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J Russell Stothard

Publications and source records attributed to J Russell Stothard.

10 recordsLinked to original sources
PubMed2026

Scalable assembly of Ascaris mitogenomes from whole-genome data reveals a novel clade.

The genus Ascaris is an important group of giant parasitic roundworms, infecting over 700 million people globally and causing substantial economic losses in domestic pigs. Whilst species of Ascaris are morphologically indistinguishable, analysis of mitochondrial loci has revealed three clades (A, B, C) broadly associated with host species and geographic distribution. The diversity within these lineages may expand with the addition of further genomic data. Here, we present a bioinformatic framework for de novo assembly of complete mitochondrial genomes (mitogenomes) from low-coverage whole-genome data through host-read depletion or mtDNA read enrichment, followed by mtDNA-specific assembly. Our approach yielded 149 high-quality Ascaris mitogenome assemblies, enabling the study of population-level diversity, including the identification of a novel clade (Clade D, designated here) associated with human samples from Ethiopia. Our analysis further revealed Clade C to comprise of pig-derived samples from Europe based on characterisation of worms isolated in Germany. The methods described here provide a scalable framework for mitogenome reconstruction with insights into roundworm population-genomic and phylogenetic studies.

Animals↗
PubMed2006

Morbidity due to Schistosoma mansoni: an epidemiological assessment of distended abdomen syndrome in Ugandan school children with observations before and 1-year after anthelminthic chemotherapy.

The objectives of this study were to determine the prevalence and distribution of distended abdomens among Ugandan school children across a range of eco-epidemiological settings and to investigate the relationship between distended abdomens and helminth infections, in particular Schistosoma mansoni, before and 1-year after anthelminthic treatment. A cross-sectional survey was conducted on 4354 school children across eight districts, with a longitudinal 1-year follow-up of 2644 children (60.7%). On both occasions, parasitological, biometrical and clinical data were collected for each child. Baseline prevalence of S. mansoni and hookworms was 44.3% and 51.8%, respectively. Distended abdomens, defined as an abdominal circumference ratio (ACR) >1.05, were observed in 2.5% of the sampled children, several of whom presented with particularly severe distensions necessitating hospital referral. ACR scores were highly overdispersed between districts and schools. Multivariate regression analysis revealed that S. mansoni infection accounted for only a small fraction of ACR variation, suggesting that either single point prevalence and intensity measures failed to reflect this more chronically evolved morbidity and/or that other interacting factors were involved, e.g. malnutrition and malaria. At 1-year follow-up, ACR scores showed an overall trend of regression towards the mean, potentially indicative of amelioration following chemotherapy, but geographic overdispersion still remained.

Abdomen↗
PubMed2006

Morbidity indicators of Schistosoma mansoni: relationship between infection and anemia in Ugandan schoolchildren before and after praziquantel and albendazole chemotherapy.

The potential relationship between Schistosoma mansoni and anemia was examined using data obtained by the Schistosomiasis Control Initiative (SCI) before (baseline) and 1 year after (follow-up) a chemotherapeutic treatment program in Uganda. Changes in hemoglobin (Hb) levels in 2,788 children in relation to their schistosomiasis and/or hookworm infection intensity category and baseline anemia status were analyzed. At baseline, significant predictors of childhood anemia were intensities of S. mansoni and hookworm infection. At follow-up, moderate or heavy hookworm as well as heavy S. mansoni infections were important. Children heavily infected with S. mansoni or hookworm had significantly lower Hb counts at baseline compared with those not infected. Among anemic children at the baseline survey, a significant increase in Hb counts of 0.834 g/dL after treatment was found. Our results suggest that anemia is associated with schistosomiasis and hookworm in Ugandan children and that such anemia shows a significant improvement after chemotherapy.

Adolescent↗
PubMed2005

Use of circulating cathodic antigen (CCA) dipsticks for detection of intestinal and urinary schistosomiasis.

An evaluation of a commercially available antigen capture dipstick that detects schistosome circulating cathodic antigen (CCA) in urine was conducted in representative endemic areas for intestinal and urinary schistosomiasis in Uganda and Zanzibar, respectively. Under field-based conditions, the sensitivity (SS) and specificity (SP) of the dipstick was 83 and 81% for detection of Schistosoma mansoni infections while positive predictive (PPV) and negative predictive values (NPV) were 84%. Light egg-positive infections were sometimes CCA-negative while CCA-positives included egg-negative children. A positive association between faecal egg output and intensity of CCA test band was observed. Estimating prevalence of intestinal schistosomiasis by school with dipsticks was highly correlated (r=0.95) with Kato-Katz stool examinations, typically within +/-8.5%. In Zanzibar, however, dipsticks totally failed to detect S. haematobium despite examining children with egg-patent schistosomiasis. This was also later corroborated by further surveys in Niger and Burkina Faso. Laboratory testing of dipsticks with aqueous adult worm lysates from several reference species showed correct functioning, however, dipsticks failed to detect CCA in urine from S. haematobium-infected hamsters. While CCA dipsticks are a good alternative, or complement, to stool microscopy for field diagnosis of intestinal schistosomiasis, they have no proven value for field diagnosis of urinary schistosomiasis. At approximately 2.6 US dollars per dipstick, they are presently too expensive to be cost-effective for wide scale use in disease mapping surveys unless Lot Quality Assurance Sampling (LQAS) strategies are developed.

Animals↗
PubMed2005

Progress towards countrywide control of schistosomiasis and soil-transmitted helminthiasis in Uganda.

Schistosomiasis caused by infection with Schistosoma mansoni is a serious public health burden in 38 of the 56 districts of Uganda. This article reviews the initial experience of the national control programme. Launched in 2003, this started with a pilot phase with the main aim of utilizing the experience to formulate feasible and appropriate methods of drug delivery. Overall, 432,746 people were treated and coverage was 91.4% in schools and 64.7% in communities. The issues raised by independent evaluators included that most communities did not participate in the selection of community drug distributors (CDD) and that teachers and CDDs needed refresher training mainly on health education and the management of side effects. As a way forward, it is suggested that the Ministry of Health should integrate deworming into the existing health infrastructure so that every time a child is reached for any health service, the child is also de-wormed.

Adolescent↗
PubMed2005

Rapid assessment of Schistosoma mansoni: the validity, applicability and cost-effectiveness of the Lot Quality Assurance Sampling method in Uganda.

Rapid and accurate identification of communities at highest risk of morbidity from schistosomiasis is key for sustainable control. Although school questionnaires can effectively and inexpensively identify communities with a high prevalence of Schistosoma haematobium, parasitological screening remains the preferred option for S. mansoni. To help reduce screening costs, we investigated the validity of Lot Quality Assurance Sampling (LQAS) in classifying schools according to categories of S. mansoni prevalence in Uganda, and explored its applicability and cost-effectiveness. First, we evaluated several sampling plans using computer simulation and then field tested one sampling plan in 34 schools in Uganda. Finally, cost-effectiveness of different screening and control strategies (including mass treatment without prior screening) was determined, and sensitivity analysis undertaken to assess the effect of infection levels and treatment costs. In identifying schools with prevalences > or =50%, computer simulations showed that LQAS had high levels of sensitivity and specificity (>90%) at sample sizes <20. The method also provides an ability to classify communities into three prevalence categories. Field testing showed that LQAS where 15 children were sampled had excellent diagnostic performance (sensitivity: 100%, specificity: 96.4%, positive predictive value: 85.7% and negative predictive value: 92.3%). Screening using LQAS was more cost-effective than mass treating all schools (US$218 vs. US$482/high prevalence school treated). Threshold analysis indicated that parasitological screening and mass treatment would become equivalent for settings where prevalence > or =50% in 75% of schools and for treatment costs of US$0.19 per schoolchild. We conclude that, in Uganda, LQAS provides a rapid, valid and cost-effective method for guiding decision makers in allocating finite resources for the control of schistosomiasis.

Adolescent↗
PubMed2005

Field evaluation of the Meade Readiview handheld microscope for diagnosis of intestinal schistosomiasis in Ugandan school children.

A novel, inexpensive handheld microscope, the Meade Readiview, was evaluated for field diagnosis of intestinal schistosomiasis by comparison of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) against conventional compound microscopy as part of a parasitologic survey in nine sentinel schools and a rapid mapping survey across 22 schools in Uganda. Fecal smears from 685 primary school children were examined and the overall prevalence of Schistosoma mansoni was 45%. However, prevalence by school ranged widely from 0% to 100%. For individual diagnosis the Readiview had a sensitivity of 85%, a specificity of 96%, a PPV of 95%, and an NPV of 88%. Due to the poorer movement control of the glass slide on the Readiview stage, fecal smears with less than four eggs could be overlooked. At the highest magnification (160x), egg-like objects could be confounding. Estimating prevalence by school was usually within +/- 7% of that of conventional microscopy. Since the Readiview is more robust and portable, both in size and weight, and one-tenth as expensive as the traditional compound microscope, a change in the logistics and costs associated with field infection surveillance is possible. This inexpensive microscope is a pragmatic alternative to the compound microscope. It could play an important role in the collection of prevalence data to better guide anthelmintic drug delivery and also empower the diagnostic capacity of peripheral health centers where compound microscopes are few or absent.

Animals↗
PubMed2004

An investigation of the "Ancyloplanorbidae" (Gastropoda, Pulmonata, Hygrophila): preliminary evidence from DNA sequence data.

The Planorbidae is the largest family of freshwater pulmonate snails, yet an understanding of their intrafamily phylogenetic relationships is lacking and existing inferences are tentative. Moreover, it has been suggested that the Ancylidae, limpet-like freshwater pulmonates, should be merged with Planorbidae according to analysis of internal organ morphology. The present study explicitly tests this hypothesis by phylogenetic inference from partial DNA sequences of three molecular markers, nuclear ribosomal small subunit 18S and the mitochondrial cytochrome oxidase, and large subunit 16S. A molecular phylogeny was inferred based upon 22 taxa representing 12 ancylid and planorbid genera; additional taxa were included from the authors' database and from available sequences from GenBank, to further explore this basic data set. Taxa from Acroloxidae, Lymnaeidae, and Physidae were used as outgroups. Ancylidae and Planorbidae were found to be paraphyletic, with Planorbidae including some members of Ancylidae. "Ancyloplanorbidae" was also found to be paraphyletic because Acroloxus (Acroloxidae) surprisingly was included. Burnupia was found to be ancestral to "Ancyloplanorbidae" (including Acroloxus). The following clades of Planorbidae were supported: Bulininae and Planorbinae, Biomphalarini (including Helisoma and Planorbarius), and Planorbini and Segmentini.

Animals↗
PubMed2003

Mechanism of genetic exchange in American trypanosomes.

The kinetoplastid Protozoa are responsible for devastating diseases. In the Americas, Trypanosoma cruzi is the agent of Chagas' disease--a widespread disease transmissible from animals to humans (zoonosis)--which is transmitted by exposure to infected faeces of blood-sucking triatomine bugs. The presence of genetic exchange in T. cruzi and in Leishmania is much debated. Here, by producing hybrid clones, we show that T. cruzi has an extant capacity for genetic exchange. The mechanism is unusual and distinct from that proposed for the African trypanosome, Trypanosoma brucei. Two biological clones of T. cruzi were transfected to carry different drug-resistance markers, and were passaged together through the entire life cycle. Six double-drug-resistant progeny clones, recovered from the mammalian stage of the life cycle, show fusion of parental genotypes, loss of alleles, homologous recombination, and uniparental inheritance of kinetoplast maxicircle DNA. There are strong genetic parallels between these experimental hybrids and the genotypes among natural isolates of T. cruzi. In this instance, aneuploidy through nuclear hybridization results in recombination across far greater genetic distances than mendelian genetic exchange. This mechanism also parallels genome duplication.

Animals↗