Density estimates of rural dog populations and an assessment of marking methods during a rabies vaccination campaign in the Philippines.

We estimated the population density of dogs by distance sampling and assessed the potential utility of two marking methods for capture-mark-recapture applications following a mass canine rabies-vaccination campaign in Sorsogon Province, the Republic of the Philippines. Thirty villages selected to assess vaccine coverage and for dog surveys were visited 1 to 11 days after the vaccinating team. Measurements of the distance of dogs or groups of dogs from transect lines were obtained in 1088 instances (N = 1278 dogs; mean group size = 1.2). Various functions modelling the probability of detection were fitted to a truncated distribution of distances of dogs from transect lines. A hazard rate model provided the best fit and an overall estimate of dog-population density of 468/km2 (95% confidence interval, 359 to 611). At vaccination, most dogs were marked with either a paint stick or a black plastic collar. Overall, 34.8% of 2167 and 28.5% of 2115 dogs could be accurately identified as wearing a collar or showing a paint mark; 49.1% of the dogs had either mark. Increasing time interval between vaccination-team visit and dog survey and increasing distance from transect line were inversely associated with the probability of observing a paint mark. Probability of observing a collar was positively associated with increasing estimated density of the dog population in a given village and with animals not associated with a house. The data indicate that distance sampling is a relatively simple and adaptable method for estimating dog-population density and is not prone to problems associated with meeting some model assumptions inherent to mark-recapture estimators.

Evaluation of a canine rabies vaccination campaign and characterization of owned-dog populations in the Philippines.

A mass canine rabies vaccination campaign in Sorsogon Province, the Republic of the Philippines, was conducted in April and May 1993. From 1 to 14 days following visits by vaccination teams to 30 selected villages (barangays), survey teams revisited the barangays to assess vaccine coverage. Modified cluster survey methods were used to gather information about vaccine coverage in the owned-dog population (210 households) and about characteristics of owned-dogs and factors influencing owner willingness to participate in the campaign. Vaccinated dogs were identified by asking owners about receipt of certificates given by the vaccinating teams and examining each animal for a special collar or paint mark placed on the animal at the time of vaccination. Survey results indicated that 73% (178/243) of eligible dogs were vaccinated and 82% of vaccinated dogs were marked with a collar or paint. Dogs were owned by 69% of households and ranged in age from 3 days to 13 years (median = 1 year), and the ratio of male to females dogs was 1:1. The dog-to-human ratio was 1:3.8, with an average of 1.4 dogs per household or 2.1 dogs per dog-owning household. Most dogs were kept as guards (83%) and most were free-ranging (85%). The most common reasons dogs were not vaccinated included they could not be restrained (11/64), the owner was not home (10/64), and fear of injury resulting from vaccination (10/64). The owners of 20% of vaccinated dogs reported some adverse reaction in their pet. Improved vaccine coverage was significantly associated with restrained dogs kept primarily for guard functions by owners who received information about the vaccination campaign from multiple sources. Vaccine coverage was sufficiently high to potentially control rabies transmission among dogs through herd immunity and indicated a successful vaccine campaign.

A comparative evaluation of a new immunoenzymatic test (RREID) with currently used diagnostic tests (DME and FAT) for dog rabies.

Diagnosis of rabies in dogs was performed in microplates which had been coated with immunoglobulin G previously sensitized to purified rabies virus antinucleocapsids. Homogenized brain suspensions were incubated in the plates and the specific binding rabies antigen was revealed by the use of the same IgG conjugated with horseradish peroxidase. Samples from the same specimens were subjected to standard rabies diagnostic tests--the direct microscopic examination (DME) or Sellers staining for Negri bodies and the fluorescent antibody test (FAT). FAT was used as the reference test or gold standard because of its proven sensitivity and accuracy. The concordance of FAT with RREID was 98.89% while that with DME was 96.67%. Sensitivity of both DME and RREID compared with FAT in this study was 100% while specificity of RREID versus FAT was 98.46% as compared with 95.38% DME versus FAT. The positive predictive value of RREID versus FAT was 96.15% while that of DME versus FAT was 89.29% although the negative predictive value of both RREID and DME compared with FAT was 100%. In the overall assessment, RREID results were demonstrated to approximate closely those of FAT. It is therefore concluded that RREID can be used in diagnostic laboratories to corroborate DME and where MIT and FAT cannot be done. RREID would also be useful in epidemiological studies where large samples are tested.