Feeding behavior of triatomines from the southwestern United States: An update on potential risk for transmission of Chagas disease
Introduction
Chagas disease, caused by Trypanosoma cruzi, is an emerging public health concern in the United States and Canada principally because of its potential to contaminate the blood transfusion supply. Immigration to the United States of asymptomatic, infected individuals from endemic areas in Latin America has led to transmission of the disease through donor blood (Young et al., 2007) as well as through surgical implantation of infected donor organs to patients in non-endemic areas (Mascola et al., 2006). Seroprevalence of infection is notable among immigrants in Miami and Los Angeles (Leiby et al., 2002), some of whom have PCR evidence of ongoing parasitemia (Leiby et al., 2008). The parasite has been found in over 18 species of mammals in the United States (John and Hoope, 1986) as well as six autochthonous cases of Chagas in humans. One case each was reported from California (where Triatoma protracta (Uhler) was implicated) (Schiffler et al., 1984) and Tennessee (Herwaldt et al., 2000), three cases from Texas (Woody and Woody, 1955, Ochs et al., 1996) and the most recent case involved a woman in Louisiana whose house and surroundings were heavily infested with T. sanguisuga (Leconte) (Dorn et al., 2007).
This study set out to determine whether or not the feeding behavior of T. protracta and Triatoma rubida (Uhler), posed a significant risk for transmission of Chagas disease to humans in the Southwest at the current time. These two species are known vectors of T. cruzi (Guzman-Bracho, 2001). Triatomine bites are common in the Southwest (Lynch and Pinnas, 1978), but are mainly feared because of their potential to cause anaphylaxis (Wood, 1942, Wood, 1950). Wood studied T. protracta and T. rubida as possible vectors of Chagas disease in the southwestern United States over 50 years ago (Wood, 1951).
We studied wild-caught, adult triatomine feeding behavior on immobilized mice, measuring their feeding duration and blood intake, recording where they fed on the mouse and whether or not they defecated after feeding. We documented how far from the host they defecated and also determined whether or not they were infected with T. cruzi.
Section snippets
Triatomines
Forty-four triatomines were captured for this study. All 44 bugs were checked for the presence of T. cruzi by PCR of abdominal segments or fecal drops. Bugs were maintained in individual, vented small glass bottles with filter paper on the bottom at ambient temperature. Water was available on moistened cotton balls. The bugs were starved and fed on average, every 14 days. Eggs were counted and removed from the bottles containing females. The geographic origins of the bugs observed in this study
Foraging
T. protracta appeared to initiate feeding more slowly than T. rubida. Almost without exception, T. rubida crawled directly to the mouse and initiated feeding within seconds of its release. On the other hand, T. protracta often froze in position when released or crawled away from the mouse. Bugs eventually initiated feeding, but often only after probing at multiple sites. On only one occasion did T. protracta crawl directly to the mouse and begin feeding. Following its release, T. rubida began
Discussion
One of the objectives of this study was to determine if native triatomines of the desert Southwest pose a risk for transmission of Chagas disease to humans. Similar studies were carried out more than 50 years ago so a current assessment is timely, especially given the increasing numbers of infected, asymptomatic immigrants moving into non-endemic areas. Individuals in non-endemic areas have contracted Chagas disease through blood transfusion or organ transplant (Mascola et al., 2006, Young et
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