Background: Despite the overall major impact of long-lasting insecticide treated nets (LLINs) in eliciting individual and collective protection to malaria infections, some sub-Saharan countries, including Burkina Faso, still carry a disproportionately high share of the global malaria burden. This study aims to analyse the possible entomological bases of LLIN limited impact, focusing on a LLIN-protected village in the Plateau Central region of Burkina Faso. Methods: Human landing catches (HLCs) were carried out in 2015 for 12 nights both indoors and outdoors at different time windows during the highest biting activity phase for Anopheles gambiae (s.l.). Collected specimens were morphologically and molecularly identified and processed for Plasmodium detection and L1014F insecticide-resistance allele genotyping. Results: Almost 2000 unfed An. gambiae (s.l.) (54% Anopheles coluzzii and 44% Anopheles arabiensis) females landing on human volunteers were collected, corresponding to a median number of 23.5 females/person/hour. No significant differences were observed in median numbers of mosquitoes collected indoors and outdoors, nor between sporozoite rates in An. coluzzii (6.1%) and An. arabiensis (5.5%). The estimated median hourly entomological inoculation rate (EIR) on volunteers was 1.4 infective bites/person/hour. Results do not show evidence of the biting peak during night hours typical for An. gambiae (s.l.) in the absence of bednet protection. The frequency of the L1014F resistant allele (n = 285) was 66% in An. coluzzii and 38% in An. arabiensis. Conclusions: The observed biting rate and sporozoite rates are in line with the literature data available for An. gambiae (s.l.) in the same geographical area before LLIN implementation and highlight high levels of malaria transmission in the study village. Homogeneous biting rate throughout the night and lack of preference for indoor-biting activity, suggest the capacity of both An. coluzzii and An. arabiensis to adjust their host-seeking behaviour to bite humans despite bednet protection, accounting for the maintenance of high rates of mosquito infectivity and malaria transmission. These results, despite being limited to a local situation in Burkina Faso, represent a paradigmatic example of how

Background: Despite the overall major impact of Long Lasting Insecticide treated Nets (LLINs) in eliciting individual and collective protection to malaria infections, some sub-Saharan Countries, including Burkina Faso, still carry a disproportionately high share of the global malaria burden. This study aims to analyse the possible entomological bases of LLIN limited impact, focusing on a LLIN-protected village in the Plateau Central region of Burkina Faso. Methods: Human Landing Catches (HLCs) were carried out in 2015 both indoors and outdoors at different time-windows during the highest biting activity phase for Anopheles gambiae s.l. Collected specimens were morphologically and molecularly identified and processed for Plasmodium detection and L1014F insecticide-resistance allele genotyping. Results: Almost 2.000 unfed An. gambiae s.l. (54% Anopheles coluzzii , 44% Anopheles arabiensis ) females landing on human volunteers were collected, corresponding to a median number of 23.5 females/person/hour. No significant differences are observed in median numbers of mosquitoes collected indoor and outdoor, nor between sporozoite rates in An. coluzzii (6.1%) and An. arabiensis (5.5%). The estimated median hourly Entomological Inoculation Rate (EIR) on volunteers is 1.4 infective bites/person/hour. Results do not show evidence of the biting peak during night hours typical for An. gambiae s.l. in the absence of bednet protection. The frequency of L1014F resistant allele (N=285) was 66% in An. coluzzii and 38% in An. arabiensis . Conclusions: The observed biting rate and sporozoite rates are in line with the literature data available for An. gambiae s.l . in the same geographical area before LLIN implementation and highlight high levels of malaria transmission in the study village. Homogeneous biting rate throughout the night and lack of preference for indoor-biting activity suggest the capacity of both An. coluzzii and An. arabiensis to adjust their host-seeking behaviour to bite humans despite bednet protection, accounting for the maintenance of high rates of mosquito infectivity and malaria transmission. These results – despite being limited to a local situation in Burkina Faso – represent a paradigmatic example of how high densities and behavioural plasticity in the vector population may contribute to explain the limited impact of LLINs on malaria transmission in holo-endemic Sudanese savannah areas in West Africa.

Background: Despite the overall major impact of Long Lasting Insecticide treated Nets (LLINs) in eliciting individual and collective protection to malaria infections, some sub-Saharan Countries, including Burkina Faso, still carry a disproportionately high share of the global malaria burden. This study aims to analyse the possible entomological bases of LLIN limited impact, focusing on a LLIN-protected village in the Plateau Central region of Burkina Faso. Methods: Human Landing Catches (HLCs) were carried out in 2015 both indoors and outdoors at different time-windows during the highest biting activity phase for Anopheles gambiae s.l. Collected specimens were morphologically and molecularly identified and processed for Plasmodium detection and L1014F insecticide-resistance allele genotyping. Results: Almost 2.000 unfed An. gambiae s.l. (54% Anopheles coluzzii , 44% Anopheles arabiensis ) females landing on human volunteers were collected, corresponding to a median number of 23.5 females/person/hour. No significant differences are observed in median numbers of mosquitoes collected indoor and outdoor, nor between sporozoite rates in An. coluzzii (6.1%) and An. arabiensis (5.5%). The estimated median hourly Entomological Inoculation Rate (EIR) on volunteers is 1.4 infective bites/person/hour. Results do not show evidence of the biting peak during night hours typical for An. gambiae s.l. in the absence of bednet protection. The frequency of L1014F resistant allele (N=285) was 66% in An. coluzzii and 38% in An. arabiensis . Conclusions: The observed biting rate and sporozoite rates are in line with the literature data available for An. gambiae s.l . in the same geographical area before LLIN implementation and highlight high levels of malaria transmission in the study village. Homogeneous biting rate throughout the night and lack of preference for indoor-biting activity suggest the capacity of both An. coluzzii and An. arabiensis to adjust their host-seeking behaviour to bite humans despite bednet protection, accounting for the maintenance of high rates of mosquito infectivity and malaria transmission. These results – despite being limited to a local situation in Burkina Faso – represent a paradigmatic example of how high densities and behavioural plasticity in the vector population may contribute to explain the limited impact of LLINs on malaria transmission in holo-endemic Sudanese savannah areas in West Africa.

Background Some species of drosophilid flies belonging to the genus Phortica feed on ocular secretions of mammals, acting as biological vectors of the zoonotic eyeworm Thelazia callipaeda. This study describes an effective breeding protocol of Phortica variegata and Phortica oldenbergi in insectary conditions. Methods Alive gravid flies of P. oldenbergi, P. variegata and Phortica semivirgo were field collected in wooded areas of Lazio region (Italy) and allowed to oviposit singularly to obtain isofamilies. Flies were maintained in ovipots (200 ml) with a plaster-covered bottom to maintain high humidity level inside. Adult feeding was guaranteed by fresh apples and a liquid dietary supplement containing sodium chloride and mucin proteins, while larval development was obtained by Drosophila-like agar feeding medium. The breeding performances of two media were compared: a standard one based on cornmeal flour and an enriched medium based on chestnut flour. All conditions were kept in a climatic chamber with a photoperiod of 14:10 h light:dark, 26 ± 2 °C and 80 ± 10% RH. Results From a total of 130 field-collected Phortica spp., three generations (i.e. F1 = 783, F2 = 109, F3 = 6) were obtained. Phortica oldenbergi was the species with highest breeding performance, being the only species reaching F3. Chestnut-based feeding medium allowed higher adult production and survival probability in both P. oldenbergi and P. variegata. Adult production/female was promising in both species (P. oldenbergi: 13.5 F1/f; P. variegata: 4.5 F1/f). Conclusions This standardized breeding protocol, based on controlled climatic parameters and fly densities, together with the introduction of an enriched chestnut-based feeding medium, allowed to investigate aspects of life history traits of Phortica spp. involved in the transmission of T. callipaeda. Obtaining F3 generation of these species for the first time paved the road for the establishment of stable colonies, an essential requirement for future studies on these vectors in controlled conditions. Graphical abstract