Evaluation of repellent activity of benzaldehyde and (E)-2-octenal for Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract

Leishmaniasis is a zoonosis caused by protozoa parasites. World Health Organization (WHO) considers a global public health problem being endemic in 97 countries. In Brazil, the visceral form of the disease has the etiological agent Leishmania (Leishmania) infantum chagasi, which has as main vector dipterous of the species Lutzomyia longipalpis. Governmental epidemiological surveillance aims to reduce lethality and morbidity rates through the diagnosis and early treatment of cases, vector control using insecticidal chemical methods and euthanasia of infected dogs. Individual protection by means of repellents is a way of preventing leishmaniasis, with N, N-diethyl-3-methylbenzamide (DEET) being the most widely used. However, there are few scientific studies to prove their action on the different species of sandflies. In addition, DEET causes adverse effects such as: alteration in the central nervous system, cardiac changes, and allergic skin reactions. The need for better repellency tests with alternative chemicals is then observed in order to develop repellents that are more effective and more secure than DEET. Previous studies with semiochemicals from dogs and donkeys resistant to tick parasitism reported the isolation of two chemical compounds: benzaldehyde and (E) -2-octenal. Both compounds presented repellent activity on the ectoparasites being classified as natural repellents. Knowing that dogs act as important reservoirs in visceral leishmaniasis, the investigation of repellent activity for sand flies of compounds that have already presented a repellent response to ticks, opens perspectives for the development of double-action collars for these arthropods. However, few studies of repellency using sand flies are reported in the literature, in part because there is no standardization for human and animal testing. Thus, the objective of this work will be the evaluation of the repellent activity of benzaldehyde and (E) -2-octenal for sandflies, after previous standardization of adequate methodology for tests with humans and animals.