Flight Initiation of <I>Triatoma infestans</I> (Hemiptera: Reduviidae) Under Natural Climatic Conditions

Abstract

Flight dispersal of Triatoma infestans Klug is probably the most important mechanism for house reinfestation at a village scale after residual spraying with insecticides. The aim of the current study was to estimate the flight initiation probability of field-collected T. infestans and to assess how this probability was affected by sex, adult age, partial bloodmeal, and the presence of a host inaccessible for feeding. Four experimental series, each consisting of three to six consecutive nights and repeated measurements of flight initiation on each individually marked bug, were carried out in experimental huts inside closed cages under natural climatic conditions. We demonstrate that flight initiation probability of T. infestans is much higher than previously reported, responds to temperature in a sigmoid manner, and is higher in females than males, and that the frequency distribution of the number of flights per individual is highly aggregated in female and male bugs. The age of adults had strong effects on flight initiation, whereas the presence of an inaccessible host and a partial bloodmeal exerted no significant effects in models controlling for the effects of bug weight-to-length ratio. The high flight potential found is consistent with the rapid changes in reinfestation patterns observed in the field. The present estimates of flight probabilities and the identification of factors modifying them provide essential knowledge for modeling reinfestation patterns and for improving control strategies of T. infestans. Keywords flight initiation; Triatominae; Chagas disease; reinfestation THEORETICAL AND EMPIRICAL DATA suggest that flight dispersal by Triatoma infestans Klug, the main vector of Chagas disease in South America, is the most important mechanism for reinfestation of houses at a village scale after insecticide spraying (Schofield and Matthews 1985,Cecere et al. 2004 Ceballos et al. 2005). Yet a key reference source disregards flight dispersal in favor of passive transport by humans as a major driver of local reinfestation (WHO 2002). Such misconception probably arose from the typical nocturnal activity and sporadically observed flights of T. infestans. T. infestans may easily fly >550 m or reach 1,500 m (Schweigmann et al. 1988) in an open field, and it may sustain tethered flights for >20 min at speeds of 2 m/s (Ward and Baker 1982). Flight initiation is associated with low nutritional status (estimated by weight-to-length ratio, W/L), high temperatures, and low wind speed (Lehane and Schofield 1982. Flight initiation is positively associated with adult age for up to 40-60 d and then falls to lower constant levels (Lehane and Schofield 1982). In laboratory experiments, Williams and Schofield (1985) reported higher proportions of female T. infestans flying, whereas Lehane et al. (1992) found no significant differences between sexes. Although triatomine bugs are known to be attracted by host odors and radiant heat (Lazzari and Núñez 1989,Taneja andGuerin 1995), there are no published reports on ...

Dispersal of Triatoma infestans and other Triatominae species in the arid Chaco of Argentina: Flying, walking or passive carriage? The importance of walking females

“…In laboratory experiments, Gurevitz et al (2007) found dimorphism in muscle growth in adults, observing an absence of flight muscles more frequently in males and, therefore, a potentially lower dispersive capacity. However, in field experiments with laboratory T. infestans, the number of females dispersing by flight was higher relative to males (Canale & Carcavallo 1985, Gurevitz et al 2006, Minoli & Lazzari 2006. The results presented here would indicate that T. infestans males fly more frequently than females, coinciding with the results of Vazquez-Prokopec et al (2004) and Ceballos et al (2005).…”

“…Dispersion, seasonality and weather variables -Temperatures below 23ºC, rain and winds of more than 5 km/h appear to have a negative effect on dispersal (Gurevitz et al 2006). In contrast, weather conditions seemed ideal for dispersal during the sampling period in Los Llanos.…”

“…Body length was measured from the clypeus to the abdominal tip using a hand-held calliper. These measurements were used to calculate the W/L ratio, which is used by many authors as an indicator of flight dispersal probability (Lehane & Schofield 1982, Ceballos et al 2005, Gurevitz et al 2006). …”

Sylvatic foci of the Chagas disease vector Triatoma infestans in Chile: description of a new focus and challenges for control programs

“…However, it may reflect rapid flight dispersal once they molt to the last instar (Lehane & Schofield 1982), aided by high summer temperatures (Lehane et al 1992, Gurevitz et al 2006.…”

Biology, diversity and strategies for the monitoring and control of triatomines - Chagas disease vectors

“…Understanding their host searching behaviour and activity patterns (Guerenstein & Lazzari 2009) as well as their choice of environments (Guarneri et al 2002(Guarneri et al , 2003 is also necessary. In addition to the previously mentioned characteristics, dispersion and reproductive strategies are essential for creating models to predict re-infestation processes (Gurevitz et al 2006). Altogether, these aspects represent most of the variables needed for the development of pro-active control actions against domiciliary infestation.…”