Entomologic profiling of ectoparasites on triatomines in the southwestern United States

Triatomines transmit Trypanosoma cruzi, the etiologic cause of Chagas disease. This potentially fatal parasite can cause dilated cardiomyopathy in a third of infected persons, and accounts for over 300,000 infections in the United States alone. Megaesophagus and megacolon have also been observed, contributing to digestive complications and inflammation of the gastrointestinal tract. Understanding the transmission dynamics between Triatoma species, Trypanosoma cruzi, and humans is critical as therapeutics offer limited efficacy once cardiac pathogenesis has begun, yielding prevention as the optimal public health strategy. Variation in vector transmission risk between geographic regions in the southern United States might possibly be due to presence of ectoparasites living on the triatomine vector, which could lead to lowered vector fitness. Our study aimed to profile and describe the presence and characteristics of ectoparasites living on triatomines collected along the Mexico-United States border. Approximately 15% of Triatoma rubida collected in southern Arizona were found to host ectoparasites; corporeal distribution was variable, including the head, thorax, foreleg, midleg, hindleg, and abdomen of the host. Seven was the maximum number of ectoparasites per specimen. Ectoparasite positive triatomines originated from multiple sampling sites, implying that their presence was not restricted to one mammalian host den.  All ectoparasite positive triatomines were unengorged, suggesting their presence might influence bloodmeal seeking behaviors. Our study warrants further entomologic investigation of potential biologic control of these vectors, which hold significant public health importance.