May 15, 2014
In a range of studies, the breeds found to be highly represented in biting incidents were German Shepherd Dog,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,50 mixed breed,1,4,6,8,10,11,12,19,17, 20,50 pit bull type,5,9,13,16,21,20,22,23,24,25,26,27 Rottweiler,15,18,22,24,25,28 Jack Russell Terrier,21,25,26 and others (Chow Chow,7,23 Spaniel,14,26 Collie,3,29 Saint Bernard,20 and Labrador Retriever2).
If you consider only the much smaller number of cases that resulted in very severe injuries or fatalities,21,23 pit bull-type dogs are more frequently identified. However this may relate to the popularity of the breed in the victim's community, reporting biases and the dog's treatment by its owner (e.g., use as fighting dogs21). It is worth noting that fatal dog attacks in some areas of Canada are attributed mainly to sled dogs and Siberian Huskies,56 presumably due to the regional prevalence of these breeds. See Table 1 for a summary of breed data related to bite injuries.
The prevalence of particular dog breeds can also change rapidly over time, often influenced by distinct peaks of popularity for specific breeds. It seems that increased popularity is sometimes followed by increases in bite reports in some large breeds. For example there was a distinct peak in American Kennel Club registration of Rottweilers30 between 1990 and 1995, and they come at the top of the list of 'biting breeds' for the first time in studies of bites causing hospitalization in the late 90s and early 2000s.25,28,15,58 While it must be noted that other fad breeds such as Dalmatians and Irish setters do not seem to make similar appearances, any estimate of breed-based risk must take into account the prevalence of the breed in the population at the time and place of serious biting events.17,31
For example, researchers can compare well-documented bite cases with matched control households. Using this method, one study found that the breeds disproportionately involved in bite injuries requiring medical attention in the Denver area (where pit bull types are not permitted) were the German Shepherd Dog and Chow Chow.64
Other studies use estimates of breed prevalence that do not relate specifically to the households where the bites occurred, such as general community surveys, breed registries, licensed dogs or animal shelter populations (See Table 2.). A study in Rome, Italy where molloser dogs like mastiff are reputed to be the most dangerous dogs, found they were not disproportionately involved in biting incidents when taking into account their prevalence in the community.32 These prevalence referenced studies attribute higher risk to the German Shepherd Dog and crosses60,61,62,63,64, and various other breeds (mixed breed,62,63 Cocker spaniel,61,65 Chow Chow,64,65 Collie,61 Doberman,60 Lhasa Apso,44,65 Rottweiler,49 Springer Spaniel,43 Shih Tsu,43 and Poodle62).
Based on behavioral assessments and owner surveys the breeds that were more aggressive towards people were small to medium-sized dogs such as the collies, toy breeds and spaniels.33,34,35,36,37 For example, a survey of general veterinary clientele in Canada (specifically practices in New Brunswick, Novia Scotia, and Prince Edward Island) identified Lhasa Apso, Springer spaniel and Shih Tsu as more likely to bite.43
While small dogs may be more aggressive their size means they are less likely to inflict serious bite injury except on vulnerable individuals or as part of a pack attack, which also allows dogs to seriously or injury healthy older children or adults.38,39 Referrals for aggression problems more closely approximate the breeds implicated in serious bite attacks, probably because owners are more likely to seek treatment for aggression in dogs that are large enough to be dangerous. Larger dogs (regardless of breed) are implicated in more attacks on humans40 and other dogs.41
Certain large breeds are notably under-represented in bite statistics such as large hounds and retrievers (e.g., Labrador Retrievers and Golden Retrievers)35,43—although even these breeds may have known aggressive subtypes.42 Results relating to German Shepherd Dogs are mixed,36,43 suggesting there may be particularly high variability in this breed, perhaps depending on regional subtypes or ownership factors.
Owners of pit bull-type dogs deal with a strong breed stigma,44 however controlled studies have not identified this breed group as disproportionately dangerous. The pit bull type is particularly ambiguous as a "breed" encompassing a range of pedigree breeds, informal types and appearances that cannot be reliably identified. Visual determination of dog breed is known to not always be reliable.45 And witnesses may be predisposed to assume that a vicious dog is of this type.
It should also be considered that the incidence of pit bull-type dogs' involvement in severe and fatal attacks may represent high prevalence in neighborhoods that present high risk to the young children who are the most common victim of severe or fatal attacks. And as owners of stigmatized breeds are more likely to have involvement in criminal and/or violent acts46—breed correlations may have the owner's behavior as the underlying causal factor.
Most serious dog bite injuries (requiring hospital treatment) in the United States are the victim being a young child54 and the dog being un-neutered and familiar (belonging to the family, a family friend or neighbor).32,47,48,54 Therefore responsible ownership and supervision is key to minimizing the risk of dog bites in communities.
While some study authors suggest limiting ownership of specific breeds might reduce injuries (e.g., pit bull type,49 German Shepherd Dog50) it has not been demonstrated that introducing a breed-specific ban will reduce the rate or severity of bite injuries occurring in the community.8,51 Strategies known to result in decreased bite incidents include active enforcement of dog control ordinances,52 and these may include ordinances relating to breed.53
Maulings by dogs can cause terrible injuries47 and death—and it is natural for those dealing with the victims to seek to address the immediate causes. However as Duffy et al (2008) wrote of their survey based data: "The substantial within-breed variation…suggests that it is inappropriate to make predictions about a given dog's propensity for aggressive behavior based solely on its breed." While breed is a factor, the impact of other factors relating to the individual animal (such as training method, sex and neutering status), the target (e.g. owner versus stranger), and the context in which the dog is kept (e.g. urban versus rural) prevent breed from having significant predictive value in its own right. Also the nature of a breed has been shown to vary across time, geographically, and according to breed subtypes such as those raised for conformation showing versus field trials.37
Given that breed is a poor sole predictor of aggressiveness and pit bull-type dogs are not implicated in controlled studies it is difficult to support the targeting of this breed as a basis for dog bite prevention. If breeds are to be targeted a cluster of large breeds would be implicated including the German shepherd and shepherd crosses and other breeds that vary by location.
National Animal Control Association Guideline Statement: "Dangerous and/or vicious animals should be labeled as such as a result of their actions or behavior and not because of their breed."
Table OneStudies of Serious Dog Bite Injury by Breed
Table TwoStudies of Serious Dog Bite Injury by Breed taking into Account Breed Prevalence