Mild-Vectolysis: A Nondestructive DNA Extraction Method for Vouchering Sand Flies and Mosquitoes

Pathogen prospecting of museums: Reconstructing malaria epidemiology

Malaria is a disease of global significance. Ongoing changes to the earth's climate, antimalarial resistance, insecticide resistance, and socioeconomic decline test the resilience of malaria prevention programs. Museum insect specimens present an untapped resource for studying vector-borne pathogens, spurring the question: Do historical mosquito collections contain Plasmodium DNA, and, if so, can museum specimens be used to reconstruct the historical epidemiology of malaria? In this Perspective, we explore molecular techniques practical to pathogen prospecting, which, more broadly, we define as the science of screening entomological museum specimens for human, animal, or plant pathogens. Historical DNA and pathogen prospecting provide a means of describing the coevolution of human, vector, and parasite, informing the development of insecticides, diagnostics, therapeutics, and vaccines.

Nondestructive Methods of Pathogen Detection: Importance of Mosquito Integrity in Studies of Disease Transmission and Control

Mosquitoes are vectors of many pathogens, including viruses, protozoans, and helminths, spreading these pathogens to humans as well as to wild and domestic animals. As the identification of species and the biological characterization of mosquito vectors are cornerstones for understanding patterns of disease transmission, and the design of control strategies, we conducted a literature review on the current use of noninvasive and nondestructive techniques for pathogen detection in mosquitoes, highlighting the importance of their taxonomic status and systematics, and some gaps in the knowledge of their vectorial capacity. Here, we summarized the alternative techniques for pathogen detection in mosquitoes based on both laboratory and field studies. Parasite infection and dissemination by mosquitoes can also be obtained via analyses of saliva- and excreta-based techniques or of the whole mosquito body, using a near-infrared spectrometry (NIRS) approach. Further research should be encouraged to seek strategies for detecting target pathogens while preserving mosquito morphology, especially in biodiversity hotspot regions, thus enabling the discovery of cryptic or new species, and the determination of more accurate taxonomic, parasitological, and epidemiological patterns.

A Non-Destructive High-Speed Procedure to Obtain DNA Barcodes from Soft-Bodied Insect Samples with a Focus on the Dipteran Section of Schizophora

While the need for biodiversity research is growing, paradoxically, global taxonomical expertise is decreasing as a result of the neglected funding for young academics in taxonomy. Non-destructive approaches for DNA barcoding are necessary for a more efficient use of this dwindling expertise to fill gaps, and identify incorrect entries in sequence databases like BOLD or GenBank. They are efficient because morphological re-examination of species vouchers is still possible post-DNA barcoding. Non-destructive approaches for Diptera with a comprehensive species representation or the consideration of diagnostic fragile morphological characters are missing. Additionally, most non-destructive approaches combine a time intensive and non-destructive digestion step with common DNA extraction methods, such as commercial kits or CTAB DNA isolation. We circumvented those approaches and combined a modified non-destructive TE buffer high-speed DNA extraction, with a PCR inhibitor-resistant PCR reaction system, to a non-destructive DNA barcoding procedure for fresh and frozen samples of the Schizophora (Diptera). This method avoids morphological impairment and the application of harmful chemicals, is cost and time effective, restricts the need for laboratory equipment to a minimum, and prevents cross-contamination risk during DNA isolation. Moreover, the study indicates that the presented non-destructive DNA barcoding procedure is transferable to other soft-bodied insects. We suggest that PCR inhibitor-resistant master mixes enable the development of new—and the modification of existing—non-destructive approaches with the avoidance of further DNA template cleaning.

Novel and PCR ready rapid DNA isolation from Drosophila

INTRODUCTION

Isolation of genomic DNA is an initial step in molecular biology techniques. The quality of isolated DNA depends on procedures and chemicals, as well as source and types of the sample used. Several existing procedures are expensive and time consuming. In this study, we isolated high quality genomic DNA with an inexpensive and least time consuming procedure using Drosophila melanogaster flies, larvae, and pupae.

METHODS

Drosophila melanogaster samples were collected from pre-cultured bottles, and genomic DNA was extracted using a proposed novel and PCR-ready method from three different pools of flies [PF1, PF2, and PF3], similarly from larvae and pupae [PL1, PL2, PL3, PP1, PP2, and PP3, respectively]. Isolated genomic DNA was subjected to PCR amplification with different dilutions using the COI gene and further amplicons were used for RAPD and DNA sequencing.

RESULTS

The high quality of isolated genomic DNA was confirmed by 0.8% agarose gel electrophoresis and the purity and quantity of the DNA isolated from single fly, larva and pupa was similar to the purity and quantity of the DNA isolated using the NucleoSpin^R Tissue kit method. Isolated genomic DNA was successfully amplified when the template was diluted in the ratio of 1:10. Further successful RAPD amplification and sequencing analysis of the COI gene confirms the efficiency of the downstream application of the proposed novel method.

CONCLUSION

The present Novel and PCR ready rapid DNA isolation method will be potentially beneficial, and it can be successfully used for quick isolation of high molecular weight DNA from Drosophila flies larvae and pupae for DNA barcoding, identification of new species, genotyping, RAPD analysis, etc. Moreover, it can also be easily scaled up for bulk preparations.

Sand Fly (Diptera: Psychodidae: Phlebotominae) Population Dynamics and Natural Leishmania Infections in Attica Region, Greece

A 2-yr sand fly (Diptera: Psychodidae) seasonality study was performed in Attica Region, Greece, from June 2017 until November 2018, aiming also to detect the presence of Leishmania infection in the collected sand flies. In total, 701 sand flies were collected from urban areas within the Attica Region using BG-Sentinel traps, set weekly in eight fixed sites. Five species were identified morphologically and molecularly, namely Phlebotomus tobbi (Adler and Theodor), which was most the most commonly collected species, followed by P. Neglectus (Tonnoir), P. papatasi (Scopoli), P. simici (Theodor), and Sergentomyia minuta (Rondani). During both survey years sand fly populations peaked in late August to early September. Fifty-nine monospecific pools were examined for Leishmania detection by analyzing the ITS1 nuclear region using both RFLPs and sequencing, seven of which were found positive. Leishmania DNA was identified as L. infantum in six pools (five P. papatasi and one P. tobbi), whereas in one P. papatasi pool Leishmania DNA was identified as L. tropica. This is the first time that L. tropica has been detected in naturally infected sand flies from the Attica Region as well as in central Greece, while previously it has only been detected in sand flies collected from Central Macedonia (Northern Greece).

Parasitoids of Chrysopidae Eggs in Sinaloa Mexico

The eggs parasitoids Myartsevaia chrysopae (Crawford) (Hymenoptera: Encyrtidae), Telenomus lobatus Johnson, Telenomus tridentatus Johnson (Hymenoptera: Scelionidae) and Trichogramma atopovirilia Oatman and Platner (Hymenoptera: Trichogrammatidae) are reported for the first time or in new localities in Mexico. Their occurrence was first discovered in 2018 during a survey of parasitism on chrysopid eggs, conducted on Sorghum bicolor L. Moench (Poales: Poaceae) and Zea mays L. (Poales: Poaceae) in different locations in Sinaloa, Mexico. The identity of the parasitoids was determined by morphology and for both species of Telenomus the barcode region of the cytochrome oxidase 1 gene (CO1) was generated to facilitate molecular diagnosis of these species in future studies.

Optimization of DNA Extraction from Individual Sand Flies for PCR Amplification

Numerous protocols have been published for extracting DNA from phlebotomines. Nevertheless, their small size is generally an issue in terms of yield, efficiency, and purity, for large-scale individual sand fly DNA extractions when using traditional methods. Even though this can be circumvented with commercial kits, these are generally cost-prohibitive for developing countries. We encountered these limitations when analyzing field-collected Lutzomyia spp. by polymerase chain reaction (PCR) and, for this reason, we evaluated various modifications on a previously published protocol, the most significant of which was a different lysis buffer that contained Ca²⁺ (buffer TESCa). This ion protects proteinase K against autolysis, increases its thermal stability, and could have a regulatory function for its substrate-binding site. Individual sand fly DNA extraction success was confirmed by amplification reactions using internal control primers that amplify a fragment of the cacophony gene. To the best of our knowledge, this is the first time a lysis buffer containing Ca²⁺ has been reported for the extraction of DNA from sand flies.

Direct Multiplex PCR (dmPCR) for the Identification of Six Phlebotomine Sand Fly Species (Diptera: Psychodidae), Including Major Leishmania Vectors of the Mediterranean

Sand flies (Diptera: Psychodidae, subfamily Phlebotominae) are hematophagous insects that are known to transmit several anthroponotic and zoonotic diseases. Reliable identification of sand flies at species level is crucial for their surveillance, the detection and spread of their pathogens, and the implementation of targeted pest control strategies. Here, we designed a novel, time-saving, cost-effective and easy-to-apply molecular methodology, which avoids sequencing, for the identification of the following six Eastern Mediterranean sand fly species: Phebotomus perfiliewi Parrot, Phebotomus simici Theodor, Phebotomus tobbi Adler and Theodor, Phebotomus papatasi Scopoli, Sergentomyia dentata Sinton, and Sergentomyia minuta Theodor. This methodology, which is a multiplex PCR assay using one common and six diagnostic primers, is based on species-specific single-nucleotide polymorphisms of the nuclear 18S rRNA gene. Amplification products were easily and reliably separated in agarose gel yielding one single clear band of diagnostic size for each species. Further, we verified its successful application on tissue samples that were immersed directly to the PCR mix, skipping DNA extraction. The direct multiplex PCR can be completed in < 3 h, including all operating procedures, and costing no more than a simple PCR. The applicability of this methodology in the detection of hybrids is an additional considerable benefit.

Species composition, activity patterns and blood meal analysis of sand fly populations (Diptera: Psychodidae) in the metropolitan region of Thessaloniki, an endemic focus of canine leishmaniasis

Species composition, activity patterns and blood meal analysis of sand fly populations were investigated in the metropolitan region of Thessaloniki, North Greece from May to October 2011. Sampling was conducted weekly in 3 different environments (animal facilities, open fields, residential areas) along the outskirts of the city in areas of increased canine leishmania transmission. Six sand fly species (Phlebotomus perfiliewi, Phlebotomus tobbi, Phlebotomus simici, Plebotomus papatasi, Sergentomya minuta and Sergentomya dentata) were identified using both classical and molecular techniques. DNA barcodes were characterized for the first time for two (P. simici and S. dentata) of the six recorded species. Phylogenetic analysis based on the COI gene sequences confirmed the grouping of P. tobbi, P. perniciosus and P. perfiliewi (subgenus Larrousius) and the monophyly of P. simici (subgenus Adlerius). By far the most prevalent species was P. perfiliewi, followed by P. simici and P. tobbi. The largest populations of sand flies were collected from animal facilities, followed by residential areas and open agricultural fields. Peak activity of sand flies overall occurred mid-August to mid-September and then declined sharply in October. Blood meal analysis showed that P. perfiliewi and P. simici feed preferentially on humans (88% & 95%, respectively) but also feed on chickens and goats. When designing a control strategy to alleviate sand fly nuisance in the region of Thessaloniki the following conclusions can be reached from this study: a) August and September are high risk months due to increased sand fly activity levels, b) animal facilities within or adjacent to urban settlements are high risk areas and may act as a maintenance and amplification foci for the vector as well as the parasite, and c) the abundance, ubiquity and feeding behavior of P. perfiliewi and P. simici establishes them as potentially important vectors of Leishmania in the region.