Detection of Zika virus in Anopheles stephensi Liston, 1901 (Diptera: Culicidae) in India - First report

Zika virus (ZIKV) a mosquito-borne, causing acute febrile illness associated with rash, arthralgia and conjunctivitis in the patient, was reported from Thiruvananthapuram, Kerala, as an outbreak with 83 cases. Entomological surveillance revealed the presence of aedine mosquitoes viz., Aedes aegypti (Linnaeus, 1762), Ae. albopictus (Skuse, 1894) and Ae. vittatus (Bigot, 1861) and nonaedine mosquitoes viz., Anopheles stephensi Liston,1901, Mansonia uniformis (Theobald, 1901), Culex tritaeniorhynchus Giles, 1901 and Cx. gelidus Theobald,1901. Aedes (Ae. aegypti, Ae. vittatus and Ae. Albopictus) mosquito larvae were high in the Zika affected areas. Moreover ZIKV was detected in An. stephensi mosquitoes collected from Parassala, Thiruvananthapuram (the native place of the first ZIKV confirmed case in the present outbreak in Kerala). Molecular diagnostics of Ae. Aegypti, Ae. vittatu and An. stephensi mosquitoes revealed that the species were loaded with ZIKV. Significantly this is the first ever report of ZIKV detecting in An. stephensi in the world. Aedes adults (male and female) and An. stephensi emerged from fourth instar larvae and pupae were found to have ZIKV, indicating transovarial transmission of the virus.

Towards environmental detection of Chagas disease vectors and pathogen

Background: Accurate surveillance of triatomine household infestation is crucial for Chagas disease vector control. However, no gold standard detection method with high levels of sensitivity or specificity is currently available. Several intrinsic features of triatomine bug behaviour and the lifecycle of Trypanosoma (T.) cruzi lead to deposition of environmental DNA (eDNA) in infested houses. This study evaluated the use of FTA cards and cotton-tipped swabs as low-technology, cost-effective tools for simultaneous detection of T. cruzi and vector eDNA in the laboratory and field. Methods/Principal Findings: This study had two components: (1) laboratory evaluation and optimisation of QIAcard® FTA® classic cards to detect Rhodnius (R.) prolixus eDNA by altering five different environmental variables (darkness, triatomine number, temperature, feeding status and degradation at ambient temperature); (2) detection of R. prolixus and T. cruzi eDNA from cotton-tipped house wall swabs from an endemic region in Casanare Department, Colombia. eDNA was extracted from all specimens and amplified using a multiplex TaqMan qPCR assay targeting the R. prolixus 12S rRNA gene and T. cruzi satellite DNA region. R. prolixus eDNA from five 3rd/4th instar nymphs was successfully amplified from FTA cards after as little as 15 minutes of contact time under standard insectary conditions. Factors significantly increasing eDNA detection from FTA cards were increasing temperature from 21oC to 27-32oC, triatomine bug density from 1-25 bugs and recent blood-feeding. eDNA was detectable from FTA cards stored at room temperature for at least two weeks. In cotton-tipped swabs from the field, the sensitivity and specificity of R. prolixus eDNA detection was 60.6% (n=20/33) and 100% (n=33/33), respectively. T. cruzi eDNA was amplified from 93.9% (n=31/33) of infested houses. Conclusions/Significance: FTA cards are a highly sensitive tool for entomological surveillance of R. prolixus and exhibit little variability under different environmental conditions. Additionally, cotton-tipped swabs are a relatively sensitive tool for entomological and parasitological surveillance of R. prolixus and T. cruzi in situ, but more feasible due to low cost. Both methods could be utilised by citizen science initiatives to contribute to the control of Chagas disease in endemic communities.

Entomological surveillance of mosquitoes (Diptera: Culicidae), vectors of arboviruses, in an ecotourism park in Cachoeiras de Macacu, state of Rio de Janeiro-RJ, Brazil

Arboviruses are arthropod-dependent viruses to complete their zoonotic cycle. Among the transmitting arthropods, culicids stand out, which participate in the cycle of several arboviruses that can affect humans. The present study aimed to identify species of culicidae and to point out the risk of circulation, emergency, or reemergence of pathogenic arboviruses to humans in the region of the Jequitibá headquarters of the Parque Estadual dos Três Picos (PETP), in Cachoeiras de Macacu, state of Rio de Janeiro, Brazil. Sampling was carried out at five Sample Points (SP) demarcated on trails from the headquarters, with CDC light traps, HP model with dry ice attached to the side, for 48 hours of activity each month. Additionally, active catches were made with a castro catcher in the period of one hour per day in the field, from six to eleven o’clock in the morning, in each PM. After the captures, thematic map was assembled using the ArcGIS 10 software and performing a multidimensional scaling (MDS). A total of 1151 specimens were captured and the presence of culicids already incriminated as vectors of arboviruses circulating in the region was observed: Aedes fluviatilis Lutz, 1904 (71 specimens); Aedes scapularis Rondani, 1848 (55 specimens); Haemagogus leococelaenus Dyar and Shannon, 1924 (29 specimens). In addition to the subgenus Culex (culex) spp. (163 specimens). In this sense, we highlight the importance of strengthening the actions of continuous entomological surveillance of the emergence and re-emergence of new arboviruses in ecotourism visitation parks.

Anopheles salivary antigens as serological biomarkers of vector exposure and malaria transmission: A systematic review with multilevel modelling

<b>Background:</b> Entomological surveillance for malaria is inherently resource-intensive and produces crude population-level measures of vector exposure which are insensitive in low-transmission settings. Antibodies against Anopheles salivary proteins measured at the individual-level may serve as proxy biomarkers for vector exposure and malaria transmission, but their relationship is yet to be quantified. <b>Methods:</b> A systematic review of studies measuring antibodies against Anopheles salivary antigens (PROSPERO: CRD42020185449). Multilevel modelling (to account for multiple study-specific observations (level-one), nested within study (level-two), and study nested within country (level-three)) estimated associations between seroprevalence with Anopheles human biting rate (HBR) and malaria transmission measures. <b>Results:</b> From 3981 studies identified in literature searches, 42 studies across 16 countries were included contributing 393 study-specific observations of anti-Anopheles salivary antibodies determined in 42,764 samples. A positive association between HBR (log transformed) and seroprevalence was found; overall a 2-fold (100% relative) increase in HBR was associated with a 23% increase in odds of seropositivity (OR: 1.23, 95%CI: 1.10-1.37, p<0.001). The association between HBR and Anopheles salivary antibodies was strongest with concordant, rather than discordant Anopheles species. Seroprevalence was also significantly positively associated with established epidemiological measures of malaria transmission: entomological inoculation rate, Plasmodium spp. prevalence, and malarial endemicity class. <b>Conclusions:</b> Anopheles salivary antibody biomarkers can serve as a proxy measure for HBR and malaria transmission, and could monitor malaria receptivity of a population to sustain malaria transmission. Validation of Anopheles species-specific biomarkers are important given the global heterogeneity in the distribution of Anopheles species. Salivary biomarkers have the potential to transform surveillance by replacing impractical, inaccurate entomological investigations, especially in areas progressing towards malaria elimination. <b>Funding:</b> Australian National Health and Medical Research Council, Wellcome Trust.

Low Malaria Transmission in Rosso, an Irrigated Rice-Growing Area in Mauritania

The construction of dams along the Senegal River resulted in an increase in irrigated land areas and changes in the epidemiology and transmission of water-related diseases. The objective of this study was to update epidemiological data on malaria in Rosso, one of the major Mauritanian cities along the Senegal River. Febrile patients (n = 318) were screened for malaria using a rapid diagnostic test (RDT) for malaria and microscopic examination of blood smears. Diagnosis was later confirmed by polymerase chain reaction (PCR). The mean age of 318 febrile patients was 25.1 (range 1–80 years). Only 7 (2.2%) and 2 (0.6%) had a positive RDT and thick smear, respectively. PCR confirmed the diagnosis in two Plasmodium vivax-infected patients. Most participants (198/318, 62.3%) had no recent travel history outside Rosso. The majority of the febrile patients (90%, 284/311) owned at least one insecticide-treated net (ITN). The frequency of the use of ITNs was not significantly associated with season (rainy vs. dry seasons; p = 0.9) or with the number of ITNs per household (rs = 0.07; n = 285; p = 0.19). Of 285 individuals with ITNs, only two (0.7%) with no travel history were PCR-positive for malaria. Despite the presence of mosquito breeding sites related to rice irrigation, malaria transmission in Rosso remained very low, possibly due to the high coverage and frequent use of bed nets. Regular entomological surveillance for possible changes in the prevalence of Anopheles mosquito species and their behavioural aspects should be implemented.

Mosquito excreta reveals circulation of West Nile virus and its underlying ecosystem

Emerging and endemic mosquito-borne viruses can be difficult to detect and monitor because they often cause asymptomatic infections in human or vertebrate animals or cause nonspecific febrile illness with a short recovery waiting period. Cases’ detection in vertebrate hosts can be complemented by entomological surveillance, but this method is not adapted to low infection rates in mosquito populations that typically occur in low or non-endemic areas. We identified West Nile Virus circulation in Camargue, a wetland area in South of France, using a cost effective innovative xenomonitoring method based on the molecular detection of virus in excreta from trapped mosquitoes. We also succeeded at identifying the mosquito community diversity dynamic on several sampling sites, together with the vertebrate hosts on which they fed prior to be captured using amplicon-based metagenomic on mosquito excreta without processing any mosquito. Mosquito excreta-based virus surveillance can be considered as a cost-effective and non-invasive strategy that offers the additional asset to reveal the ecological network underlying arbovirus circulation.

Potential Development of Digital Environmental Surveillance System in Dengue Control: A Qualitative Study

Background: The development of digital environmental technology can be conducted to implement reports, surveillance, and manage dengue control. Therefore, this study aims to determine the barriers to the use of paper-based and the potential development of digital environmental technology in dengue control. Methods In-depth qualitative interviews were conducted using 14 key informants and four focus group discussions (FGD) from May-August 2021 in Denpasar City, Bali. The interviews were consistent with the flow of the epidemiological and entomological surveillance system, the obstacles to the dengue control program, the potential for the application of digital technology, and the challenges in the application of digital surveillance technology. Furthermore, open-ended questions and content analysis by qualitative study procedures were adopted. The results were transcribed verbatim and triangulation of sources was conducted for data validation. Results The reporting system that used paper-based was not optimally implemented due to repetition of reporting, speed of information, data bias, performance measurement as well as case surveillance and reporting system constraints. An integrated digital environmental surveillance system (SILIRA) was also developed for dengue control. In the current Covid-19 pandemic, the need for digital applications is high due to the policy of not accepting guests and keeping a distance. Epidemiological surveillance for case data collection, entomological surveillance for larva density, case reporting, and educational videos are the required data in the application. Conclusion The development of an integrated application for an environmental monitoring system can be created for the continuous reporting of case information and larval density for dengue hemorrhagic fever control. Keywords: digital, surveillance, environment, dengue

Coleção de Vetores de Tripanosomatídeos (Fiocruz/COLVET) held at the institution Fiocruz Minas in Brazil: diversity of Triatominae (Hemiptera, Reduviidae) and relevance for research, education, and entomological surveillance

The Coleção de Vetores de Tripanosomatídeos (Fiocruz/COLVET), Minas Gerais, Brazil, stands out as one of the most important collections of blood-sucking triatomines, the vectors of Trypanosoma cruzi that causes Chagas disease. The aim is to describe the collection and the services it provides to support scientific research, educational activities, and entomological surveillance between 2013–2019.The data associated with the specimens held in Fiocruz/COLVET is available from the Sistema de Informação sobre a Biodiversidade Brasileira (SiBBr). These specimen metadata were analyzed and either tabulated or plotted on graph and maps. The records of services provided by the collection between 2013–2019 were also categorized and analyzed. There are 12,568 triatomine specimens deposited in the collection that belong to 77 species and 11 genera, from 15 American countries. Of the ~ 65 species of triatomines found in Brazil, 38 (57.6%) are present in the collection, including specimens from all biomes and all but three Brazilian states. The occurrence of Triatoma costalimai, Triatoma lenti, Rhodnius nasutus, and Panstrongylus lenti apparently collected beyond their known distribution ranges are reported and discussed. The collection provided 168 services, supporting educational activities (41.7%), scientific research (35.7%), and regional/national entomological surveillance of triatomines (22.6%). Between the years 2014 and 2020, the number of biological specimens deposited in the Fiocruz/COLVET repository increased from 4,778 to 12,568 triatomine specimens. In addition to its great value to biodiversity conservation, the collection is of great importance because of its support of research and educational activities, and contributions to entomological surveillance, and, therefore, to public health.

Semi-field evaluation of novel chemical lures for Aedes aegypti, Culex quinquefasciatus, and Anopheles minimus (Diptera: Culicidae) in Thailand

Background Entomological surveillance is an important means of assessing the efficacy of insect vector management programs and estimating disease transmission thresholds. Among baited traps, Biogents’ BG-Sentinel (BGS) trap baited with BG-Lure is considered to have the most similar outcome to, and be a possible replacement for, human-landing catches for the epidemiologically relevant monitoring of adult Aedes aegypti and Culex quinquefasciatus. In contrast to the BGS trap, the Black Hole ultraviolet (UV) light trap, which is widely used to catch nocturnal flying insects, is not baited with synthetic human odor-mimicking lures. Methods We evaluated the l-lactic acid-based Kasetsart University (KU)-lures nos. 1–6 as novel candidate chemical lures for the diurnal species Ae. aegypti and the nocturnal species Cx. quinquefasciatus using two commercial traps (the BGS trap and the Black Hole UV light trap) in a semi-field screen (SFS) house. Firstly, we optimized the dose of each KU-lure in an SFS house (140 m3). Secondly, six different candidate KU-lures were screened by comparing their percent attraction using a single discriminating dose (0.5 g). Finally, we evaluated the synergism of the KU-lures selected in this way with commercially available traps. Results BGS traps baited with KU-lure no. 1 exhibited the greatest percent attraction for Ae. aegypti (29.5% ± 14.3%), whereas those baited with KU-lure no. 6 most strongly attracted Cx. quinquefasciatus (33.3% ± 10.7%). Interestingly, BGS traps treated with 10 g BG-Lure did not significantly attract more Ae. aegypti or Cx. quinquefasciatus than the untreated BGS traps. CO2 at a flow rate of 250 ml/min most strongly attracted both Ae. aegypti and Cx. quinquefasciatus (42.2% ± 14.2% and 75.1% ± 16.9%, respectively). BGS and Black Hole UV light traps with KU-lure no. 6 exhibited a stronger attraction for Cx. quinquefasciatus than untreated traps, and the percent attraction did not differ between the treated traps. Conclusions Synergistic effects of KU-lures nos. 1 and 6 with the mosquito traps were demonstrated for both the diurnal and nocturnal species in the SFS house assays. However, further studies are urgently needed for the development of species-specific lures to increase trap efficacy in the field for local vector mosquitoes in Thailand. Graphical Abstract