Coupling Chemical and Antennal Responses: A Streamlined GC-MS-EAD Approach in Sand Flies

A recent study presented a simplified gas chromatography-mass spectrometry-electroantennographic detection (GC-MS-EAD) setup adapted for screening bioactive compounds in sand flies, in which the chemical identification and antennal responses are recorded simultaneously. A paper based on this work was published in Parasites & Vectors (1).

Phlebotomine sand flies, a subfamily of the Psychodidae family of flies, are transmitters of pathogens (such as viruses, bacteria and protozoa) in general, and of Leishmania spp. specifically,to many animal species, including humans (2,3). Leishmania spp.is the contributing cause of leishmaniases, a disease which may occur with three clinical presentations: visceral (VL), cutaneous, and mucocutaneous (2,4). The visceral form, whose symptoms include fever, weight loss, skin lesions and enlargement of the liver, spleen and lymph nodes, may, if not adequately treated, be fatal (5). In the Mediterranean basin, the Middle East, Latin America and China, VL is caused by Leishmania infantum, which has domestic dogs and, occasionally, cats, wild leporids, and rats as its primary reservoirs, among other wildlife species (6–12). Other important drivers behind the global spread of VL include human and animal migrations, urbanization, ecotourism and climate change (13,14).

The method developed by the research team integrates: (i) a flow-splitter for balancing the flow rate of the two outgoing streams; (ii) GC columns with different lengths and diameters in the two sections splitter-MS and splitter-EAD; and (iii) an antennal signal amplifier. The GC-MS-EAD analysis was applied to headspace solid-phase microextraction (HS-SPME) extracts from a healthy dog, and antennal responses were recorded in female P. perniciosus sand flies. The canine VOC profile exhibited was mostly composed of aldehydes, with hexanal and nonanal eliciting the strongest antennal responses in P. perniciosus (1).

This simplified GC-MS-EAD system proved to be effective for the detection of semiochemicals which elicit antennal stimulus in P. perniciosus females. The integration of chemical and electrophysiological analytical techniques, according to the team, reduced the costs, eliminating the need for a flame ionization detector (FID), the experimental time and sample quantity needed, also minimizing the risk of EAD-active peak misidentification. The application of the system may be further validated by other host–vector pairs, which would potentially advance the understanding of their interactions and enable strategic interventions. The team believes that future research should investigate the repellence or attractiveness of the EAD-active compounds identified in this investigation and which have not yet been assessed in P. perniciosus. Bioassays such as Y-tube olfactometry or wind tunnel experiments using compounds such as hexane, heptanal, 6-methylheptan-2-one, octanal, 7-hydroxy-3,7-dimethyl-, caryophyllene and 2-methylundecane-2-thiol (tentatively identified) have the potential to reveal unique tools for the integration of vector monitoring and control (1).

References

1. Pistillo, O. M.; Farina, P.; Bezerra-Santos, M. A. et al. A Simplified System for the Detection of Antennal Responses to Host-Borne Volatile Organic Compounds in Sand Flies. Parasit. Vectors 2025, 18 (1), 352. DOI: 10.1186/s13071-025-06998-3
2. Dantas-Torres, F.; Solano-Gallego, L.; Baneth, G. et al. Canine Leishmaniosis in the Old and New Worlds: Unveiled Similarities and Differences. Trends Parasitol. 2012, 28 (12), 531-538. DOI: 10.1016/j.pt.2012.08.007
3. Maroli, M.; Feliciangeli, M. D.; Bichaud, L.et al. Phlebotomine Sandflies and the Spreading of Leishmaniases and other Diseases of Public Health Concern. Med. Vet. Entomol. 2013, 27 (2), 123-147. DOI: 10.1111/j.1365-2915.2012.01034.x
4. de Freitas Milagres, T.; Maia, C. Phlebotomus perniciosus. Trends Parasitol. 2024, 40, 649–650. DOI: O10.1016/j.pt.2024.04.007
5. Scarpini, S.; Dondi, A.; Totaro, C. et al. Visceral Leishmaniasis: Epidemiology, Diagnosis, and Treatment Regimens in Different Geographical Areas with a Focus on Pediatrics. Microorganisms 2022, 10, 1887. DOI: 10.3390/microorganisms10101887
6. Burza, S.; Croft, S. L.; Boelaert, M. Leishmaniasis. Lancet 2018, 392, 951–970. DOI: 10.1016/S0140-6736(18)31204-2
7. Carbonara, M.; Iatta, R.; Miró, G. et al. Affiliation Feline leishmaniosis in the Mediterranean Basin: A Multicenter Study. Parasit. Vectors 2024, 17, 346. DOI: 10.1186/s13071-024-06419-x
8. Martín-Sánchez, J.; Torres-Medina, N.; Morillas-Márquez, F. et al. Role of Wild Rabbits as Reservoirs of Leishmaniasis in a Non-Epidemic Mediterranean Hot Spot in Spain. Acta Trop. 2021, 222, 106036. DOI: 10.1016/j.actatropica.2021.106036
9. Helhazar, M.; Leitão, J.; Duarte, A. et al. Natural Infection of Synanthropic Rodent Species Mus musculus and Rattus norvegicus by Leishmania infantum in Sesimbra and Sintra-Portugal. Parasit. Vectors 2013, 6, 88. DOI: 10.1186/1756-3305-6-88
10. Galán-Puchades, M. T.; Solano, J.; González, G. et al. Molecular Detection of Leishmania infantum in Rats and Sand Flies in the Urban Sewers of Barcelona, Spain. Parasit. Vectors 2022, 15, 211. DOI 10.1186/s13071-022-05309-4
11. Abbate, J. M.; Arfuso, F.; Napoli, E. et al. Leishmania infantum in Wild Animals in Endemic Areas of Southern Italy. Comp. Immunol. Microbiol. Infect Dis. 2019, 67, 101374 DOI: 10.1016/j.cimid.2019.101374
12. Dantas-Torres, F. Canine Leishmaniasis in the Americas: Etiology, Distribution, and Clinical and Zoonotic Importance. Parasit. Vectors 2024, 17, 198. DOI: 10.1186/s13071-024-06282-w
13. Conn, D. B.; Soares Magalhães, R. J. Climate Change: A Health Emergency for Humans, Animals, and the Environment. One Health 2024, 19, 100867. DOI: 10.1016/j.onehlt.2024.100867
14. Wilke, A. B. B.; Farina, P.; Ajelli. M. et al. Human Migrations, Anthropogenic Changes, and Insect-Borne Diseases in Latin America. Parasit. Vectors 2025, 18, 4. DOI: 10.1186/s13071-024-06598-7