourhood trial's authors note that, to their knowledge, the two household-scale trials by the first group and their own are the only randomised, placebo-controlled, double-masked studies examining acaricidal treatments against tick abundance, tick encounters and tick-borne disease together.⁴

12.0b And both groups say so

The neighbourhood trial's authors describe their result as consistent with the household trial, which is two independent teams reaching the same conclusion by different routes.³

12.1 Different products, different scales, same result

A synthetic pyrethroid sprayed at individual homes, and a rodent-targeted fipronil device plus a fungal spray across whole neighbourhoods, both reducing ticks and neither reducing human disease.¹⁴

12.2 Which makes a product-specific explanation unlikely

If one chemistry had failed, a better one might succeed. When several fail in the same way, the problem is more likely in the chain than in the chemistry.

13. Why these trials carry weight

Every feature the earlier integrated studies lacked, masking, placebo, scale, balance and human outcomes, is present in these.³

13.0b And the household trial checked illness against records

Rather than accepting a resident's report of a diagnosis, which removes a second source of reporting error from the disease outcome.¹

13.1 And masking is the feature that matters most here

Tick encounters are self-reported, and a resident who knew their yard was treated might report fewer encounters simply from expectation.

13.2 The placebo arms remove that

Both treated and untreated households believed they might be protected, so a difference in reporting would have to come from the ticks.³

14. The surrogate endpoint

Our framing.

A surrogate is a measurement taken because it is easier than the outcome and assumed to move with it. Tick counts on a treated property are the surrogate here, and tick-borne disease is the outcome. Both trials showed the surrogate moving and the outcome not.

14.0a The trials tested the whole chain at once

Ticks on the property, encounters reported by residents, and illness confirmed in records, which is what allowed the break in the chain to be located.¹

14.0b And the surrogate was chosen for convenience

Counting ticks on a drag cloth takes an afternoon. Counting infections in a population takes years and thousands of households.

14.0c And the gap between them is where the value is claimed

A service is sold on the outcome and demonstrated on the surrogate, which works only for as long as nobody measures both.

14.1 This is the classic failure

Medicine has many examples of treatments that improved a laboratory marker and not the patient. This is the same shape in a yard.

14.2 And it was invisible until the outcome was measured

Studies counting ticks could never have revealed it, because they did not ask whether anybody got sick less.

15. Which this journal keeps meeting

In other forms.

Our house fly article found a laboratory measure of susceptibility that did not predict the field result. Our efficacy data articles found performance claims resting on the easier measurement. Our callback and bait uptake articles found activity counted in place of outcome.

15.0b And in the reference strain article

Where a resistance ratio was a real measurement of the wrong comparison, which is the same problem one step removed.

15.1 This is the cleanest example yet

Because the outcome was measured properly, in masked trials, by public health researchers with no product to sell.

16. Explanation one: not deep enough

The first hypothesis.

One potential reason is that the treatments did not reduce tick abundance below some putative threshold needed for reduced disease risk.³ Much stronger reductions may be necessary to reduce encounters or cases.⁴

16.0b And the relationship may not be linear

If disease depends on the chance of any infected bite over a season, halving ticks may reduce that chance much less than half, especially where ticks were abundant to begin with.

16.1 Which would mean half is not enough

A property with half its ticks still has ticks, and a single infected bite is all a case requires.

That arithmetic is ours.

16.2 Which the second trial could not rescue

Combining two methods did not deepen the reduction enough to change human outcomes, since the spray added little to the bait boxes.⁴

17. Explanation two: ticks are met elsewhere

The second.

Humans might frequently encounter ticks in locations other than their yards.³ One review notes that the risk of infection at the neighbourhood scale has been shown to be 57 per cent greater than at the yard scale.⁹

17.0a Which also explains the review's figure

If risk is greater at the neighbourhood scale than at the yard scale, a treatment confined to the yard is working on the smaller share.⁹

17.0b And a yard is a small part of anybody's week

Parks, trails, school grounds and other people's gardens all contribute, and a treatment confined to one property addresses only the share of exposure that happens there.

17.0c And children and pets range further than the yard

Which widens the gap between the treated area and the places where a household actually meets ticks.

17.1 Which is why the second trial went neighbourhood-wide

And why its null result makes the explanation harder to rely on than it first appears.³

18. The participation problem

In each neighbourhood of about a hundred properties, 26–41% of residents agreed to participate.⁵

18.0a And participation was not random within neighbourhoods

Households chose whether to take part, although treatment assignment among neighbourhoods was randomised, so the treated homes in any neighbourhood were those willing to enrol.⁵

18.0b A familiar constraint

Participation in any voluntary neighbourhood programme is partial, which our rodent and waste articles found limits every area-wide intervention that depends on individual consent.

18.1 So even neighbourhood treatment was partial

Most properties in every treated neighbourhood were untreated, which leaves room for the second explanation to operate within the trial.

That inference is ours and the authors do not draw it in our extracts.

19. Explanation three: relaxed vigilance

The one with consequences.

If residents whose properties are treated with acaricides relax their vigilance against tick bites, then the failure of tick-control interventions could have the perverse outcome of increasing exposure risk.⁸

19.0b And it inverts the usual logic of safety

Ordinarily a measure that fails does nothing. A measure that fails while persuading people to drop the measures that work does less than nothing.

19.1 Offered as a possibility

The sentence is conditional, and the authors do not report measuring it.

20. Which would make the treatment harmful

Our reading.

A resident who stops checking for ticks after bathing, stops using repellent in the garden, or lets children play in long grass because the yard was treated, has traded the protections that work for one that has not been shown to.

20.0a And it would be invisible to the seller

A customer who later falls ill after dropping precautions does not tell the company that treated the yard, and nobody connects the two.

20.0b The mechanism is ordinary

People adjust caution to perceived risk, and a treatment sold as protection lowers perceived risk whether or not it lowers the real one.

20.1 The trials cannot tell us whether this happened

Masking means residents did not know whether their yard was treated, so behaviour change from knowing is precisely what the design removed.¹

20.1b Masking protects the trial from exactly this

Which is its purpose, and also why the trial cannot measure the behaviour a sold treatment would produce.

20.2 Which means real customers may do worse than the trial

A paying customer knows the yard was treated, and the trials' null result was obtained without that knowledge.

21. What the researchers concluded

In their own words.

It seems prudent to assume that residential tick control by the widely available commercial products may not protect residents against exposure to tick-borne infections.⁸

21.0a Vaccination is not yet available here

Our attachment-duration article recorded that there is no vaccine for general use in Canada, so the researchers' preferred future strategy is not a present option for anybody locally.

21.0b Prudent is the operative word

Not a finding that treatment fails, but a recommendation about what to assume while the reasons remain unknown.⁸

21.0c And the conclusion is about commercial products specifically

The widely available commercial products, which is the category any pest control company offering tick treatment is working in.⁸

21.1 And the project summary goes further

Suggesting that reducing tick-borne disease in people might be quite difficult to achieve by managing ticks in neighbourhoods or individual yards, and that vaccination may be the better strategy going forward.⁶

22. What this does not show

Which matters as much.

That the products do not kill ticks, which they do. That tick reduction has no value, since a yard with fewer ticks is a yard with fewer ticks. Or that every method in every setting fails, since two trials in one region test particular products at particular intensities.¹³

22.0a Nor that tick treatment has no place

A household may reasonably want fewer ticks where children play or dogs run, and a treatment that delivers that is delivering something real.

22.0b Nor that the pet effect is nothing

Outdoor pets spend their time in the treated yard, which is the setting where a yard treatment should matter most, and the result may be real even if its authors are cautious.⁵

22.0c Nor that deer or landscape measures fail

Other approaches, including devices that treat deer and changes to vegetation and yard edges, were not tested in these two trials and are not addressed by them.⁹

22.1 A null result is not proof of no effect

The neighbourhood trial was powered for a large effect, and a smaller real effect could have been missed.³

23. What an honest description says

Our standard.

That a yard treatment reduces ticks on the treated property, that the best trials found no reduction in bites or illness among residents, and that personal precautions remain necessary whether or not the yard is treated.

23.0a And it names the precautions alongside it

Checking for ticks after being outdoors and removing them promptly, which is the advice our attachment-duration article gave and which works regardless of the yard.

23.0b And it does not require abandoning the service

Fewer ticks on a property is a real result a customer may reasonably want, for nuisance, for pets or for peace of mind, provided it is not sold as disease prevention.

23.1 Which is less than the product is usually sold on

Disease prevention is the reason anybody buys it, and it is the claim the evidence does not support.

24. What still protects people

From our earlier tick article.

Our article on the attachment-duration rule set out that transmission depends on how long a tick feeds, which makes checking for ticks and removing them promptly the measure that addresses the mechanism directly.

24.0a A daily check fits the mechanism

Our earlier article set the threshold at 36 hours, so a daily check after exposure puts removal inside it in most cases, wherever the tick was met.

24.0b And it is the one measure under the person's control

A yard treatment depends on where the tick was met. A tick check after coming indoors works wherever it was met.

24.1 Which neither trial undermines

Both measured environmental tick control, and neither concerns what a person does after coming indoors.

24.2 And the explanations in §§16 to 19 all favour it

Whether the problem is depth, location or complacency, a person checking themselves after being outdoors is protected against all three.

25. Why a masked trial was needed

Our argument.

An unmasked study of treated households would compare people who chose treatment, and who may differ in caution, landscaping and outdoor habits, with people who did not. Randomisation and placebo remove both problems.

25.0a Which is how most treatment claims are supported

By comparing people who bought a service with people who did not, which is the design these trials were built to replace.

25.0b Self-selection is the specific problem

People who buy tick treatment may also be the people who check for ticks, which would make treated households look safer for reasons that have nothing to do with the spray.

25.1 And customer satisfaction could never have found this

A household that paid for treatment and did not get sick would credit the treatment, whether or not it had done anything.

26. What we take from it

Three things.

Killing ticks and preventing disease are different outcomes. Section 14.¹

The yard may be the wrong unit of protection. Section 17.⁹

And a treatment that makes people less careful could do net harm. Section 19.⁸

26.1 And one thing we cannot take from it

Whether tick treatment reduces disease in Manitoba, which nobody has tested and which the American result makes doubtful rather than disproven.

27. Our own position

The disclosure.

This company offers tick treatments. This article reports that the best available trials found yard tick control reduced ticks without reducing tick-borne disease among residents, which is a finding against the reason customers buy the service.

27.0b And the article's conclusion does not favour our service

It favours personal precautions, which no company sells, and vaccination, which is not ours to offer.⁶

27.1 And it sets a standard we can be held to

Section 23 describes what an honest account of the service says, and a customer is entitled to compare what we tell them against it.

28. The Manitoba position

28.1 The tick is established here

Our frontier article traced blacklegged tick establishment across southern Manitoba, so the question is local even though the trials were not.

28.1b And the public health question is the same here

Whether treating a yard reduces illness among the people who live there, which no Canadian study we found has asked.

28.2 What we could not find

Any Canadian trial of residential tick control against human outcomes, and any Canadian public health guidance on yard acaricide treatment of the kind the household trial describes as American advice.

28.2b The tick season here is shorter

The surveillance our frontier article described collected ticks in autumn and spring, in a province with long winters, which leaves a shorter window each year for exposure away from the yard or for any treatment to matter.

28.3 And conditions here differ

Lower tick density and a shorter season than the trial region, which could make any real effect smaller or the treatment less relevant, and we have no evidence either way.

29. Limitations and open questions

Both trials are from the northeastern United States. Tick density, host communities, housing and outdoor habits there may differ from southern Manitoba, and we found no trial here.¹³

That is the most important limitation because a treatment's effect on disease depends on where people meet ticks, which is exactly what varies between regions.

We read abstracts, summaries and extracts. The household trial reaches us through its abstract and descriptions by later authors, and the neighbourhood trial through extracts of the paper, a follow-up and a 2026 synthesis.¹⁴⁵

A rodent-targeted household trial is known to us only by title. The neighbourhood authors cite a 2021 randomised trial of bait boxes in Connecticut, whose results we did not read.⁴

The 57 per cent figure is second-hand. It comes from a review summarising another study, which we did not read.⁹

Risk compensation is hypothesised, not measured. Section 19 reports a plausible mechanism the researchers raise, not an observed effect.⁸

Sections 11.1, 14, 16.1, 18.1, 20, 23 and 25 are our reasoning. The surrogate endpoint framing, the arithmetic of partial reduction, the participation inference, the account of how paying customers differ from masked participants and the proposed honest description are ours rather than sourced positions.

30. Conclusion

Acaricides kill ticks. Controlled studies show a single springtime application killing 68 to 100 per cent of them, and public health advice has recommended treating yards, though whether that prevented bites or disease was unknown.¹ A randomised, double-blinded, placebo-controlled trial among 2,727 households applied bifenthrin or water according to recommended practice, and found 63 per cent fewer questing nymphs on treated properties and no reduction in tick encounters or tick-borne disease.¹⁴ A second masked trial treated whole neighbourhoods with fipronil bait boxes for rodents and a fungal spray, alone and together. The bait boxes halved questing ticks and ticks on rodents; the spray did less; and neither reduced human encounters or human disease, with a reduction in outdoor pet diagnoses that its own authors ask readers to treat cautiously.⁴⁵³

That is a surrogate endpoint failing in plain view. Tick counts were the measurement taken for decades, and disease was the outcome assumed to follow, and when the outcome was finally measured it did not follow. The researchers offer three explanations. The reduction may not be deep enough; people may meet ticks away from their yards, a possibility sharpened by the fact that only 26 to 41 per cent of households in each treated neighbourhood took part; or residents of treated properties may relax their precautions, which would give a failed treatment the perverse effect of increasing exposure.³⁵⁸ The third cannot be tested by a masked trial, because masking removes the knowledge that would change behaviour, which means a paying customer who knows the yard was treated may do worse than a trial participant.

None of this shows that tick treatment is useless. It shows that its value lies in fewer ticks on a property, not in demonstrated protection from disease, and that the protections that do address the mechanism, checking for ticks and removing them promptly, remain necessary whatever is done to the yard. The researchers' own conclusion is that it seems prudent to assume the widely available commercial products may not protect residents from tick-borne infection.⁸ This company offers tick treatment, and that is the standard our description of it should meet.

References

1. Effectiveness of residential acaricides to prevent Lyme and other tick-borne diseases in humans, published in an infectious diseases journal in 2016 and read as its abstract. Peer-reviewed material and the first of the two central trials. Source for the statement that in controlled studies a single springtime application of acaricide has been shown to kill 68 to 100 per cent of ticks; for the statement that although public health authorities recommend acaricides to control tick populations in yards, their effectiveness in preventing tick bites or human tick-borne disease was unknown; and for the design of a two-year, randomised, double-blinded, placebo-controlled trial among 2,727 households in three northeastern states, in which households received a single springtime barrier application of bifenthrin or water according to recommended practices, tick drags were conducted three to four weeks after treatment on ten per cent of properties, information on encounters and disease was collected by monthly surveys, and reports of illness were validated by medical record review. https://academic.oup.com/jid/article-abstract/214/2/182/2572107
2. Study of the effects of residential acaricide treatments on patterns of pathogen coinfection in blacklegged ticks, published in a journal and accessed through a public biomedical archive, read as an extract of its introduction. Peer-reviewed material. Source for the characterisation of acaricides as expected to aid in preventing exposure by reducing tick abundance, with the two household trials and the neighbourhood trial cited as the exceptions to that expectation. https://pmc.ncbi.nlm.nih.gov/articles/PMC11770522/
3. Effects of tick-control interventions on tick abundance, human encounters with ticks and incidence of tick-borne diseases in residential neighbourhoods, published in an emerging infectious diseases journal in 2022 and read as extracts. Peer-reviewed material and the second central trial. Source for the statement that field trials generally show chemical or biological acaricides reducing tick numbers by 50 to 90 per cent; for the account of earlier integrated studies as limited by lack of masking, lack of placebo controls, small scale, unbalanced designs and low power, and as generally lacking human health outcomes; for the description of the household trial's result and the two proposed explanations, that reductions may not reach a threshold needed for reduced disease risk and that people may encounter ticks away from their yards; for the design using six replicate neighbourhoods in each of four treatment groups with 80 per cent power to detect a 60 per cent effect, masked assignment, and placebo spraying from identical trucks; for the caution that the pet result should be interpreted carefully because there was no corresponding effect on pet encounters, diagnoses were not confirmed with veterinarians, and pet disease was the only outcome for which the fungal spray showed a significant effect; and for the summary that the interventions were not associated with significant reductions in human encounters with ticks or human tick-borne disease, consistent with the household trial. https://wwwnc.cdc.gov/eid/article/28/5/21-1146_article
4. Follow-up analysis of the impacts over time of neighbourhood-scale interventions to control ticks and tick-borne disease, accessed through a public biomedical archive and read as extracts. Peer-reviewed material. Source for the description of bait boxes applying fipronil to small mammals and of the fungal spray containing spores of a Metarhizium brunneum strain applied to ground and low vegetation; for the finding that questing ticks and ticks attached to small mammals were reduced by about half with active bait boxes while the spray had a more modest effect, with no significant effect of either or both on tick-borne disease in people; for the conclusion that neighbourhood deployment is unlikely to be an effective means of protecting the public despite moderately strong tick control; for the report that the household trial found a 63 per cent reduction in questing nymphs without effects on encounters or disease incidence, and that much stronger reductions may be necessary; and for the statement that, to the authors' knowledge, the two household-scale trials and their own are the only randomised, placebo-controlled, double-masked studies of acaricidal treatments examining abundance, encounters and disease, including a 2021 trial of bait boxes in Connecticut. https://pmc.ncbi.nlm.nih.gov/articles/PMC9993163/
5. Synthesis of the ecological and epidemiological consequences of the neighbourhood trial, published in a transboundary and emerging diseases journal in January 2026 and read as extracts. Peer-reviewed material. Source for the description of 24 neighbourhoods in one county randomly assigned to four groups, each of about 100 residential properties with 26 to 41 per cent of residents agreeing to participate, and treatment assignments masked from participants and data collectors; for the finding that despite roughly halved nymphal tick density with bait boxes there was no effect of either intervention or both on reported encounters of human or outdoor-pet residents with ticks, and no reduction in reported human tick-borne disease; and for the observation of significantly reduced tick-borne disease in outdoor pets in bait box neighbourhoods, with no reduction associated with the fungal spray. https://onlinelibrary.wiley.com/doi/10.1155/tbed/4940832
6. Project page for the neighbourhood tick trial, published by the ecological research institute that led it. Institutional summary material from the researchers. Source for the statement that federal research had found spraying individual yards did not reduce tick-borne illness or tick encounters; for the description of the bait box as delivering fipronil to mice and chipmunks, which are largely responsible for infecting ticks with the Lyme bacterium; for the summary that bait boxes reduced ticks in yards by about half, the fungal spray did not reduce tick numbers, and tick-borne disease incidence in people was not affected by either; and for the conclusion that reducing tick-borne disease in people might be quite difficult to achieve by managing ticks in neighbourhoods or yards, and that vaccination may be the better strategy going forward. https://www.caryinstitute.org/science/tick-project
7. Event page describing a presentation of the neighbourhood trial's results by its directors, published by the same institute. Institutional material. Source for the figures of more than 2,380 people and 849 pets participating across 24 neighbourhoods, with households completing biweekly surveys about tick encounters. https://www.caryinstitute.org/news-insights/lecture-video/tick-project-focus
8. Article asking whether experimental reduction of blacklegged tick abundance reduces Lyme disease incidence, published in a pathogens journal in 2023. Peer-reviewed material. Source for the statement that until the causes of the lack of efficacy of tick control in preventing disease are better understood, it seems prudent to assume that residential tick control by widely available commercial products may not protect residents against exposure to tick-borne infections; and for the statement that if residents of treated properties relax their vigilance against tick bites, the failure of tick control could have the perverse outcome of increasing exposure risk. https://doi.org/10.3390/pathogens12050714
9. Review of new paradigms for controlling Lyme disease by targeting ticks, pathogens and reservoir hosts, accessed through a public biomedical archive and read as an extract. Peer-reviewed review material. Source for the summary that environmental acaricide spraying reduced questing ticks around homes by more than 60 per cent with no effect on Lyme disease transmission to homeowners when used on their own property only; for the suggestion that homeowners may be acquiring infection from ticks outside their property; and for the statement, citing another study, that the risk of infection at the neighbourhood scale has been shown to be 57 per cent greater than at the yard scale. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7744311/