Nitrogenous compounds as attractants of Triatoma infestans (Klug)

A. FONTÁN; R. ALZOGARAY; P. SANTO ORIHUELA; E. ZERBA; D. FERNÁNDEZ; F. CAMPS; A. CORK

Foz do Iguazú, Brasil

Congreso; XXI International Congress of Entomology; 2000

The haematophagous bug Triatoma infestans is the major vector of Chagas Disease in South America. The ability of its own feces to elicit aggregation in nymphs and adults is well known. The presence of nitrogenous compounds such as 4-methyl and 2,4 dimethyl quinazolines and the emission of NH3 were reported. Other authors could verify no attractant effect when doses of 0.1-100 ng of quinazolines were tested in immature stadiums. Behavioral and electrophysiological assays have demonstrated the capability of NH3 to attract nymphs and the presence of NH3 antenna receptors. However, for practical purposes the finding of an active source of NH3 is indispensable. In this work, the activity of a number of hygroscopic ammonium salts with different NH3 release rates was tested. Ammoniym chloride, ammonium acetate and ammonium carbonate were tested using a video tracking system on a circular arena, 20-cm diameter. After 30 minutes of acclimatization of the insect, 2 mg of the compound to be tested was introduced in the middle of the arena on thin glass. The approach of the insect around the compound source was recorded for 30 minutes. The attractant effect was quantified as the number of visits of the insect to the centeral zone during the assay. Ammonium carbonate or acetate did not elicit any response on nymph V. Howeverm ammonium chloride proved to be attractive, increasing significantly the mean number of visit to the center zone (from 0.1 to 2.7). Aqueous solutions of methyl amine ranging from 10-3 to 10-1 M significantly increased the mean number of visits of nymph V around the source from 0.1 to 1.3. No significant effect was observed when 2 mg of ethylammonium chloride was tested. A mixture of synthetic quinazolines obtained from 2-aminoacetophenone, in a ratio similar to that found in feces (1:1) was tested on females and males. Mixtures containing 50 mg of each compound elicited a very significant attractive effect on females. Toxicological assays are now in progress to establish if placing quinazolines in a pyrethroid film would enhance the kill of T. infestans.