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| Journal of the New Zealand Medical Association,
10-August-2007, Vol 120 No 1259
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Fatal dog bites in New Zealand
David Healey
Dog bites in New ZealandDog 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
Who gets bittenIn 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.
Site of the biteUpper 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
Breed-specific factorsAlthough 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
International comparisonsThe 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
The social costApart 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
 Dog bite-related fatalities in New ZealandTo 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.
A dog bite victimIn 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
 DiscussionIt 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:
david.healey@dent.otago.ac.nz
References:
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