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The chicken or the egg? Exploring bi-directional associations between Newcastle disease vaccination and village chicken flock size in rural Tanzania.

ABSTRACT: Newcastle disease (ND) is a viral disease of poultry with global importance, responsible for the loss of a potential source of household nutrition and economic livelihood in many low-income food-deficit countries. Periodic outbreaks of this endemic disease result in high mortality amongst free-ranging chicken flocks and may serve as a disincentive for rural households to invest time or resources in poultry-keeping. Sustainable ND control can be achieved through vaccination using a thermotolerant vaccine administered via eyedrop by trained "community vaccinators". This article evaluates the uptake and outcomes of fee-for-service ND vaccination programs in eight rural villages in the semi-arid central zone of Tanzania. It represents part of an interdisciplinary program seeking to address chronic undernutrition in children through improvements to existing poultry and crop systems. Newcastle disease vaccination uptake was found to vary substantially across communities and seasons, with a significantly higher level of vaccination amongst households participating in a longitudinal study of children's growth compared with non-participating households (p = 0.009). Two multivariable model analyses were used to explore associations between vaccination and chicken numbers, allowing for clustered data and socioeconomic and cultural variation amongst the population. Results demonstrated that both (a) households that undertook ND vaccination had a significantly larger chicken flock size in the period between that vaccination campaign and the next compared with those that did not vaccinate (p = 0.018); and (b) households with larger chicken flocks at the time of vaccination were significantly more likely to participate in vaccination programs (p < 0.001). Additionally, households vaccinating in all three vaccination campaigns held over 12 months were identified to have significantly larger chicken flocks at the end of this period (p < 0.001). Opportunities to understand causality and complexity through quantitative analyses are limited, and there is a role for qualitative approaches to explore decisions made by poultry-keeping households and the motivations, challenges and priorities of community vaccinators. Evidence of a bi-directional relationship, however, whereby vaccination leads to greater chicken numbers, and larger flocks are more likely to be vaccinated, offers useful insights into the efficacy of fee-for-service animal health programs. This article concludes that attention should be focused on ways of supporting the participation of vulnerable households in ND vaccination campaigns, and encouraging regular vaccination throughout the year, as a pathway to strengthen food security, promote resilience and contribute to improved human nutrition.

SUBMITTER: de Bruyn J

PROVIDER: S-EPMC5690622 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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The chicken or the egg? Exploring bi-directional associations between Newcastle disease vaccination and village chicken flock size in rural Tanzania.

de Bruyn Julia J Thomson Peter C PC Bagnol Brigitte B Maulaga Wende W Rukambile Elpidius E Alders Robyn G RG

PloS one 20171116 11

Newcastle disease (ND) is a viral disease of poultry with global importance, responsible for the loss of a potential source of household nutrition and economic livelihood in many low-income food-deficit countries. Periodic outbreaks of this endemic disease result in high mortality amongst free-ranging chicken flocks and may serve as a disincentive for rural households to invest time or resources in poultry-keeping. Sustainable ND control can be achieved through vaccination using a thermotolerant ...[more]

PMID: 29145463

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Project description:BackgroundPoultry represent a widely held economic, nutritional, and sociocultural asset in rural communities worldwide. In a recent longitudinal study in western Kenya, the reported mean number of chickens per household was 10, with increases in flock size constrained principally by mortality. Newcastle disease virus is a major cause of chicken mortality globally and hypothesized to be responsible for a large part of mortality in smallholder flocks. Our goal was to determine the impact of routine Newcastle disease virus (NDV) vaccination on flock size and use this data to guide programs to improve small flock productivity.MethodsWe conducted a factorial randomized controlled trial in 537 households: in 254 households all chickens were vaccinated every 3 months with I-2 NDV vaccine while chickens in 283 households served as unvaccinated controls. In both arms of the trial, all chickens were treated with endo- and ecto parasiticides every 3 months. Data on household chicken numbers and reported gains and losses were collected monthly for 18 months.ResultsConsistent with prior studies, the overall flock size was small but with increases in both arms of the study over time. The mean number of chickens owned at monthly census was 13.06±0.29 in the vaccinated households versus 12.06±0.20 in the control households (p = 0.0026) with significant gains in number of chicks (p = 0.06), growers (p = 0.09), and adults (p = 0.03) in the vaccinated flocks versus the controls. Household reported gains were 4.50±0.12 total chickens per month when vaccinated versus 4.15±0.11 in the non-vaccinated controls (p = 0.03). Gains were balanced by voluntary decreases, reflecting household decision-making for sales or household consumption, which were marginally higher, but not statistically significant, in vaccinated households and by involuntary losses, including mortality and loss due to predation, which were marginally higher in control households.ConclusionQuarterly NDV vaccination and parasiticidal treatment resulted in an increase in flock size by a mean of one bird per household as compared to households where the flock received only parasiticidal treatment. While results suggest that the preventable fraction of mortality attributable to Newcastle disease is comparatively small relatively to all-cause mortality in smallholder households, there was a significant benefit to vaccination in terms of flock size. Comparison with previous flock sizes in the study households indicate a more significant benefit from the combined vaccination and parasiticidal treatment, supporting a comprehensive approach to improving flock health and improving household benefits of production in the smallholder setting.

Project description:A large body of cross-sectional evidence finds strong and consistent associations between social support and intimate partner violence (IPV). However, the directionality of this relationship has not been firmly established due to a dearth of longitudinal evidence. Using cohort study data collected over a 3 year period from 945 women in rural Pakistan, we investigated the longitudinal relationship between IPV and social support. Friend and family social support was measured with the Multidimensional Perceived Social Support Scale, and IPV was measured with questions adopted from the World Health Organization's Violence Against Women Instrument, which was used to construct a measure of IPV severity. We estimated longitudinal associations in linear regression models that controlled for women's educational level, age at marriage, age, household composition, household assets, depressive symptoms, and Adverse Childhood Experiences. We found evidence of a bi-directional, mutually re-enforcing relationship that showed unique associations by type of social support. Specifically, we found that high social support from family, though not friends, decreased IPV severity 1 year later, and that higher IPV severity led to reductions in both friend and family social support 1 year later. Results suggest that interventions involving family members could be especially effective at reducing IPV in this context, and – given that low social support leads to many adverse health outcomes – results suggest that IPV can result in secondary harms due to diminished social support. In summary, our study confirms a bi-directional relationship between IPV and social support and suggests that IPV interventions that integrate social support may be especially effective at reducing IPV and mitigating secondary harms. Highlights • Directionality between social support and intimate partner violence (IPV) unclear.• Investigated bi-directional relationship between IPV and social support.• Used longitudinal cohort study data from rural Pakistan.• High social support from family, though not friends, decreased IPV severity.• Higher IPV severity led to reductions in both friend and family social support.

Project description:BackgroundAlthough the association between mouth ulcers and psychiatric traits has been reported by observational studies, their causal relationship remains unclear. Mendelian randomization (MR), powered by large-scale genome-wide association studies (GWAS), provides an opportunity to clarify the causality between mouth ulcers and psychiatric traits.MethodsWe collected summary statistics of mouth ulcers (sample size n = 461,106) and 10 psychiatric traits from the largest publicly available GWAS on Europeans, including anxiety disorder (n = 83,566), attention deficit/hyperactivity disorder (n = 53,293), autism spectrum disorder (n = 46,350), bipolar disorder (n = 51,710), insomnia (n = 1,331,010), major depressive disorder (n = 480,359), mood instability (n = 363,705), neuroticism (n = 168,105), schizophrenia (n = 105,318), and subjective wellbeing (n = 388,538). We applied three two-sample bi-directional MR analysis methods, namely the Inverse Variance Weighted (IVW) method, the MR pleiotropy residual sum and outlier (MR-PRESSO) method, and the weighted median method, to assess the causal relationship between each psychiatric trait and mouth ulcers.ResultsWe found significant effects of autism spectrum disorder, insomnia, major depressive disorder, and subjective wellbeing on mouth ulcers, with the corresponding odds ratio (OR) from the IVW method being 1.160 [95% confidence interval (CI): 1.066-1.261, P = 5.39 × 10-4], 1.092 (1.062-1.122, P = 3.37 × 10-10), 1.234 (1.134-1.342, P = 1.03 × 10-6), and 0.703 (0.571-0.865, P = 8.97 × 10-4), respectively. We also observed suggestive evidence for mood instability to cause mouth ulcers [IVW, OR = 1.662 (1.059-2.609), P = 0.027]. These results were robust to weak instrument bias and heterogeneity. We found no evidence on causal effects between other psychiatric traits and mouth ulcers, in either direction.ConclusionOur findings suggest a protective effect of subjective wellbeing and risk effects of autism spectrum disorder, insomnia, major depressive disorder, and mood instability on mouth ulcers. These results clarify the causal relationship between psychiatric traits and the development of mouth ulcers.

Dataset Information

The chicken or the egg? Exploring bi-directional associations between Newcastle disease vaccination and village chicken flock size in rural Tanzania.

Publications

The chicken or the egg? Exploring bi-directional associations between Newcastle disease vaccination and village chicken flock size in rural Tanzania.

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