Tags

Type your tag names separated by a space and hit enter

Predicting the impact of outdoor vector control interventions on malaria transmission intensity from semi-field studies.
Parasit Vectors. 2021 Jan 20; 14(1):64.PV

Abstract

BACKGROUND

Semi-field experiments with human landing catch (HLC) measure as the outcome are an important step in the development of novel vector control interventions against outdoor transmission of malaria since they provide good estimates of personal protection. However, it is often infeasible to determine whether the reduction in HLC counts is due to mosquito mortality or repellency, especially considering that spatial repellents based on volatile pyrethroids might induce both. Due to the vastly different impact of repellency and mortality on transmission, the community-level impact of spatial repellents can not be estimated from such semi-field experiments.

METHODS

We present a new stochastic model that is able to estimate for any product inhibiting outdoor biting, its repelling effect versus its killing and disarming (preventing host-seeking until the next night) effects, based only on time-stratified HLC data from controlled semi-field experiments. For parameter inference, a Bayesian hierarchical model is used to account for nightly variation of semi-field experimental conditions. We estimate the impact of the products on the vectorial capacity of the given Anopheles species using an existing mathematical model. With this methodology, we analysed data from recent semi-field studies in Kenya and Tanzania on the impact of transfluthrin-treated eave ribbons, the odour-baited Suna trap and their combination (push-pull system) on HLC of Anopheles arabiensis in the peridomestic area.

RESULTS

Complementing previous analyses of personal protection, we found that the transfluthrin-treated eave ribbons act mainly by killing or disarming mosquitoes. Depending on the actual ratio of disarming versus killing, the vectorial capacity of An. arabiensis is reduced by 41 to 96% at 70% coverage with the transfluthrin-treated eave ribbons and by 38 to 82% at the same coverage with the push-pull system, under the assumption of a similar impact on biting indoors compared to outdoors.

CONCLUSIONS

The results of this analysis of semi-field data suggest that transfluthrin-treated eave ribbons are a promising tool against malaria transmission by An. arabiensis in the peridomestic area, since they provide both personal and community protection. Our modelling framework can estimate the community-level impact of any tool intervening during the mosquito host-seeking state using data from only semi-field experiments with time-stratified HLC.

Authors+Show Affiliations

Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland. adrian.denz@unibas.ch. University of Basel, Petersplatz 1, Basel, Switzerland. adrian.denz@unibas.ch.Human Health Theme, International Centre of Insect Physiology and Ecology (icipe), 00100, Nairobi, Kenya. Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland. University of Basel, Petersplatz 1, Basel, Switzerland.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania. School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa. School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania. Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands. ARCTEC, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK.Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland. University of Basel, Petersplatz 1, Basel, Switzerland. Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.Human Health Theme, International Centre of Insect Physiology and Ecology (icipe), 00100, Nairobi, Kenya.Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland. University of Basel, Petersplatz 1, Basel, Switzerland. Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland. University of Basel, Petersplatz 1, Basel, Switzerland.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

33472661

Citation

Denz, Adrian, et al. "Predicting the Impact of Outdoor Vector Control Interventions On Malaria Transmission Intensity From Semi-field Studies." Parasites & Vectors, vol. 14, no. 1, 2021, p. 64.
Denz A, Njoroge MM, Tambwe MM, et al. Predicting the impact of outdoor vector control interventions on malaria transmission intensity from semi-field studies. Parasit Vectors. 2021;14(1):64.
Denz, A., Njoroge, M. M., Tambwe, M. M., Champagne, C., Okumu, F., van Loon, J. J. A., Hiscox, A., Saddler, A., Fillinger, U., Moore, S. J., & Chitnis, N. (2021). Predicting the impact of outdoor vector control interventions on malaria transmission intensity from semi-field studies. Parasites & Vectors, 14(1), 64. https://doi.org/10.1186/s13071-020-04560-x
Denz A, et al. Predicting the Impact of Outdoor Vector Control Interventions On Malaria Transmission Intensity From Semi-field Studies. Parasit Vectors. 2021 Jan 20;14(1):64. PubMed PMID: 33472661.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Predicting the impact of outdoor vector control interventions on malaria transmission intensity from semi-field studies. AU - Denz,Adrian, AU - Njoroge,Margaret M, AU - Tambwe,Mgeni M, AU - Champagne,Clara, AU - Okumu,Fredros, AU - van Loon,Joop J A, AU - Hiscox,Alexandra, AU - Saddler,Adam, AU - Fillinger,Ulrike, AU - Moore,Sarah J, AU - Chitnis,Nakul, Y1 - 2021/01/20/ PY - 2020/07/17/received PY - 2020/12/21/accepted PY - 2021/1/21/entrez PY - 2021/1/22/pubmed PY - 2021/8/6/medline KW - Anopheles arabiensis KW - Community-level impact KW - Hierarchical Bayesian model KW - Malaria KW - Outdoor transmission KW - Semi-field experiments KW - Spatial repellent KW - Stochastic modelling KW - Vector control KW - Volatile pyrethroids SP - 64 EP - 64 JF - Parasites & vectors JO - Parasit Vectors VL - 14 IS - 1 N2 - BACKGROUND: Semi-field experiments with human landing catch (HLC) measure as the outcome are an important step in the development of novel vector control interventions against outdoor transmission of malaria since they provide good estimates of personal protection. However, it is often infeasible to determine whether the reduction in HLC counts is due to mosquito mortality or repellency, especially considering that spatial repellents based on volatile pyrethroids might induce both. Due to the vastly different impact of repellency and mortality on transmission, the community-level impact of spatial repellents can not be estimated from such semi-field experiments. METHODS: We present a new stochastic model that is able to estimate for any product inhibiting outdoor biting, its repelling effect versus its killing and disarming (preventing host-seeking until the next night) effects, based only on time-stratified HLC data from controlled semi-field experiments. For parameter inference, a Bayesian hierarchical model is used to account for nightly variation of semi-field experimental conditions. We estimate the impact of the products on the vectorial capacity of the given Anopheles species using an existing mathematical model. With this methodology, we analysed data from recent semi-field studies in Kenya and Tanzania on the impact of transfluthrin-treated eave ribbons, the odour-baited Suna trap and their combination (push-pull system) on HLC of Anopheles arabiensis in the peridomestic area. RESULTS: Complementing previous analyses of personal protection, we found that the transfluthrin-treated eave ribbons act mainly by killing or disarming mosquitoes. Depending on the actual ratio of disarming versus killing, the vectorial capacity of An. arabiensis is reduced by 41 to 96% at 70% coverage with the transfluthrin-treated eave ribbons and by 38 to 82% at the same coverage with the push-pull system, under the assumption of a similar impact on biting indoors compared to outdoors. CONCLUSIONS: The results of this analysis of semi-field data suggest that transfluthrin-treated eave ribbons are a promising tool against malaria transmission by An. arabiensis in the peridomestic area, since they provide both personal and community protection. Our modelling framework can estimate the community-level impact of any tool intervening during the mosquito host-seeking state using data from only semi-field experiments with time-stratified HLC. SN - 1756-3305 UR - https://www.unboundmedicine.com/medline/citation/33472661/Predicting_the_impact_of_outdoor_vector_control_interventions_on_malaria_transmission_intensity_from_semi_field_studies_ L2 - https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-020-04560-x DB - PRIME DP - Unbound Medicine ER -