Analysis of reported dog bites to the city of San Francisco for 2003/2004

Report by T.E. Houston, PhD
November, 2005

 

Introduction

The alleged fatal attack of a 12-year old San Francisco boy by the family’s intact “pit bull” dogs became the central focus of a public outcry for more restrictive animal control measures directed at potentially dangerous breeds (1,2).  The recent passage in the California legislature of a law would allow cities and counties to impose breed specific mandatory spay/neuter programs.  The presumption behind the bill is that neutering the dogs would result in less aggressive tendencies and hence fewer dog bites.  Implementation of the program is to be based on the reported dog bites to the municipality and submitted quarterly to the state public health veterinarian. 

Dog bites reported to the City of San Francisco for 2003 and 2004 were analyzed to assess the necessity of a mandatory spay/neuter program.  The assumption is that the majority of the dog bites in the city are by intact dogs which have a tendency to be more aggressive in nature.   The purpose of this study is to evaluate the reported dog bites and consider the risk from intact dogs and neutered dogs.  In addition, what information from the reports could be useful in helping to reduce the incidence of dog bites. 

Materials and Methods

Dog bites reported to the City of San Francisco Animal Care and Control were received as an electronic file for the years 2003 and 2004.  A total of 497 reports included information on: date of the bite, victim age, victim’s first name, severity, location within the city, treatment, sex (dog), pet date of birth, pet years, pet months, breed1(primary), breed2 (secondary), animal id, owner id, victim id, and bite report number. 

The data was compiled in an excel spreadsheet and analyzed by Epi Info version 3.3.2.  Information on the city population, zip codes, and median income was from the U.S. Census Bureau database (3).

The 497 reports received indicated 279 for 2003 and 218 for 2004.  An evaluation of the data indicated duplicate reports, out of city reports and dog on other animal reports.  Location was given as physical address, neighborhood and anatomical location of the bite.  Severity of the bites was given variously as minor, moderate, serious, severe, punctures.  It was necessary to standardize the reports for analysis and to remove or re-code for consistency.  Columns added to the datasheet were day of week of bite, age category of victim, victim gender, victim species (human, dog, cat, equine), zip code of location, and dog age.  Victim age was re-coded for a range of ages.  A “0” was stated by animal control to indicate a bite to a person less than 1 year old.  However, upon reviewing the data if was apparent that in a number of cases the “0” was used to designate an unknown age of the victim.  In some incidents, two reports are given if it involves one person apparently breaking up a dog fight.  One report will give the victim’s age, while the other will list the age as “0”. These were recoded so that they were not counted twice in analysis of the age of the victim.  In other situations, the victim was certainly older, as indicated in the “treatment” column of the reports; these were indicated as “unknown”.   It was clear that the bite reports included dog on other animal bite reports.  A separate column was added to code for bites involving a person, dog, cat, horse, pig, and bat.  The designation of the severity of the bite reported was not consistent.  An attempt was made to recode the severity as minor ( < 4 punctures), moderate ( > 4 punctures), and severe (hospitalization).  Use was made of designations from comments in the wound treatment column and other reports of severity.  For the location of the bite, zip code was added.  Zip code of the reported bite was given by designation of the neighborhood of the bite or street address.  In some cases the only information given is “home”, “car”, “yard”, “Peet’s Coffee”, etc and these were reported as unknown.  In other cases, the location was reported as the anatomical location of the bite.  Dog age was added, subtracting the date of the bite report from the date of birth of the dog given in the report.  In some cases the pet years reported did not match that of the pet age from subtracting the date. 

Duplicate data was removed from the data set.  Duplicate sets were marked by same date, location, victim name, i.d. numbers, but a different bite number.  This was possible if the report came in from two different sources.  There were a total of five (5) duplicates and the one giving the most complete data remained in the data set.  There were 13 out of the city reports that were removed from the data set.  There were 6 reports that indicated the same victim but two (2) dogs were involved.  The victim age in these cases were recoded so as not to be counted twice in the analysis.  Both dogs were included.  There were 3 reports of the same dog, but 2 different victims.  These remained in the data set. 

There were 43 dog on another animal reports removed from the data.  This included 32 dog on dog reports, where it was not clear if the dog was victim or perpetrator.  There were 4 dog-cat, 4 dog-equine, and 1 dog-pig interactions.  There was also a report involving a bat and one unknown bite report.  The final data for dog bites to humans was 435 reports.  There were 249 bites in 2003 and 186 in 2004. 

 

RESULTS

Breeds:  Table 1 shows the list of dog breeds reported and the percent of total bites.  There were 74 breeds identified as the primary breed.  Included were varieties for the following:  Collie, smooth and rough-coated, Dachshunds, long-haired, standard, miniature, and wire-haired, Poodle, miniature, standard, and toy, and Schnauzer, miniature and standard.  Additionally, some “breeds” were identified as retriever, spaniel, terrier, and shepherd.  Seventy-three (73%) percent (n=319) of the dogs were identified as mixed breed.  There were 16 breeds specified as the secondary breed or “mix”.  With the large number of mixes, only the primary breed was analyzed and no distinction was made of purebred versus mixed breed in the bite reports.  The four breeds comprising 48.9% (n=213) of the 435 reports are “pitbull”, the German Shepherd, Labrador, and Rottweiler.  “Pitbull” is a generic term for several breeds and their mixes.  Seventy-six percent (76%) of the dogs identified as “pitbulls” were labeled mixed, comprising 23.4% (n=102) of the bites.  German Shepherd dogs were labeled mixed in 80% of the reports and comprised 10.3% (n=45) of the bites.  Ninety-two percent (92%) of the Labrador retrievers were identified as mixed and accounted for 9.0% (n=39) of the bites.  Rottweiler were identified as mixed in 59% of the reports and comprised 6% (n=27) of the bites. 

Age of dog:  The age of the dog in the bite reports was determined by subtracting the date of birth of the dog given from the date of the bite report.  Of the 435 dogs, age was not specified in 178 (40.9%) of the reports.  The age of the dogs ranged from less than 1 year to 18 years.  Figure 1 shows the age distribution of the dogs reported.  Dogs that were juveniles or young adults (<1 to 3 years) were responsible for 40.5% of the bites.  Adult dogs (4-10 years) were implicated in 52.5% of the bites.  Senior dogs (greater than 10 years) involved in 7% of the bites.  The average age of the dogs is 5 years, with a median of 4 years. 

Gender status of dog:  The dogs were identified in the reports as male (M), neutered male (N), female (F), spayed female (S), or unknown (U).  Of the 435 dogs, gender was given in 337 reports.  Table 2 shows the gender status of all the dogs, and the top four breeds implicated in the reports.  Overall, male dogs (both intact and neutered) were responsible for 72.1% (n=243) of the bites where gender is given.  For the top 4 breeds where gender is reported, male (intact and neutered) “pitbulls” were implicated in 67.1% (n=49, total=73), German Shepherd dogs in 83.3% (n=30, total=36), Labrador in 80.6% (n=25, total=31), and Rottweiler in 66.7% (n=14, total=21).  Intact dogs (males and females) comprised 51.3% (n=173) of the 337 bite reports where gender is given.  Intact males for all dogs represented 52.6% (n=128) where male dog is given (n=243).  For the top 4 breeds where male is given, intact “pitbull” males comprised 69.4% (n=34), German Shepherd dogs 60.0% (n=18), Labrador 44.0% (n=11), and Rottweiler 71.4% (n=10).  Table 3 shows the relative risk based on the gender and reproductive status of the dogs in the reported bites.  For all dogs, the relative risk (RR) of a bite from an intact male/neutered male with an intact female/spayed female dog is 1.1 (95% CI= 0.86-1.40).  The relative risk for an intact male “pitbull” dog to a neutered male and intact/spayed female is 1.1 (95% CI= 0.77-1.59).  German Shepherds, Labradors, and Rottweilers have some cells less than 5, so the risk numbers are not accurate.  The relative risk of a bite from any male dog (intact or neutered) and female dogs for 4 breeds to all males and females in the report: “pitbulls” RR = 0.93 (95% CI= 0.78-1.11); German Shepherd dogs RR= 1.16 (95% CI= 0.98-1.36); Labradors RR= 1.12 (95% CI= 0.93-1.35) and Rottweiler RR = 0.92 (95% CI = 0.68-1.26).  The relative risk of a bite from an intact male from one of the 4 breeds to all the dogs shows that the relative risk from an intact male “pitbull” is 1.32 (95% CI= 1.06-1.64).  A higher risk is also seen for the Rottweiler, RR = 1.36 (95% CI= 0.95-1.93).  The risks from the German Shepherd dog and the Labrador are slightly lower, GSD, RR= 1.14 and Labradors RR= 0.84.

Severity of bites:  The severity of the dog bite was reported in 372 cases.  Minor bites defined as 4 punctures or less, bruising, scratches, saliva contact comprised the majority of the bites at 85.7% (n=319).  Moderate bites, more than 4 punctures, stitches, accounted for 10.8% (n=40) bites.  Severe bites, requiring hospitalization accounted for 3.5% (n=13) of the bites.  Seventeen breeds were implicated in the moderate bites.  The largest number attributed to “pitbulls” (n=16), Labrador (n=5), and 2 each for German Shepherd dogs, Rottweiler, and Akita.  Seven breeds were involved in severe bites, including Australian Shepherd (n=1), Australian Cattle dog (n=1), Bull Mastiff (n=1), Chow Chow (n=2), Newfoundland (n=1), “pitbull” (n=5), and Rottweiler (n=2).  The gender of the dog and reproductive status was known in 287 of the reported cases for severity.  Figure 2 shows the gender/reproductive status of the dog and severity of the reported bite.   In Table 4 the severity of bites and the gender of the dogs is given for all dogs and the top 4 breeds.  Overall, for minor bites, the relative risk of a bite from a male (intact/neutered) to a female (intact/spayed) is 1.16 (95% CI= 0.86-1.56).  For the “pitbulls” and German Shepherds, the relative risk from an intact male dog was higher than for a female dog.  For “pitbulls” the RR was 1.39 ( 95% CI = 0.85-2.27).  The RR for a German Shepherd intact male dog was 1.86 (95% CI = 0.57-6.05) [Note that the cell numbers for the German Shepherd was small].  For the Labrador and the Rottweiler, the cell numbers are too small to obtain any meaningful results.  Moderate and severe bites were small in number and combined for analysis.  For moderate/severe bites the relative risk for male intact to female intact for all dogs is 0.61 (95% CI= 0.34-1.099).  For the “pitbulls” this relative risk is 0.4 (95% CI = 0.14-1.12). 

Gender and age of the victim:  Of the 374 reports where victim gender is given, males comprised 56.7% (n=212) of the bites.  Gender and age was known in 260 of the reports.  Table 5 and figure 3 shows the gender of the victim by age category.  Males in all age groups comprised 56.5% (n=147) of the reports.  Females were numerically higher only in the 20-29 age groups and just 1 more than the males in the 70-79 group.  Adults 20-59 years comprised 72.3%(n=188) of the reported bites.  Of the adults, the 30-39 age group accounted for 26% (n=68) of the 260 bite reports.  Males in the 20-59 age group were implicated in 54.8% (n=103) of the bites.  Children aged 1-9 years represented 10.0% (n=26) of the bites.  For the age groups 1-19 comprising young children to teenagers, 66.0% (n=31) of the victims were males.

Severity and age of victim:  The severity of dog bite and the age of the victim was given in 262 of the cases.  Table 6 and figure 4 show the distribution of bites by severity and age group.  For all age groups, 84.4% (n=221) of the bites for were minor.  Of the 41 moderate/severe bites, 58.5% (n=24) were in the age group 20-59.  Children 1-9 years accounted for 10.8% (n=24) of the minor bites and 12.1% (n=5) of the moderate/severe bites.  Older children and teenagers 10-19 years were victims in 22.0% (n=9) of the moderate/severe bites, compared to 4.5% (n=10) of the minor bites.  The age group and bites from all dogs and the top 4 breeds in the bite reports is given in Table 7 and figure 5.  The age group and dog breed was reported in 294 cases.  Relative to the number of bites per breed for the 1-9 year old age group, the “pitbulls” were the lowest at 4.5% (n=3) of the 66 bites for the dogs.  The Labrador had the highest percentage for the age group at 22.7% (n=5) of 22 bites.  For the age group 10-19 years, based on the relative number of bites, the Rottweiler had the highest percentage of bites 22.2% (n=4) of 18 bites.  For the age group 20-59 years, the “pitbulls” had the largest percentage of reported bites at 78.8% (n=52) of the 66 bites.  The percentage of bites from German Shepherd dogs for this age group was similar to the “pitbulls” at 75.8% (n=25) for 33 bites.  The Rottweiler had the lowest percentage at 55.6% (n=10) of the reported bites from the breed.  The highest percentage of reported bites relative to the total number from each breed in the 60-80+ age group is from the Labradors with 18.1% (n=4) of the bites. 

Bites by zip code: 

Zip code was given in 245 of the reported dog bites.  Table 8 and figure 6 show the percentage of the reported dog bites and the percentage of the population by zip code for the city.  There were 4 zip codes reporting 8-11% of the bites, 94122 (n=27), 94103 (n=24), 94110 (n=22) and 94117 (n=20).  Zip code 94122 called the “Sunset” area, had the largest percentage of reported bites at 11.0% (n=27) and contains 7.1% of the population.  The zip code region is south of Golden Gate Park.  The area called “South of Market” comprises the 94103 zip code, reporting 9.8% (n=24) of the dog bites and represents 3.0% of the population.  Zip code 94110 is called the “Mission” area, has the largest percentage of the population (9.6%) and had 9.0% (n=22) of the reported bites.  The area called the “panhandle” or the Haight-Ashbury section comprises zip code 94117 is 5.0% of the population and reported 8.2% (n=20) of the dog bites.  Figure 7 shows the number of reported bites by the top 4 breeds in the zip codes.   In zip code 94122, 40.7% (n=11) of the bites were from “pitbulls”.  For zip code 94103, 33% (n=8) of the total bites were from “pitbulls”.  In zip code 94117, “pitbulls” and German Shepherd dogs each comprised 20% (n=4) of the bites. 

In 193 of the reports gender and reproductive status of the dog was given.  Table 9 shows the zip code and the gender and neuter status of the dogs.  Of the 139 males dogs, 47.5% (n=66) were intact.  Intact female dogs were 51.8% (n=28).  The relative risk of a bite from an intact male dog to an intact female is 0.92 (95% CI = 0.67-1.25).

 
DISCUSSION

For a city the size of San Francisco with a human population of over 750,000 the number of reported dog bites is small.  Reported dog bites consisted of 249 in 2003 and 189 in 2004.  In comparison, the city of Sacramento with a population of 445,335 had 579 dog bites reported to animal control in 2003 (4).  A 1994 report by the Center for Disease Control and Prevention (CDC) estimated that the total number of dog bites in the United States were 18 per 1000 human population, reported and unreported (5).  The incidence of dog bites that receive medical attention is estimated at 3 per 1000 (6).  The reporting of bites varies with each municipality and depends on the effective cooperation of animal control, health officials, law enforcement, and the public (7).  The incidence of dog bites in San Francisco is very low at 0.3 per 1000, an order of magnitude less than nationally (6).  The CDC estimate corresponds to approximately 10% of the dog population likely to bite.  According to the San Francisco Animal Care and Control, there are an estimated 120,000 dogs in the city.  An average of approximately 200 dog bites per year represents less than 0.2 % of the dog population.
 
Of the 75 breeds of dog identified in the 435 bite reports, 73% (289) were labeled as mixed.  The city of San Francisco may have a larger percentage of mixed bred dogs than the reported estimate of nearly 40% of the dog population in veterinary caseload studies (4, 8).  A national survey put the percentage of mixed bred dogs at 51% (9, 10).  The identification of such a large number of mixes in the population raises the question of accuracy when identifying dog breeds.  Certain mixes may yield dogs that look like “pitbulls” but are in fact not.  A dog that is part Australian Cattle dog and part Labrador could easily be labeled a “pitbull” mix.  A German Shepherd dog and a Greyhound mix may be labeled the same, particularly if the dog is a “brindle”, a color associated with “pitbulls” but is not uncommon in other breeds.  The dog may be called a “pitbull”-German Shepherd mix based on coat color alone.  Breed identification is very subjective unless the parents of the dogs are known or the dogs are registered with a national registry.  Several generations of breeding mixed breed dogs with other mixed makes identification of the specific dominant breed problematic. 
 
Dogs identified as “pitbull” and their mixes (76%) comprised 23.4% (n=102) of the reported bites for the 2 year period.  The “pitbull” dogs are one of the most popular dogs in the city, representing about 6% of all the dogs licensed, ranking third, just slightly behind the German Shepherd dogs (11).  The German Shepherd and Labrador retrievers accounted for 10.3% (n=45) and 9.0% (n=39) of the reported dog bites and are also the top 2 breeds licensed with the city.  Labradors have the largest number of licensed at 14% and the German Shepherd dogs are 6%.  The Rottweiler ranks 7th in licensed dogs at 3% and comprised 6.2% (n=27) of the reported bites.  However, it should be noted that San Francisco Animal Care and Control believes only about 10% of the dog population is licensed.  “Pitbulls” are popular dogs in the urban areas and are popular in the neighboring municipalities of the bay area (11).  They also comprise a high percentage of dogs in municipal shelters according to animal control.  It is believed that the “pitbull” population could be at least 10% or more in the city.  The population range for the “pitbulls” then could be 7,200 to 12,000 dogs.
 
The dogs in reported bites age averages 5 years with a median of 4 years.  This is consistent with studies of reported dog bites in neighboring counties (4, 12).  Dog bites from younger dogs, 1 year or less may be underrepresented in reported bites.  In reported bites to the city, dogs 1 year and less accounted for 16.3%.  In 2 other studies of county dog bites, this age group was 15.0% and 12.6% (4, 12).   In a veterinary caseload study, dogs less than 1 year had a higher percentage of the reported bites at 24.6% (8).  A similar study has younger dogs at 25% of the bites in a survey (4).  The underreporting of younger dogs may be due to acceptance of puppy behavior such as mouthiness, chewing, and general rambunctious behavior.  As a dog gets older and proper behavior is not instilled by training/socialization methods then a bite from an older dog may be reported. 

The primary purpose of this analysis was to determine if intact male dogs represent a significantly higher risk in reported dog bites.  Male dogs (intact and neutered) were implicated in nearly three-quarters of the reported bites where gender and reproductive status was given.    By reproductive status of the reported bites, 52.6% were from intact male dogs, and 47.8% were intact female dogs.  Overall, the risk of a bite from an intact male dog compared to an intact female was the same.  Based on the top 4 breeds, the relative risk of a bite from an intact male was greater for German Shepherd dogs and Rottweilers, although the low number reported for female dogs make this not accurate.  For “pitbulls” the risk of a bite from an intact male relative to intact female was the same as for the overall reported bites.  For the total number of males and females by breed relative to all dogs, there was no significant relative risk between the top 4 breeds.  The risk of a bite from intact male dogs from the top 4 breeds to intact males overall indicated a higher proportion of “pitbulls” and Rottweiler.  For the Labrador, the risk from neutered males was higher.  While for German Shepherd dogs, the risk from intact males compared to all males was about the same.  The fewer numbers available for female dogs makes the analysis less accurate in ascertaining a relationship between intact females and spayed ones.   Sufficient numbers were available for “pitbulls” to indicate that intact female dogs were likely to be higher risk in the reported bites.
 
The severity of the bites shows that 85.7% of all reported bites were minor, requiring little or no medical attention.  The relative risk of a minor bite was about the same for male and female dogs.  However, for “pitbulls”, German Shepherd dogs, and Rottweilers significantly more intact males were represented in the minor bites compared to females.  A different trend is observed for the moderate/severe bites.  Overall, 25 of the moderate/severe bites were from neutered dogs (male and female) compared to 22 intact dogs.  Male dogs (intact and neutered) were responsible for 33 of the moderate/severe bites compared to 14 of the females.  However, for “pitbulls” an equal number of intact dogs and neutered dogs were reported in moderate/severe bites.  Male “pitbulls” (intact/neutered) were reported in 10 cases to 8 for females.  Only 3 of the “pitbull” males were intact.  For the other 3 breeds, 9 reports were for male dogs (intact and neutered), no reports were for female dogs.   Of the 9 dogs, 5 were intact.
 
The differences between the reported minor and the moderate/severe bites may be a result of several factors requiring further study.  Data suggest that the vast majority of dog bites are minor and go unreported (5,13,14).  With minor bites comprising nearly 85% of all the reported bites and the large percentage of these implicate intact male dogs; it is possible the perceptions of the seriousness of a bite rather than the medical severity will be a factor.  Minor bites may be self reported, however, more work is required to ascertain if there is a bias in reporting.  People view bites by large, intact male dogs as being of a greater concern than bites by female dogs (13).  In particular, bites from “pitbull” dogs are viewed as more serious due to media hype and perceptions (14, 15).  In a veterinary caseload study, neutered males had the highest risk of aggressive behavior followed by spayed females (8).  In this study, a bite from a male dog was viewed as more serious than a bite from a female dog (16).  In a similar study, male dogs were more likely to be identified as having bit (4).  There was no significant difference between male and female dogs as biters for intact dogs compared to neutered dogs.  However, if a dog were spayed/neutered, the male dogs were more likely to have bitten than the females (4).  The reporting of a bite by an unidentified dog raises the concern of rabies, even if the bite is minor involving only a scratch or saliva contact.  People who want to pursue a personal grievance or a dangerous dog complaint are more likely to report minor interactions with dogs.  In both cases, the likelihood of a report may be greater for intact male dogs for the reasons described above.  In addition, the reporting of a dog bite may be a function of social or cultural factors, as well as attitude, knowledge or educational level of the victim (17,18).  In contrast, moderate/severe dog bites may more likely be reported by health care workers if the victim seeks treatment for the injury.  Further work is required to identify the sources of reported bites and to clarify what constitutes a minor bite and reasons for reporting. 

Adults, ages 20-59 years, were the victims in 72% (n=188) of the 260 bite reports where age and gender is given.  This age range makes up 66% of the population in the City of San Francisco.  Males were identified as the victim in 54.8% (n=103) of the reports for this age range, with a larger number in all age groups except 20-29.  Over a quarter of the reports (26.2%, n=68) were in the age range 30-39.  Children ages 1-9 years in the City of San Francisco comprise 8.2% of the population, about half that for the California population for that age range (15.3%).  Reported dog bites for children 1-9 were 10.9% (n=32) in the 294 cases where age of victim is given.  Where the gender of the victim was reported in the 26 cases of children 1-9, 65.4% (n=17) were males.  For reported dog bites in neighboring counties, the percentage of bites to younger children is greater, averaging 30%, about twice the population of about 15% (4, 12).  In the 262 reports where age and severity is given, bites to children 1-9 were minor in 82.8% (n=24) of the cases.  Adults 20-59 had reported 87.3% (n=165) of the bites as minor.  For the age group 60 and over, 88% (n=22) of the bites were minor.  The age group that was most affected was the 10-19 year olds, comprising older children and teenagers.  For this group 52.6% (n=10) of the 19 reported bites were minor, with 47.4% (n=9) being moderate/severe.  Males in this age group represented 66.7% (n=14).  The age group 10-19 represented 7.5% (n=22) of the reported bites were age is given and comprises 8.3% of the San Francisco population.  The presence of children, particularly teenagers in the household may increase the risk of a dog bite (14, 16).  Teenagers may be more likely to behave in a manner and activities that may provoke the dog to bite. 

The area of the city, zip code 94124, that reports the largest percentage of “pitbulls” licensed (16%) had one of the lowest reported number of bites.  Overall, the 94124 zip code which has 4.3% of the city population, had 5.7% (n=14) of the reported bites.  There were 5 bites from “pitbulls” and 4 from Labradors. The zip code, 94122, had the largest number of reported bites at 11% (n=27) and 7.1% of the population.   There were 11 “pitbull” bites with a license of 6%.  Zip code 94103 had one of the larger percentage of reported bites at 9.8% (n=24), with only 3% of the population.  The zip code had 8 reported “pitbull” bites with 10% of the licensed population.  The 94103 zip code also had 4 Labrador bites.  The zip code 94110 had the third highest reported bites at 9.0% (n=22) and 9.6% of the population of the city.  Dog bites for the zip code reported 6 “pitbulls”, and 8% of the licensed “pitbull” population.  The reporting of a dog bite may depend on various other factors, including economic, cultural, and social.  To understand dog bites, a lot more work is required in the area.  Very little is known about the bites that go unreported.  The veterinary caseload studies indicate that smaller dogs and owner-bitten incidents may go unreported (4,16).  Little is known about the actual population distribution of dog breeds in the community.  In order to understand whether or not a breed is more prone to aggressive behavior, accurate information is required on populations and on the total percentage of dogs that bite.  A recent study suggests that the number of bites from any breed may not exceed the number of expected bites with in the population; however, some breeds may be more likely to be reported (4).
 
Reported dog bites are only as good as the accuracy of their recording.  While the form is standardized by the state, how the information is input may vary.  It is important that entry data be uniform and consistent.  In this study, there was a lack of consistency in how a bite is defined as minor, moderate, or severe.  According to the animal control office, the input of severity depends on the reporting officer’s experience.  This means that the definition of severity will be highly subjective.  The same for the identification of a dogs breed, particularly if the dog is mixed.  What is identified as a “pitbull”-Labrador mix in one year, may be identified as a Labrador-mix in the next year.  This could easily lead to a bias in reporting that would skew the distribution of breeds implicated in the bite reports.  Also of concern is the reporting of dog/dog and dog/cat incidents.  Dog and another animal aggression are common occurrences.  However, of concern is that only certain breeds may be reported in these incidents.  This would again lead to a skewed perception of the distribution of the breeds and severity of the bites in the community.   
 
The data from the City of San Francisco indicates that a mandatory spay/neuter of any specific breed based on the reported bites to the city is not an effective method of minimizing dog bites.  While intact male “pitbulls” may be highly represented in the reported minor bites this may be a result of reporting bias.  The risk from an intact dog for the moderate/severe bites shows that reproductive status is not a risk factor.  The high proportion of males as victims in reported bites also would indicate that bites are very much a human factor.   Male may engage in activities that put them at greater risk of a dog bite than females.  To minimize dog bites the issue has to be addressed to all dog owners, not just particular breeds.  Training and socialization of the dog are important factors to help minimize the risk of a dog bite. 

References

1. San Francisco Chronicle, June 4, 2005.  “S.F. boy, 12, killed by his family’s pit bulls.”

2. San Francisco Chronicle, June 21, 2005.  City leaders push dog laws with some bite.”

3. U.S. Census: http://quickfacts.census.gov/qfd/states/06/0667000.html

4. Houston, TE. “A method for studying breed effects on dog bite reporting and behavior in Sacramento County, California.”  MPVM Thesis, University of California, Davis, School of Veterinary Medicine.  2006.

5. Sacks, JJ, Kresnow, M, and Houston, B. Dog bite; how big a problem? Injury  Prevention 2:52-54,1996.

6. Weiss, H.B., Friedman, D.I., and Coben, J.H. Incidence of dog bites treated in emergence departments.  Journal of the American Medical Association 279(1), 51-53, 1998.

7. Tan, RL, Powell, KE, Lindermer, KM, et.al. Sensitivities of three county health department surveillance systems for child-related dog bites: 261 cases (2000).  J Am. Vet. Med Assoc. 225(11):1680-1683, 2004.

8. Guy, NC, Luescher, UA, Dohoo, SE, Spangler, E, Miller, JB, Dohoo, IR, and Bates, LA.  Demographic and aggressive characteristics of dogs in a general veterinary caseload.  Applied Animal Behavior Science 74:15-28, 2001.

9. American Pet Products Manufacturers Association (2000) APPMA National Pet Owners Survey. Greenwich, CT.

10. Pet Food Institute, Washington, D.C. (http://www.petfoodinstitute.org).

11. Wallack, T. “Pit bulls are top breed in Oakland, third in San Francisco.” San Francisco Chronicle, June 26, 2005.

12. El Dorado County, California:  http://www.co.el-dorado.ca.us/publichealth/pdf/FullDOGBITEREPORT.pdf

13. Guy, NC, Luescher, UA, Dohoo, SE, Spangler, E, Miller, JB, Dohoo, IR, and Bates, LA.  A case series of biting dogs: characteristics of the dogs, their behavior, and their victims.  Applied Animal Behavior Science 74:43-57, 2001.

14. Overall, KL and Love, M.  Dog bites to humans-demography, epidemiology, injury, and risk.  J. Am. Vet. Med. Assoc. 218(12):1923-1934, 2001.

15. Cohen, J and Richardson, J. Pit Bull Panic.  J. of Popular Culture 36(2):285-317, 2002.

16. Guy, NC, Luescher, UA, Dohoo, SE, Spangler, E, Miller, JB, Dohoo, IR, and Bates, LA.  Risk factors for dog bites to owners in a general veterinary caseload.  Applied Animal Behavior Science 74:29-42, 2001.

17. Beck, AM and Jones, BA. Unreported dog bites in children.  Public Health Reports 100(3):315-321, 1985.

18. Chang, Y-F, McMahon, JE, Hennon, DL, LaPorte, RE, and Coben JH. Dog bite incidence in the city of Pittsburgh: a capture-recapture approach.  Am. J. Public Health 87(10):1703-1705, 1997.

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Table 1:  Breeds of dogs and their mixes in reported dog bites to the city of San Francisco for 2003 and 2004.  There were 435 reported bites to humans.

 

Table 2: Gender status of dogs in reported dog bites to the city of San Francisco for 2003/2004. Gender and reproductive status was given for 337 of the reports. Shown are all dogs where given and the top 4 breeds in the reported bites.

BREED OF DOG	M (male)	N (neutered male)	F (female)	S (spayed female)	TOTAL
All Dogs	128	115	45	49	337
"Pit Bulls"	34	15	15	9	73
German Shepherd	18	12	2	4	36
Labrador	11	14	0	6	31
Rottweiler	10	4	1	6	21

 

Table 3: The relative risk of a dog bite in San Francisco based on the gender and reproductive status of all the dogs and the top 4 breeds in the reported bites for 2003/2004.

Risk Factor	Breed	Relative Risk  (95% CI)
males, intact/neutered to females, intact/neutered	All Dogs	1.10 ( 0.86-1.40)
	“Pitbulls”	1.11 ( 0.77-1.59)
	German Shepherd dogs	1.80 ( 0.56-5.79)*
	Labrador	*
	Rottweiler	5.00 (0.79-31.63)*
males and females (intact/neutered) by breed to all dogs	All Dogs	Ref =1.00
	“Pitbulls”	0.93 ( 0.78-1.11)
	German Shepherd dogs	1.16 ( 0.98-1.36)
	Labrador	1.12 ( 0.93-1.35)
	Rottweiler	0.92 ( 0.68-1.26)
male only intact/neutered by breed to all dogs	All Dogs	Ref = 1.00
	“Pitbulls”	1.32 ( 1.06-1.64)
	German Shepherd dogs	1.14 ( 0.83-1.56)
	Labrador	0.84 ( 0.53-1.32)
	Rottweiler	1.36 ( 0.95-1.93)
females only intact/spayed by breed to all dogs	All Dogs	Ref = 1.0
	“Pitbulls”	1.31 ( 0.90-1.90)
	German Shepherd dogs	0.70 ( 0.22-2.20)*
	Labrador	*
	Rottweiler	*

* Not accurate, the cell numbers are less than 5. 

 

Table 4:  Severity of the reported bites and the reproductive status of all dogs and the top 4 breeds implicated in the City of San Francisco for 2003/2004.  Bite reports for 287 cases indicate severity and reproductive status of the dog.

	Minor				Moderate				Severe				Total
	M	F	N	S	M	F	N	S	M	F	N	S
All Dogs	91	31	81	37	9	8	15	3	4	1	5	2	287
“Pitbulls”	23	8	6	6	3	5	5	1	0	1	2	1	61
GSD	13	2	8	4	1	0	1	0	0	0	0	0	29
Labrador	7	0	10	4	2	0	3	0	0	0	0	0	26
Rottweiler	7	1	2	4	0	0	0	0	2	0	0	0	16

M=Male
F=Female
N=Neutered male
S= Spayed female
GSD= German Shepherd dog

 

Table 5:  The gender of the victim in 260 of the dog bites reported to the City of San Francisco for 2003/2004 by age category.

Age Category of the Victim	Gender of the Victim Percentage of Total		Percent Total (n)
	%F (n)	%M (n)
1-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+	3.5 (9) 2.7 (7) 9.6 (25) 11.2 (29) 6.9 (18) 5.0 (13) 2.3 (6) 1.9 (5) 0.4 (1)	6.5 (17) 5.4 (14) 7.3 (19) 15.0 (39) 9.6 (25) 7.7 (20) 3.1 (8) 1.5 (4) 0.4 (1)	10.0 (26)  8.1 (21) 16.9 (44) 26.2 (68) 16.5 (43) 12.7 (33) 5.4 (14) 3.5 (9) 0.8 (2)
Total	43.5 (113)	56.5 (147)	100.0 (260)

 

Table 6:  Severity of reported dog bite by age group for 262 cases in the City of San Francisco for 2003/2004.

Age Category of Victim	Percentage of Total Reported Bites      Minor (n)             Moderate (n)           Severe (n)			% Total (n)
1-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+	9.2 (24) 3.8 (10) 13.7 (36) 22.1 (58) 16.0 (42) 11.1 (29) 3.4 (9) 3.8 (10) 1.2 (3)	1.5 (4) 2.3 (6) 1.1 (3) 2.3 (6) 0.8 (2) 2.3 (6) 0.4 (1) 0 0	0.4 (1) 1.1 (3) 0.8 (2) 1.5 (4) 0 0.4 (1) 0.8 (2) 0 0	11.1 (29) 7.3 (19) 15.6 (41) 26.0 (68) 16.8 (44) 13.7 (36) 4.6 (12) 3.8 (10) 1.1 (3)
Total	84.3 (221)	10.7 (28)	5.0 (13)	100 (262)

 

Table 7:  Age category of the victim with respect to all dogs and the top 4 breeds implicated in reported bites to the City of San Francisco for 2003/2004.

Age Category of victim	Percentage of all dogs and the 4 top breeds  All Dogs (n)             “Pitbulls” (n)          GSD (n)        Labrador (n)     Rottweiler (n)
1-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+	10.9 (32)   7.5 (22) 16.7 (49) 24.8 (73) 17.0 (50) 13.6 (40)   5.1 (15)   3.4 (10) 1.0 (3)	4.5 (3) 9.0 (6) 18.2 (12) 30.3 (20) 15.2 (10) 15.2 (10) 7.6 (5) 0 0	15.2 (5)  3.0 (1) 18.2 (6)   33.3 (11) 18.2 (6)  6.1 (2) 0  6.1 (2) 0	22.7 (5) 0   4.5 (1) 22.7 (5) 18.2 (4) 13.6 (3)   4.5 (1) 13.6 (3) 0	16.7 (3) 22.2 (4) 11.1 (2) 16.7 (3) 16.7 (3) 11.1 (2)   5.5 (1) 0 0
Total	100 (294)	100 (66)	100 (33)	100 (22)	100 (18)

 

Table 8:  The percentage of the population and the reported dog bites by zip code for the City of San Francisco for 2003/2004.

Zip code	Percent Population (n)	Percentage of reported dog bites (n)
94102 94103 94104 94105 94107 94108 94109 94110 94111 94112 94114 94115 94116 94117 94118 94121 94122 94123 94124 94127 94129 94130 94131 94132 94133 94134 Golden Gate Park	3.7 (28,991) 3.0 (23,016) <0.1 (374) 0.3 (2,058) 2.2 (17,368) 1.8 (13,716) 7.3 (56,322) 9.6 (74,633) 0.4 (3,335) 9.4 (73,104) 3.9 (30,574) 4.3 (33,115) 5.5 (42,958) 5.0 (38,738) 5.0 (38,939) 5.5 (42,473) 7.1 (55,492) 2.9 (22,903) 4.3 (33,170) 2.7 (20,624) 0.3 (2,228) 0.2 (1,453) 3.6 (27,897) 3.4 (26,291) 3.5 (26,827) 5.2 (40,134) 0	2.9 (7) 9.8 (24) 0 (0) 0.4 (1) 4.9 (12) 0 (0) 2.0 (5) 9.0 (22) 0 (0) 6.9 (17) 7.3 (18) 1.6 (4) 1.2 (3) 8.2 (20) 2.0 (5) 4.1 (10) 11.0 (27) 2.9 (7) 5.7 (14) 2.0 (5) 2.4 (6) 1.2 (3) 4.5 (11) 2.4 (6) 2.9 (7) 2.4 (6) 2.0 (5)
Total	100 (776,733)	100 (245)

 

Table 9:  The gender and reproductive status of the dogs in bites reported to the city of San Francisco by zip code in 2003/2004.

Zip code	Gender and reproductive status of the dog      Male       Neutered      Female     Spayed				Total
94102 94103 94105 94107 94109 94110 94112 94114 94115 94116 94117 94118 94121 94122 94123 94124 94127 94129 94130 94131 94132 94133 94134 GG Park	1 5 1 3 2 9 5 7 1 1 7 1 3 5 2 2 2 1 0 2 2 0 1 3	1 9 0 4 0 9 5 5 1 1 2 2 4 7 3 5 1 2 2 2 2 2 4 0	0 3 0 1 0 1 5 0 1 1 1 1 0 7 0 2 0 2 1 1 0 1 0 0	3 4 0 1 0 1 0 2 0 0 5 0 2 2 0 2 0 0 0 2 1 1 0 0	5 21 1 9 2 20 15 14 3 3 15 4 9 21 5 11 3 5 3 7 5 4 5 3
Total	66	73	28	26	193

 

Figure 1:  The age distribution of dogs in reported bites to the City of San Francisco for 2003/2004.  Age was identified in 257 of the reports.

 

Figure 2:  Severity of reported dog bite and the gender/reproductive status of the dog for 287 cases in the City of San Francisco for 2003/2004. 

 

Figure 3:  Age category and gender of 260 of the reported dog bite victims in the City of San Francisco for 2003/2004.

 

Figure 4:  Age and severity in 262 of the reported dog bites in the City of San Francisco for 2003/2004.

 

Figure 5:  Age group of the victim with respect to all dogs and the top 4 breeds implicated in 294 of the reported dog bites to the City of San Francisco for 2003/2004.

 

Figure 6:  The percentage of the population in the City of San Francisco by zipcode and the percentage of the reported dogs bites for 2003/2004.  There were 245 reported bites where zip code is known.  The population is based on US Census data for 2000. 

 

Figure 7:  The number of bites for the top 4 breeds in 193 reported to the City of San Francisco by zip code for 2003/2004.