Biology subjects

de Glanville, W. A.

Publications and source records attributed to de Glanville, W. A..

4 recordsLinked to original sources

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↗

bioRxiv2020

Classification and characterisation of livestock production systems in northern Tanzania

Livestock keepers in sub-Saharan Africa face a growing range of pressures, including climate change, land loss, restrictive policies, and population increase. Widespread adaptation in response to such pressures can lead to the emergence of new, non-traditional typologies of livestock production. We sought to characterise livestock production systems in northern Tanzania, a region undergoing rapid social, economic, and environmental change. Questionnaire and spatial data were collected from 404 livestock-keeping households in 21 villages in Arusha and Manyara Regions in 2016. Multiple factor analysis and hierarchical cluster analysis were used to classify households into livestock production systems based on household-level characteristics. Indicators of vulnerability, including household-level reports of hunger, illness, livestock loss, land loss and crop losses were compared between production systems. Three distinct clusters emerged through this process. The ethnic, environmental and livestock management characteristics of households in each cluster broadly mapped onto traditional definitions of pastoral, agro-pastoral and smallholder livestock production in the region, suggesting that this quantitative classification system is complementary to more qualitative classification methods. Our findings also suggest that traditional systems of livestock production continue to persist in northern Tanzania. Nonetheless, we found indicators of substantial change within livestock production systems, most notably the adoption of crop agriculture in the majority of pastoral households. Smallholder households were less likely than either pastoral or agro-pastoral households to report hunger, illness, and livestock, land or crop losses. Livelihoods that rely solely on livestock are relatively rare in northern Tanzania, which represents an important shift in production in the region, particularly among pastoralists. Policy initiatives to improve household and community well-being should recognise the continuing distinctiveness of traditional livestock production systems in the region.

systems biology↗

bioRxiv2019

Identifying age cohorts responsible for Peste des petits ruminants virus transmission among sheep, goats, and cattle in northern Tanzania

Peste des petits ruminants virus (PPRV) causes a contagious disease of high morbidity and mortality in global sheep and goat populations and leads to approximately $2 billion USD in global annual losses. PPRV is currently targeted by the Food and Agricultural Organization and World Animal Health Organization for global eradication by 2030. To better control this disease and inform eradication strategies, an improved understanding of how PPRV risk varies by age is needed. Our study used a piece-wise catalytic model to estimate the age-specific force of infection (FOI, per capita infection rate of susceptible hosts) among sheep, goats, and cattle from a cross-sectional serosurvey dataset collected in 2016 in Tanzania. Apparent seroprevalence rose with age, as would be expected if PPRV is a fully-immunizing infection, reaching 53.6%, 46.8%, and 11.6% (true seroprevalence: 52.7%, 52.8%, 39.2%) for sheep, goats, and cattle, respectively. Seroprevalence was significantly higher among pastoral animals than agropastoral animals across all ages, with pastoral sheep and goat seroprevalence approaching 70% and 80%, respectively, suggesting endemicity in pastoral settings. The best fitting piece-wise catalytic models included merged age groups: two age groups for sheep, three age groups for goats, and four age groups for cattle. However, the signal of these age heterogeneities was weak, with overlapping confidence intervals around force of infection estimates from most models with the exception of a significant FOI peak among 2.5-3.5 year old pastoral cattle. Pastoral animals had a higher force of infection overall, and across a wider range of ages than agropastoral animals. The subtle age-specific force of infection heterogeneities identified in this study among sheep, goats, and cattle suggest that targeting control efforts by age may not be as effective as targeting by other risk factors, such as management system type. Further research should investigate how specific husbandry practices affect PPRV transmission. Author SummaryAge differences in transmission are important for many infections, and can help target control programs. We used an age-structured serosurvey of Tanzanian sheep, goats, and cattle to explore peste des petits ruminants virus transmission. We estimated rate at which susceptibles acquire infection (force of infection) to determine which age group(s) had the highest transmission rates. We hypothesized that an age-varying model with multiple age groups would better fit the data than an age constant model and that the highest transmission rates would appear in the youngest age groups. Furthermore, we hypothesized evidence of immunity would increase with age. The data supported our hypothesis at the species level and the best fitting models merged age groups: two, three, and four age group models were best for sheep, goats, and cattle, respectively. The highest rates occurred among younger age groups and evidence of immunity rose with age for all species. In most models, confidence interval estimates overlapped, but there was a significant FOI peak among 2.3-3.5 year old pastoral cattle. Importantly, these data indicate that there is not sufficient evidence to support targeted control by age group, and that targeted control based on production system should be more effective.

ecology↗