bims-mosdis Biomed News
on Mosquito distribution and disease
Issue of 2020‒08‒09
thirty-one papers selected by
Richard Halfpenny
Staffordshire University


  1. Parasit Vectors. 2020 Aug 06. 13(1): 398
    Gomard Y, Lebon C, Mavingui P, Atyame CM.
      BACKGROUND: Zika virus (ZIKV) is a mosquito-borne flavivirus that recently emerged in the South Pacific islands and Americas where unprecedented outbreaks were reported. Although Aedes aegypti is considered to be the main vector for ZIKV, other mosquito species have been shown to be potential vectors and differences in vector competence with respect to mosquito strain and ZIKV strain have been demonstrated. In this study we compared the vector competence of three mosquito species Aedes albopictus, Ae. aegypti and Culex quinquefasciatus from Reunion Island for three ZIKV strains.METHODS: Five mosquito strains (2 strains of Ae. albopictus, 1 of Ae. aegypti and 2 of Cx. quinquefasciatus) were exposed to three ZIKV strains: one African strain (Dak84) and two Asian strains (PaRi_2015 and MAS66). The vector competence parameters (infection rate, dissemination efficiency and transmission efficiency) and viral loads were examined at 14 and 21 days post-infection.
    RESULTS: The two Cx. quinquefasciatus strains did not become infected and were therefore unable to either disseminate or transmit any of the three ZIKV strains. Aedes albopictus and Ae. aegypti strains were poorly competent for the two Asian ZIKV strains, while both mosquito species displayed higher infection rates, dissemination and transmission efficiencies for the African ZIKV Dak84 strain. However, this African ZIKV strain was better transmitted by Ae. aegypti as compared to Ae. albopictus.
    CONCLUSIONS: Our results show that both Ae. albopictus and Ae. aegypti, from Reunion Island, are more likely to be competent for ZIKV in contrast to Cx. quinquefasciatus which appeared refractory to all tested ZIKV strains. This improves our understanding of the role of mosquito species in the risk of the ZIKV emergence on Reunion Island.
    Keywords:  Flavivirus; Mosquito vectors; Reunion Island; Vector competence
    DOI:  https://doi.org/10.1186/s13071-020-04267-z
  2. Transbound Emerg Dis. 2020 Aug 04.
    Ferraguti M, Heesterbeek H, Martínez-de la Puente J, Jiménez-Clavero MÁ, Vázquez A, Ruiz S, Llorente F, Roiz D, Vernooij H, Soriguer R, Figuerola J.
      Vector-borne diseases, especially those transmitted by mosquitoes, have severe impacts on public health and economy. West Nile virus (WNV) and avian malaria parasites of the genus Plasmodium, are mosquito-borne pathogens that may produce severe disease and illness in humans and birds, respectively, and circulate in an endemic form in southern Europe. Here, we used field-collected data to identify the impact of Culex pipiens, Cx. perexiguus and Cx. modestus, on the circulation of both WNV and Plasmodium in Andalusia (SW Spain) using mathematical modelling of the basic reproduction number (R0 ). Models were calibrated with field-collected data on WNV seroprevalence and Plasmodium infection in wild house sparrows, presence of WNV and Plasmodium in mosquito pools, and mosquito blood feeding patterns. This approach allowed us to determine the contribution of each vector species to pathogen amplification. Overall, 0.7% and 29.6% of house sparrows were positive to WNV antibodies and Plasmodium infection, respectively. In addition, the prevalence of Plasmodium was higher in Cx. pipiens (2.0%), followed by Cx. perexiguus (1.8%) and Cx. modestus (0.7%). Three pools of Cx. perexiguus were positive to WVN. Models identified Cx. perexiguus as the most important species contributing to the amplification of WNV in southern Spain. For Plasmodium models, R0 values were higher when Cx. pipiens was present in the population, either alone or in combination with the other mosquito species. These results suggest that the transmission of these vector borne pathogens depends on different Culex species and consequently their transmission niches will present different spatial and temporal patterns. For WNV, targeted surveillance and control of Cx. perexiguus populations appears as the most effective measure to reduce WNV amplification. Also, preventing Culex populations near human settlements, or reducing the abundance of these species, are potential strategies to reduce WNV spillover into human populations in southern Spain.
    Keywords:   Culex modestus ; Culex perexiguus ; Culex pipiens ; Passer domesticus ; Basic reproduction number R0; Haemosporidia; emerging infectious diseases; flavivirus; mosquitoes; vector-borne pathogens; zoonosis
    DOI:  https://doi.org/10.1111/tbed.13760
  3. Trop Med Int Health. 2020 Aug 03.
    de Souza Leandro A, Avemir Rios J, da Silva Britto A, Roberto Galvão S, Defante Lopes R, Veleh Rivas A, Amaral Martins C, da Silva I, Michael Delai R, Dib Gonçalves D, Antônio Navarro da Silva M, Maria Palacio-Cortès A, Schuartz V, Cristiane Sibim A, Antonio Chiba de Castro W.
      OBJECTIVE: In Brazil, the most common method of controlling outbreaks of arbovirus is by the use of chemical sprays, which kill the insect vector, Aedes aegypti. The main objective of this study was to evaluate the resistance of Ae. aegypti to the insecticide, malathion, in situ. The location of this study was the municipality of Foz do Iguaçu, in the state of Paraná, Brazil.METHODS: Ultra-low volume (ULV) fogging equipment was used, by vehicle, to apply the insecticide in situ and mosquito populations after treatment were compared with those of control areas. The resistance of strains collected from the municipality was compared to the Rockefeller strain under laboratory conditions.
    RESULTS: We found 220 adult female specimens and 7,423 eggs of Ae. aegypti in the areas subjected to UBV treatment, whereas 245 adult females and 10,557 eggs were found in the control areas. The UBV treatment area showed no significant difference compared to the control area, for all the indices. Mortality of the Rockefeller colony varied more quickly when there were slight variations in malathion concentration than the Foz do Iguaçu population.
    Keywords:  Arboviruses; Chemical control; Entomological surveillance; Foz do Iguaçu; Ultra-Low Volume (ULV)
    DOI:  https://doi.org/10.1111/tmi.13474
  4. Viruses. 2020 Aug 04. pii: E853. [Epub ahead of print]12(8):
    Ribeiro Cruz AC, Pinto Nunes Neto J, Patroca da Silva S, Vieira Pinto da Silva E, Juscely Galvão Pereira G, Maia Santos M, Antônio de Oliveira Monteiro H, Barreto Dos Santos F, José de Paula Souza E Guimarães R, Fortes Aragão C, Carício Martins L.
      Chikungunya virus (CHIKV) was first reported in Brazil in 2014 and, after it spread countrywide, an outbreak of febrile illness with reports of arthralgia happened in the municipality of Xinguara, Pará, Brazil in 2017, indicating the virus' circulation. Here, we aimed to investigate CHIKV in mosquito vectors collected during an active surveillance of virus isolation in cell culture by using molecular detection and viral genome sequencing. A total of 492 Aedes, Culex and Mansonia mosquitoes were collected and separated in 36 pools according to the species and sex, and 22.2% (8/36) were positive. CHIKV was indentified in pools of Ae. aegypti females (n = 5), an Ae. aegypti male (n = 1) and in Culex quinquefasciatus females (n = 2). However, as the mosquitoes' whole bodies were macerated and used for detection, one cannot suggest the role of the latter in the viral transmission. Despite this, vector competence studies must be carried out in the different species to investigate long-term adaptations. Viral genome sequencing has characterized the East-Central-South-African (ECSA) genotype in all positive pools analyzed, corroborating previous reports for the Amazon region.
    Keywords:  Aedes aegypti; Amazon; Brazil; Chikungunya; Culex quinquefasciatus; East-Central-South-Africa genotype; entomological surveillance
    DOI:  https://doi.org/10.3390/v12080853
  5. Appl Spectrosc. 2020 Aug;74(8): 900-912
    Sroute L, Byrd BD, Huffman SW.
      Mosquito-borne diseases are responsible for considerable morbidity and mortality globally. Given the absence of effective vaccines for most arthropod-borne viruses, mosquito control efforts remain the dominant method of disease prevention. Ideal control efforts begin with entomologic surveillance in order to determine the abundance, identity, and infection status of pathogen-vectoring mosquito populations. Traditionally, much of the surveillance work involves morphological species identification by trained entomologists. Limited operational funding and lack of specialized training is a known barrier to surveillance and effective control efforts for many operational mosquito control personnel. Therefore, there is a need for surveillance workflow improvements and rapid mosquito identification methods. Herein, is presented a proof of concept study in which infrared spectroscopy coupled with partial least squares-discriminant analysis was explored as a means of automatically classifying mosquitoes at the species level. The developed method resulted in greater than 94% accuracy for four mosquitoes of public health relevance: Aedes aegypti, Aedes albopictus, Aedes japonicus, and Aedes triseriatus.
    Keywords:  Aedes aegypti; Aedes albopictus; Aedes japonicus; Aedes triseriatus; Fourier transform; container inhabiting; public health; vibrational
    DOI:  https://doi.org/10.1177/0003702820915729
  6. PLoS One. 2020 ;15(8): e0236920
    Soma DD, Zogo BM, Somé A, Tchiekoi BN, Hien DFS, Pooda HS, Coulibaly S, Gnambani JE, Ouari A, Mouline K, Dahounto A, Ouédraogo GA, Fournet F, Koffi AA, Pennetier C, Moiroux N, Dabiré RK.
      BACKGROUND: Twenty-seven villages were selected in southwest Burkina Faso to implement new vector control strategies in addition to long lasting insecticidal nets (LLINs) through a Randomized Controlled Trial (RCT). We conducted entomological surveys in the villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017) to describe malaria vectors bionomics, insecticide resistance and transmission prior to this trial.METHODS: We carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations.
    RESULTS: Eight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among seasons. All insecticide resistance mechanisms (kdr-w, kdr-e and ace-1 target site mutations) investigated were found in each members of the An. gambiae complex but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 2.61, 2.67 and 11.25 infected bites per human per month during dry cold season, dry hot season and rainy season, respectively.
    CONCLUSION: The entomological indicators of malaria transmission were high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These data will be used to evaluate the impact of complementary tools to LLINs in an upcoming RCT.
    DOI:  https://doi.org/10.1371/journal.pone.0236920
  7. J Biol Dyn. 2020 Dec;14(1): 656-678
    Huang M, Hu L.
      A novel strategy for controlling mosquito-borne diseases, such as dengue, malaria and Zika, involves releases of Wolbachia-infected mosquitoes as Wolbachia cause early embryo death when an infected male mates with an uninfected female. In this work, we introduce a delay differential equation model with mating inhomogeneity to discuss mosquito population suppression based on Wolbachia. Our analyses show that the wild mosquitoes could be eliminated if either the adult mortality rate exceeds the threshold [Formula: see text] or the release amount exceeds the threshold [Formula: see text] uniformly. We also present the nonlinear dependence of [Formula: see text] and [Formula: see text] on the parameters, respectively, as well as the effect of pesticide spraying on wild mosquitoes. Our simulations suggest that the releasing should be started at least 5 weeks before the peak dengue season, taking into account both the release amount and the suppression speed.
    Keywords:   Wolbachia ; 34D23; 37N25; 92B05; 92D30; Dengue fever; cytoplasmic incompatibility; delay differential equation model; mosquito population suppression
    DOI:  https://doi.org/10.1080/17513758.2020.1799083
  8. Viruses. 2020 Jul 30. pii: E830. [Epub ahead of print]12(8):
    Lord CC, Lounibos LP, Pohedra JJ, Alto BW.
      Arboviruses transmitted by Aedes aegypti and Aedes albopictus have been introduced to Florida on many occasions. Infrequently, these introductions lead to sporadic local transmission and, more rarely, sustained local transmission. Both mosquito species are present in Florida, with spatio-temporal variation in population composition. We developed a two-vector compartmental, deterministic model to investigate factors influencing Chikungunya virus (CHIKV) establishment. The model includes a nonlinear, temperature-dependent mosquito mortality function based on minimum mortality in a central temperature region. Latin Hypercube sampling was used to generate parameter sets used to simulate transmission dynamics, following the introduction of one infected human. The analysis was repeated for three values of the mortality function central temperature. Mean annual temperature was consistently important in the likelihood of epidemics, and epidemics increased as the central temperature increased. Ae. albopictus recruitment was influential at the lowest central temperature while Ae. aegypti recruitment was influential at higher central temperatures. Our results indicate that the likelihood of CHIKV establishment may vary, but overall Florida is permissive for introductions. Model outcomes were sensitive to the specifics of mosquito mortality. Mosquito biology parameters are variable, and improved understanding of this variation will improve our ability to predict the outcome of introductions.
    Keywords:  Aedes aegypti; Aedes albopictus; Chikungunya virus; invasion; mathematical model; transmission dynamics
    DOI:  https://doi.org/10.3390/v12080830
  9. Insect Mol Biol. 2020 Aug 02.
    Zheng X.
      Mosquitoes are major vectors of many infectious pathogens or parasites. Understanding cryptic species and the speciation of disease vectors has important implications for vector management, evolution, and host-pathogen and/or host-parasite interactions. Currently, mosquito cryptic species have been reported in many studies, most of which focus on the reproductive isolation of cryptic species and mainly on Anopheles gambiae sensu lato complex. Emerging species within the primary malaria vector Anopheles gambiae show different ecological preferences and significant prezygotic reproductive isolation, while Aedes mariae and Aedes zammitii show postmating reproductive isolation. However, data reporting the reproductive isolation in Culex and Aedes albopictus mosquito cryptic species is absent. The lack of systematic studies leaves many questions open, such as whether cryptic species are more common in particular habitats, latitudes, or taxonomic groups; what mosquito cryptic species evolutionary processes bring about reproductive isolation in the absence of morphological differentiation? How does Wolbachia infection affect in mosquitoes' reproductive isolation? In this review, we provide a summary of recent advances in the discovery and identification of sibling or cryptic species within mosquito genera.
    Keywords:  Cryptic species; Evolution; Identification; Mosquito; Reproduction isolation; Wolbachia
    DOI:  https://doi.org/10.1111/imb.12666
  10. PLoS Negl Trop Dis. 2020 Aug 07. 14(8): e0008528
    Ong J, Chong CS, Yap G, Lee C, Abdul Razak MA, Chiang S, Ng LC.
      House Index, Container Index, and Breteau Index are the most commonly used indices for dengue vector surveillance. However, these larval indices are a poor proxy for measuring the adult population-which is responsible for disease transmission. Information on the adult distribution and density are important for assessing transmission risk as well as for developing effective control strategies. This study introduces a new entomological index, Gravitrap aegypti index (GAI), which estimates the adult female Aedes aegypti population in the community and presents its association with dengue cases. Gravitraps were deployed across 34 treatment sites in Singapore from September 2013 to September 2016. The GAI, derived from the Gravitrap surveillance data, was analysed to investigate the spatio-temporal patterns of the Ae. aegypti population in Singapore. The index was further categorised into low, moderate, and high-risk groups and its association with dengue cases were examined. A Before-After Control Impact analysis was performed to evaluate the epidemiology impact of Gravitrap system on dengue transmission. The Ae. aegypti population exhibits a seasonal pattern, and spatial heterogeneity in Ae. aegypti abundance was observed among treatment sites. The Ae. aegypti population was also found to be unevenly distributed among floors of an apartment block, with low floors (floors 1-4) having a higher abundance of mosquitoes trapped than mid (floors 5-8) and high (floors ≥9) floors. Areas with high GAI were shown to have higher dengue case count. Gravitrap has also demonstrated to be a good dengue control tool. The contribution of cases by treatment sites to the national numbers was lower after Gravitraps deployment. The GAI, which is of better relevance to dengue transmission risk, could be recommended as an indicator for decision making in vector control efforts, and to monitor the spatio-temporal variability of the adult Aedes population in the country. In addition, findings from this study indicate that Gravitraps can be used as a dengue control tool to reduce dengue transmission.
    DOI:  https://doi.org/10.1371/journal.pntd.0008528
  11. J Arthropod Borne Dis. 2020 Mar;14(1): 106-115
    Manzoor F, Shabbir R, Sana M, Nazir S, Khan MA.
      Background: Present study was conducted to determine species composition of mosquitoes (larvae, pupae and adults) collected from ten different towns of Lahore from September 2014 to August 2015.Methods: Mosquito larvae, pupae and adults (male and female) were collected by using dippers and aspirators from September 2014 to August 2015 in different sites of Lahore comprising of ten towns i.e. Iqbal, Aziz Bhatti, Data Ganj Baksh, Gulberg, Nishtar, Ravi, Samanabad, Shalimar, Wagah, and Lahore Cantonment. Mosquito larvae and adults were identified by standard entomological keys. Diversity, richness and rarity of mosquito fauna were analyzed by the Shannon, Simpson and Margalef indices respectively.
    Results: In this study, a total of 8656 mosquitoes belonging to four genera namely Anopheles, Culex, Aedes and Mansonia were identified. Among fifteen species collected, Cx. quinquefasciatus was the most abundant species in the city having 25.8% relative abundance. However An. culicifacies s.l. (sensu lato) was reported as the least abundant species with 0.22% relative abundance. The highest diversity of mosquitoes was shown in the month of August (H= 2.25) while the lowest diversity was recorded June (H= 1.43). Extensive sewage water supported the maximum abundance of Cx. quinquifasciatus in urban areas of this city.
    Conclusions: This study has significantly elaborated the monthly varying species composition of mosquito fauna of this city. Hence this research will help us to find out the control strategies of mosquito borne diseases in this region.
    Keywords:  Climatic factors; Lahore; Mosquito fauna; Shannon Index; Simpson Index
    DOI:  https://doi.org/10.18502/jad.v14i1.2717
  12. PLoS Negl Trop Dis. 2020 Aug 07. 14(8): e0008541
    Li L, Liu WH, Zhang ZB, Liu Y, Chen XG, Luo L, Ou CQ.
      In 2019, dengue incidences increased dramatically in many countries. However, the prospective growth in dengue incidence did not occur in Guangzhou, China. We examined the effectiveness of early start of Grade III response to dengue in Guangzhou. We extracted the data on daily number of dengue cases during 2017-2019 in Guangzhou and weekly data for Foshan and Zhongshan from the China National Notifiable Disease Reporting System, while the data on weekly number of positive ovitraps for adult and larval Aedes albopictus were obtained from Guangzhou Center for Disease Control and Prevention. We estimated the number of dengue cases prevented by bringing forward the starting time of Grade III response from September in 2017-2018 to August in 2019 in Guangzhou using a quasi-Poisson regression model and applied the Baron and Kenny's approach to explore whether mosquito vector density was a mediator of the protective benefit. In Guangzhou, early start of Grade III response was associated with a decline in dengue incidence (relative risk [RR]: 0.54, 95% confidence interval [CI]: 0.43-0.70), with 987 (95% CI: 521-1,593) cases averted in 2019. The rate of positive ovitraps also significantly declined (RR: 0.64, 95% CI: 0.53-0.77). Moreover, both mosquito vector density and early start of Grade III response was significantly associated with dengue incidence after adjustment for each other. By comparing with the incidence in Foshan and Zhongshan where the Grade III response has not been taken, benefits from the response starting in August were confirmed but not if starting from September. Early start of Grade III response has effectively mitigated the dengue burden in Guangzhou, China, which might be partially through reducing the mosquito vector density. Our findings have important public health implications for development and implementation of dengue control interventions for Guangzhou and other locations with dengue epidemics.
    DOI:  https://doi.org/10.1371/journal.pntd.0008541
  13. Am J Trop Med Hyg. 2020 Aug 03.
    Dzib-Florez S, Ponce-García G, Medina-Barreiro A, González-Olvera G, Contreras-Perera Y, Del Castillo-Centeno F, Ahmed AMM, Che-Mendoza A, McCall PJ, Vazquez-Prokopec G, Manrique-Saide P.
      Vector control methods that mobilize and impact rapidly during dengue, Zika, and chikungunya outbreaks are urgently needed in urban contexts. We investigated whether one person using a handheld aerosolized insecticide could achieve efficacy levels comparable to targeted indoor residual spraying (TIRS), using pyrethroid-resistant Aedes aegypti in a semi-field setting with experimental houses in Mexico. The insecticide product (H24, a carbamate and pyrethroid mixture), available over-the-counter locally, was sprayed only on known Ae. aegypti-resting surfaces, for example, walls less than 1.5 m and dark hidden areas. In six identical houses with paired bedrooms, one bedroom was treated, and the other remained an untreated control. Each week for 8 weeks, 100 female pyrethroid-resistant Ae. aegypti were released in each bedroom and followed up daily. Mortality rates in treated bedrooms exceeded 90% for at least 2 weeks, and more than 80% (89.2; 95% CI: 79.98-98.35) for 3 weeks or more. Mortality rates in control houses were zero. Results demonstrate that the immediate impact of TIRS can be delivered by one person using existing products, at an estimated cost for the average household in Mexico of under US$3 per month. Triggered by early outbreak signs, dissemination via community hubs and mass/social media of instructions to treat the home immediately, with monthly re-treatment thereafter, provides a simple means to engage and empower householders. Compatible with integrated vector management strategies, it enables self-protection even if existing agencies falter, a situation exemplified by the potential impact on vector control of the restrictions imposed during the 2020 COVID-19 pandemic.
    DOI:  https://doi.org/10.4269/ajtmh.20-0515
  14. BMC Med. 2020 Aug 07. 18(1): 226
    Guzzetta G, Vairo F, Mammone A, Lanini S, Poletti P, Manica M, Rosa R, Caputo B, Solimini A, Torre AD, Scognamiglio P, Zumla A, Ippolito G, Merler S.
      BACKGROUND: The spatial spread of many mosquito-borne diseases occurs by focal spread at the scale of a few hundred meters and over longer distances due to human mobility. The relative contributions of different spatial scales for transmission of chikungunya virus require definition to improve outbreak vector control recommendations.METHODS: We analyzed data from a large chikungunya outbreak mediated by the mosquito Aedes albopictus in the Lazio region, Italy, consisting of 414 reported human cases between June and November 2017. Using dates of symptom onset, geographic coordinates of residence, and information from epidemiological questionnaires, we reconstructed transmission chains related to that outbreak.
    RESULTS: Focal spread (within 1 km) accounted for 54.9% of all cases, 15.8% were transmitted at a local scale (1-15 km) and the remaining 29.3% were exported from the main areas of chikungunya circulation in Lazio to longer distances such as Rome and other geographical areas. Seventy percent of focal infections (corresponding to 38% of the total 414 cases) were transmitted within a distance of 200 m (the buffer distance adopted by the national guidelines for insecticide spraying). Two main epidemic clusters were identified, with a radius expanding at a rate of 300-600 m per month. The majority of exported cases resulted in either sporadic or no further transmission in the region.
    CONCLUSIONS: Evidence suggest that human mobility contributes to seeding a relevant number of secondary cases and new foci of transmission over several kilometers. Reactive vector control based on current guidelines might allow a significant number of secondary clusters in untreated areas, especially if the outbreak is not detected early. Existing policies and guidelines for control during outbreaks should recommend the prioritization of preventive measures in neighboring territories with known mobility flows to the main areas of transmission.
    Keywords:  Chikungunya; Spatiotemporal spread; Transmission chain; Transmission distance
    DOI:  https://doi.org/10.1186/s12916-020-01674-y
  15. Proc Biol Sci. 2020 Aug 12. 287(1932): 20201065
    Skaff NK, Cheng Q, Clemesha RES, Collender PA, Gershunov A, Head JR, Hoover CM, Lettenmaier DP, Rohr JR, Snyder RE, Remais JV.
      Temperature is widely known to influence the spatio-temporal dynamics of vector-borne disease transmission, particularly as temperatures vary across critical thermal thresholds. When temperature conditions exhibit such 'transcritical variation', abrupt spatial or temporal discontinuities may result, generating sharp geographical or seasonal boundaries in transmission. Here, we develop a spatio-temporal machine learning algorithm to examine the implications of transcritical variation for West Nile virus (WNV) transmission in the Los Angeles metropolitan area (LA). Analysing a large vector and WNV surveillance dataset spanning 2006-2016, we found that mean temperatures in the previous month strongly predicted the probability of WNV presence in pools of Culex quinquefasciatus mosquitoes, forming distinctive inhibitory (10.0-21.0°C) and favourable (22.7-30.2°C) mean temperature ranges that bound a narrow 1.7°C transitional zone (21-22.7°C). Temperatures during the most intense months of WNV transmission (August/September) were more strongly associated with infection probability in Cx. quinquefasciatus pools in coastal LA, where temperature variation more frequently traversed the narrow transitional temperature range compared to warmer inland locations. This contributed to a pronounced expansion in the geographical distribution of human cases near the coast during warmer-than-average periods. Our findings suggest that transcritical variation may influence the sensitivity of transmission to climate warming, and that especially vulnerable locations may occur where present climatic fluctuations traverse critical temperature thresholds.
    Keywords:  California; West Nile virus; climate vulnerability; temperature; thermal thresholds; vector-borne disease
    DOI:  https://doi.org/10.1098/rspb.2020.1065
  16. PLoS One. 2020 ;15(8): e0235697
    Frake AN, Peter BG, Walker ED, Messina JP.
      In an era of big data, the availability of satellite-derived global climate, terrain, and land cover imagery presents an opportunity for modeling the suitability of malaria disease vectors at fine spatial resolutions, across temporal scales, and over vast geographic extents. Leveraging cloud-based geospatial analytical tools, we present an environmental suitability model that considers water resources, flow accumulation areas, precipitation, temperature, vegetation, and land cover. In contrast to predictive models generated using spatially and temporally discontinuous mosquito presence information, this model provides continuous fine-spatial resolution information on the biophysical drivers of suitability. For the purposes of this study the model is parameterized for Anopheles gambiae s.s. in Malawi for the rainy (December-March) and dry seasons (April-November) in 2017; however, the model may be repurposed to accommodate different mosquito species, temporal periods, or geographical boundaries. Final products elucidate the drivers and potential habitat of Anopheles gambiae s.s. Rainy season results are presented by quartile of precipitation; Quartile four (Q4) identifies areas most likely to become inundated and shows 7.25% of Malawi exhibits suitable water conditions (water only) for Anopheles gambiae s.s., approximately 16% for water plus another factor, and 8.60% is maximally suitable, meeting suitability thresholds for water presence, terrain characteristics, and climatic conditions. Nearly 21% of Malawi is suitable for breeding based on land characteristics alone and 28.24% is suitable according to climate and land characteristics. Only 6.14% of the total land area is suboptimal. Dry season results show 25.07% of the total land area is suboptimal or unsuitable. Approximately 42% of Malawi is suitable based on land characteristics alone during the dry season, and 13.11% is suitable based on land plus another factor. Less than 2% meets suitability criteria for climate, water, and land criteria. Findings illustrate environmental drivers of suitability for malaria vectors, providing an opportunity for a more comprehensive approach to malaria control that includes not only modeled species distributions, but also the underlying drivers of suitability for a more effective approach to environmental management.
    DOI:  https://doi.org/10.1371/journal.pone.0235697
  17. Sci Rep. 2020 Aug 06. 10(1): 13267
    Melo Costa M, Campos KB, Brito LP, Roux E, Melo Rodovalho C, Bellinato DF, Lima JBP, Martins AJ.
      Insecticide resistance is currently a threat to the control of Aedes agypti, the main vector of arboviruses in urban centers. Mutations in the voltage gated sodium channel (NaV), known as kdr (knockdown resistance), constitute an important selection mechanism for resistance against pyrethroids. In the present study, we investigated the kdr distribution for the Val1016Ile and Phe1534Cys alterations in Ae. aegypti from 123 Brazilian municipalities, based on SNP genotyping assays in over 5,500 mosquitoes. The alleles NaVS (1016Val+ + 1534Phe+), NaVR1 (1016Val+ + 1534Cyskdr) and NaVR2 (1016Ilekdr + 1534Cyskdr) were consistently observed, whereas kdr alleles have rapidly spread and increased in frequency. NaVS was the less frequent allele, mostly found in Northeastern populations. The highest allelic frequencies were observed for NaVR1, especially in the North, which was fixed in one Amazonian population. The double kdr NaVR2 was more prevalent in the Central-west and South-eastern populations. We introduce the 'kdr index', which revealed significant spatial patterns highlighting two to three distinct Brazilian regions. The 410L kdr mutation was additionally evaluated in 25 localities, evidencing that it generally occurs in the NaVR2 allele. This nationwide screening of a genetic mechanism for insecticide resistance is an important indication on how pyrethroid resistance in Ae. aegypti is evolving in Brazil.
    DOI:  https://doi.org/10.1038/s41598-020-70029-7
  18. Parasit Vectors. 2020 Aug 05. 13(1): 395
    Licciardi S, Loire E, Cardinale E, Gislard M, Dubois E, Cêtre-Sossah C.
      BACKGROUND: Arthropod borne virus infections are the cause of severe emerging diseases. Among the diseases due to arboviruses, dengue (DEN) and Rift Valley fever (RVF) are in the top ten in the list of diseases responsible of severe human cases worldwide. Understanding the effects of viral infection on gene expression in competent vectors is a challenge for the development of early diagnostic tools and may enable researchers and policy makers to better anticipate outbreaks in the next future.METHODS: In this study, alterations in gene expression across the entire Aedes aegypti genome during infection with DENV and RVFV were investigated in vitro at two time points of infection, the early phase (24 h) and the late phase (6 days) of infection using the RNA sequencing approach RESULTS: A total of 10 upregulated genes that share a similar expression profile during infection with both viruses at early and late phases of infection were identified. Family B and D clip-domain serine proteases (CLIP) were clearly overrepresented as well as C-type lectins and transferrin.
    CONCLUSIONS: Our data highlight the presence of 10 viral genes upregulated in Ae. aegypti during infection. They may also be targeted in the case of the development of broad-spectrum anti-viral diagnostic tools focusing the mosquito vectors rather than the mammalian hosts as they may predict the emergence of outbreaks.
    Keywords:  Aedes aegypti; Dengue; In vitro; Rift Valley fever; Transcriptomic responses
    DOI:  https://doi.org/10.1186/s13071-020-04253-5
  19. Nat Ecol Evol. 2020 Aug 03.
    Mozūraitis R, Hajkazemian M, Zawada JW, Szymczak J, Pålsson K, Sekar V, Biryukova I, Friedländer MR, Koekemoer LL, Baird JK, Borg-Karlson AK, Emami SN.
      Accumulating behavioural data indicate that aggregation pheromones may mediate the formation and maintenance of mosquito swarms. However, chemical cues possibly luring mosquitoes to swarms have not been adequately investigated, and the likely molecular incitants of these complex reproductive behaviours remain unknown. Here we show that males of the important malaria vector species Anopheles arabiensis and An. gambiae produce and release aggregation pheromones that attract individuals to the swarm and enhance mating success. We found that males of both species released significantly higher amounts of 3-hydroxy-2-butanone (acetoin), 6-methyl-5-hepten-2-one (sulcatone), octanal, nonanal and decanal during swarming in the laboratory. Feeding males with stable-isotope-labelled glucose revealed that the males produced these five compounds. A blend composed of synthetic analogues to these swarming odours proved highly attractive to virgin males and females of both species under laboratory conditions and substantially increased mating in five African malaria vectors (An. gambiae, An. coluzzii, An. arabiensis, An. merus and An. funestus) in semi-field experiments. Our results not only narrow a conspicuous gap in understanding a vital aspect of the chemical ecology of male mosquitoes but also demonstrate fundamental roles of rhythmic and metabolic genes in the physiology and behavioural regulation of these vectors. These identified aggregation pheromones have great potential for exploitation against these highly dangerous insects. Manipulating such pheromones could increase the efficacy of malaria-vector control programmes.
    DOI:  https://doi.org/10.1038/s41559-020-1264-9
  20. Viruses. 2020 Jul 30. pii: E827. [Epub ahead of print]12(8):
    Almeida PR, Eisen AKA, Demoliner M, Spilki FR.
      Zika virus (ZIKV) is an important arbovirus, responsible for recent outbreaks of Guillain Barré Syndrome and Congenital Zika Syndrome (CZS). After thousands of CZS cases, ZIKV is under constant surveillance in Brazil. Reliable and robust detection techniques are required to minimize the influence of host inhibitors from clinical samples and mosquito pool samples. Reverse transcription Digital Polymerase Chain Reaction (RT-dPCR) is a technique that allows the accurate quantification of DNA targets with high sensitivity, and it is usually less affected by inhibitors than RT-qPCR. This study aimed to assess the influence of mosquito tissue, RNA extraction and cDNA synthesis in ZIKV PCR detection. Samples containing 0, 3 and 10 mosquitoes were spiked with ZIKV MR766 and serially diluted prior to RNA extraction and RT-dPCR for ZIKV. Two reverse transcription protocols were tested. Assay sensitivity allowed the detection of 1.197 copies/µL. A higher correlation between dilution factor and target quantification was observed in 10 mosquito pool samples. The lower quantification in samples diluted without mosquitoes highlights the critical role of the reverse transcription step in RNA detection, since it could be attributed to reverse transcriptase variable performance in samples with low overall RNA concentration. The results in mosquito pools indicate that mosquito tissues do not inhibit ZIKV RT-dPCR, and the RT-dPCR technique has good sensitivity and robustness for ZIKV detection in mosquito pool samples regardless of mosquito tissue concentration.
    Keywords:  RT-dPCR; ZIKV; mosquito; quantification
    DOI:  https://doi.org/10.3390/v12080827
  21. Expert Rev Anti Infect Ther. 2020 Aug 01. 1-7
    Tozan Y, Sjödin H, Muñoz ÁG, Rocklöv J.
      INTRODUCTION: We are witnessing an alarming increase in the burden and range of mosquito-borne arboviral diseases. The transmission dynamics of arboviral diseases is highly sensitive to climate and weather and is further affected by non-climatic factors such as human mobility, urbanization, and disease control. As evidence also suggests, climate-driven changes in species interactions may trigger evolutionary responses in both vectors and pathogens with important consequences for disease transmission patterns.AREAS COVERED: Focusing on dengue and chikungunya, we review the current knowledge and challenges in our understanding of disease risk in a rapidly changing climate. We identify the most critical research gaps that limit the predictive skill of arbovirus risk models and the development of early warning systems, and conclude by highlighting the potentially important research directions to stimulate progress in this field.
    EXPERT OPINION: Future studies that aim to predict the risk of arboviral diseases need to consider the interactions between climate modes at different timescales, the effects of the many non-climatic drivers, as well as the potential for climate-driven adaptation and evolution in vectors and pathogens. An important outcome of such studies would be an enhanced ability to promulgate early warning information, initiate adequate response, and enhance preparedness capacity.
    Keywords:  Aedes-borne diseases; Climate variability; climate change; dengue; evolutionary adaptation
    DOI:  https://doi.org/10.1080/14787210.2020.1794814
  22. Am J Trop Med Hyg. 2020 Aug 03.
    Wangdi K, Canavati S, Duc TN, Nguyen TM, Tran LK, Kelly GC, Martin NJ, Clements ACA.
      Malaria in Vietnam has become focal to a few provinces, including Phu Yen. This study aimed to assess correlations between intervention (population proportion protected by insecticide-treated nets and indoor residual spraying) and climatic variables with malaria incidence in Phu Yen Province. The Vietnam National Institute of Malariology, Parasitology, and Entomology provided incidence data for Plasmodium falciparum and Plasmodium vivax for 104 communes of Phu Yen Province from January 2005 to December 2016. A multivariable, zero-inflated Poisson regression model was developed with a conditional autoregressive prior structure to identify the underlying spatial structure of the data and quantify associations with covariates. There were a total of 2,778 P. falciparum and 1,770 P. vivax cases during the study period. Plasmodium falciparum and P. vivax incidence increased by 5.4% (95% credible interval [CrI] 5.1%, 5.7%) and 3.2% (95% CrI 2.9%, 3.5%) for a 10-mm increase in precipitation without lag, respectively. Plasmodium falciparum and P. vivax incidence decreased by 7.7% (95% CrI 5.6%, 9.7%) and 10.5% (95% CrI 8.3%, 12.6%) for a 1°C increase in minimum temperature without lag, respectively. There was a > 95% probability of a higher than provincial average trend of P. falciparum and P. vivax in Song Cau and Song Hoa districts. There was a > 95% probability of a lower than provincial average trend in Tuy Dong Xuan and Hoa districts for both species. Targeted distribution of resources, including intensified interventions, in this part of the province will be required for local malaria elimination.
    DOI:  https://doi.org/10.4269/ajtmh.20-0392
  23. Sci Total Environ. 2020 Jun 19. pii: S0048-9697(20)33858-4. [Epub ahead of print]739 140336
    Kakarla SG, Bhimala KR, Kadiri MR, Kumaraswamy S, Mutheneni SR.
      Dengue fever is mosquito borne viral disease caused by dengue virus and transmitted by Aedes mosquitoes. In recent years the dengue has spread rapidly to several regions and it becomes a major public health menace globally. Dengue transmission is strongly influenced by environmental factors such as temperature and rainfall. In the present study, a climate driven dengue model was developed and predicted areas vulnerable for dengue transmission under the present and future climate change scenarios in India. The study also projected the dengue distribution risk map using representative concentration pathways (RCP4.5 and RCP8.5) in India in 2018-2030 (forthcoming period), 2031-2050 (intermediate period) and 2051-2080 (long period). The dengue cases assessed in India from 1998 to 2018 and found that the dengue transmission is gradually increasing year over year. The temperature data from 1980 to 2017 shows that, the mean temperatures are raising in the Southern region of India. During 2000-2017 periods the dengue transmission is steadily increasing across the India in compare with 1980-1999 periods. The dengue distribution risk is predicted and it is revealed that the coastal states have yearlong transmission possibility, but the high transmission potential is observed throughout the monsoon period. Due to the climate change, the expansion two more months of dengue transmission risk occurs in many regions of India. Both RCP4.5 and RCP8.5 scenarios revealed that dengue outbreaks might occur at larger volume in Southern, Eastern, and Central regions of India. Furthermore a sensitivity analysis was performed to explore the impact of climate change on dengue transmission. These results helps to suggest appropriate control measures should be implemented to limit the spread in future warmer climates. Besides these, a proper plan is required to mitigate greenhouse gas emissions to reduce the epidemic potential of dengue in India.
    Keywords:  Dengue; India; RCP4.5 & RCP8.5; Rainfall; Reproductive rate; Temperature
    DOI:  https://doi.org/10.1016/j.scitotenv.2020.140336
  24. Med Vet Entomol. 2020 Aug 06.
    Sultana A, Sunahara T, Tsurukawa C, Tuno N.
      Aedes (Stegomyia) albopictus and Aedes (Stegomyia) flavopictus are related species that have overlapping distributions from southern to central Japan. To understand how they interact, we studied reproductive interference between them, particularly focusing on the body size difference between the mating pair. Here, we examined the effects of conspecific, heterospecific and double mating (i.e. heterospecific mating followed by conspecific mating) on copulation duration, egg production and hatchability of eggs using mosquitoes that varied in body size. Females mated only with heterospecific males produced few viable eggs, indicating that post-mating isolation is almost complete. When mated with heterospecific males before conspecific mating, the production of viable eggs was lower than when mated only with conspecific males, revealing the occurrence of reproductive interference. The degree of reproductive interference was larger in Ae. flavopictus than in Ae. albopictus when the female size was small but did not differ between them when the female size was large. Aedes albopictus females appear to be able to distinguish Ae. flavopictus males from conspecific males and larger females are more successful in the rejection of heterospecific males. On the other hand, Ae. flavopictus were not able to discriminate between conspecific and heterospecific males.
    Keywords:  body-size difference; copulation duration; egg hatchability; mating isolation
    DOI:  https://doi.org/10.1111/mve.12469
  25. J Arthropod Borne Dis. 2020 Mar;14(1): 1-7
    Abbasi M, Doosti S, Vatandoost H, Hosseini-Vasoukolaei N.
      Background: Aquatic insects include groups of arthropods which at least one step of their life happens in water. Some of these insects play an important role in the transmission of various diseases to human and animals. Because there is a little information about the fauna of aquatic insects in Iran, this study was aimed to collect and identify aquatic insects in northwestern Iran.Methods: A descriptive cross sectional study was performed in July 2017 in Rivers of three villages of Osku County of East Azerbaijan Province, northwestern Iran. The specimens were collected using different methods including D frame net-collector, standard mosquito dipper, Sweep Netting and plastic pipette. The collected specimens were identified based on the systematic keys of aquatic insects.
    Results: Totally 285 samples were collected. Four orders including Diptera, Hemiptera, Ephemeroptera and Coleoptera were identified. Collected samples belonged to seven families of Tipulidae, Chironomidae, Corixidae, Culicidae, Hydrophilidae, Baetidae and Dytiscidae. The most predominant family was Culicidae belonging to order Diptera. Culiseta longiareolata was the most frequent species collected in the study area.
    Conclusion: Aquatic insects usually play an important role in the food chain of animals and some species of them act as predators and play an important role in the biological control of vectors. Therefore, more studies are required to carry out in the field of aquatic insects.
    Keywords:  Aquatic insects; Azerbaijan; Fauna; Iran
    DOI:  https://doi.org/10.18502/jad.v14i1.2698
  26. Malar J. 2020 Aug 06. 19(1): 283
    Asingizwe D, Poortvliet PM, van Vliet AJH, Koenraadt CJM, Ingabire CM, Mutesa L, Leeuwis C.
      BACKGROUND: Malaria control remains a challenge globally and in malaria-endemic countries in particular. In Rwanda, a citizen science programme has been set up to improve malaria control. Citizens are involved in collecting mosquito species and reporting mosquito nuisance. This study assessed what people benefit from such a citizen science programme. The analysis was conducted on how the citizen science programme influenced perceptions and behaviour related to malaria control.METHODS: This study employed a mixed-methods approach using dissemination workshops, a survey, and village meetings as the main data collection methods. Dissemination workshops and village meetings involved 112 volunteers of the citizen science programme and were conducted to explore: (1) the benefits of being involved in the programme and (2) different ways used to share malaria-related information to non-volunteers. The survey involved 328 people (110 volunteers and 218 non-volunteers) and was used to compare differences in malaria-related perceptions and behaviour over time (between 2017 and 2019), as well as between volunteers and non-volunteers.
    RESULTS: Malaria-related perceptions and behaviour changed significantly over time (between 2017 and 2019) and became favourable to malaria control. When the findings were compared between volunteers and non-volunteers, for perceptions, only perceived self-efficacy showed a significant difference between these two groups. However, volunteers showed significantly more social interaction, participation in malaria-related activities at the community level, and indoor residual spraying (IRS) acceptance. In addition, both volunteers and non-volunteers reported to have gained knowledge and skills about the use of malaria control measures in general, and mosquito species in particular among volunteers.
    CONCLUSION: The reported knowledge and skills gained among non-volunteers indicate a diffusion of the citizen science programme-related information in the community. Thus, the citizen science programme has the potential to provide individual and collective benefits to volunteers and society at large.
    Keywords:  Behaviour change; Benefits; Citizen science; Collective action; Diffusion; Malaria; Perceptions; Social interaction
    DOI:  https://doi.org/10.1186/s12936-020-03349-8
  27. Malar J. 2020 Aug 03. 19(1): 277
    Guerra CA, Fuseini G, Donfack OT, Smith JM, Ondo Mifumu TA, Akadiri G, Eyang DEM, Eburi CO, Motobe Vaz L, Micha VM, Okenve LA, Janes CR, Andeme RM, Rivas MR, Phiri WP, Slotman MA, Smith DL, García GA.
      At the beginning of 2019, a sudden surge of malaria cases was observed in the district of Riaba, Bioko Island. Between January and April, confirmed malaria cases increased 3.8-fold compared to the same period in 2018. Concurrently, anopheline human biting rate (HBR) increased 2.1-fold. During the outbreak, 82.2% of the district population was tested for malaria with a rapid diagnostic test; 37.2% of those tested had a detectable infection and were treated according to national guidelines. Vector control interventions, including indoor residual spraying and larval source management were scaled-up. After the interventions, the number of confirmed cases decreased by 70% and the overall parasite prevalence in the communities by 43.8%. Observed prevalence in a follow up malaria indicator survey, however, was significantly higher than elsewhere on the island, and higher than in previous years. There was no significant reduction in HBR, which remained high for the rest of the year. The surge was attributed to various factors, chiefly increased rainfall and a large number of anthropogenic anopheline breeding sites created by construction works. This case study highlights the need for sustained vector control interventions and multi-sector participation, particularly in malaria control and elimination settings with persistently high local malaria receptivity.
    DOI:  https://doi.org/10.1186/s12936-020-03347-w
  28. J Med Entomol. 2020 Aug 02. pii: tjaa154. [Epub ahead of print]
    Yang L, Agramonte N, Linthicum KJ, Bloomquist JR.
      Research on the functions of insect chemoreceptors have primarily focused on antennae (olfactory receptors) and mouthparts (gustatory receptors). However, chemoreceptive sensilla are also present on other appendages, such as the leg tarsi and the anterior wing margin, and their specific roles in chemoreception and mosquito behavior remain largely unknown. In this study, electrophysiological analyses in an electroantennogram recording format were performed on Aedes aegypti (L., Diptera: Culicidae) antennae, mouthparts, tarsi, and wings during exposure to a variety of insect repellent and attractant compounds. The results provide evidence that the tarsi and wings can sense chemicals in a gaseous form, and that the odors produce differing responses on different appendages. The most consistent and strongest response occurred when exposed to triethylamine (TEA). Antennae and mouthparts showed nearly identical responses pattern to all tested compounds, and their rank orders of effectiveness were similar to those of fore- and mid-leg tarsi. Hindleg tarsi only responded to TEA, indicating that the hind legs are not as chemoreceptive. Wings responded to a range of odorants, but with a different rank order and voltage amplitude. Insights gleaned into the function of these appendages in insect chemoreception are discussed.
    Keywords:   Aedes aegypti ; 1-octen-3-ol; DEET; electroantennogram; repellent
    DOI:  https://doi.org/10.1093/jme/tjaa154
  29. J Virol. 2020 Aug 05. pii: JVI.01070-20. [Epub ahead of print]
    Cross ST, Maertens BL, Dunham TJ, Rodgers CP, Brehm AL, Miller MR, Williams AM, Foy BD, Stenglein MD.
      Partitiviruses are segmented, multipartite dsRNA viruses that until recently were only known to infect fungi, plants, and protozoans. Metagenomic surveys have revealed that partitivirus-like sequences are also commonly associated with arthropods. One arthropod-associated partitivirus, galbut virus, is common in wild populations of Drosophila melanogaster To begin to understand the processes that underlie this virus's high global prevalence, we established colonies of wild-caught infected flies. Infection remained at stably high levels over three years, with between 63-100% of individual flies infected. Galbut virus infects fly cells and replicates in tissues throughout infected adults, including reproductive tissues and the gut epithelium. We detected no evidence of horizontal transmission via ingestion but vertical transmission from either infected females or infected males was ∼100% efficient. Vertical transmission of a related partitivirus, verdadero virus, that we discovered in a laboratory colony of Aedes aegypti mosquitoes was similarly efficient. This suggests that efficient biparental vertical transmission may be a feature of at least a subset of insect-infecting partitiviruses. To study the impact of galbut virus infection free from the confounding effect of other viruses, we generated an inbred line of flies with galbut virus as the only detectable virus infection. We were able to transmit infection experimentally via microinjection of homogenate from these galbut-only flies. This sets the stage for experiments to understand the biological impact and possible utility of partitiviruses infecting model organisms and disease vectors.IMPORTANCE Galbut virus is a recently discovered partitivirus that is extraordinarily common in wild populations of the model organism Drosophila melanogaster Like most viruses discovered through metagenomics, most of the basic biological questions about this virus remain unanswered. We found that galbut virus, along with a closely related partitivirus found in Aedes aegypti mosquitoes, is transmitted from infected females or males to offspring with ∼100% efficiency and can be maintained in laboratory colonies over years. This efficient transmission mechanism likely underlies the successful spread of these viruses through insect populations. We created Drosophila lines that contained galbut virus as the only virus infection and showed that these flies can be used as a source for experimental infections. This provides insight into how arthropod-infecting partitiviruses may be maintained in nature and sets the stage for exploration of their biology and potential utility.
    DOI:  https://doi.org/10.1128/JVI.01070-20
  30. Vector Borne Zoonotic Dis. 2020 Aug 03.
    Palermo PM, Orbegozo J, Morrill JC, Watts DM.
      White-tailed deer (WTD) are abundant mammals widely distributed across the United States. As a result, WTD are considered to be excellent sentinels for detecting arboviral activity in certain geographic areas. Evidence of West Nile virus (WNV) antibody in WTD has been reported previously in several states. However, WNV infection in WTD has not been reported from Texas, where the incidence of human West Nile (WN) cases is among the highest in the United States. Therefore, the aim of this study was to determine the prevalence of WNV antibody in WTD in central Texas. Sera samples (n = 644) were collected from deer during the fall and winter in western Travis County, Texas from 2014 to 2018 and tested for WNV immunoglobulin G (IgG) antibody by an indirect enzyme-linked immunosorbent assay (ELISA). ELISA antibody-positive samples were further tested for WNV and St. Louis encephalitis virus (SLEV) antibodies by an 80% plaque-reduction neutralization tests (PRNT80). Overall, 9% (n = 58) and 0.31% (n = 2) of the deer samples had serological evidence of WNV and SLEV infections, respectively. WNV seroprevalence differed significantly by age (p < 0.05), but there was no significant difference between sex. Interestingly, 3.1% (n = 20) of the samples were positive for Flavivirus IgG antibody by ELISA, but negative for SLEV and WNV antibodies, suggesting that other Flaviviruses may be circulating among WTD in Texas. Finally, these results supported WNV infection among WTD and highlight their potential role as sentinels for the detection of WNV in Texas and warrant further studies to determine the role WTD play in the maintenance and transmission of WNV.
    Keywords:  Texas; West Nile; antibodies; deer
    DOI:  https://doi.org/10.1089/vbz.2020.2641
  31. Viruses. 2020 Jul 29. pii: E823. [Epub ahead of print]12(8):
    Shin D, Kang S, Smartt CT.
      A Chikungunya virus (CHIKV) outbreak in Italy in 2007 spread to include the islands of the Caribbean and most of the Americas and still circulates in Europe and Africa. Florida being close in distance to the Caribbean islands experienced a CHIKV outbreak in 2014 and continues to have a few travel-related cases each year. It is known that different environmental conditions in different regions can result in genetic variation that favor changes in competence to arbovirus. We evaluated the vector competence of Florida Aedes aegypti for CHIKV and determined if there is a geographic component that influences genes involved in CHIKV competence. We utilized a genomic approach to identify the candidate genes using RNA sequencing. The infection and dissemination results showed that field populations were more competent vectors for CHIKV than a lab population. The differentially expressed genes in the two field-collected CHIKV-infected populations, compared to the Rockefeller strain, were related to the Wnt/Notch signaling pathway, with similarity to genes scattered throughout the signaling pathway. This result suggested the possibility of identifying genes involved in the determination of vector competence in different gene pools of Ae. aegypti.
    Keywords:  Aedes aegypti 2; chikungunya virus 1; notch signaling pathway 4; wnt signaling pathway 3
    DOI:  https://doi.org/10.3390/v12080823