08/17/17
dog bites who gets bitten by which dogs

Which people get bitten by which dogs?

dog bites who gets bitten by which dogs

Dog bites are one of my niche areas of interest, so I when I came across this 2008 bite study, I was keen to read. The overall objective of this study was to work out the similarities between biting dogs and people injured by them, to be able to understand dog bites in such a way that public health could be influenced.

And dog bites are a bit public health problem. In 1986, dog bites were among the top 12 causes of nonfatal injury in the US. in 2005, an estimated 800 000 dog bites needed medical attention in the US. On average, 18 people die per year in the US as a result of dog bites. The number of reported dog bites is going up each year, suggesting this is a growing problem. (Though, personally, I think the number is probably going up to growing intolerance of dog bites in the community.)

So this study was a retrospective cohort study, looking at data for incidents that occurred in the 2002/2003 financial year in Multonomah County, Oregon. In this study period, 636 dog bites were reported to Animal Control Services, while there were 47, 526 dogs licensed in the county.

What followed was a whole lot of number crunching that I don’t entirely understand. From where I’m sitting, it looks like a fair bit of extrapolation went into the figures seen below, but without sampling every single household for dogs and other aspects, I’m not sure if there’s a much better way to go about it.

But regardless, onto the results…

The Biters

From this study, dogs were more likely to bite if:

  • They were of particular types (terrier, working, herding, and nonsporting),
  • They were sexually intact and male, and
  • They were purebred.

Instead of using dog breed, they used dog type, to try to avoid problems in identification. (For example, the general public has a hard time determining between a border collie and coolie, but they do know it’s some kind of herding dog.) The breeds listed above were more likely to bite than dogs that were sporting breeds, hounds, non-AKC breeds, and toy breeds. This study suggested that the dogs in the ‘problematic’ groups have instincts they’re likely to revert to if left untrained (which doesn’t ring true to me for the nonsporting group), and threat they are a ‘size and strength’ to cause damage (which doesn’t seem right considering the size of most terriers).

More intact male dogs bit than any other neuter/sex ratio. This is different to other studies I’ve reviewed.

It’s really perplexing that purebred dogs were more likely to bite in this study. I guess this goes to the breeding practices, but it’s curious to think that crossbreed dogs, presumably bred by people who are ‘accidental’ breeders, end up with less-bitey temperaments. Something for breeders to think about. While these dog factors existed, there was also a range of other elements to a dog bite.

“Factors that determine whether a dog-human interaction will result in a bite are complex and involve characteristics of the dog, the injured person, the owner, and the dog’s environment.”

The Owners of the Biters

Biting dogs were more likely than nonbiting dogs to live in neighbourhoods where the residents’ median incomes were less than the county median income value. If controlling for breed category and controlling for sex, “dogs living in census block groups that had incomes less than the county median were 1.5 times as likely to be reported as a biting dog than reported as a nonbiting dog”. When dog owner data was compared to population density, percentage sex by age, percentage nonwhite race, and percentage without high school diploma, there was still not an association with biting. It was correlated just with income!

So what’s going on here? What’s different in areas were less income? Less money spent on training? On fences? Different attitudes towards child raising? This study suggests that people in these areas may be inclined to select particular breeds (i.e. especially those with reputations for aggressive behaviours). (Though this study didn’t look at whether some breeds were more likely to be owned by different groups.) They also suggest that low income areas may socialise their dogs in a different way, and therefore change the bite potential of the dog, or perhaps they’re not trained or supervised in a way that minimises dog bite risk.

“In another study examining dog bite injuries in St Louis, Mo, bite injuries occurring in low income areas were attributed to large numbers of children playing outdoors, few homes with adequate fencing, poor dog control, and a high proportion of large-breed dogs owned for protective purposes.”

As a personal comment, in my experience, crossbreed large dogs are cheaper than small dogs or purebred dogs. This means low income areas are likely to own bigger dogs, and we know bigger dogs are more likely to have their bites reported. While studies of the past have looked at breed and sex-neuter status, this study reveals a new area for further research: block group income levels.

But there’s more: It’s not just about the dog and who owns it, but also where the bite took place.

The Place of the Bites

Dog bites occurred:

  • 35.1% of bites happened in the dog’s home or yard.
  • 23.4% of bites happened in ‘neutral territory’
  • 17% of bites happened in dog/victim household (i.e. the parties lived together)
  • 10.1% of bites happened in household of victim (not dog’s place)
  • 7.1% bites unknown place
  • 3.8% at “place of employment” – e.g. vet clinic, rooming facility, MCAC
  • 3.6% “Neighbour’s Property” (which could be grouped with the 35.1%)

This reinstates the idea that parents need to be extra vigilant when they are visiting houses with dogs.

Other Statistics

Other tid bits of interest:

  • Boys and girls aged 5-9 years had highest rate of injury, boys a bit higher (but not significantly so).
  • Of the 636 biting dogs, 49% had a license number. There are some estimates that less than half of all dogs are registered. (I really wonder what this kind of statistic would look like in Australia.)
  • 36% of dog bite victims didn’t know the dog that bit them. (The largest portion.)
  • But: Among children, 46% were bitten by the family dog.
  • More dog bites in summer months.
  • No significant difference between male and females being bitten.

Limitations

Like all studies, there are a number of problems. In this study, the results are limited by.

  • Not all dog bites will be reported. Dog bites are a reportable incident in Oregon, but the records are incomplete. There’s a problem with recording of dog bites. A previous study, referenced in this one, suggested that only 17% of bites are reported to any authority. (And while this may be the case, how else should we be analysing dog bites except through dog bite records? This model is probably the best we have.)
  • We know members of the public are not very good at reporting dog bites by breeds.
  • Dog license data can only be used as an estimate of breed-populations – especially because we know perhaps only half of all dogs are registered. Further, if owners of some breeds are less likely to license their dogs, the breed specific bite rates are further skewed.
  • When a large-breed bites, that bite is more likely to be reported and more likely to need medical care, meaning that there is a reporting bias that can increase the number of these dogs seemingly involved in incidents.

 

Conclusion

This study made recommendations for reducing dog bites:

  • Combined approaches from human medical communities, veterinary communities, and animal control to help foster healthy relationships between people and pets.
  • Focus on low income neighbourhoods.
  • Paediatricians to counsel parents (dog owning and not) on dog safety during routine medical visits.
  • Low cost spay neuter.
  • Education programs (perhaps through animal control).

“Innate tendencies dictated by breed, sex-neuter status, and size play a role in the potential of a dog to bite, but owners are ultimately responsible for their dogs’ action[,]… and need to make every effort to minimisze their dogs’ bite potential through obedience training; neutering; and supervision, especially around children.”

Source:

Shuler, CM, DeBess, EE, Lapidus, JA, and Hedberg, K 2008, “Canine and human factors related to dog bite injuries”, JAVMA, vol 232, no 4.

07/16/17
Litter Size - Can we predict it?

Litter Size – What the research says

Litter Size - Can we predict it?

There is an ongoing paucity in the literature surrounding most dog matters, and that means dog knowledge is often based on anecdotes and experience instead of facts and figures. Dog breeding is no exception. Breeders will tell you that they get bigger litters if x, smaller litters if y, that they’ll never mate a bitch if z. While personal experiences can provide case studies, I am interested in much bigger data.

Enter a Norwegian study looking at 10,810 litters.

This study used data held by the Norwegian Kennel Club to look at every litter registered in 2006 and 2007, across 224 breeds. Statistical analysis was then done to determine all the wonderful figures summarised below.

The aim of this study was to determine what actually makes a difference in litter size. (Litter size being the number of puppies born, alive or dead.)

Firstly, an overall average had to be determined. For this data set, the average litter size, considering all breeds, was 5.4 puppies.

For those interested in average litter size by breed: The largest average litter size was in the Rhodesian Ridgeback with an average of 8.9 pups per litter. The Toy Poodle and Pomeranian had the smallest average litter size – 2.4 pups per litter. And the Border Terrier (because I’m biased) had an average litter size of 5.1 pups per litter.

This study found that litter size was influenced by the size of the breed, the method of mating, and the age of the bitch. Litter size was not affected by season of birth, or the number of litters a bitch had had.

Size of the breed

This study examined dogs based on average breed size. They were classed as miniature breeds (<5kgs), small breeds (5-10kgs), medium breeds (10-25kgs), large breeds (25-45kgs), and giant breeds (>45kgs). Bitches were recorded against the average size of a dog for their breed and not specifically on the size of that given bitch.

“When looking at all the … litters…, mean litter size increased with the size of the breed. The mean litter size was 3.5 in miniature breeds, 4.2 in small breeds, 5.7 in medium breeds, 6.9 in large breeds, and 7.1 in giant breeds.”

The feature of larger dog breeds having larger litters is not a new thing – this phenomena is consistent across other studies. But this study is different as it found that it wasn’t just size of the breed that mattered…

Age of the bitch

The first analysis of this data showed no significance with the age of the bitch, however, once breed size was taken into account, there were two trends apparent:

  • In small and miniature dogs, young and old bitches had smaller litters than the ages in between.
  • In larger breeds, increasing age corresponded with decreasing litter size. (Young bitches of larger breeds produced the largest litters – unlike small and miniature breeds.)

Predicted litter size by the age of the bitch for the five different breed size groups from Borge et al. study.These results are a little different to other studies, which have shown smaller litter sizes as bitches get older. (As in, the results this study got for larger breeds was seen in all breeds in previous studies.) It could be that smaller sample sizes in other studies may have missed this, or that other studies used larger breeds as their data set instead of small or miniature breeds. One suggestion is that small breeds may not mature as quickly as previously believed, and so they’re not able to reproduce until they reach that mark. (To me, this kind of makes sense – considering small breeds often live longer, then it’s likely that they mature more slowly, too.)

Method of mating

Like the age of the bitch, the first analysis on the data didn’t show a significance change in litter size based on mating method. However, when the data set was adjusted for breed, breed size, and age, naturally mated bitches had significantly larger litters than those who had been AIed (either fresh or frozen).

A decrease in mean litter size of 0.4 puppies would be expected for litters conceived with AI with fresh semen and 1.3 for AI with frozen semen, both compared to natural mating.

Things that didn’t matter

The number of litters a bitch had previously didn’t influence the size of her litter. (However, older bitches normally had had more litters – and their age did influence litter size.)

The season the litter was born in did not influence litter size.

Conclusion

Size of the breed, age of the bitch, and the method of mating are three factors work together in determining litter size. It’s not one thing – it’s all three.

“… the size of the breed, the age of the bitch and the method of mating were found to influence litter size in purebred dogs when controlling for breed, with the size of the breed as the strongest determinant.”

This study is better than past studies in this area for its huge sample size, its variety of breeds, and the fact that it considers all puppies in a litter (not just those registered, as some past studies have done). In this way this study is unique. It is probably a pretty reliable data pool for purebred dogs, too, as 90% of purebred dogs in Norway are registered with their kennel club.

Things to consider regarding the vigour of the results:

  • It’s a retrospective study.
  • It does not include data from litters where all pups were born dead.
  • Calculating mean litter size is hard, because of % made up of small or large breeds. Small breeds are currently popular, so could perhaps pull down the mean litter size seen in this study. Studies done in different countries, with different breeds being popular, is likely to result in different results.
  • There is a relatively small sample of bitches who were mated not-naturally in this study, so the results should be interpreted cautiously, however the results are consistent with previous findings.
  • This study only groups dogs by weight – not by body shape. This might yield differences. (A neapolitan mastiff is really different to a greyhound.) And they group them by weight average of breed, not the weight of the individual bitch
  • This study looked at only two years and the researchers wonder if there might have been more variation in season of birth if there was more time taken into consideration.

In conclusion: Based on this study, breed size is the strongest determinant for litter size in a dog. The age of the bitch and the method of mating were also significant predictors of litter size. These three things interact, making litter size predictions difficult!

Acknowledgements:

Borge, KS, Tonnessen, R, Nodtvedt, A, & Indrebo, A 2011, “Litter size at birth in purebred dogs – A retrospective study of 224 Breeds”, Theriogenology, 75, 911-919.

Thank-you to Waldwiese Kennels for the cover image – a litter of longhair weimaraner puppies.

02/25/14

Vaccinations Last At Least Three Years

ResearchBlogging.orgWhen reading Terrierman he made reference to the work Schultz has done on the duration of vaccines. Intrigued, I decided to read one of his articles. I dug up a review Shultz wrote on the duration of vaccines. It looks at available research on vaccines and their ‘duration of vaccinal immunity’ (i.e. how long they last).

Whether a dog has immunity can be determined either by antibody titres (a ‘titre test’) or a challenge study (e.g. deliberately exposing the dogs to the pathogen).

 

For distemper, parvovirus, and adenovirus the published data suggests an immunity period of 3 years or longer minimum.

Using blood products to test immunity, it seems that vaccines last 3 years or longer.  When using challenge studies, dogs that were vaccinated 11 years ago did not contract the virus.

According to this article, if a cat or dog is:

  • Vaccinated with core vaccines at 12 weeks of age or older,
  • Is revaccinated at 1 year old, and
  • Receives a vaccination “not more often than every 3 years”

then this would be as protective to the pet as annual vaccination.

However, non-core vaccinations last a year or less.

Table 1 shows estimated minimum duration of immunity for the 4 core canine vaccines.

How long does a dog vaccination last?

Shultz concludes, “Extending the revaccination intervals for canine and feline core vaccines does not place the animal at increased risk to developing vaccine preventable disease, but it does reduce the potential for adverse reactions”

He also recommends using titre tests to ensure that a puppy’s final vaccine enduces an immune response – and to revaccinate if the titre does not indicate that an immune response was produced.

Oh, and on cats? According to this paper, feline vaccines less researched, but feline parvovirus, calcivirus and herpes seems to last at least 7.5 years. Exception is feline leukemia which provides immunity for 1 year or less.

 

Reference:
Ronald D. Schultz (2006). Duration of immunity for canine and feline vaccines: A review Veterinary Microbiology, 117 (1), 75-79 DOI: 10.1016/j.vetmic.2006.04.013

02/4/14

Aggressive Breeds via Owner Accounts

Establishing ‘aggressive breeds’ without using dog bite data: Using owner reports to establish the most aggressive dog breeds

 

ResearchBlogging.orgIn 2008, data was published on the ‘most aggressive dogs breeds’, with dachshunds, chihuahuas, and jack russells, coming out on top. Recently, various media reports having been reappearing on my newsfeed on this study, with titles like “The 3 Most Aggressive Breeds Revealed“.

Before we begin, please do acknowledge that I adamantly against BSL. I am heavily influenced by research and evidence and, currently, all the evidence points to breed specific legislation never being effective in reducing the incidence of dog bites, in any place globally.

That being said, because I am interested in science, I am interested in studies like this.

So what can this study teach us about aggression in particular dog breeds?

Cindy the Jack Russell Terrier: In the top three aggressive breeds according to this study.

A Jack Russell Terrier: in the top three aggressive breeds according to this study.

 

The Flaws in Breed Aggression Research

Aggression is a difficult characteristic to assess in dogs.  There are a variety of methods that researchers have used, and all have their ‘downsides’.

Using dog bite statistics is not the best course, as most dog bites go unreported, the dog breeds involved cannot be verified and, even if they are verified, it is impossible to understand how many dogs of that paricular breed exist in the community.

If you’re only looking at caseloads from behavioural clinics, then this data is likely to be biased.  Generally, people with larger and more dangerous (because of their size) dogs are more likely to seek help, as are people who have dogs aggressive to members of their family. (This article doesn’t mention it, but finances also play a role here – only those owners with the finances to attend behavioural clinics would be represented in such a study.)

There has been some popularity in behavioural tests (cough – D&CMB proposal – cough) where they do threatening or scary things to a dog and score their responses.  The problem with this is how this actually relates to the ‘real world’ and the aggression the dog displays in everyday life.

When you ask owners about their dog’s behaviour, their experiences and responses are subjective. And ‘experts’ aren’t much better, with many of them representing ‘shared stereotypes’ whether conclusions from their own experiences.

 

Study Design

In this particular study, C-BARQ was used. C-BARQ has a good record as being pretty reliable when it comes to asking owners what their dogs are like, temperamentally.

Members of 11 AKC club (‘club sample’) and vet clinic clients (‘online sample’) were invited to partake.

1,553 C-BARQs were completed by the club sample, with 29 excluded as they did not meet criteria.

8,260 C-BARQs were completed by the online sample, with 1,257 excluded for being mixed breeds or with no breed indicated, and 2,051 excluded as there was less than 45 of that breed represented – so in the end the sample was 4,952 responses for 33 different breeds.

They were rated on aggression towards strangers, owners, and other dogs.

 

Summarised Findings

The online sample and breed club sample differed in some ways.  Breed clubs submitted more intact dogs, more female dogs, and older dogs than those in the online sample. Despite this, the results were quite consistent across the two samples.

Dog aggression was the most common and most severe type of aggression in the study, but dog aggression was not correlated with aggression to people. This supports the widely held view that ‘dog aggression’ does not indicate a risk to people. Similarly, aggression towards household-dogs was not associated with aggression towards other dogs or people. From the data in this study, more than 20% of Akitas, Jack Russell Terriers, and Pit Bulls had serious aggression towards unfamiliar dogs.

When it came to aggression towards people, the highest rates were found in smaller breeds, ‘presumably’ because aggression from smaller (and so more manageable and less dangerous) dogs is more tolerable.

When it came to aggression towards owners, more than half of the aggressive displays towards owners were associated with the owner taking food or something else away from the dog.

While fear in animals is associated with aggression, fear was not strongly correlated with aggression in this study. Some dogs were aggressive but not fearful, some were fearful but not aggressive, and some were fearful and aggressive.

A quote from the study on their findings,

“Although some breeds appeared to be aggressive in most contexts (e.g., Dachshunds, Chihuahuas and Jack Russell Terriers), others were more specific. Aggression in Akitas, Siberian Huskies, and Pit Bull Terriers, for instance, were primarily directed toward unfamiliar dogs. These findings suggest that aggression in dogs may be relatively target specific, and that independent mechanisms may mediate the expression of different forms of aggression.”

Screen shot 2014-02-02 at 5.01.31 PM

Further results on a more breed-by-breed basis (breeds listed alphabetically):

  • Akitas rated higher for aggression towards other dogs than other breeds.
  • American Cocker Spaniels rated higher for aggression towards their owners than other breeds.
  • Australian Cattle Dogs rated higher for aggression towards other dogs than other breeds, and also rater higher for aggression towards strangers.
  • Basset Hounds rated higher for aggression towards their owners than other breeds, but were below average when it came to stranger directed aggression.
  • Beagles rated higher for aggression towards their owners than other breeds.
  • Bernese Mountain Dogs were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Boxers rated higher for aggression towards other dogs than other breeds.
  • Brittanys were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Chihuahuas rated higher for aggression towards people (both owners and strangers) and higher for aggression towards other dogs than other breeds.
  • Dachshunds rated higher for aggression towards people (both owners and strangers) and higher for aggression towards other dogs than other breeds.
  • English Springer Spaniels rated higher for aggression towards other dogs than other breeds, and also rated higher for aggression towards owners. Showed bred English Springer Spaniels were more aggressive than field bred lines.
  • German Shepherd Dogs rated higher for aggression towards other dogs than other breeds.
  • Golden Retrievers were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Greyhounds were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Jack Russell Terriers rated higher for aggression towards people (both owners and strangers) than other breeds and higher for aggression towards other dogs than other breeds.
  • Labrador Retrievers were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression. Field bred labradors were more aggressive than show bred labradors.
  • Pit Bulls rated higher for aggression towards other dogs than other breeds.
  • Siberian Huskies ranked below average on stranger directed aggression.
  • West Highland White Terriers rated higher for aggression towards other dogs than other breeds.
  • Whippets were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.

 

Warning against reaching conclusions on the genetic basis of aggression…

The authors caution, “Demographic and environmental risk factors for the development of canine aggression need to be investigated across a variety of breeds so that both generalized and breed-specific influences can be identified.”

 

So what do you think? Are these studies results consistent with your experiences?

 

Reference:

Deborah L. Duffy, Yuying Hsu, & James A. Serpell (2008). Breed differences in canine aggression Applied Animal Behaviour Science, 114 (3), 441-460 DOI: 10.1016/j.applanim.2008.04.006

View PDF.

 

Further Reading

More on C-BARQ: Can breeders breed better?

01/24/14

How safe are dog car travel harnesses?

Last year, we heard that 100% of dog car harnesses were failing safety tests.  The Center for Pet Safety is quoted as saying,”We tested them to the child safety restraint standard and we experienced a 100-percent failure rate to protect either the consumer or the dog”.

It’s a concerning claim. Many pet owners put their dogs on a harness because they want them to be safe during an accident, and yet it seems that harnesses won’t achieve these aims. So what’s a pet owner to do?

Golden retriever puppy in back seat of car.

 

Center of Pet Safety Study

Firstly, have a look at the CPS’s study.  A complete summary of CPS’s investigation can be read on this PDF, but the research methods are best summarised by this flowchart:

Click to see PDF source.

Click to see PDF source.

So, firstly, they only tested harnesses that claimed to be tested, or claimed to offer crash protection.

Then, they did ‘quasi static testing’, which is basically they pulled on the harness attachment really hard for a sustained period to see if the harness survived or not. (Watch a video of the quasi static test.)

The following products did not pass the quasi static testing:

  • USA K-9 Outfitters; Champion.
  • In the Company of Animals; Clix.
  • Coastal; EZ-Rider.
  • Snoozer; Pet Safety Harness and Adapter.

It is only if the product passed both of those initial stages that they proceeded to crash testing.

In the same PDF, a nifty little flow chart is displayed – and ultimately it lists the harness, from left to right, as best to worst (of those tested).

Crash test harness results.

So, basically, the testing concluded that the ‘best’ harness (of those tested) was the Sleepypod Clickit Utility.

A complete analysis is available on page 10 of the results.

You can find out more about the Sleepypod Clickit harness from the Sleepypod website.

 

NRMA Insurance Test

From my research, the only other test I can find was performed by NRMA Insurance, and yielded not dissimilar results: The Sleepypod Clickit Harness was rated on the top, and the Purina Roadie Harness was second.  NRMA Insurance tested 25 harnesses, and only the above two passed. That is, 92% of harnesses failed. You can read NRMA’s brief press release: Paws and Secure Your Puppy

 

But harnesses are still better than nothing…

I would like to warn against ‘giving up’ on harnesses, because most of the harnesses do stop dogs become a projectile, and injuring people in the car. Little comfort, but please do restrain your pets.

Screen shot 2014-01-15 at 8.46.34 AM

 

My choice

Personally, I have had trouble with harnesses in the car. Any of my dogs that I have tried them on walk around and around in circles, twisting up their limbs in their harness, and looking miserable and uncomfortable.

After reading the two studies above, I am glad I made the choice to crate my dogs in the car. The crates are secured in my car with tie downs to anchor points. I am very happy with my choice, and feel that it is probably the safest option for car travel, especially in light of this study.

Our next blog post will look into ways you can advocate for better harnesses.

 

Further reading: Pet Auto Safety Blog