Repellent activity of essential oils on Triatoma infestans

Chagas disease is a parasitic disease caused by Trypanosoma cruzi, transmitted to humans by some Triatominae species, affecting an estimated in 28 million people in Latin America [1]. Triatoma infestans is the most widespread vector in South America, extending from the Peruvian highlands to the northeast Brazilian regions, including the plains of Argentina [2].

A recommendable method to lower the incidence of the disease is to control the proliferation of the vectors of the parasite. It is known that the insects behavior can be affected by volatile substances which transfer chemical information [3] and essential oils may contain such a type of substances. In this work we tested the repellent activity of 24 essential oils, from plants of the Bolivian flora, on fourth instar nymphs of Triatoma infestans. The tests were carried out in a glass tube (60cm long and 5cm internal diameter) having a hole in the middle to introduce the insects. The insects were allowed to distribute randomly over an accordion-folded filter paper sheet placed inside the tube and exposed to the volatiles of an essential oil. The direction, magnitude and rapidity of their displacement regarding the sample of the essential oil was recorded. Most of the tested essential oils showed a repulsive effect. The most pronounced repellent activities were observed with the essential oils of Eucalyptus globulus, Coriandrum sativum, Chrysanthemum parthenium, Coniza rurigena, Vernonia patens, Mynthostachys andina, Custos albiflora, Aloysia gratissima and Foeniculum vulgare.

Acknowledgements: We thank SIDA-SAREC Swedish Cooperation and the French MRT for financial support.

References: 1. http://www.who.int/tdr/publications/publications/pdf/swg_chagas.pdf

2. Schofield, C.J. (1994). Triatominae: Biology and Control. Eurocommunica Publications. Bognor Regis. West Sussex, UK.

3. Shorey, H.H. & J.J. McKelvey, Jr. (eds.) (1977). Chemical Control of Insect Behavior. John Wiley. New-York, USA.