bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒06‒07
thirty-six papers selected by
Richard Halfpenny
Staffordshire University

  1. J Vector Ecol. 2020 Jun;45(1): 104-117
    Johnson T, Braack L, Guarido M, Venter M, Gouveia Almeida AP.
      Most data on species associations and vector potential of mosquitoes in relation to arboviral infections in South Africa date back from the 1940s to late 1990s. Contextual information crucial for disease risk management and control, such as the sampling effort, diversity, abundance, and distribution of mosquitoes in large parts of South Africa still remains limited. Adult mosquitoes were collected routinely from two horse farms in Gauteng Province; two wildlife reserves in Limpopo Province, at Orpen Gate in Kruger National Park (KNP) and Mnisi Area in Mpumalanga Province between 2014-2017, using carbon dioxide-baited light and tent traps. Mosquito diversity and richness are greater in untransformed natural and mixed rural settings. In untransformed wilderness areas, the most dominant species were Culex poicilipes, Anopheles coustani, and Aedes mcintoshi, while in mixed rural settings such as the Mnisi area, the two most abundant species were Cx. poicilipes and Mansonia uniformis. However, in peri-urban areas, Cx. theileri, Cx. univittatus, and Cx. pipiens sensu lato were the most dominant. Aedes aegypti, Ae. mcintoshi, Ae. metallicus, Ae. vittatus, Cx. pipiens s.l., Cx. theileri, and Cx. univittatus had the widest geographical distribution in northern South Africa. Also collected were Anopheles arabiensis and An. vaneedeni, both known malaria vectors in South Africa. Arbovirus surveillance and vector control programs should be augmented in mixed rural and peri-urban areas where the risk for mosquito-borne disease transmission to humans and domestic stock is greater.
    Keywords:  Mosquitoes; distribution; diversity; landscape; sampling; species richness
  2. PLoS One. 2020 ;15(6): e0233669
    Boyer S, Marcombe S, Yean S, Fontenille D.
      Only few data exist in Cambodia on mosquito diversity and their potential role as vectors. Many arboviruses, such as dengue and Japanese encephalitis, are endemic and mostly affect children in the country. This research sets out to evaluate vector relative abundance and diversity in primary schools in Cambodia in an attempt to explain the apparent burden of dengue fever, severe dengue (DEN), Japanese encephalitis (JE), other arboviral diseases and malaria among children, 15 years and under, attending selected primary schools through vector surveys. Entomological surveys were implemented in primary schools in two provinces of Cambodia to assess the potential risk of exposure of schoolchildren to mosquito vector species. Light traps and BG traps were used to collect adult mosquitoes in 24 schools during the rainy and dry seasons of 2017 and 2018 in Kampong Cham and Tboung Khmum provinces. A total of 61 species were described, including Aedes, Culex and Anopheles species. The relative abundance and biodiversity of mosquito species were dependent on the month and school. Of the 37,725 mosquitoes caught during the study, three species accounted for three-quarters of the relative abundance: Culex vishnui, Anopheles indefinitus and Culex quinquefasciatus. More importantly, nearly 90% of the mosquitoes caught in the schools were identified as potential vectors of pathogens including Japanese encephalitis, dengue, and malaria parasites. Our results showed that schools in Cambodia represent a risk for vector-borne disease transmission and highlight the importance of implementing vector control in schools in Cambodia to decrease the risk of transmission.
  3. J Med Entomol. 2020 Jun 02. pii: tjaa101. [Epub ahead of print]
    Cataldo NP, Lea CS, Kelley T, Richards SL.
      Aedes aegypti (L.) is the primary vector of Zika, dengue, yellow fever, and chikungunya viruses. Insecticides used in mosquito control can help prevent the spread of vector-borne diseases. However, it is essential to determine insecticide resistance (IR) status before control measures are undertaken. Only the most effective insecticides should be used to avoid ineffective control and/or promotion of IR. Pyrethroids and organophosphates are the most commonly used insecticides for mosquito control. Here, the efficacy of two active ingredients (AIs; permethrin [pyrethroid], chlorpyrifos [organophosphate]), two formulated products (FPs; Biomist [AI: permethrin]) and (Mosquitomist [AI: chlorpyrifos]), and three synergists (piperonyl butoxide, diethyl maleate, S-S-S-tributyl phosphorotrithioate) was evaluated in two Ae. aegypti colonies (pyrethroid resistant and susceptible). Mosquitomist was most effective against the pyrethroid-resistant colony (100% mortality at diagnostic time). Pre-exposure to synergists did not increase the efficacy of AIs against the pyrethroid-resistant colony. Further research is needed to discover how synergists may affect the efficacy of insecticides when used on pyrethroid-resistant mosquitoes.
    Keywords:   Ae aegypti ; Biomist; Mosquitomist; organophosphate; pyrethroid
  4. J Vector Ecol. 2020 Jun;45(1): 100-103
    Pearson MA, Blore K, Efstathion C, Aryaprema VS, Muller GC, Xue RD, Qualls WA.
      Current methods of broad area application of contact insecticides used in mosquito control are becoming less effective, primarily due to resistance within mosquito populations. New methods that can deliver ingestible insecticides are being investigated as a means to mitigate resistance. This study evaluated insecticide delivery through toxic sugar baits (TSB) and resulting mortality of susceptible and resistant strains of Aedes aegypti. Two Ae. aegypti strains were evaluated using a 1% boric acid TSB: the susceptible Orlando 1952 (ORL) strain and the resistant Puerto Rican (PR) strain. The TSB resulted in high mortality for both ORL and PR strain of Ae. aegypti. Average mortality of female mosquitoes given TSB was 90.8% for PR and 99.3% for ORL. Our study suggests that targeting resistant mosquitoes with ingestible insecticides through TSBs could be a viable alternative to current mosquito control strategies and should be considered when developing an integrated vector management program.
    Keywords:  Aedes aegypti; Toxic sugar bait; insecticide resistance; integrated vector management; sugar-feeding
  5. J Med Entomol. 2020 Jun 02. pii: tjaa103. [Epub ahead of print]
    de Araújo WS, Vieira TM, de Souza GA, Bezerra IC, Corgosinho PHC, Borges MAZ.
      Mosquitoes (Diptera: Culicidae) are one of the most important disease vector species in the world. Many species have a high degree of anthropophilia and are often found in human habitations. In the present study, we have inventoried the nocturnal mosquito assemblage in intra-, peri-, and extradomicile environments in four municipalities in Pará, Brazil. At each municipality, a residence was selected and the mosquitoes were sampled using the protected human attraction capture and Shannon trap methods in April (rainy season) and August 2018 (dry season). We have collected a total of 696 mosquito specimens belonging to 8 genera and 17 species. The most abundant species were Mansonia (Mansonoides) titillans (Walker) (366/696, 52.6%), Anopheles (Nyssorhynchus) albitarsis Lynch-Arribálzaga (97/696, 13.9%), and Culex (Culex) quinquefasciatus Say (93/696, 13.4%). Mosquito richness, abundance, and composition did not differ between intra-, peri-, and extradomicile environments suggesting limited habitat segregation among the different species. However, mosquito species richness and mosquito species abundance were significantly higher during the rainy season than during the dry season, suggesting increased mosquito activity during the rainy season. We detected several important vector species of human diseases including Aedes (Stegomyia) aegypti (Linnaeus), Anopheles (Nyssorhynchus) darlingi Root, Haemagogus (Conopostegus) leucocelaenus (Dyar and Shannon), Coquillettidia (Coquillettidia) venezuelensis (Theobald), and Culex (Culex) quinquefasciatus which are the main transmitters of dengue, malaria, yellow fever, mayaro, and oropouche fever, respectively. As inventories of disease-carrying mosquitoes in the region are very scarce, mainly in residential environments, our results suggest high potential for mosquito-borne disease transmission in Pará State.
    Keywords:  Anthropophilia; Culicidae; mosquitoes-borne diseases; seasonality; vector ecology
  6. Insects. 2020 Jun 03. pii: E342. [Epub ahead of print]11(6):
    Eastwood G, Sang RC, Lutomiah J, Tunge P, Weaver SC.
      As new and re-emerging vector-borne diseases are occurring across the world, East Africa represents an interesting location, being the origin of several arboviruses with a history of urbanization and global spread. Rapid expansion of urban populations and alteration of natural habitats creates the opportunity for arboviruses to host-switch from wild, sylvatic hosts or vectors into urban transmission affecting human populations. Although mosquito surveillance regularly takes place in urban areas of Kenya, for example identifying vectors of dengue virus or malaria viruses, little work has been carried out to determine the distribution and abundance of sylvatic vectors. Here, we describe the mosquito vector species and diversity collected at twelve forest habitats of rural Kenya. We conducted arbovirus screening of over 14,082 mosquitoes (47 species, 11 genera) as 1520 pools, and detected seven viruses (six bunyaviruses, and one flavivirus-bunyavirus co-infection) isolated from pools of Aedes dentatus, Anopheles funestus, Culex annulioris, and Cx. vansomereni. Awareness of sylvatic vector species and their location is a critical part of understanding the ecological foci and enzootic cycling of pathogens that may be of concern to public, animal or wildlife health. As natural ecosystems come under anthropogenic pressures, such knowledge can inform us of the One Health potential for spillover or spillback leading to outbreaks, and assist in vector control strategies.
    Keywords:  East Africa; Sylvatic; arbovirus; disease; distribution; emerging; mosquito; species diversity; vector
  7. Int J Environ Res Public Health. 2020 Jun 03. pii: E3960. [Epub ahead of print]17(11):
    Caputo B, Manica M, Russo G, Solimini A.
      The invasion of Aedes albopictus has played a major role in the resurgence of mosquito-borne diseases in Italy, generating the two largest chikungunya outbreaks in Europe (2007, 2017). Knowledge, attitude and practice (KAP) are important in order to prevent Aedes-borne disease transmission, yet so far they have not been assessed. To this scope we used multivariate logistic regression to investigate KAP of citizen-to-Aedes ecology and transmitted diseases. Data were collated by a structured questionnaire (18 questions) in 2016. Participants were selected in the Lazio region from members of native populations and two resident communities (RC) originating from the Indian subcontinent where Aedes-transmitted diseases are endemic. Results showed that compared to Italians, RC respondents had a higher knowledge and concern of Aedes-transmitted diseases (Odds Ratio = 2.61 (95%CI: 1.03-6.05); OR = 3.13 (2.15-4.65)) as well as their life cycles (OR = 2.49 (1.75-3.56); OR = 9.04 (6.22-13.66)). In contrast, they perceived a lower nuisance due to the presence of Ae. albopictus (OR = 0.2 (0.13-0.32); OR = 0.55 (0.38-0.78). These findings suggest that citizens in the Lazio region are not prepared to face a potential outbreak of arboviruses and further efforts should be made to increase knowledge, awareness and best practices.
    Keywords:  Aedes albopictus; Aedes-borne diseases; KAP mosquito; arboviruses; awareness and practice; infectious disease; knowledge; mosquito; mosquito life cycle
  8. J Vector Ecol. 2020 Jun;45(1): 135-139
    Merdić E, Klobučar A, Žitko T, Sudarić Bogojević M, Vrućina I, Turić N, Vignjević G.
      Improvement of morphological and molecular identification methods allows the detection of new species of mosquitoes. The mosquito fauna of Croatia currently includes 52 species, belonging to eight genera, including Anopheles (12 species), Aedes (24 species), Coquillettidia (one species), Culex (seven species), Culiseta (six species), Orthopodomyia (one species), and Uranotaenia (one species). This is an updated checklist, which includes five new species found in Croatian mosquito fauna. Two of these are invasive mosquito species, Aedes albopictus (Skuse, 1895) and Aedes japonicus (Theobald 1901), which are spreading across Europe and Croatia. The other three species, Culex laticinctus (Edwards 1913), Culex torrentium (Martini 1925), and Anopheles daciae (Linton, Nicolescu & Harbach 2004) are autochthonous species which haven't been recorded so far. Since there are several more invasive species spreading across Europe, we assume that this is not the final list.
    Keywords:  Checklist; Croatia; Culicidae; Europe; invasive species; mosquitoes
  9. J Vector Ecol. 2020 Jun;45(1): 118-126
    Whelan PI, Kurucz N, Pettit WJ, Krause V.
      The Northern Territory (NT) of Australia is currently free of the dengue mosquito Aedes (Stegomyia) aegypti (L). However, on 17 February 2004, two Ae. aegypti adults were captured in two routine CO2 -baited encephalitis virus surveillance traps in Tennant Creek, located 990 km south of Darwin in the NT. The detection triggered an immediate survey and control response undertaken by the NT Department of Health and Community Services, followed by a Commonwealth of Australia-funded Ae. aegypti elimination program. This report details the methods and results of the detection and subsequent elimination activities that were carried out between 2004 and 2006, returning the NT to its dengue vector-free status. There have been very few successful Ae. aegypti elimination programs in the world. This purposeful mosquito elimination for Australia was officially declared on 5 April 2006.
    Keywords:  Aedes aegypti; Australia; elimination; mosquito surveillance; mosquito-borne disease; vector control
  10. J Vector Ecol. 2020 Jun;45(1): 2-15
    Dixson A, Jackson RN, Rowe RD, Nease R, Fryxell RTT.
      Interspecific associations between two mosquito species can lead to effects such as competition, species displacement, and species stability. To better understand Aedes albopictus (Skuse) and other Aedes species, we monitored eggs in artificial oviposition cups (ovitraps) within Knox County, TN, U.S.A., during the 2016 and 2017 mosquito seasons. In 2016, one black and one white ovitrap were placed at 18 sites for 21 weeks, while in 2017 black and white ovitraps baited with grass-infused or deionized water were placed at 11 sites for nine weeks. Eggs were identified to species and resulting counts were used to determine the degree of interspecific association using Cole's coefficients (C7 ) and the degree of heterogeneity across space and time using generalized linear mixed models (GLMM). Here, Aedes mosquitoes are generally ovipositing in black cups with grass-infused water, and Ae. albopictus eggs co-occurred with other Aedes species more often than would be expected. Finding a positive significant interspecific association between Ae. albopictus and other Aedes eggs suggests that methods used to control Ae. albopictus may also control other Aedes mosquitoes. Finding that Ae. albopictus co-occurs with other Aedes mosquitoes warrants additional research to evaluate outcomes associated with co-occurrence within the study area.
    Keywords:  Aedes; Culicidae; distribution; ecology; oviposition; surveillance
  11. Acta Trop. 2020 May 30. pii: S0001-706X(19)31508-6. [Epub ahead of print] 105556
    Nararak J, Giorgio CD, Sukkanon C, Mahiou-Leddet V, Ollivier E, Manguin S, Chareonviriyaphap T.
      The activity of β-caryophyllene oxide as either a contact or noncontact repellent was evaluated against two laboratory strains (Aedes albopictus and Anopheles dirus) using an excito-repellency test system. N, N-Diethyl-3-methylbenzamide (DEET) was used as a standard reference baseline for comparative purposes. β-Caryophyllene oxide and DEET were tested at concentrations of 0.1, 0.25, 0.5 and 1.0% (v/v). In addition, the phototoxic and genotoxic effects of β-caryophyllene oxide were investigated on Balb/c 3T3 mouse fibroblasts (3T3-L1) and Chinese hamster ovary cell line (CHO-K1). The results demonstrated that the higher concentrations of test compounds (0.5 and 1.0%) produced greater behavioral responses. Aedes albopictus was more sensitive to β-caryophyllene oxide than An. dirus. Moderate avoidance response rates (25-56% escape) of Ae. albopictus at 0.5% and 1.0% β-caryophyllene oxide were observed in contact and noncontact trials compared with low response rates from An. dirus (26-31% escape). DEET at ≤1% displayed lower irritancy and repellency (1-38%) than β-caryophyllene oxide when tested against the two mosquito species. Knockdown responses (37%) were only observed in An. dirus exposed to 1% β-caryophyllene oxide in the contact trial. β-Caryophyllene oxide did not show any phototoxic potential (PIF= 0.38) nor was there any significant genotoxic response as indicated by no increase in micro-nucleated cells with or without metabolic activation. β-Caryophyllene oxide could be considered as a safe repellent, effective against mosquitoes.
    Keywords:  Excito-repellency test system; Genotoxic; Mosquitoes; Phototoxic; β-Caryophyllene oxide
  12. J Am Mosq Control Assoc. 2020 Mar;36(1): 16-21
    Dzib-Florez S, Ponce-García G, Che-Mendoza A, Medina-Barreiro A, Gray L, González-Olvera G, Delfin-Gonzalez H, Chan-Espinoza D, Vadillo-Sánchez J, Del Castillo-Centeno L, Vazquez-Prokopec G, Manrique-Saide P.
      Commercial aerosolized insecticides can be implemented as a community-based approach to targeted indoor residual spraying against Aedes aegypti, but their efficacy on pyrethroid-resistant mosquitoes has not yet been evaluated. Two commercial aerosolized products (H24 Poder Fulminante Ultra Eficaz®, carbamate, and Baygon Ultra Verde®, pyrethroid) were sprayed on common indoor surfaces e.g., cement, plywood, and cloth, and tested for their residual efficacy on susceptible and field-derived pyrethroid-resistant Ae. aegypti strains using the WHO cone bioassays. Overall, ≥80% 24-h mortality was observed for both products for at least 4 wk regardless of the mosquito strain or surface type used. H24 Poder Fulminante Ultra Eficaz showed the highest residual potency, sustaining >80% mortality for 7-wk posttreatment regardless of mosquito strain and surface type. For Baygon Ultra Verde, the mean mortality of female Ae. aegypti remained >80% for a shorter period (4-6 wk). Nonpyrethroid commercial aerosolized formulations can provide a lasting residual effect indoors compatible with the need for rapid and lasting mosquito control during outbreaks and may be suitable for community-based targeted indoor residual spraying.
    Keywords:  Aedes aegypti; Mexico; aerosol; household insecticides; indoor residual spraying; surface spraying
  13. Parasit Vectors. 2020 Jun 01. 13(1): 277
    Perugini E, Guelbeogo WM, Calzetta M, Manzi S, Virgillito C, Caputo B, Pichler V, Ranson H, Sagnon N, Della Torre A, Pombi M.
      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 high densities and behavioural plasticity in the vector populations may contribute to explaining the limited impact of LLINs on malaria transmission in holo-endemic Sudanese savannah areas in West Africa.
    Keywords:  Anopheles; Bednet; Malaria transmission; Sporozoite rate; Vector behaviour
  14. J Med Entomol. 2020 May 30. pii: tjaa097. [Epub ahead of print]
    Muturi EJ, Hay WT, Doll KM, Ramirez JL, Selling G.
      The use of essential oils as ecofriendly tools for vector management is one of the mainstreams for biopesticide research. We evaluated the larvicidal properties of Commiphora erythraea (opoponax) essential oil and its fractions against Culex restuans Theobald, Culex pipiens L., and Aedes aegypti L. The use of bio-based amylose-N-1-hexadecylammonium chloride inclusion complex (Hex-Am) and amylose-sodium palmitate inclusion complex (Na-Palm) as emulsifiers for C. erythraea essential oil was also investigated. Bisabolene was the most abundant chemical constituent in the whole essential oil (33.9%), fraction 2 (62.5%), and fraction 4 (23.8%) while curzerene (32.6%) and α-santalene (30.1%) were the dominant chemical constituents in fractions 1 and 3, respectively. LC50 values for the whole essential oil were 19.05 ppm for Cx. restuans, 22.61 ppm for Cx. pipiens, and 29.83 ppm for Ae. aegypti and differed significantly. None of the four C. erythraea essential oil fractions were active against mosquito larvae. Two CYP450 genes (CYP6M11 and CYP6N12) and one GST gene (GST-2) were significantly upregulated in Ae. aegypti larvae exposed to C. erythraea essential oil suggesting their potential involvement in metabolic pathways for C. erythraea essential oil. Essential oil emulsions produced with Hex-Am were more toxic than the whole essential oil while those produced with Na-Palm had similar toxicity as the whole essential oil. These findings demonstrate that C. erythraea essential oil is a promising source of mosquito larvicide and that the use of Hex-Am as an emulsifier can enhance the insecticidal properties of C. erythraea essential oil.
    Keywords:   Commiphora erythraea ; emulsions; essential oil; larvicidal activity; mosquitoes
  15. Acta Trop. 2020 May 28. pii: S0001-706X(20)30549-0. [Epub ahead of print] 105549
    Somboon P, Phanitchakun T, Namgay R, Wangdi T, Pemo D, Harbach RE.
      This paper reports the results of a molecular and morphological study of Anopheles baileyi in Bhutan and Thailand. Phylogenetic analyses of ribosomal (ITS2) and mitochondrial DNA (COI) sequences revealed the presence of four genetically distinct clades, three in Bhutan (Clades I, II and III) and one in Thailand (Clade IV). Most of the larvae in the Bhutanese clades differed from those in the Thai clade in having seta 4-C branched, whereas it is single in the latter. The adults of each clade showed variation of wing markings and overlapping characters. The combination of characteristics of thoracic setae 1,2-P and abdominal seta 3-I was found to be useful for distinguishing the larvae. Pupae were inseparable. We provisionally recognize mosquitoes of Clades I, II, III and IV as members of a sibling species complex, the Baileyi Complex, denoted as species A, B, C and D, respectively. Species A is most likely the type form of An. baileyi s.s. because it was found adjacent to the type locality (Yatung, Tibet), and the others are unrecognized species.
    Keywords:  Anopheles baileyi; Bhutan; COI; ITS2; Mosquito; Taxonomy; Thailand
  16. J Am Mosq Control Assoc. 2020 Mar;36(1): 51-54
    Drago A, Simonato G, Vettore S, Martini S, Marcer F, di Regalbono AF, Cassini R.
      Aquatain® is an alternative larvicide formulation to the currently used larvicides. Its efficacy can be assessed monitoring emerging adults with a floating device that was recently developed for use in catch basins. In this study, the efficacy of Aquatain in controlling Aedes albopictus and Culex pipiens complex was investigated by comparing the adults emerging from 25 treated catch basins with that of 25 control basins in northeastern Italy. Basins were monitored weekly for 9 times and the efficacy was evaluated using the Mann-Whitney U-test and calculating the inhibition of emergence at each sampling. Aquatain was effective in reducing the number of emerging mosquitoes for both species, but its duration was affected by rainfall. Intensive showers (>10 mm daily) seem to reduce the efficacy of the product, allowing an increase in emerging adults after about 2 wk. This finding suggests that climatic factors should be taken into account to decide the right time for reapplication of Aquatain during routine larval treatments.
    Keywords:  Aquatain; catch basins; efficacy; floating system; mosquitoes
  17. Photodiagnosis Photodyn Ther. 2020 May 30. pii: S1572-1000(20)30194-0. [Epub ahead of print] 101840
    de Souza LM, Venturini FP, Inada NM, Iermak I, Garbuio M, Mezzacappo NF, de Oliveira KT, Bagnato VS.
      Combating the Aedes aegypti vector is still the key to control the transmission of many arboviruses, such as Dengue, Zika, and Chikungunya. Nowadays, as few products are efficient for Aedes aegypti control, the search for new strategies became pivotal. Therefore, the use of substances with photodynamic activity, such as curcumin and their formulations, are strongly encouraged, due to their multi-target mechanism of action. In this study, we evaluated the photolarvicidal and ovicidal activity of curcumin in the presence of sucrose (named SC) and D-mannitol (named DMC). To support the understanding of the larvicidal action of these formulations, Raman micro-spectroscopy was employed. We also studied the morphological changes in Danio rerio (Zebrafish) gills, a non-target organism, and demonstrate that this is an environmentally friendly approach. Both SC and DMC presented a high photo-larvicidal potential. DMC showed the highest larval mortality, with LC50-24h values between 0.01 and 0.02 mg.L-1. DMC also significantly decreased egg hatchability, reaching a hatching rate of 10% at 100 mg.L-1. The analysis of molecular mechanisms via Raman micro-spectroscopy showed that DMC is highly permeable to the peritrophic membrane of the larva, causing irreversible damage to the simple columnar epithelium of the digestive tube. Histological changes found in the D. rerio gills were of minimal or moderate pathological importance, indicating an adaptive trait rather than detrimental characteristics. These findings indicate that curcumin in sugar formulations is highly efficient, especially DMC, proving it to be a promising and safe alternative to control Aedes mosquitoes. Moreover, Raman micro-spectroscopy demonstrated high potential as an analytical technique to understand the mechanism of action of larvicides.
    Keywords:  Aedes aegypti; Curcumin; Photochemotherapy; Photolarvicidal; Raman analysis; Vector control
  18. Environ Sci Pollut Res Int. 2020 Jun 05.
    Rizvi SAH, Ling S, Zeng X.
      The Aedes albopictus mosquito is a vector of several deadly diseases of humans and domesticated animals. Usually, synthetic insecticides are used for mosquito control. The excessive use of synthetic insecticides is hazardous for humans and the environment. Therefore, there is a need to develop environment-friendly and novel mosquito larvicides. In the current study, we evaluated larvicidal and bite protection properties of Seriphidium brevifolium essential oil (SBEO) and its active constituents against this mosquito. SBEO and its active constituents, α, β-thujone, and limonene, were toxic to A. albopictus, with LC50 values of 21.43, 45.99, 47.38, and 49.46 μg/mL. The cream formulation of EO at 5 % (w/v) provided complete protection against mosquito bites until 70 min after application. Among the EO constituents tested, α and β-thujone showed considerable protections against mosquito bites but lower as compared with the whole oil. Furthermore, 1:1 combinations of active constituent α-thujone and β-thujone and 1:1:1 combinations of α-thujone, β-thujone, and limonene displayed a synergistic effect against the larvae. Particularly, the EO and its active constituents were safer to Poecilia reticulata a mosquito predator, with LC50 ranging from 3934.33 to 14,432.11 μg/mL. Our current study indicated that SBEO and some of its constituents can be used for the control of A. albopictus mosquito, as a novel alternative to hazardous synthetic insecticides and to overcome the problem of increasing insecticides resistance.
    Keywords:  Bio-pesticides; Eco-friendly; Larvicidal activity; Mosquito; Responsible Editor: Giovanni Benelli; Toxicity
  19. Malar J. 2020 Jun 02. 19(1): 195
    Gowelo S, McCann RS, Koenraadt CJM, Takken W, van den Berg H, Manda-Taylor L.
      BACKGROUND: To further reduce malaria, larval source management (LSM) is proposed as a complementary strategy to the existing strategies. LSM has potential to control insecticide resistant, outdoor biting and outdoor resting vectors. Concerns about costs and operational feasibility of implementation of LSM at large scale are among the reasons the strategy is not utilized in many African countries. Involving communities in LSM could increase intervention coverage, reduce costs of implementation and improve sustainability of operations. Community acceptance and participation in community-led LSM depends on a number of factors. These factors were explored under the Majete Malaria Project in Chikwawa district, southern Malawi.METHODS: Separate focus group discussions (FGDs) were conducted with members from the general community (n = 3); health animators (HAs) (n = 3); and LSM committee members (n = 3). In-depth interviews (IDIs) were conducted with community members. Framework analysis was employed to determine the factors contributing to community acceptance and participation in the locally-driven intervention.
    RESULTS: Nine FGDs and 24 IDIs were held, involving 87 members of the community. Widespread knowledge of malaria as a health problem, its mode of transmission, mosquito larval habitats and mosquito control was recorded. High awareness of an association between creation of larval habitats and malaria transmission was reported. Perception of LSM as a tool for malaria control was high. The use of a microbial larvicide as a form of LSM was perceived as both safe and effective. However, actual participation in LSM by the different interviewee groups varied. Labour-intensiveness and time requirements of the LSM activities, lack of financial incentives, and concern about health risks when wading in water bodies contributed to lower participation.
    CONCLUSION: Community involvement in LSM increased local awareness of malaria as a health problem, its risk factors and control strategies. However, community participation varied among the respondent groups, with labour and time demands of the activities, and lack of incentives, contributing to reduced participation. Innovative tools that can reduce the labour and time demands could improve community participation in the activities. Further studies are required to investigate the forms and modes of delivery of incentives in operational community-driven LSM interventions.
    Keywords:  Bacillus thuringiensis israelensis; Community; Larval source management; Malaria; Malawi
  20. Acta Trop. 2020 May 30. pii: S0001-706X(20)30309-0. [Epub ahead of print] 105558
    Gowelo SA, Chirombo J, Koenraadt CJM, Mzilahowa T, Berg H, Takken W, McCann RS.
      INTRODUCTION: Increasing the knowledgebase of anopheline larval ecology could enable targeted deployment of malaria control efforts and consequently reduce costs of implementation. In Malawi, there exists a knowledge gap in anopheline larval ecology and, therefore, basis for targeted deployment of larval source management (LSM) for malaria control, specifically larvicides. We set out to characterize anopheline larval habitats in the Majete area of Malawi on the basis of habitat ecology and anopheline larval productivity to create a basis for larval control initiatives in the country.METHODS: Longitudinal surveys were conducted in randomly selected larval habitats over a period of fifteen months in Chikwawa district, southern Malawi. Biotic and abiotic parameters of the habitats were modelled to determine their effect on the occurrence and densities of anopheline larvae.
    RESULTS: Seventy aquatic habitats were individually visited between 1-7 times over the study period. A total of 5,123 immature mosquitoes (3,359 anophelines, 1,497 culicines and 267 pupae) were collected. Anopheline and culicine larvae were observed in sympatry in aquatic habitats. Of the nine habitat types followed, dams, swamps, ponds, borehole runoffs and drainage channels were the five most productive habitat types for anopheline mosquitoes. Anopheline densities were higher in aquatic habitats with bare soil making up part of the surrounding land cover (p<0.01) and in aquatic habitats with culicine larvae (p<0.01) than in those surrounded by vegetation and not occupied by culicine larvae. Anopheline densities were significantly lower in highly turbid habitats than in clearer habitats (p<0.01). Presence of predators in the aquatic habitats significantly reduced the probability of anopheline larvae being present (p=0.04).
    CONCLUSIONS: Anopheline larval habitats are widespread in the study area. Presence of bare soil, culicine larvae, predators and the level of turbidity of water are the main determinants of anopheline larval densities in aquatic habitats in Majete, Malawi. While the most productive aquatic habitats should be prioritised, for the most effective control of vectors in the area all available aquatic habitats should be targeted, even those that are not characterized by the identified predictors. Further research is needed to determine whether targeted LSM would be cost-effective when habitat characterisation is included in cost analyses and to establish what methods would make the characterisation of habitats easier.
    Keywords:  Habitat characterization; Larval ecology; Malaria mosquito
  21. J Am Mosq Control Assoc. 2020 Mar;36(1): 1-10
    Hirabayashi K, Nihei N, Kobayashi M, Tsuda Y, Sawabe K.
      Nagano and Yamanashi prefectures of Japan comprise an inland mountain area that extends widely north and south, with elevation varying greatly by location. Mosquitoes transmitting infectious disease have a diversity of habitats in Nagano and Yamanashi, and many species can be expected there. However, there have been few reports on mosquito fauna; in particular, little information is available on mosquitoes such as Aedes albopictus. The mosquito fauna was investigated to clarify their elevational distribution ranging from 317 to 1,534 m, focusing especially on Ae. albopictus, in 24 areas in Nagano and Yamanashi prefectures from July to September in 2012-16. Adult mosquitoes were collected using the Centers for Disease Control and Prevention traps in each area, in addition to larval mosquito collections at several temple and shrine precincts in each area. At sites where elevations were >800 m (14 sites), no adult Ae. albopictus were captured. In addition, larval Ae. albopictus were not collected at elevations >728 m (15 sites). Aedes albopictus was captured at 20 other sites (annual mean air temperature ranged from 9.4 to 15.2°C, July-September mean air temperature ranged from 19.9 to 25.0°C).
    Keywords:  Annual mean air temperature; Centers for Disease Control and Prevention trap; elevation; habitat; larval survey
  22. J Am Mosq Control Assoc. 2020 Mar;36(1): 37-42
    Britch SC, Linthicum KJ, Kline DL, Aldridge RL, Golden FV, Wittie J, Henke J, Hung K, Gutierrez A, Snelling M, Lora C.
      Standard residual pesticides applied to US military materials such as camouflage netting can reduce mosquito biting pressure in the field but may contribute to the evolution of resistance. However, residual applications of a spatial repellent such as transfluthrin could allow mosquitoes the opportunity to escape, only inducing mortality if insects linger, for example after becoming trapped in a treated tent. In this study we investigated the capability of transfluthrin on 2 types of US military material to reduce natural populations of disease vector mosquitoes in a cool-arid desert field environment in southern California. We found that transfluthrin could reduce Culex tarsalis incursion into protected areas by up to 100% upon initial treatment and up to 45% for at least 16 days posttreatment, showing that this compound could be an effective element in the US Department of Defense integrated vector management system appropriate for further study.
    Keywords:  Integrated vector management; military operational entomology; passive control; residual pesticide; resistance management
  23. J Med Entomol. 2020 May 31. pii: tjaa078. [Epub ahead of print]
    Case E, Shragai T, Harrington L, Ren Y, Morreale S, Erickson D.
      Aedes albopictus (Skuse), an invasive disease vector, poses a nuisance and public health threat to communities in the Northeastern United States. Climate change and ongoing adaptation are leading to range expansion of this mosquito into upstate New York and other northeastern states. Organized mosquito control can suppress populations, but it is time consuming, costly, and difficult as Ae. albopictus oviposits in small, artificial, water-holding containers. Unmanned aerial vehicles (UAVs), with centimeter-resolution imaging capabilities, can aid surveillance efforts. In this work, we show that a convolutional neural network trained on images from a UAV is able to detect Ae. albopictus habitat in suburban communities, and the number of containers successfully imaged by UAV predicted the number of containers positive for mosquito larvae per home. The neural network was able to identify some, but not all, potential habitat, with up to 67% precision and 40% recall, and can classify whole properties as positive or negative for larvae 80% of the time. This combined approach of UAV imaging and neutral network analysis has the potential to dramatically increase capacity for surveillance, increasing the reach and reducing the time necessary for conventional on-the-ground surveillance methods.
    Keywords:   Aedes albopictus ; aerial surveillance; machine learning; vector control
  24. J Vector Ecol. 2020 Jun;45(1): 16-24
    Schwarz M, Byrd BD, Marayati BF, Blum PW, Wells MB, Greene AD, Taylor M, Wasserberg G.
      The vertical dimension constitutes an important niche axis along which mosquitoes may adjust their distribution. Here, we evaluated whether the vertical distribution of container-inhabiting Aedes mosquitoes differs along a gradient of anthropogenic land-use intensity within an urban landscape. Using a pulley system, we hung oviposition cups at three heights (ground level, 4.5, and 9 m) and in three habitats: forest, park, and a built environment. We hypothesized that mosquito abundance and diversity would be highest in the least disturbed forest habitat, decrease in the park, and be lowest at the UNC-Greensboro campus. We also expected Aedes albopictus (Skuse) and Ae. triseriatus (Say) to mainly oviposit at ground level and Ae. hendersoni (Cockerell) at canopy height. Aedes albopictus was the most common species (68.8%) collected in all three habitat types and was the only species found in the built environment. In that habitat, Ae. albopictus exhibited a bimodal distribution with the lowest activity at the intermediate height (4.5 m). Aedes triseriatus (28.9%) did not differ in egg abundance between the forest and park habitats but did exhibit diverse vertical habitat use while avoiding the canopy in the park habitat. Aedes hendersoni (2.3%) was the most sylvatic species and oviposited only at ground level. Our results indicate that the vertical distribution of mosquitoes is affected by the type of habitat in which they occur, and that this variation could be driven via local-scale modification of microclimatic factors.
    Keywords:  Aedes albopictus; Aedes hendersoni; Aedes triseriatus; La Crosse encephalitis virus; landscape ecology; urban ecology; vertical oviposition site selection
  25. BMC Public Health. 2020 Jun 05. 20(1): 857
    Boccolini D, Menegon M, Di Luca M, Toma L, Severini F, Marucci G, D'Amato S, Caraglia A, Maraglino FP, Rezza G, Romi R, Gradoni L, Severini C, .
      BACKGROUND: The European region achieved interruption of malaria transmission during the 1970s. Since then, malaria control programs were replaced by surveillance systems in order to prevent possible re-emergence of this disease. Sporadic cases of non-imported malaria were recorded in several European countries in the past decade and locally transmitted outbreaks of Plasmodium vivax, most probably supported by Anopheles sacharovi, have been repeatedly reported from Greece since 2009. The possibility of locally-transmitted malaria has been extensively studied in Italy where the former malaria vector An. labranchiae survived the control campaign which led to malaria elimination. In this study, we present paradigmatic cases that occurred during a 2017 unusual cluster, which caused strong concern in public opinion and were carefully investigated after the implementation of the updated malaria surveillance system.METHODS: For suspected locally-transmitted malaria cases, alerts to Ministry of Health (MoH) and the National Institute of Health (ISS) were mandated by the Local Health Services (LHS). Epidemiological investigations on the transmission modes and the identification of possible infection's source were carried out by LHS, MoH and ISS. Entomological investigations were implemented locally for all suspected locally-transmitted cases that occurred in periods suitable to anopheline activity. Molecular diagnosis by nested-PCR for the five human Plasmodium species was performed to support microscopic diagnosis. In addition, genotyping of P. falciparum isolate was carried out to investigate putative sources of infection and transmission modalities.
    RESULTS: In 2017, a cluster of seven non-imported cases was recorded from August through October. Among them, P. ovale curtisi was responsible of one case whereas six cases were caused by P. falciparum. Two cases were proved to be nosocomial while the other five were recorded as cryptic at the end of epidemiological investigations.
    CONCLUSIONS: The epidemiological evidence shows that the locally acquired events are sporadic, often remain unresolved and classified as cryptic ones despite investigative efforts. The "cluster" of seven non-imported cases that occurred in 2017 in different regions of Italy therefore represents a conscious alert that should lead us to maintain a constant level of surveillance in a former malaria endemic country.
    Keywords:  Anopheles labranchiae; Cryptic case; Genotyping; Hospital-acquired infection; Malaria vector; Non-imported malaria; Plasmodium falciparum; Plasmodium ovale spp.
  26. Infect Dis Poverty. 2020 Jun 05. 9(1): 61
    Bonnet E, Fournet F, Benmarhnia T, Ouedraogo S, Dabiré R, Ridde V.
      BACKGROUND: Several studies highlighted the impact of community-based interventions whose purpose was to reduce the vectors' breeding sites. These strategies are particularly interesting in low-and-middle-income countries which may find it difficult to sustainably assume the cost of insecticide-based interventions. In this case study we determine the spatial distribution of a community-based intervention for dengue vector control using different entomological indices. The objective was to evaluate locally where the intervention was most effective, using spatial analysis methods that are too often neglected in impact assessments.METHODS: Two neighbourhoods, Tampouy and Juvenat in Ouagadougou, Burkina Faso, were chosen among five after a survey was conducted, as part of an assessment related to the burden of dengue. As part of the community-based intervention conducted in Tampouy between August and early October 2016, an entomological survey was implemented in two phases. The first phase consisted of a baseline entomological characterization of potential breeding sites in the neighbourhood of Tampouy as well as in Juvenat, the control area. This phase was conducted in October 2015 at the end of the rainy season. The mosquito breeding sites were screened in randomly selected houses: 206 in Tampouy and 203 in Juvenat. A second phase took place after the intervention, in October 2016. The mosquito breeding sites were investigated in the same yards as during the baseline phase. We performed several entomological analyses to measure site productivity as well as before and after analysis using multilevel linear regression. We used Local Indicators of Spatial Association (LISAs) to analyse spatial concentrations of larvae.
    RESULTS: After the intervention, it is noted that LISAs at Tampouy reveal few aggregates of all types and the suppression of those existing before the intervention. The analysis therefore reveals that the intervention made it possible to reduce the number of concentration areas of high and low values of pupae.
    CONCLUSIONS: The contribution of spatial methods for assessing community-based intervention are relevant for monitoring at local levels as a complement to epidemiological analyses conducted within neighbourhoods. They are useful, therefore, not only for assessment but also for establishing interventions. This study shows that spatial analyses also have their place in population health intervention research.
    Keywords:  Community-based intervention; Spatial analysis; Vector-borne diseases
  27. J Am Mosq Control Assoc. 2020 Mar;36(1): 33-36
    Hernández-Guevara LF, Sánchez-Rámos FJ, Chan-Chable RJ, Hernández-Triana LM, Valdés-Perezgasga MT, González-Acosta C, Correa-Morales F.
      Collections of mosquitoes were conducted for the surveillance of species of medical importance in the state of Morelos, Mexico, in June 2017. Species collected included Mansonia (Mansonia) dyari, which was identified using morphological characters and cytochrome c oxidase I DNA barcoding. Although 3 species of genus Mansonia have been previously reported in Mexico, this is the 1st confirmed record of Ma. dyari in Morelos State, where no Mansonia species had been recorded. Historical records of Ma. dyari and Ma. indubitans in Mexico were reviewed. Therefore, this record increases the number of mosquito species occurring in Morelos to 46. The specimens collected in this study were deposited in the Culicidae collection of the Universidad Autónoma Agraria Antonio Narro, Unidad Laguna.
    Keywords:  Distribution; Mansonia dyari; Mexico; mosquito surveillance
  28. Malar J. 2020 Jun 01. 19(1): 197
    Mundagowa PT, Chimberengwa PT.
      BACKGROUND: Ninety percent of the global annual malaria mortality cases emanate from the African region. About 80-90% of malaria transmissions in sub-Saharan Africa occur indoors during the night. In Zimbabwe, 79% of the population are at risk of contracting the disease. Although the country has made significant progress towards malaria elimination, isolated seasonal outbreaks persistently resurface. In 2017, Beitbridge District was experiencing a second malaria outbreak within 12 months prompting the need for investigating the outbreak.METHODS: An unmatched 1:1 case-control study was conducted to establish the risk factors associated with contracting malaria in Ward 6 of Beitbridge District from week 36 to week 44 of 2017. The sample size constituted of 75 randomly selected cases and 75 purposively selected controls. Data were collected using an interviewer-administered questionnaire and Epi Info version was used to conduct descriptive, bivariate and multivariate analyses of the factors associated with contracting malaria.
    RESULTS: Fifty-two percent of the cases were females and the mean age of cases was 29 ± 13 years. Cases were diagnosed using rapid diagnostic tests. Sleeping in a house with open eaves (OR: 2.97; 95% CI 1.44-6.16; p < 0.01), spending the evenings outdoors (OR: 2.24; 95% CI 1.04-4.85; p = 0.037) and sleeping in a poorly constructed house (OR: 4.33; 95% CI 1.97-9.51; p < 0.01) were significantly associated with contracting malaria while closing eaves was protective (OR: 0.45; 95% CI 0.20-1.02; p = 0.055). After using backward stepwise logistic regression, sleeping in a poorly constructed house was associated with five-fold odds of getting sick from malaria (AOR: 8.40; 95% CI 1.69-41.66; p = 0.009). Those who had mosquito nets did not use them consistently. The district health team and the rural health centre were well prepared to response despite having limited human resources.
    CONCLUSION: Health promotion messages should emphasize the importance of closing the entry points of the malaria vector, and the construction of better houses in the future. Residents had to be educated in the importance of consistent use of mosquito nets. The district had to improve malaria preventive measures like distribution of mosquito nets and lobby for more human resources to assist with malaria surveillance thus, curbing the recurrence of malaria outbreaks.
    Keywords:  Beitbridge; Case–control; Eaves; Housing construction; Malaria outbreak
  29. Insects. 2020 May 28. pii: E331. [Epub ahead of print]11(6):
    Powers JC, Turangan R, Joosse BA, Hillyer JF.
      The immunological strategies employed by insects to overcome infection vary with the type of infection and may change with experience. We investigated how a bacterial infection in the hemocoel of the African malaria mosquito, Anopheles gambiae, prepares the immune system to face a subsequent bacterial infection. For this, adult female mosquitoes were separated into three groups-unmanipulated, injured, or infected with Escherichia coli-and five days later all the mosquitoes were infected with a different strain of E. coli. We found that an injury or a bacterial infection early in life enhances the ability of mosquitoes to kill bacteria later in life. This protection results in higher mosquito survival and is associated with an increased hemocyte density, altered phagocytic activity by individual hemocytes, and the increased expression of nitric oxide synthase and perhaps prophenoloxidase 6. Protection from a second infection likely occurs because of heightened immune awareness due to an already existing infection instead of memory arising from an earlier, cured infection. This study highlights the dynamic nature of the mosquito immune response and how one infection prepares mosquitoes to survive a subsequent infection.
    Keywords:  Anopheles gambiae; immunity; insect; nitric oxide synthase; phagocytosis; prophenoloxidase; survival
  30. Travel Med Infect Dis. 2020 May 27. pii: S1477-8939(20)30232-5. [Epub ahead of print] 101753
    Grobusch MP, van der Fluit KS, Stijnis C, De Pijper CA, Hanscheid T, Gautret P, Schlagenhauf P, Goorhuis A.
      It has been well documented that Zika virus (ZIKV) can be sexually transmitted. Dengue virus (DENV) shows many similarities with ZIKV; both belong to the genus Flavivirus and share the same main vector route of transmission. Moreover, they share overall architectural features on a molecular level, with a highly similar structure and distinctive insertions, deletions and mutations of their respective E proteins, and it has been suggested that they use a common pathophysiological pathway. In view of similarities with other sexually transmissible viruses, the question arises as to whether DENV could also be sexually transmissible. Limited animal model data do not suggest otherwise. The presence of dengue virus in - and human-to-human, non-vector transmission from - various bodily fluids other than semen or vaginal secretions has been documented anecdotally. Several anecdotal reports described prolonged presence of DENV in semen, urine and vaginal secretions. In 2019, two cases of likely sexual transmission were reported from Spain and South Korea, respectively. We discuss the evidence for and against a relevant DENV sexual transmission potential, highlight controversies and propose a future research agenda on this issue.
    Keywords:  DENV; Dengue; Semen; Sexual transmission; Vaginal fluid
  31. Biomed Opt Express. 2020 May 01. 11(5): 2560-2569
    Goodwin A, Glancey M, Ford T, Scavo L, Brey J, Heier C, Durr NJ, Acharya S.
      Targeted vector control strategies aiming to prevent mosquito borne disease are severely limited by the logistical burden of vector surveillance, the monitoring of an area to understand mosquito species composition, abundance and spatial distribution. We describe development of an imaging system within a mosquito trap to remotely identify caught mosquitoes, including selection of the image resolution requirement, a design to meet that specification, and evaluation of the system. The necessary trap image resolution was determined to be 16 lp/mm, or 31.25um. An optics system meeting these specifications was implemented in a BG-GAT mosquito trap. Its ability to provide images suitable for accurate specimen identification was evaluated by providing entomologists with images of individual specimens, taken either with a microscope or within the trap and asking them to provide a species identification, then comparing these results. No difference in identification accuracy between the microscope and the trap images was found; however, due to limitations of human species classification from a single image, the system is only able to provide accurate genus-level mosquito classification. Further integration of this system with machine learning computer vision algorithms has the potential to provide near-real time mosquito surveillance data at the species level.
  32. Malar J. 2020 Jun 05. 19(1): 198
    Kattenberg JH, Gumal DL, Ome-Kaius M, Kiniboro B, Philip M, Jally S, Kasian B, Sambale N, Siba PM, Karl S, Barry AE, Felger I, Kazura JW, Mueller I, Robinson LJ.
      BACKGROUND: In the past decade, national malaria control efforts in Papua New Guinea (PNG) have received renewed support, facilitating nationwide distribution of free long-lasting insecticidal nets (LLINs), as well as improvements in access to parasite-confirmed diagnosis and effective artemisinin-combination therapy in 2011-2012.METHODS: To study the effects of these intensified control efforts on the epidemiology and transmission of Plasmodium falciparum and Plasmodium vivax infections and investigate risk factors at the individual and household level, two cross-sectional surveys were conducted in the East Sepik Province of PNG; one in 2005, before the scale-up of national campaigns and one in late 2012-early 2013, after 2 rounds of LLIN distribution (2008 and 2011-2012). Differences between studies were investigated using Chi square (χ2), Fischer's exact tests and Student's t-test. Multivariable logistic regression models were built to investigate factors associated with infection at the individual and household level.
    RESULTS: The prevalence of P. falciparum and P. vivax in surveyed communities decreased from 55% (2005) to 9% (2013) and 36% to 6%, respectively. The mean multiplicity of infection (MOI) decreased from 1.8 to 1.6 for P. falciparum (p = 0.08) and from 2.2 to 1.4 for P. vivax (p < 0.001). Alongside these reductions, a shift towards a more uniform distribution of infections and illness across age groups was observed but there was greater heterogeneity across the study area and within the study villages. Microscopy positive infections and clinical cases in the household were associated with high rate infection households (> 50% of household members with Plasmodium infection).
    CONCLUSION: After the scale-up of malaria control interventions in PNG between 2008 and 2012, there was a substantial reduction in P. falciparum and P. vivax infection rates in the studies villages in East Sepik Province. Understanding the extent of local heterogeneity in malaria transmission and the driving factors is critical to identify and implement targeted control strategies to ensure the ongoing success of malaria control in PNG and inform the development of tools required to achieve elimination. In household-based interventions, diagnostics with a sensitivity similar to (expert) microscopy could be used to identify and target high rate households.
    Keywords:  Epidemiology; LLINs; Malaria; Malaria control; Plasmodium falciparum; Plasmodium vivax; Spatial heterogeneity
  33. Trop Med Health. 2020 ;48 36
    Ghimire P, Rijal KR, Adhikari N, Thakur GD, Marasini B, Thapa Shrestha U, Banjara MR, Pant SK, Adhikari B, Dumre SP, Singh N, Pigeon O, Chareonviriyaphap T, Chavez I, Ortega L, Hii J.
      Background: Understanding and improving the durability of long-lasting insecticidal nets (LLINs) in the field are critical for planning future implementation strategies including behavioral change for care and maintenance. LLIN distribution at high coverage is considered to be one of the adjunctive transmission reduction strategies in Nepal's Malaria Strategic Plan 2014-2025. The main objective of this study was to assess the durability through assessment of community usage, physical integrity, residual bio-efficacy, and chemical retention in LLINs: Interceptor®, Yorkool®, and PermaNet ®2.0 which were used in Nepal during 2009 through 2013.Methods: Assessments were conducted on random samples (n = 440) of LLINs from the eleven districts representing four ecological zones: Terai plain region (Kailali and Kanchanpur districts), outer Terai fluvial ecosystem (Surkhet, Dang, and Rupandhei districts), inner Terai forest ecosystem (Mahhothari, Dhanusa, and Illam districts), and Hills and river valley (Kavrepalanchock and Sindhupalchok districts). For each LLIN, fabric integrity in terms of proportionate hole index (pHI) and residual bio-efficacy were assessed. However, for chemical retention, a representative sample of 44 nets (15 Yorkool®, 10 Permanet®2.0, and 19 Interceptor®) was evaluated. Data were analyzed using descriptive statistics stratified by LLINs brand, districts, and duration of exposure.
    Results: On average, duration of use of LLINs was shortest for the Yorkool® samples, followed by PermaNet® 2.0 and Interceptor® with median ages of 8.9 (IQR = 0.4), 23.8 (IQR = 3.2), and 50.1 (IQR = 3.2) months, respectively. Over 80% of field distributed Yorkool® and PermaNet® 2.0 nets were in good condition (pHI< 25) compared to Interceptor® (66%). Bio-efficacy analysis showed that average mortality rates of Interceptor and Yorkool were below World Health Organization (WHO) optimal effectiveness of ≥ 80% compared to 2-year-old PermaNet 2.0 which attained 80%. Chemical retention analysis was consistent with bio-efficacy results.
    Conclusion: This study shows that distribution of LLINs is effective for malaria control; however, serviceable life of LLINs should be considered in terms of waning residual bio-efficacy that warrants replacement. As an adjunctive malaria control tool, National Malaria Control Program of Nepal can benefit by renewing the distribution of LLINs in an appropriate time frame in addition to utilizing durable and effective LLINs.
    Keywords:  Bio-efficacy; Chemical retention; Durability; Long-lasting insecticide treated nets; Malaria; Nepal; Proportionate hole index
  34. Infez Med. 2020 Jun 01. 28(2): 243-252
    Pagani G, Zanchetta N, Galimberti L, Oreni L, Passerini S, Giacomelli A, Cordier L, Gismondo MR, Rizzardini G, Galli M, Antinori S.
      Dengue Fever (DF), transmitted by Aedes mosquitoes, is the most common arthropod-borne infection, it is almost ubiquitous in tropical and subtropical areas with an estimate of 360 million infections per year. A competent vector (A. albopictus) is present in most of Southern Europe and is endemic in Italy. We conducted a 16-year retrospective study of probable/confirmed dengue fever observed at the Department of Infectious Diseases of Luigi Sacco Hospital in Milan, Italy. Overall 122 patients were included in the study, 106 with probable and 16 with proven diagnosis of dengue fever. Most patients (91%) were Italian, with a median age of 35 years (IQR 29-46 years) and similar gender distribution, travelling for tourism (80%). Asia (mainly South East Asia and Indian Subcontinent) was the most frequent travel destination (55%), followed by Central America and the Caribbeans (22%). August-September was the peak season of presentation (42.6%). The majority of our diagnoses were based on serology alone. The most common signs and symptoms were fever (99,2%), maculopapular rash (50,8%), headache (50,8%), arthralgias (50,8%) and myalgias (46,7%). Leukopenia (77%), thrombocytopenia (81%) and altered LDH, AST and ALT (respectively 60,6%, 54,1% and 45,9%) were the most common laboratory test's abnormalities. No cases of severe DF were recorded. Our epidemiological and clinical findings are largely in accordance with most recent studies about imported DF in Europe. Although very similar in presentation to other arthropod-borne illnesses, some clinical features may help in differentiating DF from other causes of fever in the returning traveler.