New research on dog bite fatalities

We’ve known for a while what kinds of dogs are at risk of biting humans: not any particular breed, but dogs who are not well socialized and not well cared for. Dogs living in houses with people are much less likely to bite than dogs living outside in yards or on chains.[1, 2] So why is this new paper about dog bite fatalities important?

Patronek G.J., Sacks J.J., Delise K.M., Cleary D.V. & Marder A.R. (2013). Co-occurrence of potentially preventable factors in 256 dog bite–related fatalities in the United States (2000–2009), Journal of the American Veterinary Medical Association, 243 (12) 1726-1736. DOI: 10.2460/javma.243.12.1726

Unlike previous researchers, who mostly approached the question of who gets bitten and what kinds of dogs bite by combing through old records, these authors monitored current events and followed up on every dog bite related fatality that was reported, for ten years (2000-2011). They interviewed law enforcement officers who were involved with these cases. They interviewed medical examiners and coroners. They followed current news articles about cases. This is all information that becomes very difficult to find when you’re trying to learn about a dog bite fatality years after the fact. As the authors write:

In our opinion, the present study represents the most comprehensive analysis of factors...associated with dog bites to date. Personal interviews with credible investigators were successfully conducted in 221 of 256 (86.3%) cases... Law enforcement personnel provide first-hand information not reported in the media and often identified errors of fact in the media reports.

Some information was still very difficult to obtain, and the most interesting part of the paper for me may have been the description of the lengths the investigators went to in their attempts to ascertain the reliability of reports of what breed some of these dogs were. They note that “the source of breed descriptors in media reports is usually unknown” and therefore not trustworthy. Interestingly, this paper never put that comment into context, but it is hard to read it without thinking about how challenging it can be to visually identify the heritage of a mixed-breed dogs, and all the implications that this has for news stories which seem to reflexively identify aggressive mixed-breed dogs as “pit bulls.”

In the context of the debate about whether pits get disproportionately named in media reports about dog aggression, this paper provides some interesting fodder. The authors calculated how often media reports contradicted each other: 21.6% of the time in reports about incidents involving single dogs, 36.4% in incidents involving multiple dogs. How often media reports differed from the animal control officer’s report: 34.9% in incidents involving single dogs, 43.3% in incidents involving multiple dogs. In the rare cases when a pedigree or DNA testing was available, that data disagreed with media reports in 7/19 cases for single dog incidents and 7/28 cases for multiple dog incidents.

What this paper found overall was mostly a vindication of what we already believed: there is no single factor that leads a dog to bite a human. But one very important factor is whether the dog is a “family” dog or a “resident” dog. The paper provides some lovely verbiage on the difference:

A resident dog was a dog, whether confined within the dwelling or otherwise, whose owners isolated them from regular, positive human interactions. A family dog was a dog whose owners kept them in or near the home and also integrated them into the family unit, so that the dogs learned appropriate behavior through interaction with humans on a regular basis in positive and humane ways.

Later in the paper, they add:

Dogs that are deprived of human interaction or direction are denied access to accurate information about appropriate behaviors with humans. Consequently, dogs in stressful, potentially dangerous situations or when maltreated may behave in ways primarily to protect themselves.

In other words, dogs who are not given a chance to learn how to interact appropriately with humans may not act appropriately with humans.

The rest of the paper is packed with nice statistics which I am not going to try to reproduce here. Suffice to say I expect to see excerpts from it on slides in presentations about canine aggression for years to come. I do want to explicitly point out that this paper only covered dog bite fatalities, not dog bites alone; fatalities due to dog bites are extremely rare (this paper found 256 in the United States over a 10 year period), whereas dog bites alone are quite common. I think it’s easy when reading this paper to want to extrapolate all this lovely data about the causes of fatal dog bites out to the causes of non-fatal dog bites. That’s understandable but a little dangerous: it usually requires repeated bites to kill a human, so I imagine such an attack to be different from the more common single bite. But I still believe all this data is very relevant to how we keep our dogs and how to prevent bites. The message the authors give is: be responsible with dogs and they will treat you well. Don’t, and you might be on dangerous ground.

References
 
[1] Patronek, Gary J., et al. "A community approach to dog bite prevention." Journal of the American Veterinary Medical Association 218.11 (2001): 1732-1749. http://avmajournals.avma.org/doi/pdf/10.2460/javma.2001.218.1732

[2] CDC. Home and recreational safety. Dog bites. http://www.cdc.gov/homeandrecreationalsafety/dog-bites/index.html

Number Needed to Ban: a new tool for calculating the benefits of banning particular dog breeds

A study published this month in the Journal of the American Veterinary Association (JAVMA) takes on the issue of whether breed-specific legislation (BSL) is effective. BSL is a tool used by some communities to attempt to reduce injuries from dog bites. The idea is that particular breeds of dogs are responsible for more than their share of injuries, so banning or otherwise controlling those breeds will result in a reduction in injuries. The group of breeds collectively known as “pit bulls” receive the most attention today, though other breeds (Rottweilers, Dobermans, German Shepherds) have received attention in the past.

But does BSL actually work? Experts say no; how the dog is trained and managed is a better predictor of aggression than its breed. Nevertheless, new BSL continues to be enacted. So why do legislators reach for this tool?


The authors of “Use of a number-needed-to-ban calculation to illustrate limitations of breed-specific legislation in increasing the risk of dog bite-related injury” believe that BSL’s appeal comes from:

• Misperception of risk. Poor reporting of the number of dog bites that occur and of their severity makes it very difficult for the public to get a handle on how often they occur.
• Stereotyping and misinformation. The media may portray particular breeds as especially aggressive, in the face of scientific studies which suggest that they are not.
• Erroneous beliefs about efficacy of BSL. There is currently no evidence for the effectiveness of BSL, but  there is evidence to suggest that it is ineffective.

The authors hope to provide a tool for use in understanding the effectiveness of BSL, and they hijack some terminology from the medical community to do so. “Number needed to treat” (NNT) is a concept used to understand the effectiveness of a particular medication or therapy. For example, you have a patient showing signs of a stroke. Should you give him tPA (tissue plasminogen activator)? One measure you might use in making this decision is NNT. How many similar patients would you treat with tPA, on average, before you saw one patient improve? A smaller NNT implies a more effective therapy. In human medicine, we expect the NNT of an effective therapy to be in the tens or at most hundreds.

The authors suggested evaluating BSL’s effectiveness using a “number needed to ban” (NNB) concept. If BSL is implemented in a particular community, how many dogs will need to be banned (removed from the community) before one dog bite (or dog bite related injury, or dog bite related fatality) is prevented?

The authors point out that because our knowledge of the true prevalence of dog bites is so poor (many are never reported), this calculation is hard to do. I think the important thing to understand is that what they are offering is a tool that can be applied to different statistics. After all, dog bite prevalence will vary among different communities. This tool can be used to understand the possible benefit of BSL in different communities. It’s an algorithm to apply to a variety of data inputs!

However, the paper would have been really unsatisfying without some numbers, so they applied their algorithm to some statistics (much appreciated, because I hate arithmetic).

• Based on the reported number of dog bite related emergency department visits, 5,128 dogs would have to be banned to prevent a single emergency department visit in one year.
• In Kansas City, 4,255 dogs would have to be banned to prevent a single emergency department visit in one year.
• 30,663 dogs would need to be banned to prevent a single reconstructive surgery in one year.
• 109,495 dogs would need to be banned to prevent a single hospitalization in one year.
• 59,523 dogs would need to be banned to prevent a single insurance claim in one year.

The authors note that these calculations were based on legislation banning a particular breed or breeds entirely. For legislation which simply requires that dogs of a particular breed(s) be muzzled while in public, these numbers would be even higher, because such legislation would not prevent bites on private property (which is where many of them occur).

It is the authors’ hope that “easily understood communication tools, such as NNB, can help put the lack of efficacy of BSL into perspective and narrow the perception gap.” This is a great tool and I hope we see it used more. I am concerned that proponents of BSL will argue that any tool is only as good as the data put in to it, and that the lack of reliable reporting of dog bites will mean that this tool isn’t itself reliable. However, as long as we are focusing on enacting BSL instead of focusing on understanding the true problem, our data will continue to be flawed. This article represents a step forward in understanding data about the causes of dog bites. Our next step is improving the accuracy of that data.

Patronek GJ, Slater M, & Marder A (2010). Use of a number-needed-to-ban calculation to illustrate limitations of breed-specific legislation in decreasing the risk of dog bite-related injury. Journal of the American Veterinary Medical Association, 237 (7), 788-92 PMID: 20919843

Links post

• The illustrated guide to a Ph.D. (Matt Might)
• The Zen of Presentations, in at least 34 parts (Neurodojo): Neurodojo has apparently been writing about the zen of presentations for a while. This link is to all of the posts so far.
• Disrupting with data (Book of Trogool): The Journal of Neuroscience has begun refusing to accept “supplemental materials” (the researchers’ raw data). Dorothea Salo reflects on why this is good news for librarians and the future of scientific publications.
• Stop and think before greeting a strange dog (Pet Connection): Video about greeting a strange dog, one of my favorite topics. Flash is broken on my computer right now, so unfortunately I can’t preview this to make sure it's interesting, but I trust Pet Connection.
• Peer review, schmeer review (Lab Spaces)
• Meta-encounters and non-overlapping magisteria (or, why Virginia Heffernan wrote what she wrote about ScienceBlogs) (John Pavlus)
• If it bites, it must be a pit bull, right? (Pet Connection): More on media bias in pit bull reporting, written by a vet.

Report from the trenches of local politics: pit pull ordinance hearing

Last night I attended a city council meeting in Worcester, in which the public was allowed to speak about the proposed pit bull ordinance. As a reminder, this ordinance would require pit bull type dogs in the city of Worcester to be muzzled when in public, and would require owners to post a sign warning that a pit bull type dog was in residence. Last night’s meeting was ably reported by the Telegram and Gazette, the local paper. I’ll give my own report here, and I’ll say up front that I don’t support the ordinance, and my reporting is biased (for the unbiased version, see the T&G).

As a Grafton resident, I was not allowed to speak at this meeting. I attended because I was curious, and to show support from the nearby vet school for opponents of the ordinance. Four other vet students attended with me (and maybe others that I didn’t know about). The room filled to overflowing, and was standing room only by the time the meeting came to order.

The first speaker was a state representative, who said that he had served on committees for animal legislation. He felt strongly that this ordinance doesn’t go far enough, and that pit bull type dogs should in fact be banned. He believed that “punish the deed, not the breed” was not a good argument against breed specific legislation, citing anecdotal evidence of pit bull type dogs having injured people. (He did not explain why he felt that breed was a better predictor of a dangerous dog than irresponsible ownership, something that often frustrates me about proponents of breed-specific legislation, because it seems to be such an obvious question to me.) His speech was greeted with loud boos from the audience, causing Mayor O’Brien to have to ask for quiet and for people to behave respectfully.

A representative of the Worcester Animal Rescue League also spoke. She made her case well, I thought, covering the important points: we have no reason to believe this ordinance will be effective; accurate identification of pit bull type dogs is very difficult; this ordinance will make people think the problem is solved when it is not. She was a good public speaker, something not to take for granted when a busy urban shelter needs to find someone to present their case at a city council meeting.

One person spoke in favor of the ordinance, saying that he had seen pit bull type dogs owned by drug dealers. Again, I felt that his case was lacking in some logic — perhaps ownership by a drug dealer might be a better predictor of a dog’s temperament than its breed.

Then people from the floor started lining up to speak against the ordinance. Mayor O’Brien attempted to alternate pro versus con speakers, but no one else was offering to speak in favor of the ordinance. So for the next 45 minutes, we heard from people against it. One speaker was a veteran of two wars who has a pit bull type dog with a Canine Good Citizen title, who is training her dog to do therapy work (going to places like hospitals and nursing homes to visit sick or elderly people who want to spend time with a dog). She was an excellent speaker who made good, logical points, but also had good emotional appeal.

Other speakers appealed solely to emotion, but I think that’s as important as appealing to logic in a situation like this. One elderly gentleman explained in detail how sweet his neighbor’s pit bull type dog was and how it liked to lick his face. While speeches like this seemed useless to one of my vet school compatriots, who wanted logic, logic, logic, I’m guessing that the less scientifically-trained in the audience found that sort of appeal more effective in some ways.

The ordinance will be voted on at the next city council meeting, in early September. In the meantime, apparently some motions were brought after I left, to modify the text of the ordinance to target dangerous dogs regardless of breed. That sounds like a good change to me. I’m hopeful that the suggestions that were presented to the city council will cause them to think this ordinance through over the next month, and possibly even work with the Worcester Animal Rescue League to redesign the ordinance. Something does need to be done, but whatever is done needs to target dangerous dogs, not dogs of a particular breed.

[ETA: Unfortunately, the ordinance passed, 9-2. It takes effect April 1, 2011.]

Links post

Links about science blogging

• The Nature of Science Blog Networks (Science in the Open): Reflections on what’s next for science blogging networks, since we seem to be all assuming that Scienceblogs.com is dead.
• It’s not information overload, nor is it filter failure: It’s a discovery deficit (Science in the Open)
• Science Blogging Networks: What, Why and How (Blog Around the Clock): More thoughts from the godfather of science blogging, Bora, on the post-Pepsigate future
• Some thoughts about science blog aggregation (Word Munger)

Links about medicine (sometimes veterinary)

• Orthopaedics vs anesthesia: “This work is fictional and any resemblance to reality is completely coincidental. No orthopaedic registrars, anaesthetic registrars or patients were harmed during filming.” Video.
• Position Regarding Dangerous Animal/Dog Legislation (Massachusetts Veterinary Medical Association): the MVMA’s position on breed-specific legislation (e.g., the proposed pit bull ordinance I have been posting links about)

Links post

• Following on the topic I posted about recently, the Worcester Animal Rescue League (a shelter in Worcester) has stated that if Worcester passes its proposed breed-specific legislation, the shelter will no longer accept any dogs from Worcester. They cite fears of rising surrender rates as a result of this legislation.
• Don’t be a dick (Thoughts from Kansas): analysis of a speech about the effectiveness of not being a dick
• The gut’s “friendly” viruses revealed. DNA sequencing reveals a new world of bacterial viruses in our intestines (Nature News): More on the ecology existing inside us.
• A Farewell to Scienceblogs: the Changing Science Blogging Ecosystem (coturnix): It is a novel. The best bits are at the end, so if you start to get overwhelmed, skip ahead.
  

Muzzling the real solution to the problem

Some new legislation has been proposed in Worcester, the city next door to my town. This legislation proposes specific restrictions on pit bulls and their owners. Most importantly, pit bulls would have to be muzzled when out in public, though other restrictions are proposed as well, such as requiring pit bull owners to put signs in their front yards advertising that a pit bull lives there. The local paper has some details.

The MSPCA has a brief article about the legislation, with some quotes from one of the sponsors of the bill:

District 5 Councilor William J. Eddy pointed out that over the past three years, only 2 percent of the dogs licensed by the city are pit bulls, while 25 percent of all dog bites over the same period were caused by that breed... “Some will say this is not a (dog) breed problem, but an (dog) owner problem,” Mr. Eddy said. “These are aggressive dogs that can cause great damage. There isn't another breed in Worcester that has that kind of statistics.”

I am one of the people who will say that this is not a dog breed problem, but a dog owner problem. So how do I answer Mr. Eddy?

More bites are caused by pit bulls than by any other breed. Therefore pit bulls are dangerous.

First of all, is it “more bites” or “more reported bites”? Is it possible that people are more likely to report a pit bull bite because of the way the breed is perceived? Is it possible that mixed-breed dogs that bite are assumed to be pit bulls, because it is very hard to tell what is and isn’t a pit bull and because people assume that pits are liable to bite? The National Research Council released a report in 2007 arguing that there is a media bias against pit bulls, and that pit bull bites are more likely to be widely reported than bites involving dogs of other breeds.

But let’s say pits do bite more than other dogs. Is that a problem with the breed, or with perceptions of the breed, and therefore with the kind of people likely to own pits? Pits are the most popular breed used in the underground and illegal sport of dog fighting, for which they are bred and trained. The National Research Council reports that dogs which are not kept as pets, and dogs which are not humanely controlled by their owners, are the dogs which are most likely to bite. Are people more likely to treat pit bulls this way than Labrador retrievers? I think so.

Eddy is further quoted:

“We have a problem in this city and we have an opportunity to address this problem. Frankly, I think it’s long overdue.”

Yes, it is long overdue, and yes, let’s address this problem! (Lucky for Worcester, they have a veterinary school with a behavior department right next door.) So why is BSL (breed specific legislation) a bad answer?

Because it won’t work. This is the really important point! I don’t argue against BSL because I think it’s acceptable for dogs to bite children. I absolutely do not think that is acceptable. But BSL is not the answer. What will BSL actually do?

• Irresponsible owners who disobey the new muzzle law and are fined may surrender their dogs to a shelter instead of paying the fine. This is what happened in nearby Boston when a muzzle law was enacted there. (Original article in the Boston Herald is behind a pay wall; I linked to a version archived on an anti-BSL site, but don’t be confused by the URL. The article is from a real newspaper.)
• If the law successfully prevents dog fighters from using pit bulls, there is nothing to stop them from choosing another breed. The law isn’t targeted at dog fighters, however. Having to muzzle their dogs in public shouldn’t be much of a problem for people who don’t generally take their dogs out in public.
• In fact, there is really no such thing as a pit bull. The term refers to a loose group of dog breeds. Telling what is a “pit bull” and what isn’t has made BSL enforcement somewhat arbitrary in other cities. Take the test, see if you can do it. So this law is likely to be applied to dogs for whom it is not really intended.
  

But why not just try it? After all:

“We’re not talking about banning this dog; rather what we’re saying is that when you’re out on the public streets, pit bulls should be muzzled,” [Eddy] added.

So what’s the harm?

• Passing this law will be a Band-aid measure which will make the public think that the problem has been solved. There are some useful ways to address the problem of dog bites, but if this good energy for change is directed into a poorly designed law, there will be no impetus to find real solutions.
• A muzzle requirement will make it harder for responsible owners to socialize their dogs. How would you react to a muzzled dog which you met on the street? Would you want to pet it, or would you be afraid of it? If you were a dog and every human you met on the street was afraid of you, would you be enthusiastic about meeting new humans? Not to mention the human socialization problem! If your new neighbor had a sign in her front yard proclaiming that a pit bull lived there, would you be as likely to go over to welcome her to the neighborhood with some food? (My neighbors actually did that when I moved in. It was great.)
  

Dog Zombie, you are so right. I have seen the light. But does that mean we should sit back and do nothing?

I almost always have opinions on what should be done to fix the world!

• The AVMA (American Veterinary Medical Association) put together a task force on dog bite prevention which, in 2001, published a lovely article titled “A community approach to dog bite prevention.” This article has some specific suggestions for how communities should handle the problem, including both suggestions for prevention (controlling loose dogs, educating of animal control officers), and suggestions for how to handle bite incidents (having a protocol which includes reporting of the bite and follow-up investigation).
  
• Sue Sternberg (who is well known in the shelter community) is promoting a “Lug Nuts” program, in which teens who might otherwise participate in dog fighting are encouraged to instead enter their dogs in pulling competitions. What a creative idea for redirection! Extra points to Sternberg for working within the parameters of the problem instead of supporting rules passed down from on high.
• I think people need consequences. People need to be fined if their dogs are aggressive in public. Dog aggression needs to be taken seriously before bites happen, and no matter what breed is involved (“punish the deed, not the breed”). And laws against dog fighting need to be actively enforced.
  

My final message to Mr. Eddy: You have hold of an important issue. Please take steps to address it wisely. The solution you have proposed will be successful only in winning you votes, not in reducing dog bites. There are better ways. Find one.