Effectiveness of breed-specific legislation in decreasing the incidence of dog-bite injury hospitalisations in people in the Canadian province of Manitoba

Background: The city of Winnipeg was the first among several jurisdictions in Manitoba, Canada, to introduce breed specific legislation (BSL) by banning pit-bull type dogs in 1990. The objective of the present work was to study the effectiveness of BSL in Manitoba.

Methods: Temporal differences in incidence of dog-bite injury hospitalisations (DBIH) within and across Manitoba jurisdictions with and without BSL were compared. Incidence was calculated as the number of unique cases of DBIH divided by the total person-years at risk and expressed as the number per 100000 person-years. Year of implementation determined the pre-BSL and post-BSL period for jurisdictions with BSL; for jurisdictions without BSL to date, the entire study period (1984-2006) was considered as the preimplementation period. The annual number of DBIH, adjusted for total population at risk, was modelled in a negative binomial regression analysis with repeated measures. Year, jurisdiction and BSL implementation were independent variables. An interaction term between jurisdiction and BSL was introduced.

Results: A total of 16 urban and rural jurisdictions with pit-bull bans were identified. At the provincial level, there was a significant reduction in DBIH rates from the pre-BSL to post-BSL period (3.47 (95% CI 3.17 to 3.77) per 100000 person-years to 2.84 (95% CI 2.53 to 3.15); p=0.005). In regression restricted to two urban jurisdictions, DBIH rate in Winnipeg relative to Brandon (a city without BSL) was significantly (p<0.001) lower after BSL (rate ratio (RR)=1.10 in people of all ages and 0.92 in those aged <20 years) than before (RR=1.29 and 1.28, respectively).

Conclusions: BSL may have resulted in a reduction of DBIH in Winnipeg, and appeared more effective in protecting those aged <20 years.