Our population-based study (1) on the effectiveness of breed-specific legislation (BSL) targeting pit-bull (terrier) type dogs in the Canadian province of Manitoba generated some interest in the media and among policy -makers and the public in Canada and the United States (2-10). With this experience of listening to different stakeholders and communicating with some, we hope to elaborate on our findings in language that is accessible to all. The objective of the study was to determine trends in the frequency of dog-bite injury hospitalizations (DBIH) over time for jurisdictions with and without a ban on pit bull (terrier)-type dogs in Manitoba (1).

We reported that at the provincial level in Manitoba, there was a decrease in incidence of DBIH from 3.47 to 2.84 per 100,000 person-years associated with implementation of a ban on pit-bull terrier type dogs. That is, there was a decrease by 0.63 per 100,000 persons per year (an 18.1% decrease in DBIH rate) in 16 self-selected urban and rural jurisdictions. Correspondingly, in people aged 0 to < 20 years, there were 1.76 fewer DBIH per 100,000 person-years (a 25.5% decrease in DBIH rate) in Manitoba. This decrease in rates of DBIH may be a conservative finding because enforcement of legislation, which was not measured and is known to have varied across the jurisdictions and over the years, is assumed to be minimal, if at all. While the type of legislation studied was specifically a ban, no jurisdictions were known to have outlawed pit bulls overnight. As existing individual dogs were allowed to live out their lifetimes, no drastic reduction in numbers of pit bulls, and by extension, in numbers of DBIH, was expected in jurisdictions that implemented bans only gradually since 1990.

What does the change in incidence of DBIH at the provincial level mean? The Canadian province of Ontario, with a population about 11 times larger than Manitoba, has a province-wide ban on pit-bull terrier type dogs since 2005 (11). Assuming that Ontario's DBIH rate, rate of penetration of dog population (i.e., dogs per capita of human population) and dog-breed distributions are similar to those in Manitoba, we applied the decrease of 0.63 DBIH per 100,000 people per year to Ontario's population of 12.8 million in 2011 (12,13). (While Manitoba's rural population is considered to be 28%, Ontario's rural population is reported to be 15%.) We estimate that there may have been 81 fewer DBIH in 2011 alone in Ontario on account of the province-wide ban. As Ontario's population of those aged < 20 years was 3 million (13), 54 (66.7%) of the estimated decrease by 81 DBIH among all ages in 2011 would have been in people aged < 20 years.

When considering rate differences in post-legislation period compared with pre-legislation period in Winnipeg alone, our data do not indicate a change in DBIH rate. Therefore, it is natural to assume that BSL does not work. However, our study does not account for changes in overall number of dogs over the long period under study. Based on growth in number of pet dog populations in the United States over the last two decades (14,15), we propose that any hypothesized decrease in the number of DBIHs due to pit-bull attacks is likely masked, and the effect of legislation diluted, by a simultaneous increase in DBIHs due to attacks by dogs from other breeds or breed groups. Again, this explanation is quickly assumed to be evidence that breed bans do not work. After all, an argument against BSL is that breed composition in dog populations can change such that other dangerous dogs replace dogs from banned breeds. A limitation of the study was our inability to separate the proportion of DBIHs caused by dogs of banned breeds from the proportion caused by dogs of other breeds or breed groups. However, with the assumption that replacement is necessarily different from addition of more dangerous dogs to the existing numbers, we compared DBIH rates in jurisdictions with pit bull-specific ban (e.g., Winnipeg) to DBIH rates in jurisdictions without such bans (e.g., Brandon). The idea behind this analysis is that, unlike pit-bull specific bans, voluntary changes in breed popularity have no boundaries, and jurisdictions with bans are assumed to be similar to jurisdictions without bans in every respect other than the existence of the ban. Such an analytic approach is also an improvement over a pre/post analysis of data from a single jurisdiction adopting the ban.

We adopted a generalized estimating equations (GEE) model for this comparative analysis. This multivariate model allowed us to isolate the effect of legislation while modeling annual DBIH counts adjusted for human population counts, calendar year of DBIHs and baseline differences in underlying DBIH rates across jurisdictions with and without legislation. The model yielded an incidence rate ratio--i.e., the rate of DBIHs in jurisdictions with a ban relative to the rate in jurisdictions without a ban.

The results from the GEE model were not remarkable when data from all Manitoba jurisdictions were analyzed, but as control jurisdictions were more likely to be rural jurisdictions, there was a high inter-correlation among variables. One way of controlling for the confounding effects of rurality of jurisdictions is to stratify the dataset into rural and urban. Therefore, we restricted analyses to urban jurisdictions alone. The results indicated that for every one DBIH in Brandon, there were 1.29 DBIHs in Winnipeg before the pit-bull ban and 1.10 DBIHs after the ban. This is a 14.7% reduction in rate of DBIH in people of all ages. In people younger than 20 years old, for every one DBIH in Brandon, there were 1.28 DBIHs in Winnipeg before the ban and 0.92 DBIHs after the ban. This amounts to a 28.1% reduction in rate of DBIH. These findings were statistically significant. Other reasons for this decrease cannot be ruled out in this real-world, observational study which can be thought of as a non-randomized, self-selected community trial. However as far as we can ascertain, no other dog-control legislation is different between the two jurisdictions.

Going forward, researchers should compare DBIH rates temporally as well as geographically. Future (controlled) studies in other places where pit-bull specific bans have been in effect long-term are still necessary to conclusively understand if rates of DBIHs generally and gradually decline when pit-bulls are removed from the population. This is because effectiveness (or magnitude of rate decrease) may be variable depending on local conditions, even if everyone agreed that pit-bulls caused a disproportionate number of DBIHs. For example, if rate of pit-bull penetration is high, then magnitude of effectiveness of a pit-bull ban would likely be higher than observed in our study, if a cause-effect relationship truly exists. However, if rate of pit-bull penetration is zero (i.e., no pit bulls), then a ban that was proven to be 100% effective elsewhere (hypothetically speaking) would bring about little change to DBIH rate as, technically, there are no dogs to be banned. Furthermore, pit bulls in one region of the world may be less aggressive than pit bulls in another region owing to potentially different lineages and differences in dog-owning cultures. While the value inherent in local data should not be underestimated for the purposes of local policies, data from larger jurisdictions with bigger populations of dogs, including those from the banned breeds, and higher rates of DBIHs will further shed light on this public health topic that appears to attract a lot of public and stakeholder interest.

References

1. Raghavan M, Martens P, Chateau D, Burchill C. Effectiveness of breed-specific legislation in decreasing the incidence of dog-bite injury hospitalizations in people in the Canadian province of Manitoba. Injury Prevention doi:10.1136/injuryprev-2012-040389. E-pub ahead of print.

2. Blackwell T. Controversial pit bull bans result in fewer dog bites: study. National Post, July 5, 2012. http://news.nationalpost.com/2012/07/05/controversial-pit-bull-bans-result -in-fewer-dog-bites-study/ (accessed 9 September, 2012).

3. Kaufman B. Calgary bylaw boss dismisses pit bull breed ban study. Calgary Sun. July 6, 2012. http://www.calgarysun.com/2012/07/06/calgary- bylaw-boss-dismisses-pit-bull-breed-ban-study (accessed 9 September, 2012).

4. Kay B. Study proves pit bull ban is justified. National Post, July 6, 2012. http://fullcomment.nationalpost.com/2012/07/06/barbara-kay- study-proves-pitbull-ban-is-justified/ (accessed 9 September, 2012).

5. DogsBite Blog. New Canadian study shows pit bull bans result in fewer hospitalizations. Dogsbite.org, Austin, Texas. July 9, 2012. http://blog.dogsbite.org/2012/07/new-canadian-study-shows-pit-bull- bans.html (accessed 9 September, 2012).

6. Anonymous. Winnipeg, Manitoba far behind Calgary in community safety. National Canine Research Council, LLC , Amenia, New York. July 9, 2012. http://www.nationalcanineresearchcouncil.com/blog/winnipeg-manitoba -far-behind-calgary-in-community-safety/ (accessed 9 September, 2012).

7. Parsons L. Severe bites down after pit bull ban. Winnipeg Metro, July 10, 2012. http://metronews.ca/news/winnipeg/291327/severe-dog-bites- down-in-winnipeg-since-pit-bull-ban-study/ (accessed 9 September, 2012).

8. Jonas G. The state has no business in the dog houses of the nation. National Post, July 11, 2012. http://fullcomment.nationalpost.com/2012/07/11/george-jonas-the-state-has- no-business-in-the-doghouses-of-the-nation/ (accessed 9 September, 2012).

9. Editorial: Pit bull bans may actually be working. The Hamilton Spectator, July 11, 2012. Excerpt reprinted from The St. John's Telegram.

10. Raghavan M. Invited presentation: Study on the effectiveness of breed-specific legislation in decreasing dog-bite injury hospitalizations in Manitoba--what it means to researchers, policy-makers and the public. Manitoba Agriculture, Food and Rural Initiatives (MAFRI) Lunch & Learn Session. August 13, 2012, Winnipeg, Manitoba.

11. Ontario Ministry of the Attorney General. Information on the dog owners' liability act and public safety related to dogs statute law amendment act, 2005. http://www.attorneygeneral.jus.gov.on.ca/english/about/pubs/dola- pubsfty/dola-pubsfty.asp#TOC_03 (accessed 9 September, 2012).

12. Statistics Canada. Population, urban and rural, by province and territory. http://www.statcan.gc.ca/tables-tableaux/sum- som/l01/cst01/demo62a-eng.htm (accessed 9 September, 2012).

13. Statistics Canada. Focus on geography series, 2011 census-- province of Ontario. http://www12.statcan.gc.ca/census-recensement/2011/as -sa/fogs-spg/Facts-pr-eng.cfm?Lang=Eng&GK=PR&GC=35 (accessed 9 September, 2012).

14. PRWeb. New survey reveals pet ownership at its highest level in two decades and pet owners are willing to pay when it comes to pet's health. American Pet Products Association Press Release, Greenwich, CT (Vocus/PRWEb) April 04, 2011. http://www.prweb.com/releases/2011/4/prweb8252684.htm (accessed 2Feb 2012).

15. Shepherd AJ. Results of the 2006 AVMA survey of companion animal ownership in US pet-owning households. J Am Vet Med Assoc 2008;232:695-6.

Conflict of Interest:

None declared

When Lusk et al. submit to the editor a formal list of errata to be attached to their article, I expect they will duly correct all the errors, omissions, and false statements that have been brought to their attention, and not just the three they chose to mention here. This would include amongst other items providing a correct explanation for their choices of particular termination points (rather than the nonsensical one found in footnote 2 to their Table 1), and retracting their false statement that the path and comparison streets have similar cross traffic and numbers of intersections. And as I also already objected, the authors need to explain how they got the usage data for the year 2000 they claim to have for the de Maisonneuve path segment. Considering that no municipality maintains automatic counters there, and that the authors' study was not underway in 2000, contrary to their claim it would seem they do not have data as they describe for that year.

Since I expect the authors will do their duty and correct these faults, I use the space remaining to correct two new errors they have introduced, and to object further.

(1) The path segment they claimed to have studied from 1999 to 2008 but that did not exist for almost the entirety of that period was created in 2007, not 1997.

(2) The corresponding length correction would have been approximately 180 metres, if they had gotten the extra length right to begin with. They did not, and so the correction should be instead approximately 350 metres. The authors are yet to explain how they got their lengths.

(3) The authors tell us not to worry about their selections of comparison streets: these were done "a priori, without knowledge of their safety record, in consultation with local cycling advocates". In fact the biases are so extreme that they are obvious without any measurement. Who were these sight, smell, and hearing impaired local advocates? Their contribution is not identified in either the contributorship statement or the acknowledgements, and the genesis of the study's path and comparison samples remains as mysterious as ever.

(4) The authors say their failures to describe the radical divergences between their path and comparison streets "do not affect the study results." They need to be reminded that without appropriate comparisons, their study lacks validity. Indeed, showing that a comparison is preposterous does not change the results so calculated: instead, it discredits them.

(5) I object to the authors' claim that "not even one comparison pair showed significantly greater risk" for the path. Let us be clear: even with the biased nature of the comparisons, over the near decade of the study period, according to their methods the actual injury rates on the paths were in three cases respectively 21%, 18%, and 1% worse than on the comparison streets. That none of these were found statistically significant is an indictment of the imprecision of the authors' methods, not an endorsement of the paths. I particularly object to this exploitation of the confusion between statistical and public health significance because I already called the authors on it in my previous criticism.

The authors bemoan the fact that on-street path construction has been "hampered" by the AASHTO guidelines, and present their own results as enough against them that it should no longer be discouraged. This summer a cyclist riding on the Christophe Colomb path segment studied by the authors-- a cyclist who did everything right by the rules of the path, and therefore much wrong by the ordinary rules of the road-- was killed by a truck [1] in circumstances exactly as warned about on page 34 of the AASHTO guidelines [2].

References

1. http://www.cbc.ca/news/canada/montreal/story/2012/07/24/montreal-cyclist-hit-24-07-2012.html?cmp=rss, accessed Aug 26 2012.

2. AASHTO Task Force on Geometric Design (1999). Guide for the development of bicycle facilities. Washington, DC: American Association of State Highway and Transportation Officials.

Conflict of Interest:

None declared

1. Rue de Brebeuf Cycle Track vs. Rue St. Denis between Rachel and Laurier.

These streets are not comparable.

Brebeuf (which has a cycle track) is a narrow 40kph slow-moving one- way residential street with one traffic lane and one parking lane.

Rue St. Denis (which has no cycle track) is a six-lane (two lanes often taken up by parking) 50kph limit two-way highway in a commercial area with lots of stores and distractions.

It seems to me that more accidents will naturally occur on the six- lane highway with a faster speed limit. It's unsurprising then that the study did indeed find a statistically significant advantage in terms of safety for Rue de Brebeuf. However, I would argue that this has nothing to do with the safety of the cycle track and everything to do with the very different nature of the roads compared.

2. Rue Berri Cycle Track vs. Rue St. Denis between Cherrier and Viger.

These streets are not comparable.

Rue Berri (which has a cycle track) is a 50kph limit divided highway along 1/3rd of its length with the cycle track removed from busy intersections by an underpass, so cyclists are naturally removed from the possibility of intersection accidents.

Along this stretch of Rue St. Denis, the road (which has no cycle track) is a one-way street with a 50kph speed limit. However it is a much busier road than Rue Berri in terms of people doing their business somewhere along that stretch, with a relatively narrow street and lots of intersections and distractions in the form of little shops and cafes along the whole route.

Rue Berri showed a statistically significant reduction in injuries compared with its reference street. However, more accidents are bound to occur where there are lots of intersections and where drivers are likely to be distracted. It seems reasonable that the advantage in terms of reduced injury results on Rue Berri derive from the very different nature of the roads compared and not from the presence of a cycle track.

3. Boulevard de Maisonneuve Cycle Track vs. Rue Sherbrooke and Rue Ste. Catherine between Claremont and Wood.

Boulevard de Maisonneuve (which has a cycle track) is a quiet 30kph one-way two lane residential street along much of its length. The bike track goes through a park for 1/5th of its length, thus removing any possibility of intersection conflicts in that area. The presence of the park effectively reduces the chance of traffic collisions by 20%.

Sherbrooke (which has no cycle track) is a downtown 40kph commercial street with four lanes of moving traffic and parking on both sides. It has numerous business distractions along its length. It should be noted that a recent study found that Sherbrooke is the single most dangerous route in Montreal for cyclists. Ste. Catherine (which also has no cycle track) is a similar downtown street, but with a 30kph limit and just two lanes of moving traffic and a lane for parking on both sides.

The idea that these streets are comparable on anything but the most superficial level (i.e. they are streets) is a joke. It is ridiculous, in my view, to attribute a reduction of injuries on Boulevard de Maisonneuve to the presence of a cycle track, when the streets being compared are not at all similar - and when the street with the cycle track has obvious and significant advantages in terms of safety that are unrelated to the bicycle track itself.

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Here we have what seems to me to be a clear case of selection bias.

Note: Even though the three other street comparisons show similar bias, the remaining street comparisons showed statistically insignificant results.

Conflict of Interest:

None declared

Injury Prevention asks that responses to articles be kept to less than about 300 words. The volume of errors and omissions in this article by Lusk et al. is so excessive that it took me rather more than that-- including photographs of the actual streets-- just to document them. The result is now hosted on John S. Allen's bicycle pages and can be directly found by searching the internet for e.g. these terms: compendium errors Lusk.

A very small sample:

-Authors report results for a path section that did not exist for almost the entirety of their claimed study period.

-Errors of up to 100% in the claimed lengths of path segments, and thus corresponding errors in the reported rates of incidents per kilometre.

-Biased selection of comparison streets, such as comparing a path on a one-way, one or two traffic lane, lightly trafficked residential street having a 30 km/hr speed limit, with cycling on a two-way, 4 traffic lane numbered provincial highway having a 50 km/hr speed limit, located in a heavily trafficked commercial district, with numerous alcohol-serving establishments.

The authors went 10 blocks out of the way to find this comparison street, even though the path-adjacent streets are nearly identical in character to the path street.

-False claim of similar numbers of intersections on path and comparison streets.

-Complete reliance on an untested, illogical, ad hoc indicator of danger to cyclists (contrary to the authors' description as if it were routinely used for this purpose), one whose usefulness is refuted by the authors' own data.

-Here and elsewhere, the authors applaud bicycle paths for substantially skewing the character of the user base, from young athletic males to women, children and seniors. Thus even if the authors did their study properly and reported their results correctly-- they did not-- would their conclusion that cycle paths at least do not increase the injury rates really be an endorsement of the cycle paths, or an indictment of them?

Conflict of Interest:

None declared