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Title: A novel in vitro bioassay to explore the repellent effects of compounds against mosquito Aedes Aegypti (Diptera: Culicidae)

Author
item REHMAN, JUNAID - University Of Mississippi
item TABANCA, NURHAYAT - University Of Mississippi
item KHAN, IKHLAS - University Of Mississippi

Submitted to: Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2015
Publication Date: 11/20/2015
Publication URL: http://handle.nal.usda.gov/10113/62608
Citation: Rehman, J.U., Tabanca, N., Khan, I.A. 2015. A novel in vitro bioassay to explore the repellent effects of compounds against mosquito Aedes Aegypti (Diptera: Culicidae). Medical Entomology. 0:1-9. doi: 10.1093/jme/tjv182

Interpretive Summary: Repellents play an important role in reducing mosquito bites and hence the risk of spread of mosquito borne diseases. To test a repellent property of compounds, extracts and essential oils, currently, human arm based bioassay systems are used. Risks involved with human arm based (in vivo) systems are allergic reactions and variation in data. These systems require large quantity of test materials which limits the number of replications. We designed an in vitro bioassay method “NCNPR repellent bioassay” that can closely simulate cloth patch bioassay system used to determine repellency against mosquitoes. This NCNPR repellent bioassay uses heat as a stimulus to attract mosquito and edible collagen sheet as alternate to human skin. The minimum effective dose (MED’s) (mg/cm2) of compounds: DEET, carvacrol, thymol, undecanoic acid, thymol methyl ether and 2-nonanone determined in this in-vitro system were similar to cloth path bioassay system. This NCNPR repellent bioassay can be used to screen compounds at a faster rate than the cloth patch bioassay, which involves the use of human subjects, with reasonable reproducibility of the data.

Technical Abstract: Mosquitoes are vectors for many pathogens that can cause human diseases which can result in high rates of human morbidity and mortality at significant levels of transmission. Repellents play an important role in reducing mosquito bites and hence the risk of spread of mosquito borne diseases. Currently, human arm based bioassay systems are used to identify repellent/deterrent properties of compounds, extracts and essential oils. Risks involved with human arm based (in vivo) systems are allergic reactions and variation in data. These systems require large quantity of test materials which limits the number of replications. We are reporting an in vitro bioassay method "National Center for Natural Product Research (NCNPR) repellent bioassay" that can closely simulate cloth patch bioassay system used to determine repellency against mosquitoes. The NCNPR repellent bioassay uses heat as a stimulus to attract mosquito and edible collagen sheet as alternate to human skin. This system consists of a heating base plate of cup warmer fixed to Plexiglas sheet having a rectangular liquid reservoir of 3 x 4 em used for feeding solution. This base plate containing the feeding solution covered with treated collagen sheet is introduced in 12 x 12 x 12 inches cage containing approximately 200 starved female mosquitoes. Treatments prepared in EtOH were applied in concentrations ranging between 1.5 to 0.011 mg/cm2 in a volume of 50 jJl/20 cm2 area of collagen sheet. Number of mosquito commencing to bite was recorded visually. The minimum effective dose (MED's) (mg/cm2) of compounds: DEET (0.021), carvacrol (0.011), thymol (0.013), undecanoic acid (0.023), thymol methyl ether (0.269) and 2-nonanone (>0.375 mg/cm2)determined in this in vitro system were similar to cloth path bioassay system. This NCNPR repellent bioassay can be used to screen compounds at a faster rate than the cloth patch bioassay, which involves the use of human subjects, with reasonable reproducibility of the data.