Host-Seeking Behavior and Dispersal of Triatoma infestans, a Vector of Chagas Disease, under Semi-field Conditions

Abstract

Chagas disease affects millions of people in Latin America. The control of this vector-borne disease focuses on halting transmission by reducing or eliminating insect vector populations. Most transmission of Trypanosoma cruzi, the causative agent of Chagas disease, involves insects living within or very close to households and feeding mostly on domestic animals. As animal hosts can be intermittently present it is important to understand how host availability can modify transmission risk to humans and to characterize the host-seeking dispersal of triatomine vectors on a very fine scale. We used a semi-field system with motion-detection cameras to characterize the dispersal of Triatoma infestans, and compare the behavior of vector populations in the constant presence of hosts (guinea pigs), and after the removal of the hosts. The emigration rate – net insect population decline in original refuge – following host removal was on average 19.7% of insects per 10 days compared to 10.2% in constant host populations (p = 0.029). However, dispersal of T. infestans occurred in both directions, towards and away from the initial location of the hosts. The majority of insects that moved towards the original location of guinea pigs remained there for 4 weeks. Oviposition and mortality were observed and analyzed in the context of insect dispersal, but only mortality was higher in the group where animal hosts were removed (p-value <0.01). We discuss different survival strategies associated with the observed behavior and its implications for vector control. Removing domestic animals in infested areas increases vector dispersal from the first day of host removal. The implications of these patterns of vector dispersal in a field setting are not yet known but could result in movement towards human rooms.

Activity levels of female Triatoma infestans change depending on physiological condition

“…It is known that oviposition exhibits a strong circadian rhythm with a peak at the same temporal window as dispersal and search for food [ 49 ]. Although other authors did not find a clear pattern of egg-laying distribution [ 28 ], in our study all eggs were found inside and around the shelter, suggesting a particular spatial egg-laying preference, strategically localized in the opposite corner to the host.…”

“…Nuñez [ 27 ] reported similar activity levels in R. prolixus with equivalent fasting intervals; although as the activity recording continued, and consequently starvation intensified, activity was augmented, mainly in the host presence. Castillo-Neyra et al [ 28 ] observed that host removal lead to increased T. infestans activity. However, in both mentioned studies [ 27 , 28 ], methodological differences do not allow a direct comparison with the present data.…”

“…Castillo-Neyra et al [ 28 ] observed that host removal lead to increased T. infestans activity. However, in both mentioned studies [ 27 , 28 ], methodological differences do not allow a direct comparison with the present data. For instance, we used fed control groups as well as different reproductive stages, host species and recording system.…”

“…These reasons led us to query whether fertilized females, maintained in laboratory conditions, express different behavior when other females in different reproductive states are together. Additionally, host presence or absence is a crucial environmental factor affecting dispersal [ 27 , 28 ]. The response of insects to the presence of a potential host depends on the multimodal integration of a variety of external cues, insect physiological states and individual previous experience [ 29 ].…”

Dispersal patterns of Trypanosoma cruzi in Arequipa, Peru

“…Human subject research participants provided written consent for the collection of bugs from his or her household and for human subject research. The IACUC of Universidad Peruana Cayetano Heredia is registered in the National Institutes of Health at the United States of America with PHS Approved Animal Welfare Assurance Number A5146-01 and adheres to the Animal Welfare Act of 1990 [3,39].…”