The human–canine environment: A risk factor for non-play bites?

Abstract

Few dog bite risk factor studies have been conducted. This veterinary clinic-based retrospective cohort study was aimed at identifying human–canine environmental risk factors for non-play bites in Kingston, Jamaica (660) and San Francisco (SF), USA (452). Data were analysed using modified Poisson regression with confounders selected using directed acyclic graphs (DAGs) and the change-in-estimate procedure.

Dogs acquired for companionship were more likely (RR = 1.66; 95% CI 1.02–2.70) to bite than those acquired for protection. Routinely allowing a dog into the presence of visitors was also positively associated with it biting. A dog sleeping in a family member’s bedroom was a risk factor for biting in Kingston (RR = 2.54; 95% CI 1.43–4.54) but not in SF, while being able to leave the yard unaccompanied was a risk factor for biting in SF (RR = 3.40; 95% CI 1.98–5.85) but not in Kingston. Overall, dogs which were less restricted in their interactions with humans were at elevated risk for biting. An observed association with dog bites in one cultural setting might not exist in another.

Introduction

Dog bites to humans are a worldwide problem (Chomel and Trotignon, 1992, Bhanganada et al., 1993, Thompson, 1997, Kumar, 1999, Chen et al., 2000, Ozanne-Smith et al., 2001, Frangakis and Petridou, 2003, Horisberger et al., 2004, Van Eeckhout and Wylock, 2005, Morgan and Palmer, 2007). In the United States there are 300–1000 bites per 100,000 persons per year (Beaver, 1997, Cornwell, 1997), and reports from Switzerland and Belgium have indicated national bite rates of 180 (Horisberger et al., 2004) and 900 (Gisle et al., 2002) per 100,000 per year, respectively. These figures are striking given that some studies suggest that far less than 50% of dog bites are reported (Beck and Jones, 1985, Chomel and Trotignon, 1992, Kahn et al., 2003, De Keuster et al., 2006).

Research has largely focused on (1) the circumstances of incidents (Beck et al., 1975, Beck and Jones, 1985, Szpakowski et al., 1989, Mathews and Lattal, 1994, Thompson, 1997, Guy et al., 2001a, Frangakis and Petridou, 2003, Horisberger et al., 2004), (2) the characteristics of both biting dogs (Beck and Jones, 1985, Szpakowski et al., 1989, Gershman et al., 1994, Mathews and Lattal, 1994, Cornwell, 1997, Thompson, 1997, Guy et al., 2001b, Horisberger et al., 2004) and persons bitten (Beck and Jones, 1985, Bhanganada et al., 1993, Mathews and Lattal, 1994, Cornwell, 1997, Thompson, 1997, Savino et al., 2002, Horisberger et al., 2004), (3) the estimation of public health costs (Bhanganada et al., 1993, Weiss et al., 1998), (4) the pathological sequelae to attacks (Fishbein and Robinson, 1993, Mendez Gallart et al., 2002, Peters et al., 2004, Van Eeckhout and Wylock, 2005), and (5) wound care for the victims (Van Eeckhout and Wylock, 2005, Morgan and Palmer, 2007).

Unfortunately, few investigators have employed a formal reference series in their studies (Gershman et al., 1994, Chen et al., 2000, Guy et al., 2001c, Drobatz and Smith, 2003, Reisner et al., 2005), and thus research to date has been of limited value in accurately identifying risk factors. In addition, because hospital based data formed the basis for inferences for all except a few studies, it is questionable whether these results are applicable to the general dog population. An analysis of a case series of 227 biting dogs obtained from a veterinary clientele has reported that 73%, 17.9% and 21.5% animals had bitten an adult (>18 years), a teenager (13–18 years), and children (⩽12 years), respectively, at least once (Guy et al., 2001a). This stands in contrast to hospital data which suggest that children are over represented among dog bite victims (Ozanne-Smith et al., 2001). A consequence of the limited scope of dog bite research is the paucity of epidemiological evidence supporting the belief that a dog’s tendency to bite depends on an interaction of genetics (including sex), early experiences, later socialization and training, reproductive status, quality of ownership, supervision, and the potential victim’s behaviour (American Veterinary Medical Association, 2001).

We conducted a retrospective cohort study in San Francisco (SF), USA, and Kingston, Jamaica (JA) to identify human–canine environmental risk factors for non-play bites to humans. Work by a few authors has suggested that both human–canine attitudes and interactions in the Caribbean differ considerably from those in the continental United States with some studies from Caribbean territories reporting that 56–70% of dogs are kept entirely outdoors (Fielding and Mather, 2001, Davis et al., 2007, Ortega-Pacheco et al., 2007). In the US, this figure is 15–20% (American Pet Products Manufacturers Association, 2005–2006). In selecting divergent cultures with respect to attitudes to human–canine relationships, we hoped to identify, if present, heterogeneity by country.