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

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

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. 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 behaviors and hence fewer dog bites. Implementation of the program is to be based on reported dog bites to the municipality 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. There were 497 dog bites reported to the city for the 2 year period. After evaluating and coding the data for consistency, 435 reports were analyzed. Removed from the data base were duplicates, out of city incidents, dog and other animal reports that included other dogs, cats, horses, and a pig. The final database comprised 249 bites for 2003 and 186 in 2004.

Breeds of dogs:

There were 74 primary breeds identified in the 435 reports. The dogs were labeled as mixes in 73% of the reports, ranging from 59-92%. There were 4 primary breeds that comprised nearly one-half of the bites; these were “pitbulls”, German Shepherd dogs, Labradors, and Rottweilers. Seventy-six (76%) percent 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). Ninety-two percent (92%) of the Labradors were identified as mixed and accounted for 9.0% (n=39) of the bites. Rottweilers were identified as mixes in 59% of the reports and comprised 6.0% (n=27).

Gender and reproductive status of the dogs:

Of the reports, 337 recorded the gender and reproductive status of the dog. Overall, male dogs (intact and neutered) were responsible for 72.1% (n=243) of the reported bites. Of the 243 male dogs, 52.6% (n=128) were intact. Based on this information, a person is equally likely to be bitten by a neutered male as an in tact male dog. Table 1 shows the gender and reproductive status of all the dogs implicated in the bites and the top 4 breeds reported. Intact “pitbulls” comprised 69.4% (n=34) of the 49 males identified. For the other breeds where males dogs are listed, German Shepherd intact males comprised 60.0% (n=18) of 30; intact male Labradors, 44.0% (n=11) of 25; and intact male Rottweilers, 71.4% (n=10) of 14.

Severity of bites:

The severity of the bites was recorded in 372 cases (Table 2 and Figure 1). The majority of the bites, 85.7% (n=319) were minor. There were 40 moderate bites (10.8%) and 13 severe bites (3.5%). The gender of the dog and its reproductive status wasreported in 287 of the reported cases for severity. For minor bites, the overall relative risk of a bite from an intact male dog to a female dog is non-significant; that is a person is equally likely to be bitten by an intact male as an intact female. For the top 4 breeds for minor bites, the intact male dogs were highly represented. For “pitbulls”, the risk of a bite from an intact male was about 1.4 times that from an intact female. The risk from an intact male German Shepherd was about 1.8 times that from an intact female.

However, for moderate/severe bites, the risk from an intact male dog decreases. The relative risk from an intact male is less than that from an intact female. Essentially, a person is equally likely to be bitten by a neutered dog as an intact one for moderate to severe bites.

The question arises as to why minor bites are more highly represented with intact male dogs. It is possible that a larger number of the minor bites are self-reported, and a person is more likely to report a bite from a large dog, particularly an intact male dog because they are perceived as being more dangerous, even if the bite is minor and requires little to no treatment. Further work is necessary to test this hypothesis.

Zipcode:

The dog’s gender and reproductive status is reported in 193 cases. Intact males comprised 34.3% (n=66), neutered males 37.8% (n=73). Of particular note, the zip code with the largest percentage of licensed “pitbulls” (94124) had one of the lowest number of reported bites, 5 from “pitbulls, and 4 from Labradors.

Victim: Gender and Age:

Of the 374 reports where the victim’s gender is known, males comprised 56.7% (n=212). Females exceeded males victims in the 20-29 age group. Age and gender were reported in 260 cases. Adults 20-59 years comprised 72.3% (n=188) of the reported bites. The age group 30-39 alone accounted for the largest number of bites, 26% (n=68) of the 260 cases. Children 1-9 years represented 10% (n=26) of the bites. Children less than 1 year were not included because it was not clear from the reports. A “0” was used according to animal control to represent a child less than 1 year. However, from the reports this also included unknown age, duplicates, reports involving 2 dogs and the same victim.

Severity of bite by age group was known for 262 reports, with 84.4% (n=221) being minor, requiring little to no treatment. Of the 41 moderate/severe bites, 58.5% (n=24) were in the 20-59 age group. Children age 1-9 had 12.1% (n=5) of the 41 moderate/severe bites. Older children and teenagers aged 10-19 were the victims in 22.0% (n=9) of the moderate/severe bites.

Conclusions:

Based on dog bites reported to the City of San Francisco for 2003 and 2004 a mandatory spay/neuter for any breed is not going to significantly reduce the incidence of bites. Moderate/severe bites show an equal risk between intact and neutered dogs. Minor bites may have a higher number of reported intact dogs if these are self-reporting and the perception by individuals that certain breeds and intact dogs are more dangerous.

For a city the size of San Francisco, the numbers of reported bites are very low. With an estimated dog population of 120,000, only about 0.2% of the dogs are being reported. If the city is targeting specific breeds, like the “pitbulls”, this represents about 50 bites per year, or 0.04% of the dog population.

Information from the reported dog bites needs to be standardized and consistent. There are several problems with the current situation, there is no uniformity of reporting the severity of a bite, location of the bite (either anatomical or by zip code), and especially problematic is the identification of the large number of mixes in the population. In addition, a number of reports were dog/dog or dog/cat aggression incidents. These should be clearly indicated in the reports and should not be included in analysis of dog bites to humans. Dog/dog and dog/cat aggression is not uncommon, but the problem arises that the reporting may be strongly biased towards particular breeds of dogs. A program directed to all dog owners as well as to the general public that would educate on dog behavior and how to reduce dog bites would be an effective method.

---------

Table 1: 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 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

 

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.