Papers by Margaret Pinder
Malaria Journal, Oct 6, 2020
Following publication of the original article [1], the authors reported an error in one of the co... more Following publication of the original article [1], the authors reported an error in one of the coordinates provided in the subsection 'Study design and study area'. Where it says "10° 31′ 6.07″ N, 4° 18′ 48.01″ E", it should instead say "10° 31′ 6.07″ N, 4° 18′ 48.01″ W" (that is, West instead of East). Similarly, where is says "10° 36′ 17.56″ N, 4° 22′ 22.17″ E", it should instead say "10° 36′ 17.56″ N, 4° 22′ 22.17″ W" (that is, West instead of East).
Malaria Journal, Dec 1, 2019
Background: Long-lasting insecticidal nets (LLINs) treated with pyrethroids are the foundation of... more Background: Long-lasting insecticidal nets (LLINs) treated with pyrethroids are the foundation of malaria control in sub-Saharan Africa. Rising pyrethroid resistance in vectors, however, has driven the development of alternative net formulations. Here the durability of polyethylene nets with a novel combination of a pyrethroid, permethrin, and the insect juvenile hormone mimic, pyriproxyfen (PPF), compared to a standard permethrin LLIN, was assessed in rural Burkina Faso. Methods: A compound-randomized controlled trial was completed in two villages. In one village 326 of the PPFpermethrin nets (Olyset Duo) and 327 standard LLINs (Olyset) were distributed to assess bioefficacy. In a second village, 170 PPF-permethrin nets and 376 LLINs were distributed to assess survivorship. Nets were followed at 6-monthly intervals for 3 years. Bioefficacy was assessed by exposing permethrin-susceptible and resistant Anopheles gambiae sensu lato mosquito strains to standard World Health Organization (WHO) cone and tunnel tests with impacts on fertility measured in the resistant strain. Insecticide content was measured using high-performance liquid chromatography. LLIN survivorship was recorded with a questionnaire and assessed by comparing the physical integrity using the proportionate hole index (pHI). Results: The PPF-permethrin net met WHO bioefficacy criteria (≥ 80% mortality or ≥ 95% knockdown) for the first 18 months, compared to 6 months for the standard LLIN. Mean mosquito mortality for PPF-permethrin nets, across all time points, was 8.6% (CI 2.6-14.6%) higher than the standard LLIN. Fertility rates were reduced after PPF-permethrin net exposure at 1-month post distribution, but not later. Permethrin content of both types of nets remained within the target range of 20 g/kg ± 25% for 242/248 nets tested. The pyriproxyfen content of PPF-permethrin nets declined by 54%, from 10.4 g/kg (
Malaria Journal, Oct 21, 2022
Background: The housing stock of rural sub-Saharan Africa is changing rapidly. With millions of n... more Background: The housing stock of rural sub-Saharan Africa is changing rapidly. With millions of new homes required over the coming decades, there is an opportunity to protect residents by screening homes from malaria mosquitoes. This study, undertaken in the Upper River Region of The Gambia, explores local perceptions of what a good house should provide for its inhabitants and responses to living in a house that has been modified as part of a randomized control trial designed to assess whether improved housing provided additional protection against clinical malaria in children (the RooPfs trial). Methods: This descriptive, exploratory study was undertaken over 22 months using mixed-methods (informal conversations, observations, focus group discussions, photovoice, and a questionnaire survey) in a parallel convergent design. Analysis was conducted across the data sets using a framework approach. Following coding, the textual data were charted by a priori and emerging themes. These themes were compared with the quantitative survey results. The nature and range of views about housing and the RooPfs study modifications and the relationships among them were identified and described. Results: The data were derived from a total of 35 sets of observations and informal conversations in 10 villages, 12 discussions with the photovoice photographers, 26 focus group discussions (across 13 villages) and 391 completed questionnaires. The study participants described a 'good house' as one with a corrugate-metal roof, cement walls (preferably cement block, but mud block covered with cement plaster was also an acceptable and cheaper substitute) and well-fitting doors. These features align with local perceptions of a modern house that provides social status and protection from physical harms. The RooPfs modifications were largely appreciated, although poor workmanship caused concerns that houses had become insecure. However, the long-term trusting relationship with the implementing institution and the actions taken to rectify problems provided reassurance and enhanced acceptability. Conclusion: In developing housing to address population needs in Africa, attention should be paid to local perceptions of what is required to make a house secure for its inhabitants, as well as providing a healthy environment.
Clinical science. Supplement (1979), Jul 1, 2002
Human Genetics, Mar 1, 2004
Malaria Journal, Jul 13, 2020
Background: Recording behaviours that have the potential to impact health can be doubly challengi... more Background: Recording behaviours that have the potential to impact health can be doubly challenging if the behaviour takes place in private spaces that cannot be observed directly, and where respondents answer what they think the recorder may want to hear. Sleeping under a long-lasting insecticidal net (LLIN) is an important intervention for malaria prevention, yet it is difficult to gauge the extent to which coverage (how many nets are in the community) differs from usage (how many people actually sleep under a net). List randomization, a novel method which partially obscures respondents' answers to sensitive questions, was employed to estimate LLIN usage in The Gambia. Methods: 802 heads-of-household from 15 villages were recruited into a randomized controlled trial assessing the effect of a housing intervention on malaria. These houses were randomly assigned to a housing intervention versus control, with stratification by village so as to ensure balance between arms. From these, 125 households (63 intervention, 52 control) were randomly selected for participation in the list randomization experiment, along with 68 households from the same villages but which were not part of the housing improvement study, resulting in a total of 196 households for the list randomization experiment. Approximately half (n = 97) of the 196 study participants were randomly assigned to the control group and received a four-question list about non-sensitive behaviours; the intervention group (n = 99) received the same list, with the addition of one question on a sensitive behaviour: whether or not they had used a bed net the previous night. Participants were read the list of questions and then said how many of the statements were true. Bed net usage was estimated by calculating the difference in means between the number of affirmative responses between the two groups. Results: The mean number of affirmative responses in the control group was 2.60 of four statements (95% confidence interval, 95% CI 2.50-2.70), compared with 3.68 (95% CI 3.59-3.78) in the intervention group. Such difference (1.08; 95% CI 94.9-100%) suggests near universal bed net usage. Conclusions: Bed net usage by household heads in these rural villages was found to be high. Though not entirely unexpected given other studies' estimates of high bed net usage in the area, the list randomization method should be further validated in an area with lower coverage.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is believed to confer protection against Plas... more Glucose-6-phosphate dehydrogenase (G6PD) deficiency is believed to confer protection against Plasmodium falciparum malaria, but the precise nature of the protective effect has proved difficult to define as G6PD deficiency has multiple allelic variants with different effects in males and females, and it has heterogeneous effects on the clinical outcome of P. falciparum infection. Here we report an analysis of multiple allelic forms of G6PD deficiency in a large multicentre case-control study of severe malaria, using the WHO classification of G6PD mutations to estimate each individual's level of enzyme activity from their genotype. Aggregated across all genotypes, we find that increasing levels of G6PD deficiency are associated with decreasing risk of cerebral malaria, but with increased risk of severe malarial anaemia. Models of balancing selection based on these findings indicate that an evolutionary trade-off between different clinical outcomes of P. falciparum infection could have been a major cause of the high levels of G6PD polymorphism seen in human populations.
Environmental Epigenetics in Toxicology and Public Health, 2020
The ability of the filarial nematode Loa loa to infect 2 species of primates was studied. The pri... more The ability of the filarial nematode Loa loa to infect 2 species of primates was studied. The primate species selected were closely related to species known to be susceptible. A mandrill (Mandrillus sphinx) and 6 cynomolgus monkeys (Macaca fascicularis) were infected by subcutaneous injection of third-stage larvae of human L. loa from Gabon. The mandrill developed microfilaremia with an estimated prepatent period of 147 days, but microfilariae were not detected in any of the cynomolgus monkeys. Thus, mandrills appear permissive to human L. loa, whereas cynomolgus monkeys are not. Serum antibody responses were examined on western blots of adult L. loa antigens. Preinfection sera from all animals gave no reactions, but, after infection, sera from cynomolgus monkeys reacted more intensely and with more antigens than mandrill sera. Antibodies were still detectable in cynomolgus monkeys 15 mo postin- fection. These reactions were compared with those found using human infection sera. Reac...
Methods of Information in Medicine, 2006
Summary Objectives: Computers are widely used for data management in clinical trials in the devel... more Summary Objectives: Computers are widely used for data management in clinical trials in the developed coutries, unlike in developing countries. Dependable systems are vital for data management, and medical decision making in clinical research. Monitoring and evaluation of data management is critical.In this paper we describe database structures and procedures of systems used to implement, coordinate, and sustain data management in Africa. We outline major lessons, challenges and successes achieved, and recommendations to improve medical informatics application in biomedical research in sub-Saharan Africa. Methods: A consortium of experienced research units at five sites in Africa in studying children with disease formed a new clinical trials network, Severe Malaria in African Children. In December 2000, the network introduced an observational study involving these hospital-based sites. After prototyping, relational database management systems were implemented for data entry and veri...
Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), 1992
The full length cDNA of the immunodominant Ov33 protein of Onchocerca volvulus was expressed in E... more The full length cDNA of the immunodominant Ov33 protein of Onchocerca volvulus was expressed in E. coli using various vector constructs. Expression was best with the vectors pGEX2T and pCG808fx, yielding fusion protein Ov33-GST and Ov33-MBP, respectively. Purified fusion protein Ov33-GST and O. volvulus antigen extracts (OvAg) were used to compare antibody responses (IgM and IgG-subclasses) of patients infected with O. volvulus, Brugia malayi, Wuchereria bancrofti, Mansonella perstans/Loa loa and of Sudanese control sera. Sera of all groups contained IgM reacting with Ov33-GST and with OvAg. There was no IgG1 response to Ov33-GST. IgG1 responses to OvAg were only detected in filariasis sera. IgG2 and IgG3 responses were not detectable or marginal in all groups. The IgG4 reaction of onchocerciasis patients to Ov33-GST and to OvAg was high, whereas few other filariasis sera contained IgG4 antibodies to Ov33-GST and to OvAg. A serodiagnostic test for onchocerciasis based on detection o...
Copyright information: Taken from "Chloroquine/Sulphadoxine-Pyrimethamine for Gambian Childr... more Copyright information: Taken from "Chloroquine/Sulphadoxine-Pyrimethamine for Gambian Children with Malaria: Transmission to Mosquitoes of Multidrug-Resistant "PLoS Clinical Trials 2006;1(3):-.Published online 21 Jul 2006PMCID:PMC1513405. © 2006 Hallett et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Bars represent prevalence of gametocyte carriage, with error bars showing 95% CIs. Lines represent arithmetic mean gametocyte density in carriers only.
Journal of the Royal Society Interface, Apr 1, 2023
Rural houses in sub-Saharan Africa are typically hot and allow malaria mosquitoes inside. We asse... more Rural houses in sub-Saharan Africa are typically hot and allow malaria mosquitoes inside. We assessed whether passive or active ventilation can reduce house entry of malaria mosquitoes and cool a bedroom at night in rural Gambia. Two identical experimental houses were used: one ventilated and one unventilated (control). We evaluated the impact of (i) passive ventilation (solar chimney) and (ii) active ventilation (ceiling fan) on the number of mosquitoes collected indoors and environmental parameters (temperature, humidity, CO 2 , evaporation). Although the solar chimney did not reduce entry of Anopheles gambiae sensu lato , the ceiling fan reduced house entry by 91% compared with the control house. There were no differences in indoor nightly temperature, humidity or CO 2 between intervention and control houses in either experiment. The solar chimney did not improve human comfort assessed using psychrometric analysis. While the ceiling fan improved human comfort pre-midnight, in the morning it was too cool compared with the control house, although this could be remedied through provision of blankets. Further improvements to the design of the solar chimney are needed. High air velocity in the ceiling fan house probably reduced mosquito house entry by preventing mosquito flight. Improved ventilation in houses may reduce malaria transmission.
American Journal of Tropical Medicine and Hygiene, Jul 1, 2003
In a randomized controlled trial, chloroquine monotherapy was compared with the combination of ar... more In a randomized controlled trial, chloroquine monotherapy was compared with the combination of artesunate and chloroquine for treating uncomplicated Plasmodium falciparum malaria in 536 Gambian children. Chloroquine-treated children exhibited a 28-day clinical failure rate of 15% (95% confidence interval [CI] ס 9.2−22%) compared with 11% (7.8−15%) among children receiving the combination (P ס 0.08, by Wilcoxon test). Seventy-three percent of chloroquine-treated children exhibited parasitemia during follow-up compared with 49% of children receiving the combination (relative risk ס 1.5, 95% CI ס 1.3−1.7; 2 ס 21.18, P < 0.001). A significant reduction in clinical and parasitologic treatment failure in the combination group occurred in the first two weeks following treatment, but this was eroded over weeks three and four of follow-up. The impact of combination therapy on the transmission of chloroquineresistant parasites is discussed. Chloroquine plus artesunate is not sufficiently efficacious to justify its introduction as a replacement for chloroquine monotherapy in The Gambia.
The Journal of Immunology
The mechanism(s) of resistance to African trypanosomiasis caused by Trypanosoma congolense was in... more The mechanism(s) of resistance to African trypanosomiasis caused by Trypanosoma congolense was investigated by using the Dinderesso/80/CRTA/3 isolate to which C57B1/6 are resistant (low parasitemia and self-cure) and BALB/c sensitive (high parasitemia and death). The resistance of C57B1/6 is similar to that found in some natural hosts of African trypanosomes such as certain indigenous West African cattle and wild Bovidae. The antibody response to epitopes exposed on the variant surface glycoprotein of a clone obtained from the Dinderesso/80/CRTA/3 isolate was measured by a complement-mediated lysis assay in C57B1/6 and BALB/c. After infections with 10(4), 10(5), or 10(7) motile organisms, antibody appeared in C57B1/6 4 to 8 days earlier than in BALB/c. Peak antibody titers were similar in both strains but were reached about 4 days earlier in C57B1/6. In this strain, antibody appeared during and controlled the first wave of parasitemia, whereas in BALB/c, parasitemia reached a platea...
The Journal of Immunology
... 389 Page 2. 390 MARGARET PINDER, KATHLEEN S. WITHEY, ANDGEORGES E. ROELANTS [VOL. 127 ... 6. ... more ... 389 Page 2. 390 MARGARET PINDER, KATHLEEN S. WITHEY, ANDGEORGES E. ROELANTS [VOL. 127 ... 6. 7. 8. 9. 10. 11. 12. 13. 14. Brown, C. D. G.. DA Stagg. R. E. Purnell, GK Kanhai. and R. C. Payne. infective particles of Theileria parva. Nature 254:lOl. 1973. ...
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Papers by Margaret Pinder