Biology subjects

Lankester, F.

Publications and source records attributed to Lankester, F..

6 recordsLinked to original sources

bioRxiv2024

A randomized controlled trial of the effectiveness of a community-based rabies vaccination strategy

BackgroundApproximately 60,000 people die from dog-mediated rabies annually. Low and heterogeneous coverage reduces the effectiveness of dog vaccination campaigns that can eliminate rabies. Campaigns typically involve teams travelling annually to villages to deliver cold chain stored vaccines from centralized headquarters. Thermotolerant vaccines enable novel decentralized delivery of locally-stored vaccines by communities throughout the year. We compared the effectiveness of annual team-based versus continuous community-based dog vaccination strategies. MethodsWe conducted a cluster randomized controlled trial across Mara region, Tanzania. Trial clusters were administrative wards (112, on average four villages each). For the team-based arm vaccinators hosted annual static-point clinics, whilst for the community-based arm, a ward-based animal health officer with a village community leader managed vaccinations using vaccines stored within the ward. We measured vaccination coverage, the primary outcome, twice annually per cluster (month 1 and 11) through household surveys over three years (November 2020 to October 2023) and examined spatial and temporal coverage variations as secondary outcomes. FindingsCommunity-based delivery achieved significantly higher coverage (49-62%) than team-based delivery (22-46%), and consistently exceeded the critical threshold for herd immunity (40%), Odds ratio (OR): 1.48-3.49. The lower less uniform coverage achieved through team-based delivery had a higher monthly probability of falling below the critical threshold (0.6, 95% CI: 0.38-0.81) vs 0.18 (95% CI: 0.04-0.40). Greater declines in coverage over the year were recorded in the team-based arm compared to the community-based ConclusionCommunity-based mass dog vaccination achieves higher more consistent coverage than team-based delivery across settings typical of many sub-Saharan African countries. This approach could play an important role in national rabies elimination programmes aiming to end human rabies deaths by 2030 as part of the global zero by 30 strategy. FundingDepartment of Health and Human Services of the National Institutes of Health (R01AI141712), Wellcome Trust (207569/Z/17/Z, 224520/Z/21/Z) and MSD Animal Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

immunology↗

bioRxiv2024

Reducing spatial heterogeneity in coverage improves the effectiveness of dog vaccination against rabies

Vaccination programs are the mainstay of control for many infectious diseases. Heterogeneous coverage is hypothesised to reduce vaccination programme effectiveness, but this impact has not been quantified in real systems. We address this gap using fine-scale data from two decades of rabies contact tracing and dog vaccination campaigns in Serengeti district, Tanzania. We also aimed to identify drivers of continued circulation of rabies in the district despite annual vaccination campaigns. Using generalised linear mixed models, we find that current focal (village-level) dog rabies incidence decreases with increasing recent focal vaccination coverage. However, current focal incidence depends most on recent incidence, both focally and in the wider district, consistent with high population connectivity. Removing the masking effects of prior non-focal incidence shows that, for the same average prior non-focal (wider-district) vaccination coverage, increased heterogeneity in coverage among the non-focal villages leads to increased focal incidence. These effects led to outbreaks following years when vaccination campaigns missed many villages, whereas when heterogeneity in coverage was reduced, incidence declined to low levels (<0.4 cases/1,000 dogs annually and no human deaths) and short vaccination lapses thereafter did not lead to resurgence. Through transmission-tree reconstruction, we inferred frequent incursions into the district each year (mean of 7). Inferred incursions substantially increased as a percentage of all cases in recent years, reaching 50% in 2022, suggesting regional connectivity is driving residual transmission. Overall, we empirically demonstrate how population connectivity and spatial heterogeneity in vaccination can impact disease outcomes, highlighting the importance of fine-scale monitoring in managing vaccination programs.

ecology↗

bioRxiv2024

The value of livestock abortion surveillance in Tanzania: identifying disease priorities and informing interventions

BackgroundLack of reliable data on the aetiology of livestock diseases, especially in Africa, is a major factor constraining the design of effective livestock health interventions to improve livelihoods, food security and public health. RationaleLivestock abortion is an important disease syndrome that affects productivity and livestock economies, and poses risks to public health. Worldwide, several pathogens are associated with livestock abortions but across Africa livestock disease surveillance data rarely include information from abortion events, little is known about the aetiology and impacts of livestock abortions, and data are not available to inform prioritisation of disease interventions. MethodsThis paper describes outcomes from a surveillance platform that was set up in 15 wards in northern Tanzania spanning pastoral, agropastoral and smallholder agro-ecological systems to investigate the causes and impacts of livestock abortion. Abortion cases were reported by farmers to Ministry of Livestock and Fisheries livestock field officers and on to investigation teams. The abortion was eligible for inclusion if the research field team or livestock field officer could attend within 72 hours of the event occurring. If so, a field investigation was carried out to collect diagnostic samples from aborted materials and aborting dams and questionnaire data on herd/flock management. Laboratory diagnostic tests were carried out for a range of abortigenic pathogens, and laboratory and questionnaire data analysed to investigate a) determinants of attribution; b) patterns of investigated events, including species and breed affected, previous abortion history and recent stressful events, and the seasonality of cases; c) determinants of reporting, investigation and attribution; (d) cases in which zoonotic pathogens were detected. ResultsOver a two-year period (2017-2019), 215 abortion events in cattle (n=71), sheep (n=44) and goats (n=100) were investigated from 13 of the 15 wards. The number of investigated cases varied widely across wards, with three of the 15 field officers (20%) reporting 70% of investigated cases. Aetiological attribution, achieved for 19.5% of cases through PCR-based diagnostics, was significantly affected by delays in obtaining samples from field investigation. Histopathology proved less useful than PCR diagnostics due to rapid deterioration of field samples. Vaginal swabs from aborting dams provided a practical and sensitive source of diagnostic material for pathogen detection. Discussion / ConclusionLivestock abortion surveillance, even at a small scale and when capturing only a small proportion of events, can generate valuable information on causes of zoonotic disease outbreaks, livestock reproductive losses and can identify important pathogens that are not easily captured through other forms of livestock disease surveillance. This study demonstrated the feasibility of establishing an effective reporting and investigation system that could be implemented across a range of settings, including remote rural areas. This has been achieved through effective engagement of community-based field officers, establishment of practical sample collection protocols and application of molecular diagnostic platforms.

zoology↗

bioRxiv2022

Development, feasibility and potential effectiveness of community-based continuous mass dog vaccination delivery strategies: lessons for optimization and replication

ObjectivesDog vaccination can eliminate rabies, but annual delivery strategies do not sustain vaccination coverage between campaigns. We describe the development of a community-based continuous mass dog vaccination (CBC-MDV) approach designed to improve and maintain vaccination coverage in Tanzania and examine the feasibility of delivering this approach as well as lessons for its optimization. MethodsWe developed three delivery strategies of CBC-MDV and tested them against the current annual vaccination strategy following the UK MRCs guidance: i) developing an evidence-based theoretical framework of intervention pathways and ii) piloting to test feasibility and inform optimization. For our process evaluation of CBC-MDV we collected data using non-participant observations, meeting reports and implementation audits and in-depth interviews, as well as household surveys of vaccination coverage to assess potential effectiveness. We analyzed qualitative data thematically and quantitative data descriptively. ResultsThe final design included delivery by veterinary teams supported by village-level one health champions. In terms of feasibility, we found that less than half of CBC-MDVs components were implemented as planned. Fidelity of delivery was influenced by the strategy design, implementer availability and appreciation of value intervention components, and local environmental and socioeconomic events (e.g. elections, funerals, school cycles). CBC-MDV activities decreased sharply after initial campaigns, partly due to lack of supervision. Community engagement and involvement was not strong. Nonetheless, the CBC-MDV approaches achieved vaccination coverage above the critical threshold (40%) all-year-round. CBC-MDV components such as identifying vaccinated dogs, which village members work as one health champions and how provision of continuous vaccination is implemented need further optimization prior to scale up. InterpretationCBC-MDV is feasible to deliver and can achieve good vaccination coverage. Community involvement in the development of CBC-MDV, to better tailor components to contextual situations, and improved supervision of activities are likely to improve vaccination coverage in future. AUTHOR SUMMARYAnnual mass dog vaccination campaigns that reach at least 70% of the dog population, should maintain sufficient herd immunity between campaigns to interrupt rabies transmission. However, it is often challenging to reach 70% of the dog population with annual vaccination campaigns. We hypothesized that a community-based continuous approach to dog vaccination could better maintain high levels of vaccination coverage all-year-round. We describe the development of a community-based continuous approach to dog vaccination in Tanzania, and assessed the feasibility of delivering its components, its potential effectiveness and lessons for its optimization. We found that the approach was well accepted, as its development involved key stakeholders. Although less than half of the components of the community-based continuous approach were delivered exactly as planned, over 70% of dogs were vaccinated and the approach maintained coverage above the critical vaccination threshold throughout the year. We conclude that it is feasible to deliver a community-based continuous approach to dog vaccination, but that some components need further improvement; more supervision and community involvement should lead to better outcomes.

immunology↗

bioRxiv2021

An outbreak of Rift Valley fever among peri-urban dairy cattle in northern Tanzania, 2018

Undetected Rift Valley fever (RVF) outbreaks are expected in endemic countries but little is known about their size or frequency. We describe a previously unreported RVF outbreak involving dairy cattle that appeared to be limited to the edge of the town of Moshi, Tanzania and occurred from May through August, 2018. The outbreak was detected retrospectively using samples collected as part of a cohort study investigating the causes of livestock abortion across northern Tanzania. A total of 14 RVF-associated cattle abortions were identified using a combination of serology and quantitative reverse transcription PCR (RT-qPCR). Milk samples from three (21%) of 14 cases were also RT-qPCR positive. Genotyping revealed circulation of RVF viruses from two lineages. The occurrence of an RVF outbreak among peri-urban dairy cattle, and evidence for RVF viral shedding in milk, highlights the potential for emerging zoonotic risks associated with the growth of urban and peri-urban livestock populations.

ecology↗

bioRxiv2021

Prospective cohort study reveals unexpected aetiologies of livestock abortion in northern Tanzania

Livestock abortion is an important cause of productivity losses worldwide and many infectious causes of abortion are zoonotic pathogens that impact on human health. Little is known about the relative importance of infectious causes of livestock abortion in Africa, including in subsistence farming communities that are critically dependent on livestock for food, income, and wellbeing. We conducted a prospective cohort study of livestock abortion, supported by cross-sectional serosurveillance, to determine aetiologies of livestock abortions in livestock in Tanzania. This approach generated several important findings including detection of a Rift Valley fever virus outbreak in cattle; high prevalence of C. burnetii infection in livestock; and the first report of Neospora caninum, Toxoplasma gondii, and pestiviruses associated with livestock abortion in Tanzania. Our approach provides a model for abortion surveillance in resource-limited settings. Our findings add substantially to current knowledge in sub-Saharan Africa, providing important evidence from which to prioritise disease interventions.

systems biology↗