bims-mosdis 2020-03-29 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2020–03–29
seventeen papers selected by
Richard Halfpenny, Staffordshire University

Cemeteries in Miami-Dade County, Florida are important areas to be targeted in mosquito management and control efforts.
Different populations of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) from Central Africa are susceptible to Zika virus infection.
An assessment of adult mosquito collection techniques for studying species abundance and diversity in Maferinyah, Guinea.
Use of Microbiota to Fight Mosquito-Borne Disease.
Vaccination with Aedes aegypti AgBR1 Delays Lethal Mosquito-Borne Zika Virus Infection in Mice.
Resistance status of Anopheles gambiae (s.l.) to four commonly used insecticides for malaria vector control in South-East Nigeria.
Toxic assessment, growth disrupting and neurotoxic effects of red seaweeds' botanicals against the dengue vector mosquito Aedes aegypti L.
NS4/5 mutations enhance flavivirus Bamaga virus infectivity and pathogenicity in vitro and in vivo.
The role of windows of selection and windows of dominance in the evolution of insecticide resistance in human disease vectors.
Variation in the microbiota across different developmental stages of Aedes albopictus is affected by ampicillin exposure.
Comparative genomic analysis and mosquito larvicidal activity of four Bacillus thuringiensis serovar israelensis strains.
Evaluation of Malaria Cases Detected in Antalya Province between 2012 and 2017
Structural Variation of the X Chromosome Heterochromatin in the Anopheles gambiae Complex.
Quantifying geographic accessibility to improve efficiency of entomological monitoring.
Mosquito Community Composition, Seasonal Distributions, and Trap Bias in Northeastern Florida.
School-based health education for dengue control in Kelantan, Malaysia: Impact on knowledge, attitude and practice.
Mechanism and plasticity of vectors' host-seeking behavior.

PLoS One. 2020 ;15(3): e0230748

Cemeteries in Miami-Dade County, Florida are important areas to be targeted in mosquito management and control efforts.

André B B Wilke, Chalmers Vasquez, Augusto Carvajal, Maday Moreno, Yadira Diaz, Teresa Belledent, Laurin Gibson, William D Petrie, Douglas O Fuller, John C Beier.

Definable habitats at the neighborhood level provide a wide range of favorable habitats with optimal conditions and environmental resources for mosquito survival. Problematic habitats for controlling mosquitoes in urban environments such as tire shops, bromeliad patches, and construction sites must be taken into consideration in the development of effective mosquito management and control in urban areas. Cemeteries are often located in highly urbanized areas serving as a haven for populations of vector mosquito species due to the availability of natural resources present in most cemeteries. Even though Miami-Dade County, Florida was the most affected area in the United States during the Zika virus outbreak in 2016 and is currently under a mosquito-borne illness alert after 14 confirmed locally transmitted dengue cases, the role of cemeteries in the proliferation of vector mosquitoes is unknown. Therefore, our objective was to use a cross-sectional experimental design to survey twelve cemeteries across Miami-Dade County to assess if vector mosquitoes in Miami can be found in these areas. Our results are indicating that vector mosquitoes are able to successfully exploit the resources available in the cemeteries. Culex quinquefasciatus was the most abundant species but it was neither as frequent nor present in its immature form as Aedes aegypti and Aedes albopictus. This study revealed that vector mosquitoes, such as Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus are successfully exploiting the resources available in these areas being able to thrive and reach high numbers. Mosquito control strategies should consider both long-term strategies, based on changing human behavior to reduce the availability of aquatic habitats for vector mosquitoes; as well as short-term strategies such as drilling holes or adding larvicide to the flower vases. Simple practices would greatly help improve the effectiveness of mosquito management and control in these problematic urban habitats.

DOI: https://doi.org/10.1371/journal.pone.0230748
PLoS Negl Trop Dis. 2020 Mar 23. 14(3): e0008163

Different populations of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) from Central Africa are susceptible to Zika virus infection.

Basile Kamgang, Marie Vazeille, Armel Tedjou, Aurélie P Yougang, Theodel A Wilson-Bahun, Laurence Mousson, Charles S Wondji, Anna-Bella Failloux.

Zika virus (ZIKV) is a Flavivirus (Flaviviridae) transmitted to humans mainly by the bite of an infected Aedes mosquitoes. Aedes aegypti is the primary epidemic vector of ZIKV and Ae. albopictus, the secondary one. However, the epidemiological role of both Aedes species in Central Africa where Ae. albopictus was recently introduced is poorly characterized. Field-collected strains of Ae. aegypti and Ae. albopictus from different ecological settings in Central Africa were experimentally infected with a ZIKV strain isolated in West Africa. Mosquitoes were analysed at 14- and 21-days post-exposure. Both Ae. aegypti and Ae. albopictus were able to transmit ZIKV but with higher overall transmission efficiency for Ae. aegypti (57.9%) compared to Ae. albopictus (41.5%). In addition, disseminated infection and transmission rates for both Ae. aegypti and Ae. albopictus varied significantly according to the location where they were sampled from. We conclude that both Ae. aegypti and Ae. albopictus are able to transmit ZIKV and may intervene as active Zika vectors in Central Africa. These findings could contribute to a better understanding of the epidemiological transmission of ZIKV in Central Africa and develop suitable strategy to prevent major ZIKV outbreaks in this region.

DOI: https://doi.org/10.1371/journal.pntd.0008163
Parasit Vectors. 2020 Mar 24. 13(1): 150

An assessment of adult mosquito collection techniques for studying species abundance and diversity in Maferinyah, Guinea.

Cintia Cansado-Utrilla, Claire L Jeffries, Mojca Kristan, Victor A Brugman, Patrick Heard, Gnepou Camara, Moussa Sylla, Abdoul H Beavogui, Louisa A Messenger, Seth R Irish, Thomas Walker.

   BACKGROUND: Several mosquito collection methods are routinely used in vector control programmes. However, they target different behaviours causing bias in estimation of species diversity and abundance. Given the paucity of mosquito trap data in West Africa, we compared the performance of five trap-lure combinations and Human Landing Catches (HLCs) in Guinea.
METHODS: CDC light traps (LT), BG sentinel 2 traps (BG2T), gravid traps (GT) and Stealth traps (ST) were compared in a 5 × 5 Latin Square design in three villages in Guinea between June and July 2018. The ST, a portable trap which performs similarly to a LT but incorporates LEDs and incandescent light, was included since it has not been widely tested. BG2T were used with BG and MB5 lures instead of CO2 to test the efficacy of these attractants. HLCs were performed for 5 nights, but not as part of the Latin Square. A Generalised Linear Mixed Model was applied to compare the effect of the traps, sites and collection times on mosquito abundance. Species identification was confirmed using PCR-based analysis and Sanger sequencing.
RESULTS: A total of 10,610 mosquitoes were captured across five traps. ST collected significantly more mosquitoes (7096) than the rest of the traps, but resulted in a higher number of damaged specimens. ST and BG2T collected the highest numbers of Anopheles gambiae (s.l.) and Aedes aegypti mosquitoes, respectively. HLCs captured predominantly An. coluzzii (41%) and hybrids of An. gambiae and An. coluzzii (36%) in contrast to the five traps, which captured predominantly An. melas (83%). The rural site (Senguelen) presented the highest abundance of mosquitoes and overall diversity in comparison with Fandie (semi-rural) and Maferinyah Centre I (semi-urban). Our results confirm the presence of four species for the first time in Guinea.
CONCLUSIONS: ST collected the highest number of mosquitoes suggesting this trap may play an important role for mosquito surveillance in Guinea and similar sites in West Africa. We recommend the incorporation of molecular tools in entomological studies since they have helped to identify 25 mosquito species in this area.

Keywords:  BG sentinel 2 trap; CDC light trap; Gravid Trap; Guinea; Mosquito; Stealth trap

DOI:  https://doi.org/10.1186/s13071-020-04023-3
Front Genet. 2020 ;11 196

Use of Microbiota to Fight Mosquito-Borne Disease.

Wei Huang, Sibao Wang, Marcelo Jacobs-Lorena.

  Mosquito-borne diseases cause more than 700 million people infected and one million people die (Caraballo and King, 2014). With the limitations of progress toward elimination imposed by insecticide- and drug-resistance, combined with the lack of vaccines, innovative strategies to fight mosquito-borne disease are urgently needed. In recent years, the use of mosquito microbiota has shown great potential for cutting down transmission of mosquito-borne pathogens. Here we review what is known about the mosquito microbiota and how this knowledge is being used to develop new ways to control mosquito-borne disease. We also discuss the challenges for the eventual release of genetically modified (GM) symbionts in the field.

Keywords:  arboviruses; insect microbiota; malaria; mosquito-pathogen interactions; paratransgenesis

DOI:  https://doi.org/10.3389/fgene.2020.00196
Vaccines (Basel). 2020 Mar 25. pii: E145. [Epub ahead of print]8(2):

Vaccination with Aedes aegypti AgBR1 Delays Lethal Mosquito-Borne Zika Virus Infection in Mice.

Yuchen Wang, Alejandro Marin-Lopez, Junjun Jiang, Michel Ledizet, Erol Fikrig.

  Zika Virus (ZIKV) is transmitted primarily by Aedes aegypti mosquitoes, resulting in asymptomatic infection, or acute illness with a fever and headache, or neurological complications, such as Guillain-Barre syndrome or fetal microcephaly. Previously, we determined that AgBR1, a mosquito salivary protein, induces inflammatory responses at the bite site, and that passive immunization with AgBR1 antiserum influences mosquito-transmitted ZIKV infection. Here, we show that the active immunization of mice with AgBR1 adjuvanted with aluminum hydroxide delays lethal mosquito-borne ZIKV infection, suggesting that AgBR1 may be used as part of a vaccine to combat ZIKV.

Keywords:  Aedes aegypti mosquito; Zika virus; salivary protein; vaccine

DOI:  https://doi.org/10.3390/vaccines8020145
Parasit Vectors. 2020 Mar 24. 13(1): 152

Resistance status of Anopheles gambiae (s.l.) to four commonly used insecticides for malaria vector control in South-East Nigeria.

Okechukwu Chukwuekezie, Emmanuel Nwosu, Udoka Nwangwu, Festus Dogunro, Cosmas Onwude, Nneka Agashi, Ebuka Ezihe, Clementina Anioke, Stephen Anokwu, Emelda Eloy, Peter Attah, Francis Orizu, Sylvester Ewo, Angela Okoronkwo, Anumba Joseph, Ijeoma Ikeakor, Sylvester Haruna, Virgile Gnanguenon.

   BACKGROUND: Progress made in the control of malaria vectors globally is largely due to the use of insecticides. However, success in the fight against malaria has slowed down or even stalled due to a host of factors including insecticide resistance. The greatest burden of the disease is felt in Africa, particularly Nigeria. Unfortunately, adequate information on insecticide resistance is lacking in many parts of the country, particularly the South-East Zone. Hence, this study aims to bridge the information gap in the Zone.
METHODS: The study was conducted from April to December 2016. Anopheles gambiae (s.l.) larvae and pupae were collected from one community each, in the five states of the South-East Zone and reared to the adult stage. The adults were subjected to bioassays for insecticide resistance in accordance with the World Health Organization test procedures, across the four classes of insecticides used in public health. The mosquitoes were also subjected to molecular identification to the species level, and genotyped for West African knockdown resistance mutation (L1014F) and insensitive acetylcholinesterase-1 resistance mutation (G119S).
RESULTS: The mosquitoes were susceptible (100%) to bendiocarb but resistant to pirimiphos-methyl (39.6%), deltamethrin (57%) and dichlorodiphenyltrichloroethane (DDT) (13%). Molecular analysis revealed that only An. gambiae (sensu stricto) was found in all the states except for Ebonyi, where only Anopheles coluzzii was present. High frequencies (0.6-0.9) of the L1014F mutation were found across the zone. The L1014F mutation was significantly higher in An. gambiae (s.s.) than in An. coluzzii (P < 0.0001). A relatively low frequency (0.2) of the G119S mutation was found in An. coluzzii, and only in Ebonyi State.
CONCLUSION: The results show that mosquitoes collected from the South-East Zone of Nigeria were resistant to all insecticides used, except for bendiocarb. The presence of L1014F and G119S resistance mutations reported in this study calls for urgent attention to stop the growing threat of insecticide resistance in the country.

Keywords:  Acetylcholinesterase-1 resistance; Anopheles; Insecticide resistance; Knockdown resistance; South-East Nigeria

DOI:  https://doi.org/10.1186/s13071-020-04027-z
Ecotoxicol Environ Saf. 2020 Mar 18. pii: S0147-6513(20)30290-6. [Epub ahead of print]195 110451

Toxic assessment, growth disrupting and neurotoxic effects of red seaweeds' botanicals against the dengue vector mosquito Aedes aegypti L.

Rabia Bibi, Rajput Muhammad Tariq, Munawwer Rasheed.

  Application of synthetic pesticides over decades to control insects, pests, and disease vectors has resulted in negative impacts on environment and health. The current study assessed the toxicological effects of 12 botanicals obtained from 4 different red seaweeds against the dengue vector mosquito Aedes aegypti L. (Diptera: Culicidae). Four species of red seaweeds, namely Laurencia karachiana, Gracilaria foliifera, Jania rubens, Asparagopsis taxiformis, were collected from Karachi coast and extracted with hexane, dichloromethane and methanol. The efficiency of these extracts was determined by using a dose-response bioassay method against 4th instar larvae of Ae. aegypti. Separate investigations on the toxicity and IGI effects were done. Comparative studies showed that the hexane extracts induced more toxic effects. Based on the LC50 values, obtained after 24 h of treatments, hexane extract of J. rubens (HJ) exhibited toxic effects with LC50 32 μg/mL, (equivalent to GHS category 3), followed by G. foliifera (HG) (LC50 76.8 μg/mL). HJ also showed prominent neurotoxic effects within 1-6 h. Comparatively, higher morphological abnormalities and growth inhibiting (IGI) effects were obtained in the dichloromethane and methanol extracts treated larvae, after 48-96 h, resulting in the formation of immature life forms such as larvi-pupae and pupi-adult. Presumptive growth inhibiting effects were also noted. These included formation of albino and black pupae, deformities in the internal structure of the treated larvae and the chitin synthesis related effects such as 'inhibiting effect on adult emergence'. Finding revealed that red seaweeds, harvested from the Arabian Sea, have potentials to affect Ae. aegypti survival and thus can be utilized as green pesticides.

Keywords:  Aedes aegypti; Asparagopsis taxiformis; Gracilaria foliifera; Jania rubens; Laurencia karachiana; Pesticidal effects

DOI:  https://doi.org/10.1016/j.ecoenv.2020.110451
PLoS Negl Trop Dis. 2020 Mar;14(3): e0008166

NS4/5 mutations enhance flavivirus Bamaga virus infectivity and pathogenicity in vitro and in vivo.

Agathe M G Colmant, Helle Bielefeldt-Ohmann, Laura J Vet, Caitlin A O'Brien, Richard A Bowen, Airn E Hartwig, Steven Davis, Thisun B H Piyasena, Gervais Habarugira, Jessica J Harrison, Jody Hobson-Peters, Roy A Hall.

Flaviviruses such as yellow fever, dengue or Zika viruses are responsible for significant human and veterinary diseases worldwide. These viruses contain an RNA genome, prone to mutations, which enhances their potential to emerge as pathogens. Bamaga virus (BgV) is a mosquito-borne flavivirus in the yellow fever virus group that we have previously shown to be host-restricted in vertebrates and horizontally transmissible by Culex mosquitoes. Here, we aimed to characterise BgV host-restriction and to investigate the mechanisms involved. We showed that BgV could not replicate in a wide range of vertebrate cell lines and animal species. We determined that the mechanisms involved in BgV host-restriction were independent of the type-1 interferon response and RNAse L activity. Using a BgV infectious clone and two chimeric viruses generated as hybrids between BgV and West Nile virus, we demonstrated that BgV host-restriction occurred post-cell entry. Notably, BgV host-restriction was shown to be temperature-dependent, as BgV replicated in all vertebrate cell lines at 34°C but only in a subset at 37°C. Serial passaging of BgV in Vero cells resulted in adaptive mutants capable of efficient replication at 37°C. The identified mutations resulted in amino acid substitutions in NS4A-S124F, NS4B-N244K and NS5-G2C, all occurring close to a viral protease cleavage site (NS4A/2K and NS4B/NS5). These mutations were reverse engineered into infectious clones of BgV, which revealed that NS4B-N244K and NS5-G2C were sufficient to restore BgV replication in vertebrate cells at 37°C, while NS4A-S124F further increased replication efficiency. When these mutant viruses were injected into immunocompetent mice, alongside BgV and West Nile virus chimeras, infection and neurovirulence were enhanced as determined by clinical scores, seroconversion, micro-neutralisation, viremia, histopathology and immunohistochemistry, confirming the involvement of these residues in the attenuation of BgV. Our studies identify a new mechanism of host-restriction and attenuation of a mosquito-borne flavivirus.

DOI: https://doi.org/10.1371/journal.pntd.0008166
Evol Appl. 2020 Apr;13(4): 738-751

The role of windows of selection and windows of dominance in the evolution of insecticide resistance in human disease vectors.

Andy South, Rosemary Lees, Gala Garrod, Jessica Carson, David Malone, Ian Hastings.

  Persistent insecticides sprayed onto house walls, and incorporated into insecticide-treated bednets, provide long-acting, cost-effective control of vector-borne diseases such as malaria and leishmaniasis. The high concentrations that occur immediately postdeployment may kill both resistant and susceptible insects. However, insecticide concentration, and therefore killing ability, declines in the months after deployment. As concentrations decline, resistant insects start to survive, while susceptible insects are still killed. The period of time after deployment, within which the mortality of resistant individuals is lower than that of susceptible ones, has been termed the "window of selection" in other contexts. It is recognized as driving resistance in bacteria and malaria parasites, both of which are predominantly haploid. We argue that paying more attention to these mortality differences can help understand the evolution of insecticide resistance. Because insects are diploid, resistance encoded by single genes generates heterozygotes. This gives the potential for a narrower "window of dominance," within the window of selection, where heterozygote mortality is lower than that of susceptible homozygotes. We explore the general properties of windows of selection and dominance in driving resistance. We quantify their likely effect using data from new laboratory experiments and published data from the laboratory and field. These windows can persist months or years after insecticide deployments. Differential mortalities of resistant, susceptible and heterozygous genotypes, after public health deployments, constitute a major challenge to controlling resistance. Greater attention to mortality differences by genotype would inform strategies to reduce the evolution of resistance to existing and new insecticides.

Keywords:  dose–response; drug resistance; insecticide resistance; insecticide resistance management; malaria; vector‐borne diseases; window of dominance; window of selection

DOI:  https://doi.org/10.1111/eva.12897
Microbiologyopen. 2020 Mar 24. e1026

Variation in the microbiota across different developmental stages of Aedes albopictus is affected by ampicillin exposure.

Wan Qing, Xue Zhijing, Yu Guangfu, Meng Fengxia, Liu Qiyong, Zhang Zhong, Zhang Ruiling.

  The microbiota plays an important role in the growth of mosquitoes and the transmission of mosquito-borne pathogens. The effects of changes in aquatic habitats in which mosquitoes live, as one of the major factors closely associated with the microbial communities of mosquitoes, on the microbiota of different developmental stages remain to be elucidated. Here, we compared the microbiota of larvae and pupae of Aedes albopictus exposed to different ampicillin concentrations and investigated the bacterial composition of adult females. The results demonstrate that the microbial community differed substantially between developmental stages and that samples of the same stages shared similarities, whereas differences were observed between adult females. Based on all observations, we hypothesize that the use of ampicillin caused dysbiosis rather than excluding bacteria from mosquitoes and that the disturbing effect of ampicillin was obvious in adults. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that most of the bacteria identified in this study were significantly associated with metabolism. Taken together, our results indicate that ampicillin can change the abundance of bacteria, while microbial communities of Ae. albopictus showed obvious stage-specific characteristics. Further investigations are needed to characterize specific bacterial components that are affected by ampicillin exposure and to quantify their functions, thereby providing a better understanding of the influence of antibiotics on microbial communities at different life stages.

Keywords:  16S rRNA gene; Asian tiger mosquito; antibiotic; stage-specific

DOI:  https://doi.org/10.1002/mbo3.1026
Sci Rep. 2020 Mar 26. 10(1): 5518

Comparative genomic analysis and mosquito larvicidal activity of four Bacillus thuringiensis serovar israelensis strains.

Giselly B Alves, Fernando L Melo, Eugenio E Oliveira, Khalid Haddi, Lara T M Costa, Marcelo L Dias, Fabrício S Campos, Eliseu J G Pereira, Roberto F T Corrêa, Sergio D Ascêncio, Gil R Santos, Guy Smagghe, Bergmann M Ribeiro, Raimundo W S Aguiar.

Bacillus thuringiensis serovar israelensis (Bti) is used to control insect vectors of human and animal diseases. In the present study, the toxicity of four strains of Bti, named T0124, T0131, T0137, and T0139, toward Aedes aegypti and Culex quinquefasciatus larvae was analyzed. The T0131 strain showed the highest larvicidal activity against A. aegypti (LC50 = 0.015 µg/ml) and C. quinquefasciatus larvae (LC50 = 0.035 µg/ml) when compared to the other strains. Furthermore, the genomic sequences of the four strains were obtained and compared. These Bti strains had chromosomes sizes of approximately 5.4 Mb with GC contents of ~35% and 5472-5477 putative coding regions. Three small plasmids (5.4, 6.8, and 7.6 kb) and three large plasmids (127, 235, and 359 kb) were found in the extrachromosomal content of all four strains. The SNP-based phylogeny revealed close relationship among isolates from this study and other Bti isolates, and SNPs analysis of the plasmids 127 kb did not reveal any mutations in δ-endotoxins genes. This newly acquired sequence data for these Bti strains may be useful in the search for novel insecticidal toxins to improve existing ones or develop new strategies for the biological control of important insect vectors of human and animal diseases.

DOI: https://doi.org/10.1038/s41598-020-60670-7
Turkiye Parazitol Derg. 2020 Mar 20. 44(1): 1-6

Evaluation of Malaria Cases Detected in Antalya Province between 2012 and 2017

Önder Ser.

   Objective: Malaria is an important infectious disease that is transmitted by female mosquitoes of the genus Anopheles infected with parasites of the genus Plasmodium. In this research, it was aimed to contribute to the ongoing studies on malaria control in Antalya.
Methods: In this study, malaria data between 2012-2017 obtained from Antalya Provincial Directorate of Health were used. The patients with malaria were evaluated in terms of the years and months they were detected in, age group, gender, parasite species which were detected and their sources.
Results: During the 6-year period, a total of 1905 blood samples were surveyed and 36 (1.89%) patients were reported. The most patients occurred in June and August (5 patients in each month, 13.89%). Of the patients, 94.44% (34 patients) were 15 years old and over. By gender, 83.33% (n=30) of patients were male, 16.67% (n=6) were female. The disease agent responsible for most of the patients with malaria was P. falciparum (80.55%, 29 patients), followed by P. vivax (11.11%, 4 patients), P. ovale (5.56%, 2 patients) and P. malariae (2.78%, 1 patient). All patients with malaria were from abroad.
Conclusion: For malaria control, studies on the early diagnosis and treatment of the disease and the integrated mosquito control programs should be uninterruptedly maintained.

Keywords:  Anopheles; Antalya; epidemiology; malaria; Plasmodium

DOI:  https://doi.org/10.4274/tpd.galenos.2019.6466
Genes (Basel). 2020 Mar 19. pii: E327. [Epub ahead of print]11(3):

Structural Variation of the X Chromosome Heterochromatin in the Anopheles gambiae Complex.

Atashi Sharma, Nicholas A Kinney, Vladimir A Timoshevskiy, Maria V Sharakhova, Igor V Sharakhov.

  Heterochromatin is identified as a potential factor driving diversification of species. To understand the magnitude of heterochromatin variation within the Anopheles gambiae complex of malaria mosquitoes, we analyzed metaphase chromosomes in An. arabiensis, An. coluzzii, An. gambiae, An. merus, and An. quadriannulatus. Using fluorescence in situ hybridization (FISH) with ribosomal DNA (rDNA), a highly repetitive fraction of DNA, and heterochromatic Bacterial Artificial Chromosome (BAC) clones, we established the correspondence of pericentric heterochromatin between the metaphase and polytene X chromosomes of An. gambiae. We then developed chromosome idiograms and demonstrated that the X chromosomes exhibit qualitative differences in their pattern of heterochromatic bands and position of satellite DNA (satDNA) repeats among the sibling species with postzygotic isolation, An. arabiensis, An. merus, An. quadriannulatus, and An. coluzzii or An. gambiae. The identified differences in the size and structure of the X chromosome heterochromatin point to a possible role of repetitive DNA in speciation of mosquitoes. We found that An. coluzzii and An. gambiae, incipient species with prezygotic isolation, share variations in the relative positions of the satDNA repeats and the proximal heterochromatin band on the X chromosomes. This previously unknown genetic polymorphism in malaria mosquitoes may be caused by a differential amplification of DNA repeats or an inversion in the sex chromosome heterochromatin.

Keywords:  Anopheles; X chromosome; heterochromatin; mitotic chromosome; mosquito; satellite DNA; sex chromosome

DOI:  https://doi.org/10.3390/genes11030327
PLoS Negl Trop Dis. 2020 Mar 23. 14(3): e0008096

Quantifying geographic accessibility to improve efficiency of entomological monitoring.

Joshua Longbottom, Ana Krause, Stephen J Torr, Michelle C Stanton.

BACKGROUND: Vector-borne diseases are important causes of mortality and morbidity in humans and livestock, particularly for poorer communities and countries in the tropics. Large-scale programs against these diseases, for example malaria, dengue and African trypanosomiasis, include vector control, and assessing the impact of this intervention requires frequent and extensive monitoring of disease vector abundance. Such monitoring can be expensive, especially in the later stages of a successful program where numbers of vectors and cases are low.
METHODOLOGY/PRINCIPAL FINDINGS: We developed a system that allows the identification of monitoring sites where pre-intervention densities of vectors are predicted to be high, and travel cost to sites is low, highlighting the most efficient locations for longitudinal monitoring. Using remotely sensed imagery and an image classification algorithm, we mapped landscape resistance associated with on- and off-road travel for every gridded location (3m and 0.5m grid cells) within Koboko district, Uganda. We combine the accessibility surface with pre-existing estimates of tsetse abundance and propose a stratified sampling approach to determine the most efficient locations for longitudinal data collection. Our modelled predictions were validated against empirical measurements of travel-time and existing maps of road networks. We applied this approach in northern Uganda where a large-scale vector control program is being implemented to control human African trypanosomiasis, a neglected tropical disease (NTD) caused by trypanosomes transmitted by tsetse flies. Our accessibility surfaces indicate a high performance when compared to empirical data, with remote sensing identifying a further ~70% of roads than existing networks.
CONCLUSIONS/SIGNIFICANCE: By integrating such estimates with predictions of tsetse abundance, we propose a methodology to determine the optimal placement of sentinel monitoring sites for evaluating control programme efficacy, moving from a nuanced, ad-hoc approach incorporating intuition, knowledge of vector ecology and local knowledge of geographic accessibility, to a reproducible, quantifiable one.

DOI: https://doi.org/10.1371/journal.pntd.0008096
J Med Entomol. 2020 Mar 24. pii: tjaa053. [Epub ahead of print]

Mosquito Community Composition, Seasonal Distributions, and Trap Bias in Northeastern Florida.

Bryan V Giordano, Suzanne K Bartlett, Drake A Falcon, Raymond P Lucas, Miranda J Tressler, Lindsay P Campbell.

  Mosquito control agencies monitor mosquito diversity and abundance through a variety of trap types. Although various long-term ecological data sets exist, little work has been done to address the sampling effort required to capture mosquito community diversity by trap type and few spatiotemporal distributions of vector species have been described. Here, we describe the seasonal distributions of vector species of importance, assess trapping effort needed to capture the diversity of the mosquito community, and use a partial redundancy analysis to identify trap bias from four commonly deployed adult mosquito traps in Volusia County, Florida. Collections were made with American Biophysics Corporation (ABC) light traps, Biogents Sentinel (BGS) traps, chicken coop exit traps, and gravid traps. We collected a total of 238,301 adult female mosquitoes belonging to 11 genera and 36 species, 12 of which we deemed to be vector species of epidemiological importance. We found that ABC traps not only yielded the greatest abundance and diversity but also captured several nonvector species. BGS and gravid traps yielded the highest proportions of vector species; exit traps recorded the lowest abundances and species richness. Wintertime abundances of several species demonstrated a need for year-round surveillance in the study area; partial redundancy analysis revealed that trap type explained a significant proportion of the variance in our data set, with certain vector species associated with specific trap types. Increased awareness regarding the amount of trapping effort needed to detect vector species diversity will help to optimize efforts in the field, leading to more effective resource allocation.

Keywords:  Culicidae; sampling and detection; surveillance; vector ecology

DOI:  https://doi.org/10.1093/jme/tjaa053
PLoS Negl Trop Dis. 2020 Mar 27. 14(3): e0008075

School-based health education for dengue control in Kelantan, Malaysia: Impact on knowledge, attitude and practice.

Rattanam AhbiRami, Wan Fatma Zuharah.

The massive flood in Malaysia's east coast in December 2014 has placed Kelantan in a possible dengue outbreak risk. At this point, community awareness is essential in preventing disease spread. However, no data on knowledge, attitude, and practice (KAP) of dengue in Kelantan have existed in relevance to flood disaster, although such information is necessary for the vector control programs. The purpose of this study is to assess the KAP regarding dengue among school children from flooded and unflooded areas and to evaluate the effectiveness of the dengue health education program in improving their KAP level. A school-based pre- and post-tests design was utilized in this study whereby a booklet on dengue was distributed during the interphase of the tests. The information collected was on the socio-demographic, KAP and the source of dengue information. We statistically compared the KAP between the two study sites and the pre- and post-test scores to evaluate the health education program. A total of 203 students participated in the survey, and 51.7% of them were flood victims. When comparing the baseline KAP, the respondents from the unflooded area had higher knowledge scores compared to those from the flooded area (P<0.05), while non-significant differences were observed in the attitude and practice between the two study areas (P>0.05). The health education program significantly improved knowledge and practice in the flooded area and knowledge only in the unflooded area (P<0.05). The multinomial regression analysis suggests that age and dengue history are the primary determinants that influence the high practice level in both areas. We suggest the need to increase routine dengue health education programs to all age groups targeting both high and low dengue risk areas, and the necessity to ensure the translation of positive knowledge and attitude changes into real dengue preventive practices.

DOI: https://doi.org/10.1371/journal.pntd.0008075
Curr Opin Insect Sci. 2020 Feb 14. pii: S2214-5745(20)30023-7. [Epub ahead of print]40 1-5

Mechanism and plasticity of vectors' host-seeking behavior.

Nicole E Wynne, Marcelo G Lorenzo, Clément Vinauger.

The host-seeking behavior of disease vector insects is central to the transmission of pathogens. In this context, an improved understanding of the mechanisms that allow vectors to detect, identify and locate a potential host will be crucial to refine existing control strategies and invent new ones. Host-seeking is mediated by the integration of cues that are processed by multiple sensory modalities, and provide robust information about host location and quality. Responses to these cues are plastic and vary as a function of the vector's internal state, age, and previous experience. Vectors also integrate other factors such as time of day, or even the level of defensiveness of the host. Here, we review the most recent advances on the molecular basis of host-seeking behavior, with a particular emphasis on disease vector mosquitoes.

DOI: https://doi.org/10.1016/j.cois.2020.02.001