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Achieving population-level immunity to rabies in free-roaming dogs in Africa and Asia.

Morters MK, McKinley TJ, Horton DL, Cleaveland S, Schoeman JP, Restif O, Whay HR, Goddard A, Fooks AR, Damriyasa IM, Wood JL - PLoS Negl Trop Dis (2014)

Bottom Line: This is the first longitudinal study to evaluate temporal variations in rabies vaccine-induced serological responses, and factors associated with these variations, at the individual level in previously unvaccinated free-roaming dog populations.This demonstrates the feasibility of achieving population-level immunity in free-roaming dog populations in rabies-endemic regions.These findings support annual mass vaccination campaigns as the most effective means to control canine rabies.

View Article: PubMed Central - PubMed

Affiliation: Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.

ABSTRACT
Canine rabies can be effectively controlled by vaccination with readily available, high-quality vaccines. These vaccines should provide protection from challenge in healthy dogs, for the claimed period, for duration of immunity, which is often two or three years. It has been suggested that, in free-roaming dog populations where rabies is endemic, vaccine-induced protection may be compromised by immuno-suppression through malnutrition, infection and other stressors. This may reduce the proportion of dogs that seroconvert to the vaccine during vaccination campaigns and the duration of immunity of those dogs that seroconvert. Vaccination coverage may also be limited through insufficient vaccine delivery during vaccination campaigns and the loss of vaccinated individuals from populations through demographic processes. This is the first longitudinal study to evaluate temporal variations in rabies vaccine-induced serological responses, and factors associated with these variations, at the individual level in previously unvaccinated free-roaming dog populations. Individual-level serological and health-based data were collected from three cohorts of dogs in regions where rabies is endemic, one in South Africa and two in Indonesia. We found that the vast majority of dogs seroconverted to the vaccine; however, there was considerable variation in titres, partly attributable to illness and lactation at the time of vaccination. Furthermore, >70% of the dogs were vaccinated through community engagement and door-to-door vaccine delivery, even in Indonesia where the majority of the dogs needed to be caught by net on successive occasions for repeat blood sampling and vaccination. This demonstrates the feasibility of achieving population-level immunity in free-roaming dog populations in rabies-endemic regions. However, attrition of immune individuals through demographic processes and waning immunity necessitates repeat vaccination of populations within at least two years to ensure communities are protected from rabies. These findings support annual mass vaccination campaigns as the most effective means to control canine rabies.

No MeSH data available.


Related in: MedlinePlus

Variations in titre in the Kelusa research cohort.Titres of all the dogs in the Kelusa research cohort. Upper outliers (i.e. the four dogs with day 180 titres of 11.3 IU/ml) are excluded. The median titre (thick, horizontal line), 25th and 75th percentiles (thin horizontal lines), and either minimum and maximum titres or 1.5× the interquartile range (dashed vertical lines) are shown for each time point after vaccination (at day 180 and 360).
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pntd-0003160-g003: Variations in titre in the Kelusa research cohort.Titres of all the dogs in the Kelusa research cohort. Upper outliers (i.e. the four dogs with day 180 titres of 11.3 IU/ml) are excluded. The median titre (thick, horizontal line), 25th and 75th percentiles (thin horizontal lines), and either minimum and maximum titres or 1.5× the interquartile range (dashed vertical lines) are shown for each time point after vaccination (at day 180 and 360).

Mentions: The quality of the serum samples was excellent, with only a few samples with slight to moderate haemolysis. Most dogs in Zenzele seroconverted (97% of the research and 92% of the DoA cohorts had titres ≥0.5 IU/ml at day 30), however there was considerable variability in titres at each time point (Figure 2). The estimated dog-dog variation (random effect) in peak titres (quadratic model intercept) was large (+/− 2SD 1.8–99 IU/ml) (Table S17, model 1). Excluding upper outliers, the observed geometric mean titres (GMT) at day 30 for the research cohort (of 15 IU/ml, Table S18) was comparable to experimental [34], [35] and field [48] studies of previously unvaccinated dogs. The maximum peak titre was more than double the upper limit of the other studies (40–50 IU/ml), however those dogs with peak titres >40 IU/ml included seven dogs born in Zenzele after October 2009 which were unlikely to have been vaccinated prior to commencement of the study. There was similar variability in the titres at each time point for the Bali cohorts (Figures 3–4; Table S17, models 3–6). See Table S13 for details of the dogs in Zenzele that did not seroconvert to the vaccine.


Achieving population-level immunity to rabies in free-roaming dogs in Africa and Asia.

Morters MK, McKinley TJ, Horton DL, Cleaveland S, Schoeman JP, Restif O, Whay HR, Goddard A, Fooks AR, Damriyasa IM, Wood JL - PLoS Negl Trop Dis (2014)

Variations in titre in the Kelusa research cohort.Titres of all the dogs in the Kelusa research cohort. Upper outliers (i.e. the four dogs with day 180 titres of 11.3 IU/ml) are excluded. The median titre (thick, horizontal line), 25th and 75th percentiles (thin horizontal lines), and either minimum and maximum titres or 1.5× the interquartile range (dashed vertical lines) are shown for each time point after vaccination (at day 180 and 360).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230884&req=5

pntd-0003160-g003: Variations in titre in the Kelusa research cohort.Titres of all the dogs in the Kelusa research cohort. Upper outliers (i.e. the four dogs with day 180 titres of 11.3 IU/ml) are excluded. The median titre (thick, horizontal line), 25th and 75th percentiles (thin horizontal lines), and either minimum and maximum titres or 1.5× the interquartile range (dashed vertical lines) are shown for each time point after vaccination (at day 180 and 360).
Mentions: The quality of the serum samples was excellent, with only a few samples with slight to moderate haemolysis. Most dogs in Zenzele seroconverted (97% of the research and 92% of the DoA cohorts had titres ≥0.5 IU/ml at day 30), however there was considerable variability in titres at each time point (Figure 2). The estimated dog-dog variation (random effect) in peak titres (quadratic model intercept) was large (+/− 2SD 1.8–99 IU/ml) (Table S17, model 1). Excluding upper outliers, the observed geometric mean titres (GMT) at day 30 for the research cohort (of 15 IU/ml, Table S18) was comparable to experimental [34], [35] and field [48] studies of previously unvaccinated dogs. The maximum peak titre was more than double the upper limit of the other studies (40–50 IU/ml), however those dogs with peak titres >40 IU/ml included seven dogs born in Zenzele after October 2009 which were unlikely to have been vaccinated prior to commencement of the study. There was similar variability in the titres at each time point for the Bali cohorts (Figures 3–4; Table S17, models 3–6). See Table S13 for details of the dogs in Zenzele that did not seroconvert to the vaccine.

Bottom Line: This is the first longitudinal study to evaluate temporal variations in rabies vaccine-induced serological responses, and factors associated with these variations, at the individual level in previously unvaccinated free-roaming dog populations.This demonstrates the feasibility of achieving population-level immunity in free-roaming dog populations in rabies-endemic regions.These findings support annual mass vaccination campaigns as the most effective means to control canine rabies.

View Article: PubMed Central - PubMed

Affiliation: Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.

ABSTRACT
Canine rabies can be effectively controlled by vaccination with readily available, high-quality vaccines. These vaccines should provide protection from challenge in healthy dogs, for the claimed period, for duration of immunity, which is often two or three years. It has been suggested that, in free-roaming dog populations where rabies is endemic, vaccine-induced protection may be compromised by immuno-suppression through malnutrition, infection and other stressors. This may reduce the proportion of dogs that seroconvert to the vaccine during vaccination campaigns and the duration of immunity of those dogs that seroconvert. Vaccination coverage may also be limited through insufficient vaccine delivery during vaccination campaigns and the loss of vaccinated individuals from populations through demographic processes. This is the first longitudinal study to evaluate temporal variations in rabies vaccine-induced serological responses, and factors associated with these variations, at the individual level in previously unvaccinated free-roaming dog populations. Individual-level serological and health-based data were collected from three cohorts of dogs in regions where rabies is endemic, one in South Africa and two in Indonesia. We found that the vast majority of dogs seroconverted to the vaccine; however, there was considerable variation in titres, partly attributable to illness and lactation at the time of vaccination. Furthermore, >70% of the dogs were vaccinated through community engagement and door-to-door vaccine delivery, even in Indonesia where the majority of the dogs needed to be caught by net on successive occasions for repeat blood sampling and vaccination. This demonstrates the feasibility of achieving population-level immunity in free-roaming dog populations in rabies-endemic regions. However, attrition of immune individuals through demographic processes and waning immunity necessitates repeat vaccination of populations within at least two years to ensure communities are protected from rabies. These findings support annual mass vaccination campaigns as the most effective means to control canine rabies.

No MeSH data available.


Related in: MedlinePlus