Assessing the impact of the addition of pyriproxyfen on the durability of permethrin-treated bed nets in Burkina Faso: a compound-randomized controlled trial

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 PPF-permethrin 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 (CI 10.2–10.6) to 4.7 g/kg (CI 3.5–6.0, p < 0.001) over 36 months. Net survivorship was poor, with only 13% of PPF-permethrin nets and 12% of LLINs still present in the original household after 36 months. There was no difference in the fabric integrity or survivorship between the two net types. Conclusion The PPF-permethrin net, Olyset Duo, met or exceeded the performance of the WHO-recommended standard LLIN (Olyset) in the current study but both net types failed the 3-year WHO bioefficacy criteria

Contextual and individual factors associated with dental services utilisation by Brazilian adults: A multilevel analysis

BACKGROUND: Inequalities in the utilisation of dental services in Brazil are remarkable. The aim of this study was to evaluate the association of contextual and individual factors with the utilisation of dental services by Brazilian adults using the Andersen's behavioural model. METHODS: Individual-level data from 27,017 adults residents in the State capitals who were interviewed in the 2013 Brazilian National Health Survey were pooled with contextual city-level data. The outcomes were non-utilisation of dental services and last dental visit over 12 months ago. Individual predisposing variables were age, sex, race/skin colour, schooling and social network. Individual enabling variables included income, health insurance and registration in primary health care. Individual need variables were self-perceived dental health and self-reported missing teeth. Multilevel logistic regression models were performed to estimate odds ratio (OR) and 95% confidence intervals (95% CIs) of the association of contextual and individual predisposing, enabling and need-related variables with dental services outcomes. RESULTS: Predisposing (OR = 0.89; 95% CI 0.81-0.97) and enabling (OR = 0.90; 95% CI 0.85-0.96) contextual factors were associated with non-utilisation of dental services. Individual predisposing (sex, race/skin colour, schooling), enabling (income, health insurance) and need (self-perceived oral health, missing teeth) were associated with non-utilisation of dental services and last dental visit over 12 months ago. The latter was also associated with other individual predisposing (age, social network) and need (eating difficulties due to oral problems) characteristics. CONCLUSIONS: Individual and contextual determinants influenced dental services utilisation in Brazilian adults. These factors should be on the policy agenda and considered in the organisation of health services aiming to reduce oral health inequalities related to access and utilisation of dental services

Midgut expression of immune-related genes in Glossina palpalis gambiensis challenged with Trypanosoma brucei gambiense

Tsetse flies from the subspecies Glossina morsitans morsitans and Glossina palpalis gambiensis, respectively, transmit Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense. The former causes the acute form of sleeping sickness, and the latter provokes the chronic form. Although several articles have reported G. m. morsitans gene expression following trypanosome infection, no comparable investigation has been performed for G. p. gambiensis. This report presents results on the differential expression of immune-related genes in G. p. gambiensis challenged with T. b. gambiense. The aim was to characterize transcriptomic events occurring in the tsetse gut during the parasite establishment step, which is the crucial first step in the parasite development cycle within its vector. The selected genes were chosen from those previously shown to be highly expressed in G. m. morsitans, to allow further comparison of gene expression in both Glossina species. Using quantitative PCR, genes were amplified from the dissected midguts of trypanosome-stimulated, infected, non-infected, and self-cleared flies at three sampling timepoints (3, 10, and 20 days) after a bloodmeal. At the 3-day sampling point, transferrin transcripts were significantly up-regulated in trypanosome-challenged flies versus flies fed on non-infected mice. In self-cleared flies, serpin-2 and thioredoxin peroxidase-3 transcripts were significantly up-regulated 10 days after trypanosome challenge, whereas nitric oxide synthase and chitin-binding protein transcripts were up-regulated after 20 days. Although the expression levels of the other genes were highly variable, the expression of immune-related genes in G. p. gambiensis appears to be a time-dependent process. The possible biological significance of these findings is discussed, and the results are compared with previous reports for G. m. morsitans

The transcriptional signatures of Sodalis glossinidius in the Glossina palpalis gambiensis flies negative for Trypanosoma brucei gambiense contrast with those of this symbiont in tsetse flies positive for the parasite : possible involvement of a Sodalis-hosted prophage in fly Trypanosoma refractoriness ?

Tsetse flies, such as Glossina palpalis gambiensis, are blood-feeding insects that could be subverted as hosts of the parasite Trypanosoma brucei gambiense: initiated in the tsetse fly mid gut, the developmental program of this parasite further proceeds in the salivary glands. The flies act as vectors of this human-invasive parasite when their salivary glands sustain the generation of metacyclic trypomastigotes, the exclusive morphotypes pre-programmed to further develop in the human individuals. Briefly, once the metacyclic trypomastigotes have been deposited in the skin of humans from whom the parasite-hosting tsetse flies are taking their blood meals, the complex developmental program of this Trypanosoma brucei subspecies can result in a severe disease named sleeping sickness. Unveiling the processes that could prevent, in tsetse flies, the developmental program of T. b. gambiense could contribute reducing the prevalence of the disease. Using a global approach, we were curious to extract transcriptional signatures of Sodalis glossinidius, a symbiont hosted by three distinct groups of tsetse flies. To meet this objective, the transcriptome of S. glossinidius from susceptible and refractory tsetse flies was analyzed at 3, 10 and 20 days after flies blood feed on T. b. gambiense-hosting mice. Within this temporal window, 176 trypanosome responsive genes were shown to interact in well-defined patterns making it possible to distinguish flies susceptible to the parasite infection from refractory flies. Among the modulated transcripts in the symbiont population of flies refractory to trypanosome infection many were shown to cluster within the following networks: "lysozyme activity, bacteriolytic enzyme, bacterial cytolysis, cell wall macromolecule catabolic process". These novel data are further delineated in the following questions: could the activation of prophage hosted by S. glossinidius lead to the release of bacterial agonists that trigger the tsetse fly immune system along a profile that no more allows the parasite developmental program? (C) 2014 Elsevier B.V. All rights reserved

Population dynamics of Glossina palpalis gambiensis symbionts, Sodalis glossinidius, and Wigglesworthia glossinidia, throughout host-fly development

The tsetse fly (Diptera: Glossinidae), the vector of trypanosomes causing human and animal trypanosomiasis, harbors symbiotic microorganisms including the primary symbiont Wigglesworthia glossinidia, involved in the fly's nutrition and fertility, and the secondary symbiont Sodalis glossinidius, involved in the trypanosome establishment in the fly's midgut Both symbionts are maternally transmitted to the intrauterine progeny through the fly's milk gland secretions. In this study, we investigated the population dynamics of these symbionts during fly development. Wigglesworthia and Sodalis densities were estimated using quantitative PCR performed on Glossina palpalis gambiensis at different developmental stages. The results showed that the density of the primary Wigglesworthia symbiont was higher than that of Sodalis for all host developmental stages. Sodalis densities remained constant in pupae, but increased significantly in adult flies. The opposite situation was observed for Wigglesworthia, whose density increased in pupae and remained constant during the female adult stage. Moreover, Wigglesworthia density increased significantly during the transition from the pupal to the teneral stage, while mating had a contradictory effect depending on the age of the fly. Finally, tsetse fly colonization by both symbionts appears as a continuous and adaptive process throughout the insect's development. Last, the study demonstrated both symbionts of G. p. gambiensis, the vector of the chronic form of human African trypanosomiasis, to be permanent inhabitants of the colony flies throughout their life span. This was expected for the primary symbiont, Wigglesworthia, but not necessarily for the secondary symbiont, S. glossinidius, whose permanent presence is not required for the fly's survival. This result is of importance as Sodalis could be involved in the tsetse fly vector competence and may constitute a target in the frame of sleeping sickness fighting strategies

To assess whether addition of pyriproxyfen to long-lasting insecticidal mosquito nets increases their durability compared to standard long-lasting insecticidal mosquito nets: study protocol for a randomised controlled trial

Background: The effectiveness of pyrethroid-treated bednets for malaria control in sub-Saharan Africa is under threat because of high levels of resistance to pyrethroid insecticides in the vectors. Here we assess the durability of polyethylene nets with a novel combination of permethrin, a pyrethroid, with pyriproxyfen, an insect juvenile mimic (PPF-LLIN), in comparison with a typical permethrin-treated long-lasting insecticidal net (LLIN). Methods: This is a cluster randomised controlled trial of net durability in Burkina Faso, with clustering at the level of the compound and includes entomological outcome measurements. Half the compounds in each village will be randomly allocated PPF-LLIN and half the LLIN. All sleeping places in a compound will be provided with one type of net. We will distribute the nets at the start of the first transmission season and follow net use at the start and end of each transmission season for 3 years. In one village, bio-efficacy and chemical content will be recorded immediately after net distribution and then at 6, 12, 18, 24, 30 and 36 months. In the other village net survivorship and fabric integrity will be recorded immediately after distribution, and then at 6, 12, 18, 24, 30 and 36 months. Routine measurements of indoor temperature and relative humidity will be made in both villages during the study. Residents will be followed for possible side effects of the PPF-LLIN by surveillance of known asthmatic subjects during the first month post-distribution and pregnancy outcomes will be monitored from antenatal clinic records. Discussion: The protocol is novel on two accounts. Firstly, it is the first to describe the procedure for measuring net durability following recent World Health Organisation (WHO) guidelines. Meeting the minimum requirements set in the guidelines is essential before a new type of net can be recommended by WHO’s Pesticide Evaluation Scheme (WHOPES). Secondly, it describes methods to monitor the persistence of an active ingredient that reduces vector fertility and fecundity. If the PPF-LLIN is both effective and persistent it will provide an alternative vector control strategy where pyrethroid-resistant vectors are present. Trial registration: ISRCTN30634670 webcite assigned 13 August 2014

Caractéristiques bioécologiques d'Anopheles gambiae s.s. en zones de riziculture irriguée au centre de la Côte d'Ivoire

Un suivi entomologique longitudinal de septembre 2008 à septembre 2009 a été réalisé à Abokro et Yaokoffikro, villages du centre de la Côte d’Ivoire, en zones de riziculture irriguée. L’objectif de notre étude était d’identifier quelques aspects bioécologiques des populations femelles d’Anopheles gambiae s.s. durant leur cycle gonotrophique. Les moustiques adultes ont été capturés par 72 pièges lumineux, sur sujets humains pour un effort de 72 hommes-nuits de 18 heures à 6 heures, et par pulvérisation intra-domiciliaire matinale de 60 chambres au pyrèthre. Au total, 10 312 et 7 662 moustiques adultes ont été capturés, respectivement à Abokro et Yaokoffikro. Dans les deux sites d’étude, le genre Anopheles était prépondérant. Les pièges lumineux ont été trois fois plus efficaces à Abokro qu’à Yaokoffikro. Dans les deux villages, les cycles d’agressivité des femelles d’An. gambiae s.s. ont évolué progressivement pour atteindre un pic entre minuit et 1 heure du matin. A Abokro, le comportement d’An. gambiae s.s. était fortement endophage et endophile avec un taux d’endophagie et une densité au repos respectivement égaux à 67,4 % (n = 4 798) et 14,9 femelles par chambre et par nuit. A Yaokoffikro, le comportement était indépendant de la maison, avec un taux d’endophagie et une densité respectifs de 49,3 % (n = 6 775) et 2,9 femelles par chambre et par jour