ELEONORA PERUGINI

Dottoressa di ricerca

ciclo: XXXIV



Titolo della tesi: Entomological factors contributing to sustain high malaria transmission despite insecticide treated bed net intervention: Evidences from a longitudinal survey in a rural village of Burkina Faso

INTRODUCTION: Long lasting insecticide treated bed nets (LLINs) are considered by WHO as the main malaria vector control strategy, with mass distribution campaigns recommended every three years in endemic countries. Since major malaria vectors are nocturnal and mainly anthropophilic, LLINs are used to target mosquitoes attempting to bite humans indoors by combining individual physical defence with the collective protection provided by the pyrethroid insecticides restrained in the net fibres. Despite LLINs have contributed to the 68% of the 663 million clinical cases prevented in Africa from 2000 to 2015, to date a stalling of progress in the fight against malaria has been registered in 10 sub-Saharan countries (accounting for approximately 70% of the world malaria burden), where malaria incidence remains still very high despite the large bed net coverage. Among many causal factors affecting this scenario, mosquito physiological resistance to insecticides is crucial but a non-negligible role is also played by behavioural strategies adopted by some vector species to elude the insecticidal effect of the net: increased zoophagy, outdoor biting and or altered biting rhythms diverted when humans are awake and not protected. Burkina Faso, where LLINs were introduced massively in 2010, is paradigmatic for the dramatic epidemiological situation and vector physiological insecticide resistance of West Africa. Nevertheless, sparse information about vector behavioural plasticity in response to LLINs are available for this country, as well as the role of entomological and human factors in sustaining the persistent high risk of malaria transmission. A preliminary entomological study conducted in 2011 in a rural village of Burkina Faso (Goden village) highlighted a reduced mosquito human blood index in favour of a higher zoophily, although it was observed high level of vector population infectivity: 6.4% for A. coluzzii and 4.4% for A. arabiensis. These values were then also confirmed in 2012 and, being in the range of those observed before LLIN implementation, they have clearly defined a scenario of a limited bed net effectiveness in the village. AIM OF THE THESIS: A longitudinal entomological survey has been conducted in Goden in the period 2011-2020, with the aim to explore factors which can concur in undermining LLIN efficacy in the village and to contextualize these parameters to malaria transmission risk over the years. For this purpose, it has been investigated vector population response to LLIN selective pressure by monitoring physiological resistant mechanisms and biting behaviours (i.e. host choice, biting rhythms and endo/exophagy). The implication of these factors in the transmission dynamics has been then analysed in the light of vectors infection status (sporozoite rate, SR and oocyst rate, OR), entomological inoculation rate (EIR) and human exposure to bites. MATERIALS AND METHODS: Different mosquito sampling methods were employed over the period 2011-2020 to analyse both resting and host seeking fractions of vector population in Goden village. Resting mosquito samplings were conducted by traps/aspiration (2011) and pyrethrum spray catches (2019) while host-seeking collections were performed by BG Sentinel traps (2019) and by Human Landing Catches (HLC) conducted in four central hours of the night (2015) as well as in whole period of mosquito activity from 16:00 to 8:00 (2020). All A. gambiae s.l. specimens were dissected in head/thorax and abdomen portions, processed for DNA extraction and then molecularly identified for the species. Abdomens of resting mosquitoes collected in 2019 were subjected to blood meal analysis and, together with the head/thorax of all collected females, were processed for Plasmodium sp. DNA detection to state vector infection status (infected or infective). A subsample of males and females collected in 2011, 2015 and 2019 was genotyped for two molecular markers of insecticide resistance: i) L1014F (Kdr-w) target site mutation and ii) 5 SNPs (single nucleotide polymorphisms) potentially associated with SAP2 chemosensory protein overexpression (through an in-house IMP-PCR protocol here designed), a protein acting sequestering pyrethroids in mosquito legs. Since up today SAP2 wasn’t found to be overexpressed in A. arabiensis, the species wasn’t processed for the analysis of this resistance. Finally, in the year 2020, a questionnaire was submitted to the inhabitants of half of village compounds to get information about timing of human daily activities (e.g. wake up/bed time) and net usage conditions. RESULTS and DISCUSSION: A. coluzzii and A. arabiensis were confirmed the dominant vector species in the village during the whole study period, as resulted by over 6,168 specimens currently subjected to species identification (out of over 21,000 captured). Malaria transmission risk remains consistently high over the years with an estimated EIR varying from a maximum of 9 infective bites/person -in a scenario of full human exposure during the whole mosquito biting period- to at least 1.6 infective bites/person considering the real net usage during the sleeping hours retrieved form the questionnaire. Interestingly, 0.35 infective bites/person occurred before 20:00 and after 6:00 when 100% of inhabitants are awake and thus fully exposed to bites. The high risk of malaria transmission observed in HLCs years of study, is due both to high mosquito density and infectivity. In particular, the two species showed an equal Human Biting Rate both indoors and outdoors, with a roughly homogeneous plateau of intense biting activity (mean of 20 mosquitoes/person/hour) from 22:00 to 5:00 and a significant lower but non negligible biting pressure (mean of 6.6 mosquitoes/person/hour) before and after this large time window (Generalized Additive Models, GAMs). In terms of infectivity, A. coluzzii showed a consistent sporozoite rate around 6% over the sampled years (χ2=2.48, p=0.64), while in A. arabiensis the SR decreased after 2015 from 5% to less than 1% in 2020 (χ2=3.8; P<0.0001). The different levels of SR are line with the higher anthropophily observed in 2019 for A. coluzzii as compared to A. arabiensis (53% and 13% of Human blood index, respectively; χ2= 64.9, p<0.0001). Furthermore, all human fed mosquitoes were found to be dramatically higher infective and infected by Plasmodium sp. than animal fed (human fed: SR=24.6%, abdomen positivity=49.3%; Animal fed: SR =2.3%, abdomen positivity=5.3%, with the latter that can be assimilated to the Plasmodium oocyst rate; SR human fed vs animal fed: χ2= 24.8; p<0.0001; abdomen positivity human fed vs animal fed: χ2= 162.19; p<0.0001). Based on the spatial distribution of infected blood meals taken on human hosts, infected people do not seem to be clustered in the village, but are probably randomly distributed, at least in the 31 compound sampled by PSC conducted in 2019. Therefore, a high parasite prevalence in human bitten population and a positive feedback mechanism magnifying the parasite transmission is suggested: sporozoites can manipulate mosquitoes to bite more frequently human hosts and infected humans result more attractive to mosquitoes. The high malaria transmission risk is greatly sustained even by a complicated pattern of vector behavioural plasticity and co-occurrence of different physiological resistant mechanisms detected in vector population over the study period. In particular, from the blood meal analysis emerged that both species exhibit an opportunistic host choice range, biting more frequently alternative animal host species as human is not readily accessible and protected under the nets. In addition, the absence of an endo/exophagy observed in the two species by HLCs (GAMs and Generalized Linear Mixed Models), implicates that an exposed human host is subjected to an equal biting pressure inside and outside houses while, as human-host availability is reduced indoors (because of LLIN usage), vectors can easily shift toward an outdoor biting. Last but not least, the large plateau of mosquito biting activity observed from 22:00 to 5:00 can increased vector probability in encountering an exposed human host not yet sleeping under the net or being unprotected for the whole night. Regarding the physiological resistance, A. coluzzii showed a progressively reduction of the Kdr-w mutation from 0.72 in 2011 to 0.53 in 2019 (χ2=32.79; p<0.0001), probably as a consequence of an increase of other less fitness-costly resistance mechanisms like in the case of SAP2 protein over-expression (as suggested by the increased frequency of 4 out 5 SNPs associated, of which SNP4 is statistically significant: from 0.17 to 0.30, χ2 =6.5 p=0.0387). Conversely, in Anopheles arabiensis it was observed a slow rising in the frequency of kdr-w from 0.39 in 2011 to 0.71 in 2019 (χ2=66.21; p<0.0001), probably as a consequence of an extensively high zoophagy which, reducing the insecticide pressure on vector population, has likely contributed to maintain a low level of kdr-w for a long period after LLIN introduction, minimizing the mutation impact on population fitness. The scenario of insecticide resistance can be further complicated by the coexistence of many other insecticide resistance mechanisms not explored in the context of this thesis (i.e. metabolic resistance, other kdr target sites mutation) which need to be explored in the future. CONCLUSION AND FUTURE PERSPECTIVES: This thesis work has pinpointed a complex of interweaving vector behavioural traits and physiological resistance mechanisms which can sustain a highly efficient transmission dynamic in Goden village despite over 10 years of net usage. Although the highest transmission risk is still occurring when majority of human population should be sleeping under the nets, the human biting pressure maintained in the hours when people are awake represents a dramatic gap in protection that probably provide for the hard core of residual malaria transmission in the village. Future investigations as bioassays, human parasitemia surveys, human blood meal genotyping and modelling approaches will be necessary to explore further details of the complex transmission dynamic and to estimate the impact of each entomological variable in malaria transmission intensity in the village. Since Goden can be considered paradigmatic of other West African settings where LLIN are not giving the expected protection, these studies will be the baseline for planning the implementation of specific control approaches aiming at strengthen individual and community protection indoors and outdoors in those epidemiological contexts where vectors are hardly targetable and malaria is greatly far from elimination.

Produzione scientifica

11573/1693041 - 2023 - Mosquito vectors, malaria and other vector-borne diseases
Arcà, Bruno; Bevivino, Giulia; Caputo, Beniamino; Della Torre, Alessandra; De Marco, Carlo Maria; Dipaola, Maria Greta; Gabrielli, Simona; Lombardo, Fabrizio; Longo, Eleonora; Manzi, Sara; Micocci, Martina; Modiano, David; Perugini, Eleonora; Pichler, Verena; Poggi, Cristiana; Pombi, Marco; Serini, Paola; Virgillito, Chiara - 04f Poster
congresso: La Facoltà di Farmacia e Medicina presenta le attività di ricerca scientifica dei Dipartimenti di afferenza. Highlighting the Research Activity of the Sapienza Faculty of Pharmacy and Medicine. (Sapienza University - Rome (Italy))
libro: La Facoltà di Farmacia e Medicina presenta le attività di ricerca scientifica dei Dipartimenti di afferenza. - ()

11573/1696818 - 2023 - Novel molecular approaches to study malaria transmission and mosquito-parasite-human interplay
Bevivino, G.; Dipaola, M. G.; Perugini, E.; Pombi, M.; Arcà, B.; Lombardo, F.; Modiano, D. - 04d Abstract in atti di convegno
congresso: XII European Congress of Entomology (ECE 2023) (Heraklion (Crete))
libro: XII European Congress of Entomology (ECE 2023) - ()

11573/1696831 - 2023 - A new FTA card-based trapping system for mosquito-borne e diseases surveillance
Manzi, Sara; Nelli, Luca; Perugini, Eleonora; Poggi, Cristiana; Di Luca, Marco; Toma, Luciano; Severini, Francesco; Toniolo, Federica; Michelutti, Alice; Bertola, Michela; Gradoni, Francesco; Sgubin, Sofia; Zaccaria, O.; Abbate, V.; Fortuna, Claudia; Lista, Florigio; Pazienza, Michele; Montarsi, Fabrizio; Pombi, Marco - 04d Abstract in atti di convegno
congresso: 13th European Congress of Entomology (Crete, Greece)
libro: Book of abstract european congress of entomology - ()

11573/1680243 - 2023 - The interplay between malaria vectors and human activity accounts for high residual malaria transmission in a Burkina Faso village with universal itn coverage
Perugini, E.; Guelbeogo, W. M.; Guglielmo, F.; Poggi, C.; Gabrieli, E.; Ranson, H.; Della Torre, A.; Pombi, M. - 01a Articolo in rivista
rivista: PARASITES & VECTORS (London: BioMed Central-Springer Nature.) pp. 1-14 - issn: 1756-3305 - wos: WOS:000953055700002 (0) - scopus: 2-s2.0-85150315276 (0)

11573/1693069 - 2023 - Investigating the presence of three sympatric Phortica spp. in the Latium region (Manziana, Rome, Italy)
Poggi, Cristiana; Bernardini, Ilaria; Porretta, Daniele; Máca, Jan; Perugini, Eleonora; Manzi, Sara; Paolo Lia, Riccardo; Beugnet, Frédéric; Fourie, Josephus; Otranto, Domenico; Pombi, Marco - 04d Abstract in atti di convegno
congresso: 13th European Congress of Entomology (Crete, Greece)
libro: Book of abstract european congress of entomology - ()

11573/1671480 - 2022 - Interplay between vector biting rhythms and human habits accounts for high residual malaria transmission in Burkina Faso despite the extensive coverage of insecticide treated nets (LLINs)
Perugini, Eleonora; Guelbeogo, Wamdaogo M.; Guglielmo, Federica; Poggi, Cristiana; Micocci, Martina; Gabrieli, Eugenio; Ranson, Hilary; Della Torre, Alessandra; Pombi, Marco - 04d Abstract in atti di convegno
congresso: The 22ND European Society for Vector Ecology conference “Meeting following a pandemic; bringing clarity to vector ecology in days of uncertainty” (Sofia, Bulgaria)
libro: Meeting following a pandemic; bringing clarity to vector ecology in days of uncertainty - ()

11573/1530469 - 2021 - Novel genotyping approaches to easily detect genomic admixture between the major Afrotropical malaria vector species, Anopheles coluzzii and An. gambiae
Caputo, Beniamino; Pichler, Verena; Bottà, Giordano; De Marco, Carlo; Hubbart, Christina; Perugini, Eleonora; Pinto, Joao; Rockett, Kirk A; Miles, Alistair; Della Torre, Alessandra - 01a Articolo in rivista
rivista: MOLECULAR ECOLOGY RESOURCES (Oxford : Blackwell) pp. 1504-1516 - issn: 1755-0998 - wos: WOS:000635635600001 (5) - scopus: 2-s2.0-85103953503 (6)

11573/1405553 - 2020 - Behavioural plasticity of Anopheles coluzzii and Anopheles arabiensis undermines LLIN community protective effect in a Sudanese-savannah village in Burkina Faso
Perugini, Eleonora; Moussa Guelbeogo, Wamdaogo; Calzetta, Maria; Manzi, Sara; Virgillito, Chiara; Caputo, Beniamino; Pichler, Verena; Ranson, Hilary; Sagnon, N’Fale; Della Torre, Alessandra; Pombi, Marco - 01a Articolo in rivista
rivista: PARASITES & VECTORS (London: BioMed Central-Springer Nature.) pp. 1-10 - issn: 1756-3305 - wos: WOS:000538082200004 (10) - scopus: 2-s2.0-85085909291 (10)

11573/1557168 - 2020 - Limited impact of Long lasting insecticide treated nets (LLINs) on malaria transmission in a rural village of Burkina Faso: the role of mosquito behavioral plasticity
Perugini, Eleonora; Pombi, Marco - 04d Abstract in atti di convegno
congresso: COVID-19: Facing a multi(face)phase pandemic, XI Seminar PHD DAY (Virtual Meeting Organized by the Italian National Institute of Health and Sapienza University of Rome)
libro: Istisan congressi - ()

11573/1403774 - 2019 - High Malaria transmission risk in Burkina Faso village despite bednets coverage
Perugini, E.; Pombi, M.; Guelbeogo, W. M.; Calzetta, M.; Ranson, H.; Sagnon, N.; Della Torre., A. - 04f Poster
congresso: third international StaPa retreat 2019 (Rome, Italy)
libro: third international StaPa retreat 2019 - ()

11573/1557181 - 2019 - Evaluation of the impact of long lasting insecticidal nets (llins) on malaria transmission in Burkina Faso
Perugini, Eleonora; Pombi, Marco - 04d Abstract in atti di convegno
congresso: Science for Democracy - Democracy for Science- X seminar PHD DAY (Istituto Superiore di Sanità, Viale Regina Elena, 299 – 00161 Roma)
libro: Istisan congressi - ()

11573/1090438 - 2018 - A novel nested polymerase chain reaction assay targeting Plasmodium mitochondrial DNA in field-collected Anopheles mosquitoes
Calzetta, M; Perugini, E; Seixas, G; Sousa, C A; Guelbeogo, W M; Sagnon, N; Della Torre, A; Pinto, J; Pombi, M; Mancini, E - 01a Articolo in rivista
rivista: MEDICAL AND VETERINARY ENTOMOLOGY (Blackwell Science Limited:PO Box 88, Oxford OX2 0NE United Kingdom:011 44 1865 776868, 011 44 1865 206038, EMAIL: journals.cs@blacksci.co.uk, INTERNET: http://www.blackwell-science.com, Fax: 011 44 1865 721205) pp. 1-6 - issn: 0269-283X - wos: WOS:000440655500013 (7) - scopus: 2-s2.0-85051087312 (6)

11573/1282134 - 2018 - Malaria entomological inoculation rate in a village of Burkina Faso reveals high transmission risk both indoors and outdoors despite the large coverage of LLINs
Perugini, E.; Pombi, M.; Guelbeogo, W. M.; Calzetta, M.; Ranson, H.; Sagnon, N.; Della Torre, A. - 04d Abstract in atti di convegno
congresso: XXX Congresso Nazionale Società Italiana Parassitologia (Milan; Italy)
libro: XXX Congresso Nazionale SoiPA - ()

11573/1282308 - 2018 - Evidence of low community level protection from malaria transmission despite High LLIN-coverage in a village of Burkina Faso
Perugini, Eleonora; Pombi, Marco; Guelbeogo, Wamdaogo M.; Calzetta, Maria; Pichler, Verena; Ranson, Hilary; Sagnon, N'fale; Della Torre, Alessandra - 04d Abstract in atti di convegno
congresso: American Society of Tropical Medicine Hygiene 67th Annual Meeting (New Orleans, Louisiana USA)
libro: ASTMH 67th Annual Meeting - ()

11573/1282417 - 2018 - Do the LLINs really protect from malaria at community level in areas of high transmission?
Pombi, M.; Guelbeogo, W. M.; Calzetta, M.; Perugini, E.; Fidati, Sonia; Pichler, V.; Ranson, H.; Sagnon, N.; Della Torre, A. - 04d Abstract in atti di convegno
congresso: European Society for Vector Ecology 21st Conference (Palermo, Italy)
libro: E-SOVE 21st Conference - ()

11573/1209291 - 2018 - Unexpectedly high Plasmodium sporozoite rate associated with low human blood index in Anopheles coluzzii from a LLIN-protected village in Burkina Faso
Pombi, Marco; Calzetta, Maria; Guelbeogo, Wamdaogo M.; Manica, Mattia; Perugini, Eleonora; Pichler, Verena; Mancini, Emiliano; Sagnon, N’Fale; Ranson, Hilary; Della Torre, Alessandra - 01a Articolo in rivista
rivista: SCIENTIFIC REPORTS (London: Springer Nature London: Nature Publishing Group) pp. 1-10 - issn: 2045-2322 - wos: WOS:000442607800035 (17) - scopus: 2-s2.0-85052203292 (17)

11573/1283326 - 2017 - Entomological survey in a LLIN-protected village of Burkina Faso shows unexpectedly low Human Blood Index associated to high Plasmodium sporozoite rates in the malaria vector Anopheles coluzzii
Pombi, Marco; Calzetta, Maria; Guelbeogo, W. M.; Manica, Mattia; Perugini, Eleonora; Mancini, Emiliano; Sagnon, N'fale.; Ranson, Hilary.; Della Torre, Alessandra - 04d Abstract in atti di convegno
congresso: Pan African Mosquito Control Association (Ouagadougou, Burkina Faso)
libro: 4th PAMCA ANNUAL CONFERENCE - ()

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