Animal and human bite injuries in Victoria, 1998–2004

Mammal bite injuries include puncture wounds, lacerations, avulsions and crush injuries,1 and may result in infection,1,2,3,4 disease transmission,2,3,5,6 disfigurement,7 serious injury or death.1,7 The nature and severity of bite injuries vary with the type of animal involved7,8,9,10 as well as with the characteristics of the victim, such as age and height.7,8,10,11 The different types of wounds8,12 and likelihood and nature of any infection3,8 resulting from the various mammal species have a significant effect on patient management. Additionally, the injuries caused by dog and cat bites can result in considerable expense because of the need for long-term intravenous antibiotics, surgery and other medical treatments.1 Finally, such injuries represent a preventable public health burden that may be reduced by public education about responsible pet ownership, and regulations regarding animal control.13

Our study explored the epidemiology of mammal (human and non-human) bite injuries in Victoria, examining the frequency, nature and outcomes of bites, including those from native Australian mammals. The findings will help to inform future research and ongoing injury prevention initiatives.

We studied a retrospective case series of patients who sustained mammal bite injuries in Victoria between 1998 and 2004, inclusive. Victoria has a population of about 5 million people with a median age of 36.8 years.14 Its geography and land use vary widely and it supports a diversity of domestic, introduced and native mammal species.

During the study period, 1 544 094 patients received treatment at the participating EDs, with 12 982 (0.8%) presenting with mammal bite injuries. Dogs, humans and cats inflicted almost all the bites (95.6%) (Box 1). A wide range of other mammals were involved including native, domestic, pet and exotic species. Native Australian animals caused 128 injuries (1.0%).

The median age (interquartile range) of the patients was 27 (11–42) years. Younger patients predominated, with the toddler age group (1–4 years) comprising 1528 patients (11.8%). As shown in Box 2, bites from dogs and “other” mammals (all other mammals except dogs, cats and humans) were most common among children, but there was a downwards trend in these bites among those over 30 years of age. In contrast, human and cat bites peaked in people in early and mid adulthood.

Males accounted for 7236 patients (55.7%), and more males than females were bitten by dogs (56.3%) and humans (73.7%) (Box 3). On the other hand, more females were bitten by cats (64.1%) and “other” mammals (55.6%).

Overall, hand and wrist injuries were the most common (Box 4). Dog bite injuries most commonly involved the hands/wrists, face/head or legs. Human bite injuries were most common on the hands/wrists, arms or face/head. In contrast, cat and “other” mammal bite injuries were relatively uncommon on the face and head.

Overall, 7198 patients (55.4%) were at home when bitten. A further 1381 (10.7%) were on public roads and 749 (5.8%) were at places of sport/recreation. Most human bites (44.5%) occurred on public roads and in places of sport/recreation and trades/services. Bite injuries were most common on Saturdays and Sundays (42.2% of bites) and during the warmer months (November–March).

Overall, 1504 patients (11.6%) were admitted to a hospital or observation unit. These included 12.0%, 10.1%, 10.4% and 8.6% of patients sustaining dog, human, cat, and “other” mammal bites, respectively. Two patients died after sustaining dog bites. The NCIS recorded an additional death also resulting from a dog bite injury. All three victims were male and included a toddler, a middle aged man and an elderly man.

The proportion of mammal bite injuries among ED presentations (0.8%) is consistent with the findings of other reports.2,7,8 However, differing inclusion criteria and indigenous mammal species make comparisons with other reports difficult.9,10,13,14,16,17,18,19,20 In our study, dogs were responsible for almost 80% of all injuries. Similar proportions have been reported elsewhere, although these vary between 50% and 90%.2,3,8,9,10,21 We found human bite injuries were more common than those from cats, consistent with findings in some reports,2,21,22 but not in others.6,8

Clear patterns exist between patient age and each important mammal species. The large numbers of young children with dog bite injuries have been well documented.3,12,13,16,17,23 Children are particularly vulnerable to dog attacks, due to their size and the proximity of their face to the dog’s mouth, and attacks are frequently associated with interaction with the dog (possibly provocative) before the attack.11,17 Very young children were also often bitten by mammals other than dogs, cats and humans. Horses and rats were commonly implicated in bite injuries in children aged under 10 years. However, the “other” mammals group was heterogeneous and should be examined further before firm conclusions are drawn. Finally, large numbers of human bite injuries among young adults have also been reported elsewhere4 and may be associated with the social interactions of this age group.

Others have also reported that males are more often victims of dog bites2,9,11,13,18 and females of cat bites.2,3,9

The admissions and deaths reported in our study indicate the severity of many bite injuries. The varying patterns of injury site for each mammal group are consistent with other reports.6,8,9,11 The common upper-limb injuries may have resulted from direct handling, or from attempts to separate fighting animals or aid injured ones.1

The home was clearly the most common location for bites to occur, and this is consistent with other reports.1 However, additional data, especially “time of exposure”, are required to further explore location patterns.

Our study has important limitations. The data are likely to underestimate injury incidence,2,8 as they do not account for bites not requiring medical attention, and those treated by general practitioners and other doctors, and at private or non-VEMD EDs. Furthermore, there may be an inherent selection bias in that bites from some animals (eg, dogs) may be more severe and more likely to require ED management. The VEMD is a relatively reliable and valid dataset,24 although there are identification and coding errors as well as missing data.

Mammal bite injuries represent a considerable public health burden, and ongoing prevention strategies are indicated. These should include public educational programs,25 the separation of young children from dogs, avoidance of high-risk dogs by parents, neutering and regulatory reinforcement (ie, restriction of ownership and breeding of high-risk dog breeds), and appropriate restraint of animals in public places.17 Research into bite injury rates (injuries per person-hour of contact) would better clarify the risk of injury for each species and is recommended.