Abstract
BackgroundEnumerating dog populations is essential to plan and evaluate rabies vaccination campaigns. To estimate vaccination coverage and dog population size in a Haitian commune, 15 sight-resight counts were conducted over two days following a government-sponsored vaccination campaign. MethodsDogs received temporary laminated collars and livestock wax marks on the head and sides at the time of rabies vaccination. After the vaccination campaign, pairs of surveyors walked pre-defined routes through targeted neighborhoods, photographing and recording characteristics and location of each dog seen on a standardized data sheet. On the second survey day, surveyors retraced the prior day’s track, followed the same procedure, and indicated in addition whether they believed the dogs were resighted from the prior day. After completion of the field survey, two independent evaluators reviewed photographs and characteristics of each dog to assess which had vaccination marks and which were resighted. Surveyor and photo-reviewer sight-resight decisions were compared using Cohen’s kappa, and population estimates were compared using Lincoln-Petersen 95% confidence intervals. ResultsField-surveyors identified dogs consistent with the photograph evaluations in 629 out of 800 instances (78.6%, Cohen’s kappa of 0.12). Despite this inconsistency, the population estimates resulting from the field and final determinations were not significantly different at 1,789 (95% CI 1,677 to 1,901) and 1,978 (95% CI 1,839 to 2,118). Vaccination coverage was also the same at 55% and 56%; however, an observed vaccination mark loss of 13.8% suggests that the true coverage may have been closer to 64%. ConclusionUsing photos improved dog identification during the sight-resight study, leading to a higher population estimate. Despite using a 2-mark system to temporarily identify vaccinated dogs, a significant proportion had lost all identifying marks by the second day of field surveys. Efforts to estimate vaccination coverage using sight-resight surveys should consider improvement of marking techniques or better accounting for potential loss of marks in their free-roaming dog vaccination coverage assessments.
Highlights
Rabies and other zoonotic conditions often afflict free-roaming dog populations
There were 1,523 dog sightings recorded by field surveyors across the 15 survey locations, and photos were available for 93.4% of these
Methods for estimating post-vaccination coverage in dog populations that are largely free-roaming are fraught with error [9]
Summary
Rabies and other zoonotic conditions often afflict free-roaming dog populations. An estimated 59,000 people die from rabies every⇑ Corresponding author.year, and the vast majority of those cases come from the bite of an infected dog [1]. Enumerating dog populations is essential to plan and evaluate rabies vaccination campaigns. After completion of the field survey, two independent evaluators reviewed photographs and characteristics of each dog to assess which had vaccination marks and which were resighted. Results: Field-surveyors identified dogs consistent with the photograph evaluations in 629 out of 800 instances (78.6%, Cohen’s kappa of 0.12). Despite this inconsistency, the population estimates resulting from the field and final determinations were not significantly different at 1,789 (95% CI 1,677 to 1,901) and 1,978 (95% CI 1,839 to 2,118). Efforts to estimate vaccination coverage using sight-resight surveys should consider improvement of marking techniques or better accounting for potential loss of marks in their free-roaming dog vaccination coverage assessments
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