Longitudinal monitoring of environmental factors at Culicidae larval habitats in urban areas and their association with various mosquito species using an innovative strategy

Assessment of MALDI-TOF MS for Arthropod Identification Based on Exuviae Spectra Analysis

MALDI-TOF MS is an innovative tool for identifying hematophagous and non-hematophagous arthropods at various life stages. However, identification by MALDI-TOF MS currently requires euthanizing of the specimen, hindering further phenotypic tests. All arthropods have a common factor, molting of their exoskeletons leaving a remaining structure known as the exuviae. This phenomenon is indispensable for their growth and can evidence past arthropod presence. This study assessed the performance of MALDI-TOF MS biotyping for arthropod identification using exuviae from nine distinct laboratory-reared species (Aedes aegypti, Anopheles coluzzii, Cimex lectularius, C. hemipterus, Pediculus humanus humanus, Triatoma infestans, Rhodnius prolixus, Supella longipalpa and Blattella germanica) compared its efficiency with a molecular identification approach using DNA sequencing. Molecular analysis showed low DNA quantity in exuviae (n = 108) across species, resulting in low success of COI, 16s, and 18s amplification (50.0%), depending on the species and sequencing (10.2%). The establishment of an exuviae protocol for MS submission yielded spectra of high reproducibility and specificity per species. After upgrading a homemade reference MS database with exuviae spectra, a query with remaining spectra revealed that 100% of samples were correctly identified, with 85.8% (278/324) exceeding the threshold score value for reliable identification. MALDI-TOF MS showed high efficiency in identifying various arthropod species based on their exuviae. This approach is a groundbreaking development in the field of entomology underlining that MALDI-TOF outperformed traditional methods of exuviae identification, including morphological and molecular tools. It also prevents specimen sacrifice which could be used for complementary analyses.

Investigating the impact of climate and seasonality on mosquito (Diptera: Culicidae) vector populations in the connecting areas of the Tenasserim range forests in Thailand

Mosquito-borne diseases pose a significant public health challenge globally. Our study focused on the seasonal diversity of mosquito species in the connecting areas of the Tenasserim (also known as Tanaosri) range forests in Thailand. Additionally, we employed the geometric morphometric technique to assess variations in wing size and shape among five predominant mosquito species. Throughout the study period, we collected a total of 9,522 mosquitoes, encompassing 42 species across eight genera. In these connecting areas of forests, the Simpson index and Shannon species diversity index were recorded at 0.86 and 2.36, respectively, indicating a high level of mosquito diversity. Our analysis using the Analysis of Similarities (ANOSIM) test showed significant seasonal differences in mosquito communities, with an R-value of 0.30 (p < 0.05) in the lower connecting areas and 0.37 (p < 0.05) in the upper connecting areas. Additionally, canonical correspondence analyses showed that the abundance of each mosquito species is influenced by various climate factors. Phenotypic analyses of wing size and shape have deepened our understanding of local adaptation and the seasonal pressures impacting these vectors. Notably, most species exhibited larger wing sizes in the dry season compared to other seasons. Additionally, seasonal assessments of wing shape in five predominant mosquito species revealed significant differences across seasonal populations (p < 0.05). Ongoing monitoring of these populations is crucial to enhancing our understanding of the seasonal effects on mosquito abundance and physiological adaptations. These insights are essential for developing more effective strategies to manage mosquito-borne diseases.

An overview of technologies available to monitor behaviours of mosquitoes

Mosquito-borne diseases such as malaria, dengue, Zika, and chikungunya cause significant morbidity and mortality globally, resulting in over 600,000 deaths from malaria and around 36,000 deaths from dengue each year, with millions of people infected annually, leading to substantial economic losses. The existing mosquito control measures, such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), helped to reduce the infections. However, mosquito-borne diseases are still among the deadliest diseases, forcing us to improve the existing control methods and look for alternative methods simultaneously. Advanced monitoring techniques, including remote sensing, and geographic information systems (GIS) have significantly enhanced the efficiency and effectiveness of mosquito control measures. Mosquitoes' behavioural traits, such as locomotion, blood-feeding, and fertility are the key determinants of disease transmission and epidemiology. Technological advancements, such as high-resolution cameras, infrared imaging, and artificial intelligence (AI) driven object detection models, including groundbreaking convolutional neural networks, have provided efficient and precise options to monitor various mosquito behaviours, including locomotion, oviposition, fertility, and host-seeking. However, they are not commonly employed in mosquito-based research. This review highlights the novel and significant advancements in behaviour-monitoring tools, mostly from the last decade, due to cutting-edge video monitoring technology and artificial intelligence. These advancements can offer enhanced accuracy, efficiency, and the ability to quickly process large volumes of data, enabling detailed behavioural analysis over extended periods and large sample sizes, unlike traditional manual methods prone to human error and labour-intensive. The use of behaviour-assaying techniques can support or replace existing monitoring techniques and directly contribute to improving control measures by providing more accurate and real-time data on mosquito activity patterns and responses to interventions. This enhanced understanding can help establish the role of behavioural changes in improving epidemiological models, making them more precise and dynamic. As a result, mosquito management strategies can become more adaptive and responsive, leading to more effective and targeted interventions. Ultimately, this will reduce disease transmission and significantly improve public health outcomes.

MALDI-TOF MS Profiling and Its Contribution to Mosquito-Borne Diseases: A Systematic Review

Mosquito-borne diseases are responsible for hundreds of thousands of deaths per year. The identification and control of the vectors that transmit pathogens to humans are crucial for disease prevention and management. Currently, morphological classification and molecular analyses via DNA barcoding are the standard methods used for vector identification. However, these approaches have several limitations. In the last decade, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) profiling has emerged as an innovative technology in biological sciences and is now considered as a relevant tool for the identification of pathogens and arthropods. Beyond species identification, this tool is also valuable for determining various life traits of arthropod vectors. The purpose of the present systematic review was to highlight the contribution of MALDI-TOF MS to the surveillance and control of mosquito-borne diseases. Published articles from January 2003 to August 2024 were retrieved, focusing on different aspects of mosquito life traits that could be determinants in disease transmission and vector management. The screening of the scientific literature resulted in the selection of 54 published articles that assessed MALDI-TOF MS profiling to study various mosquito biological factors, such species identification, life expectancy, gender, trophic preferences, microbiota, and insecticide resistance. Although a large majority of the selected articles focused on species identification, the present review shows that MALDI-TOF MS profiling is promising for rapidly identifying various mosquito life traits, with high-throughput capacity, reliability, and low cost. The strengths and weaknesses of this proteomic tool for vector control and surveillance are discussed.

Identification of Neotropical Culex Mosquitoes by MALDI-TOF MS Profiling

The mosquito (Diptera: Culicidae) fauna of French Guiana encompasses 242 species, of which nearly half of them belong to the genus Culex. Whereas several species of Culex are important vectors of arboviruses, only a limited number of studies focus on them due to the difficulties to morphologically identify field-caught females. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been reported as a promising method for the identification of mosquitoes. Culex females collected in French Guiana were morphologically identified and dissected. Abdomens were used for molecular identification using the COI (cytochrome oxidase 1) gene. Legs and thorax of 169 specimens belonging to 13 Culex species, (i.e., Cx. declarator, Cx. nigripalpus, Cx. quinquefasciatus, Cx. usquatus, Cx. adamesi, Cx. dunni, Cx. eastor, Cx. idottus, Cx. pedroi, Cx. phlogistus, Cx. portesi, Cx. rabanicolus and Cx. spissipes) were then submitted to MALDI-TOF MS analysis. A high intra-species reproducibility and inter-species specificity of MS spectra for each mosquito body part tested were obtained. A corroboration of the specimen identification was revealed between MALDI-TOF MS, morphological and molecular results. MALDI-TOF MS protein profiling proves to be a suitable tool for identification of neotropical Culex species and will permit the enhancement of knowledge on this highly diverse genus.

Enhanced procedures for mosquito identification by MALDI-TOF MS

Background

In the last decade, an innovative approach has emerged for arthropod identification based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Increasing interest in applying the original technique for arthropod identification has led to the development of a variety of procedures for sample preparation and selection of body parts, among others. However, the absence of a consensual strategy hampers direct inter-study comparisons. Moreover, these different procedures are confusing to new users. Establishing optimized procedures and standardized protocols for mosquito identification by MALDI-TOF MS is therefore a necessity, and would notably enable the sharing of reference MS databases. Here, we assess the optimal conditions for mosquito identification using MALDI-TOF MS profiling.

Methods

Three homogenization methods, two of which were manual and one automatic, were used on three distinct body parts (legs, thorax, head) of two mosquito laboratory strains, Anopheles coluzzii and Aedes aegypti, and the results evaluated. The reproducibility of MS profiles, identification rate with relevant scores and the suitability of procedures for high-throughput analyses were the main criteria for establishing optimized guidelines. Additionally, the consequences of blood-feeding and geographical origin were evaluated using both laboratory strains and field-collected mosquitoes.

Results

Relevant score values for mosquito identification were obtained for all the three body parts assayed using MALDI-TOF MS profiling; however, the thorax and legs were the most suitable specimens, independently of homogenization method or species. Although the manual homogenization methods were associated with a high rate of identification on the three body parts, this homogenization mode is not adaptable to the processing of a large number of samples. Therefore, the automatic homogenization procedure was selected as the reference homogenization method. Blood-feeding status did not hamper the identification of mosquito species, despite the presence of MS peaks from original blood in the MS profiles of the three body parts tested from both species. Finally, a significant improvement in identification scores was obtained for field-collected specimens when MS spectra of species from the same geographical area were added to the database.

Conclusion

The results of the current study establish guidelines for the selection of mosquito anatomic parts and modality of sample preparation (e.g. homogenization) for future specimen identification by MALDI-TOF MS profiling. These standardized operational protocols could be used as references for creating an international MS database.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05361-0.

Virome Diversity among Mosquito Populations in a Sub-Urban Region of Marseille, France

Some mosquito species have significant public health importance given their ability to transmit major diseases to humans and animals, making them the deadliest animals in the world. Among these, the Aedes (Ae.) genus is a vector of several viruses such as Dengue, Chikungunya, and Zika viruses that can cause serious pathologies in humans. Since 2004, Ae. albopictus has been encountered in the South of France, and autochthonous cases of Dengue, Chikungunya, and Zika diseases have recently been reported, further highlighting the need for a comprehensive survey of the mosquitoes and their associated viruses in this area. Using high throughput sequencing (HTS) techniques, we report an analysis of the DNA and RNA viral communities of three mosquito species Ae. albopictus, Culex (Cx.) pipiens, and Culiseta (Cs.) longiareolata vectors of human infectious diseases in a small sub-urban city in the South of France. Results revealed the presence of a significant diversity of viruses known to infect bacteria, plants, insects, and mammals. Several novel viruses were detected, including novel members of the Rhabdoviridae, Totiviridae, Iflaviviridae, Circoviridae, and Sobemoviridae families. No sequence related to major zoonotic viruses transmitted by mosquitoes was detected. The use of HTS on arthropod vector populations is a promising strategy for monitoring the emergence and circulation of zoonoses and epizooties. This study is a contribution to the knowledge of the mosquito microbiome.

Coagulation-flocculation: a potential application for mosquito Larval Source Management (LSM)

Larval mosquitoes have a more limited home range and lower resistance to adverse environment than adults, thus can be ideal targets for vector control in some cases. Coagulation-flocculation technology, which could be used for water treatment in breeding sites of several vector mosquito species, can significantly change both the distribution of organic particles and surface sediment characteristics in water environment. The aim of this study was to explore the effect, principle and possibility of using coagulation-flocculation technology in immature mosquitoes killing. In this study, dechlorinated water was treated with Poly Aluminum Chloride (PACl, sewage treatment using), and we observed the impacts of PACl treatment on the development and survival of immature Culex pipiens pallens mosquitoes. When exposed to PACl treatment, physical effect is believed to be a main reason of coagulation-flocculation caused high larvae mortality: Ⅰ) alum floc layer increases the difficulty of larvae foraging, leads larvae starving to death; (Ⅱ) the little floc particles could attach to the lateral hair of larvae, which impede floatation process and then surface respiration by larval mosquitoes. The alum floc layer had a good killing effect on the mosquito larvae, presented the half lethal time (LT₅₀) of 2d, the 90% lethal time (LT₉₀) of 8.7±7.3 ∼ 14±4.5 d, and the pupation rate of 0 ∼ (6.5±0.5)%, respectively. Our results indicates alum floc, produced by PACl coagulation-flocculation, was shown to be highly active against 1^st∼2^nd instar larvae, the high mortality rate of immature mosquitoes as a result of physical effect. The observations suggest that coagulation-flocculation technology offers a novel potential approach to a sustainable and low-impact mosquito control method.

Identification of Aedes mosquitoes by MALDI-TOF MS biotyping using protein signatures from larval and pupal exuviae

BACKGROUND

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) biotyping is an innovative strategy, applied successfully for the identification of numerous arthropod families including mosquitoes. The effective mosquito identification using this emerging tool was demonstrated possible at different steps of their life-cycle, including eggs, immature and adult stages. Unfortunately, for species identification by MS, the euthanasia of the mosquito specimen is required.

METHODS

To avoid mosquito euthanasia, the present study assessed whether aedine mosquitoes could be identified by MALDI-TOF MS biotyping, using their respective exuviae. In this way, exuviae from the fourth-instar and pupal stages of Aedes albopictus and Aedes aegypti were submitted to MALDI-TOF MS analysis.

RESULTS

Reproducible and specific MS spectra according to aedine species and stage of exuviae were observed which were objectified by cluster analyses, composite correlation index (CCI) tool and principal components analysis (PCA). The query of our reference MS spectra database (DB) upgraded with MS spectra of exuviae from fourth-instar larvae and pupae of both Aedes species revealed that 100% of the samples were correctly classified at the species and stage levels. Among them, 93.8% (135/144) of the MS profiles reached the threshold log score value (LSV > 1.8) for reliable identification.

CONCLUSIONS

The extension of reference MS spectra DB to exuviae from fourth-instar and pupal stages made now possible the identification of mosquitoes throughout their life-cycle at aquatic and aerial stages. The exuviae presenting the advantage to avoid specimen euthanasia, allowing to perform complementary analysis on alive mosquitoes.