A novel mosquito species identification method based on PCR and capillary electrophoresis
Estelle Chabanol1,2,3,4, Ottavia Romoli1, Stanislas Talaga1, Yanouk Epelboin1, Katy Heu1, Ghislaine Prévot2,3, Mathilde Gendrin1,5,*
1 Microbiota of Insect Vectors Group, Institut Pasteur de la Guyane, Cayenne, French Guiana
2 Tropical Biome and Immunophysiopathology Laboratory, Université de Guyane, Cayenne, French Guiana
3 Université de Lille, CNRS, Inserm, CHU de Lille, Institut Pasteur de Lille, U1019 – UMR 9017 – CIIL – Center for Infection and Immunity of Lille, F-59000, Lille, France
4 École Doctorale 587, Université de Guyane, Cayenne, French Guiana
5 Institut Pasteur, Université de Paris, Department of Insect Vectors, F-75015, Paris, France
* Correspondence: mathilde.gendrin@pasteur.fr
Abstract: In the Anopheles genus, various mosquito species are able to transmit Plasmodium parasites responsible for malaria, while others are non-vectors. In an effort to better understand the biology of Anopheles species and to quantify transmission risk in an area, the identification of mosquito species collected on the field is an essential but problematic task. Morphological identification requires expertise, well-preserved specimens and high-quality equipment, and it does not allow any subsequent verification when samples are later used in a destructive treatment. Moreover, it involves physical manipulations that are not compatible with experiments requiring fast sampling and processing of specimens, hence species identification is often based on DNA sequencing of reference genes or region such as the Internal Transcribed Spacer 2 (ITS2) region of nuclear ribosomal DNA. Sequencing ITS2 for numerous samples is costly, but the design of species-specific PCR primers is not always possible when local species diversity is high. Here, we introduce a molecular technique of species identification based on precise determination of ITS2 length combined with a simple visual observation, the color of mosquito hindleg tip. DNA extracted from field-collected Anopheles mosquitoes was amplified with universal Anopheles ITS2 primers and analyzed with a capillary electrophoresis device, which precisely determines the size of the fragments. We defined windows of amplicon sizes combined with fifth hind tarsus color, which allow to discriminate the majorAnopheles species found in our collections. We validated our parameters via Sanger sequencing of the ITS2 amplicons. This method can be particularly useful in situations with a moderate species diversity, i.e. when the number of local species is too high to define species-specific primers but low enough to avoid individual ITS2 sequencing. This tool will be of interest to evaluate local malaria transmission risk and this approach may further be implemented for other mosquito genera.
Keywords: Species Identification; Capillary Electrophoresis; ITS2; Length Polymorphism; Anopheles ; French Guiana