Journal of the New Zealand Medical Association, 10-August-2007, Vol 120 No 1259
Fatal dog bites in New Zealand
Dog attacks represent a significant health hazard in New Zealand. Dog bites, although common, rarely result in death however. While there has been an increase in the reporting of bites in the last 10 years,1,2 it is difficult to determine if this is real, or just an artefact of changed coding and reporting mechanisms.
New Zealanders like those in many other developed countries have a high frequency of animal ownership. It is difficult to get exact details on dog ownership, however it is estimated that there are over 600,000 dogs in New Zealand; 27% of dog owners have two or more dogs.3
Details for dog attacks in New Zealand have improved significantly with computerisation of hospital records. Prior to 1960, records are somewhat unreliable. There have been two major studies in New Zealand examining the incidence of dog bites. Unfortunately a lack of consistency with the labelling and coding of dog-related injuries meant that the records are only superficially comparable.
Langley (1992) gathered data from the Health Statistics Services injury mortality data files during the period 1979 to 1988.4 Codes including the word 'dog' and 'bite' were used. These recorded all bites, but sometimes did not distinguish dog bites per se. Other injuries from dogs such as being 'struck' were included. Langley reported an incidence rate of 4.8 hospitalisations per 100,000 in 1988 and noted that the increased incidence rate if the trend remained would reach 9.6 per 100,000 by 2000.
Marsh et al (2004) sought to update the earlier work by using a similar method to examine bites during the period 1989 to 2001.1 They similarly identified suitable cases through an examination of Electronic Mortality and Morbidity Files in the New Zealand Health Information Services (NZHIS) Database. They also catalogued an increasing incidence rate.
Between 1989 and 2001 there were 3119 hospitalisations and 1 fatality; 3025 hospitalisations were estimated to have resulted from dog bites—94 of these were estimated to have been from being 'struck' by a dog.
New Zealand Health Information Statistics recorded 309 overnight hospital visits after dog bite incidents in 2000, 293 in 2001, and 324 in 2002. Incidence rate figures peaked in 1996 at 7.5 per 100,000. Given a population of 3.9 million in 2002, the incidence rate for dog bite incidents was 8.3 per 100,000.
These figures appear to represent an escalating trend in admission statistics similar to that observed in other countries.2
In New Zealand, children aged 4 years and under accounted for nearly 24% of the cases of hospitalisation for dog bite injuries.1 High rates among children can probably be explained by their lack of physical strength or motor skills to ward off an attacking dog.
Immaturity and lack of judgment may also sometimes lead children to act in ways that animals perceive as threatening or aggressive. Specifically, they maintain eye contact, and their eye level is often the same as that of a dog. Furthermore, it has been suggested that (prior to their injury) children under 5 years of age are significantly more likely to provoke animals than older children.
When the 0–4 and 5–9 year age groups were combined, children under the age of 10 years received 39% of dog bite injuries. Those aged between 25 and 39 received 18% (n=423) of dog bite injuries.16
When the incidence rates were broken down by ethnicity, it was found that New Zealand Europeans represented 52% of the total bite victims, Māori 28%, and others 20%.1 For the period 1979 to 1988 the Māori inpatient rate was 1.8 times the non-Māori rate. Furthermore, from 1988 to 2002 the Māori outpatient rate was 2.6 times that of non-Māori.
The age-adjusted incidence rates for Māori and non-Māori were 10.6 per 100,000 population (9.4–11.7) and 5.9 (5.6–6.3) respectively. Māori were therefore over-represented within the bite statistics. These rates may be a real change or be an artefact of differences in ethnicity classification.
Thirty percent of victims were bitten at home with 6% occurring on the street and 1% on a farm; 60.5% of bites were to males.
Upper limb, head, and lower limb were the most common regions to be injured—the most common site of injury is the face. There is strong evidence of a difference in the distribution of injury location by age group (Figure 1). Injuries to the head were significantly more common for the younger age groups.8
Injuries to the upper limb most commonly occurred in those aged over 15 years—these represent defensive wounds. Lower limb injuries were more consistently spread through the age groups. Males, and children less than 9 years of age (Figure 2), had the highest rates of injury.
Figure 1. Site of dog bites by age group (Reproduced from Marsh et al 2004 with permission)
In cases where a location was noted (42% of cases), 30% of the victims were bitten while at a home (not necessarily their own). For 6% of the victims, the bite occurred on the street or highway, and 1% of bites occurred on a farm. Chained dogs were 2.8 times more likely to bite than un-chained dogs.1
Although often sited as a factor in attacks, breed-specific factors need to be treated with some caution. Not all dogs are purebred and identification in crossbreed cases can be problematic. In addition, the frequency of breed distribution is not even—more bites might be attributed to German shepherds than Alaskan malamutes, but the population of German shepherds is much higher, thus frequency representation is important to note.
Humane Society US statistics5 reflect that dogs that have not been spayed or neutered are up to three times more likely to be involved in a biting incident than neutered or spayed dogs. Male dogs are involved in 80% of all bites.
In those cases where breed-specific information was available, some breeds appear to be disproportionately represented.6
In the United States, three-quarters of all hospital-treated dog attacks were caused by just 5 of the 160 or so known dog breeds:9
Breed-specific factors contributed to the definitions in the Dog Control Amendment Act (2003, 2004, 2006) in New Zealand. Among other controls, the Act required all newly registered and dangerous dogs to be microchipped by July 2006, and banned the import of the American pit bull terrier, Brazilian fila, Japanese tosa, and dogo argentino.
Targeting specific breeds has not met with success in other countries—e.g. the UK control of pit bull terriers in 1991. Instead, a more effective approach may be to target chronically irresponsible dog owners.7
The comparison of international incidence rates is problematic for hospitalisations due to differing definitions. However New Zealand appears to compare favourably with other countries. Our incidence rate of around 8.3 per 100,000 population was similar to that observed in Australia of 7.7 for 1995 to 1996.2
For the period 1992 to 1994, the United States recorded a dog bite-related injury visit to hospital of 12.9 per 10,000 (over 10 times the New Zealand rate).8 During the period (1979–1988) the United States recorded 157 fatalities from dog bites; the average number of deaths per year was 17.9
There were almost 4.7 million victims annually—about 1.8% of the entire population, but only 0.3% sought medical attention.13 It has been estimated that, in the United States, dog bites cause 585,000 injuries necessitating medical attention yearly.10
Children aged 12 years and under made up approximately 51% of victims. Children aged 5–9 years were bitten most often, with 78% of the bites located on the extremities.11 United States statistics suggest that almost half of all children will be bitten;12 and most of these bites will remain unreported.
The United States has 73 million licensed dogs and 39% of United States households own at least one dog; 25% of owners own two dogs. More than 70% of owned dogs are spayed or neutered.5
The data indicate that rottweilers and pit bull-type dogs accounted for 67% of human dog bite-related fatalities in the United States between 1997 and 1998. It is unlikely that they accounted for anywhere near 60% of dogs in the United States during that same period and, thus, there appears to be a breed-specific problem with fatalities in that country.6
Apart from the obvious psychological cost to individuals and families from dog bites, society also bears a social cost in lost productivity and use of hospital resources. The impact of these together is difficult to estimate. However, hospital records and Accident Compensation Commission (ACC) records can quantify some of these aspects.
In a 2003 report, New Zealand’s 58 Councils reported a total of 3020 dog attacks on people in 2001/2. Extrapolating this figure gives a nationwide estimate of 3435 dog attacks in 2001/2; this is still well below ACC estimates.14
Males made up 60.5% of the hospitalisations from dog bites. In 2002/3, there were 257 new entitlement claims lodged with ACC and 55 ongoing claims, which amounted to NZ$1,041,099, and 7790 medical fee claims totalling $687,188—a substantial increase over the figures from 1999 (Figure 2).
Victims with injuries to the lower limb were more likely to stay in hospital the longest, with a mean number of 5.6 days.
Figure 2. ACC entitlement claims (in New Zealand dollars). In other words, these are moderate to serious claims that could have resulted in a week or more off work or required more support from ACC than medical treatment such as a visit or two to the doctor14
To date, New Zealand appears to have suffered five dog bite-related fatalities. Although records are not complete, it appears that there are no recordings of traumatic fatalities prior to 1969.
In 1969, a farmer was killed by a mixed-breed farm dog. There are few details available about this incident.
In April 1997, a 59-year-old Te Puke man was killed by two bull-terrier cross dogs. A veterinary postmortem of the killer dogs confirmed the breed and it found they were approximately 2 to 3 years old. The dogs had been trained to hunt pigs, but they turned on their owner when he tried to stop them from fighting.
In February 2003, a 73-year-old Northland woman died after being bitten on the foot by one of her three pure-breed Alaskan malamutes. It appears that the bite had hit an artery and she had exsanguinated without moving from her chair.
The fourth case, from 2004, is the subject of the second part of this article.
A fifth case occurred in April 2007 when a 56-year-old Murupara woman was attacked and killed by two dogs: a pit bull terrier and a Staffordshire cross. She suffered multiple bites and lacerations to both lower legs in the attack. When found, she had lost a considerable amount of blood. She died in the ambulance on the way to the hospital. The cause of death was shock and trauma. The attack took place early in the morning on a suburban street.
In 2004, a 39-year-old Dunedin woman was savaged to death by her pet bull mastiff dog: an un-neutered fully grown male, weighing 55 kg. The victim was a slightly built (46 kg). Her injuries included extensive bites to both right and left arms, originating above the elbow. The majority of these were canine puncture wounds, but on her left arm there was one incised and torn crescent shaped wound around 7 cm long.
The majority of the serious wounds were found on the victim’s face, neck, and skull. A large 8 mm-wide gash ran across bridge of her nose extending from 1 cm below the right inner canthus and terminating above her left infraorbital foramen. She had a 55 mm gash inferior to a 20 mm gash on her right neck. Her left ear and soft tissue covering the back of the skull were missing and had possibly been ingested by the dog.
A 25 mm tear ran medially over the right temporalis above the eyebrow, and a 35 mm gaping tear midway between the brow and the hairline extended from above the outer canthus of the eye to the midline. Her lower face was untouched.
The most serious wounds were to the back and left side of the neck. The back of the neck exhibited a large gaping wound 70 cm long just below the hairline, whilst the left side of the neck had a 55 mm-long tear running medially at the level of the thyroid cartilage. Superior to this were two ragged edged tears of 30 mm with a isthmus of tissue separating them. Each of these tears terminated over the region of the hyoid.
The cause of death was most likely exsanguination and asphyxia. A canine puncture wound was found in the trachea on her left side, coincident with the most caudal of the three incisions found in that region. Bleeding into the trachea had occurred. Numerous canine drag marks were visible over the skull, upper face, and arms.
Figure 3. The victim’s neck injuries showing the tear at the level of the hyoid cartilage and the tear over the hyoid (with tissue isthmus)
There were what appeared to be healed bite marks and bruises on her lower legs; there appeared to be no fresh bite marks in these areas. An examination of the dog’s bite radius and the healed marks showed a positive match.
The victim lived alone. An animal control team had been called to the property several times in the past, twice for barking, once for straying, and once for the dog’s aggressive behaviour towards the victim, however she had withdrawn consent for it to be taken to the pound. The dog was destroyed by police to allow access to the scene.
The victim's health status may have produced mitigating circumstances possibly provoking the dog to attack. She was suffering from Huntington disease (HD), also known as Huntington chorea (HC). This inherited (autosomal dominant with complete penetrance) disease is characterised by choreiform involuntary movements and slowly progressive dementia.
Between one-half and three-quarters of patients affected by HD present with primary complaints of rigidity or involuntary movements. In the rest of the cases, the presentation can be one of early mental status changes that appear as increased irritability, moodiness, or antisocial behaviour.
Patients can become argumentative, erratic, emotionally volatile, even physically aggressive. The classic choreiform movements begin as a piano-playing motion of the fingers or as facial grimaces. As the disorder advances, a characteristic dancing gait evolves. The disease is slowly but inexorably progressive.16
Figure 4. The victim’s left arm showing healing and fresh bite marks
It has been suggested that the victim may have mistreated the dog as she was known to have exhibited some of the mental characteristics typical of HD. Indeed, lack of coordinated movements, erratic behaviour, or even aggression toward the dog may have seen changes in their relationship.
Coupled with a large, powerful un-neutered male dog in a small enclosed area, this factor may have tipped the balance. This history together with the presence of healed bites suggests that the victim suffered a recent spate of aggressive incidents with the dog and it may have been attempting to assert its dominance over her.
It has been acknowledged that dogs showing dominant aggression can respond to anxiety as well as to a perceived challenge to their rank.17,18 Although entirely speculative, the victim’s health may have contributed to, or even precipitated, the attack in this case.
Clearly the incidence of both fatal and nonfatal dog bite attacks has increased in New Zealand over the past 10 years. This trend is in-line with overseas findings, however, we still have a long way to go before experiencing the almost epidemic levels seen in the United States in recent years.
Many dog bites, both nationally and internationally, show common features so awareness of these may help individuals to avoid situations where they or their family members could be at risk of injury.
Conflict of interest: None.
Ethics statement: In 2004, this tragic case generated a large amount of press coverage. The woman’s cause of death as well as her medical state were recorded in the coroner’s report that is now available as a public record.
At the time of the incident, discussions were held with the family and Coroner, and out of consideration for the family this article was held back for 2 years (3 years have now passed).
My role in this case (as with other dog attacks) was as a forensic odontologist called by the police to make a positive identification of the individual and/or animal.
Author information: David Healey, Senior Lecturer, Department of Oral Sciences, School of Dentistry, University of Otago, Dunedin
Acknowledgements: I thank Professor Jules Kieser for forensic assistance, Professor Han-Seung Yoon for forensic access, and Dunedin Coroner Dr Jim Conradson for advice.
Correspondence: David Healey, Dept of Oral Sciences, School of Dentistry, University of Otago, PO Box 647, Dunedin. email: email@example.com
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