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Background: Mass vaccinations of domestic dogs have been shown to effectively control canine rabies and hence
human exposure to rabies. Knowledge of dog population demography is essential for planning effective rabies
vaccination programmes; however, such information is still rare for African domestic dog populations, particularly so
in urban areas. This study describes the demographic structure and population dynamics of a domestic dog
population in an urban Sub-Saharan African setting. In July to November 2005, we conducted a full household-level
census and a cross-sectional dog demography survey in four urban wards of Iringa Municipality, Tanzania. The
achievable vaccination coverage was assessed by a two-stage vaccination campaign, and the proportion of feral
dogs was estimated by a mark-recapture transect study.
Results: The estimated size of the domestic dog population in Iringa was six times larger than official town records
assumed, however, the proportion of feral dogs was estimated to account for less than 1% of the whole
population. An average of 13% of all households owned dogs which equalled a dog:human ratio of 1:14, or 0.31
dogs per household or 334 dogs km-2. Dog female:male ratio was 1:1.4. The average age of the population was 2.2
years, 52% of all individuals were less than one year old. But mortality within the first year was high (72%). Females
became fertile at the age of 10 months and reportedly remained fertile up to the age of 11 years. The average
number of litters whelped per fertile female per year was 0.6 with an average of 5.5 pups born per litter. The
population growth was estimated at 10% y-1.
Conclusions: Such high birth and death rates result in a rapid replacement of anti-rabies immunised individuals
with susceptible ones. This loss in herd immunity needs to be taken into account in the design of rabies control
programmes. The very small proportion of truly feral dogs in the population implies that vaccination campaigns
aimed at the owned dog population are sufficient to control rabies in urban Iringa, and the same may be valid in
other, comparable urban settings. |
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