Estimating the size of dog populations in Tanzania to inform rabies control

Estimates of dog population sizes are a prerequisite for delivering effective canine rabies control. However, dog population sizes are generally unknown in most rabies-endemic areas. Several approaches have been used to estimate dog populations but without rigorous evaluation. We compare post-vaccination transects, household surveys, and school-based surveys to determine which most precisely estimates dog population sizes. These methods were implemented across 28 districts in southeast Tanzania, in conjunction with mass dog vaccinations, covering a range of settings, livelihoods, and religious backgrounds. Transects were the most precise method, revealing highly variable patterns of dog ownership, with human/dog ratios ranging from 12.4:1 to 181.3:1 across districts. Both household and school-based surveys generated imprecise and, sometimes, inaccurate estimates, due to small sample sizes in relation to the heterogeneity in patterns of dog ownership. Transect data were subsequently used to develop a predictive model for estimating dog populations in districts lacking transect data. We predicted a dog population of 2,316,000 (95% CI 1,573,000–3,122,000) in Tanzania and an average human/dog ratio of 20.7:1. Our modelling approach has the potential to be applied to predicting dog population sizes in other areas where mass dog vaccinations are planned, given census and livelihood data. Furthermore, we recommend post-vaccination transects as a rapid and effective method to refine dog population estimates across large geographic areas and to guide dog vaccination programmes in settings with mostly free roaming dog populations

Comparing methods of assessing dog rabies vaccination coverage in rural and urban communities in Tanzania

Rabies can be eliminated by achieving comprehensive coverage of 70% of domestic dogs during annual mass vaccination campaigns. Estimates of vaccination coverage are, therefore, required to evaluate and manage mass dog vaccination programs; however, there is no specific guidance for the most accurate and efficient methods for estimating coverage in different settings. Here, we compare post-vaccination transects, school-based surveys, and household surveys across 28 districts in southeast Tanzania and Pemba island covering rural, urban, coastal and inland settings, and a range of different livelihoods and religious backgrounds. These approaches were explored in detail in a single district in northwest Tanzania (Serengeti), where their performance was compared with a complete dog population census that also recorded dog vaccination status. Post-vaccination transects involved counting marked (vaccinated) and unmarked (unvaccinated) dogs immediately after campaigns in 2,155 villages (24,721 dogs counted). School-based surveys were administered to 8,587 primary school pupils each representing a unique household, in 119 randomly selected schools approximately 2 months after campaigns. Household surveys were conducted in 160 randomly selected villages (4,488 households) in July/August 2011. Costs to implement these coverage assessments were $12.01,$66.12, and $155.70 per village for post-vaccination transects, school-based, and household surveys, respectively. Simulations were performed to assess the effect of sampling on the precision of coverage estimation. The sampling effort required to obtain reasonably precise estimates of coverage from household surveys is generally very high and probably prohibitively expensive for routine monitoring across large areas, particularly in communities with high human to dog ratios. School-based surveys partially overcame sampling constraints, however, were also costly to obtain reasonably precise estimates of coverage. Post-vaccination transects provided precise and timely estimates of community-level coverage that could be used to troubleshoot the performance of campaigns across large areas. However, transects typically overestimated coverage by around 10%, which therefore needs consideration when evaluating the impacts of campaigns. We discuss the advantages and disadvantages of these different methods and make recommendations for how vaccination campaigns can be better monitored and managed at different stages of rabies control and elimination programs

Towards elimination of dog-mediated human rabies: experiences from implementing a large-scale demonstration project in Southern Tanzania

No abstract available

On Stirling functions of second kind

SIGLETIB Hannover: RN 5141(373) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Integrating contact tracing and whole-genome sequencing to track the elimination of dog-mediated rabies: An observational and genomic study

Background: Dog-mediated rabies is endemic across Africa causing thousands of human deaths annually. A One Health approach to rabies is advocated, comprising emergency post-exposure vaccination of bite victims and mass dog vaccination to break the transmission cycle. However, the impacts and cost-effectiveness of these components are difficult to disentangle. Methods: We combined contact tracing with whole-genome sequencing to track rabies transmission in the animal reservoir and spillover risk to humans from 2010 to 2020, investigating how the components of a One Health approach reduced the disease burden and eliminated rabies from Pemba Island, Tanzania. With the resulting high-resolution spatiotemporal and genomic data, we inferred transmission chains and estimated case detection. Using a decision tree model, we quantified the public health burden and evaluated the impact and cost-effectiveness of interventions over a 10-year time horizon. Results: We resolved five transmission chains co-circulating on Pemba from 2010 that were all eliminated by May 2014. During this period, rabid dogs, human rabies exposures and deaths all progressively declined following initiation and improved implementation of annual islandwide dog vaccination. We identified two introductions to Pemba in late 2016 that seeded re-emergence after dog vaccination had lapsed. The ensuing outbreak was eliminated in October 2018 through reinstated islandwide dog vaccination. While post-exposure vaccines were projected to be highly cost-effective ($256 per death averted), only dog vaccination interrupts transmission. A combined One Health approach of routine annual dog vaccination together with free post-exposure vaccines for bite victims, rapidly eliminates rabies, is highly cost-effective ($1657 per death averted) and by maintaining rabies freedom prevents over 30 families from suffering traumatic rabid dog bites annually on Pemba island. Conclusions: A One Health approach underpinned by dog vaccination is an efficient, cost-effective, equitable, and feasible approach to rabies elimination, but needs scaling up across connected populations to sustain the benefits of elimination, as seen on Pemba, and for similar progress to be achieved elsewhere. Funding: Wellcome [207569/Z/17/Z, 095787/Z/11/Z, 103270/Z/13/Z], the UBS Optimus Foundation, the Department of Health and Human Services of the National Institutes of Health [R01AI141712] and the DELTAS Africa Initiative [Afrique One-ASPIRE/DEL-15-008] comprising a donor consortium of the African Academy of Sciences (AAS), Alliance for Accelerating Excellence in Science in Africa (AESA), the New Partnership for Africa’s Development Planning and Coordinating (NEPAD) Agency, Wellcome [107753/A/15/Z], Royal Society of Tropical Medicine and Hygiene Small Grant 2017 [GR000892] and the UK government. The rabies elimination demonstration project from 2010-2015 was supported by the Bill & Melinda Gates Foundation [OPP49679]. Whole-genome sequencing was partially supported from APHA by funding from the UK Department for Environment, Food and Rural Affairs (Defra), Scottish government and Welsh government under projects SEV3500 and SE0421

Mobile phones as potential tools for surveillance in Tanzania.

<p>(A) Access and use of mobile phones versus computers by surveillance system users and 95% confidence intervals. The effects are shown of user (B) age and (C) self-reported use of text messaging (short message service or SMS), on the standardized time to complete surveillance forms on mobile phones, with boxes shaded in proportion to the sample size in the group (<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002002#pmed.1002002.s002" target="_blank">S2 Data</a>). Time to completion in minutes was standardized by computing z-scores by sector, because forms used by health workers for recording bite patients were longer than forms used by livestock field officers to record mass dog vaccination campaigns (<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002002#pmed.1002002.s005" target="_blank">S3 Table</a>, <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002002#pmed.1002002.s008" target="_blank">S1 Text</a>). (D) Number and percentage of mobile phone form submissions where helpline support was used (<8% overall and <3% for the most commonly used form, that for bite patient records, data in <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002002#pmed.1002002.s003" target="_blank">S1 Table</a>). Additional forms submitted by staff involved in system development and therefore familiar with the mobile phone application were excluded.</p

Example of mobile phone surveillance application.

<p>Mobile phone interface showing form being (A) completed for an example bite patient and (B) submitted.</p

The mobile-phone–based surveillance system.

<p>In the map, blue dots represent facilities that provide post-exposure prophylaxis (PEP) and report using the surveillance system (large dots represent hospitals, small dots represent health centres). The map is shaded by population density with wildlife-protected areas in white. The panels illustrate example surveillance data (<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002002#pmed.1002002.s001" target="_blank">S1 Data</a>) from different districts that are annotated on the map by their initials. These data show monthly incidence of bite patients per 100,000 people on Pemba Island (P) and Ulanga (U), PEP use and shortages for Kibaha rural (KR) and Kisarawe (K), progress switching from intramuscular (IM) to intradermal (ID) administration of PEP for Morogoro rural (MR) and Rufiji (R), and numbers of dogs vaccinated each month for Nachingwea (N) and Masasi (M).</p