Online

Keller, Judith Ina

Biology

2019

Ph. D.

Vector borne-diseases make up a significant portion of morbidity and mortality worldwide, being responsible for around 700,000 deaths annually according to the World Health Organization. Neglected, tropical diseases such as Chagas disease have a significant impact on people in Latin America, affecting millions, and especially those residing in rural areas. Chagas disease is the number one cause for heart disease in Latin America, and is caused by the Trypanosoma cruzi parasite, carried by Triatominae insect vectors. The intricate life cycle of the parasite, ecology and behavior of the vector, and lack of disease treatment options, make Chagas disease challenging to control. Prevention measures are highly sought after, and implementation science approaches such as Ecohealth management engage affected communities in disease prevention. Knowing what insect vectors are feeding on sheds light on vector ecology and behavior, aiding in vector management which is pivotal in disease prevention. While DNA-based methods have traditionally been used to study vector blood meals, they come with limitations and challenges, such as the need for fresh, high abundance blood meals. Therefore, the goal of this research was to evaluate Chagas vector blood meal sources using an innovative protein mass spectrometry-based approach. We demonstrate first the ability to utilize liquid chromatography tandem mass spectrometry (LC-MS/MS) to correctly identify hemoglobin protein peptides from mouse blood and subsequently identify Chagas vector blood meal sources from field-collected insect vectors where blood meal identification is compared with traditional DNA-based methods as a control. An experimental feeding study allowed us to then demonstrate the longevity of hemoglobin protein peptides for blood meal detection, showing LC-MS/MS-based blood meal identification outperforms DNA-based polymerase chain reaction (PCR) at least 4 weeks post-feeding and 12 weeks post-molting. This allowed us to test the limits of our innovative detection method experimentally and comparatively. Finally, we evaluated blood meals in field-caught insect vectors collected as part of a large collaborative Ecohealth project in Central America. LC-MS/MS identified two times as many blood meals in insect vectors, including those that did not have blood meals detected with DNA-based PCR. As single vectors often feed on multiple sources, we also validated our ability to decipher multiple blood meals from an individual vector and showed the ability to quantify a blood meal using synthetic AQUA (Absolute QUAntification) peptides, a first step in using quantification data for identifying blood meals not currently in our underlying database. Furthermore, we show that lower resolution mass spectrometers are able to identify blood meals from taxa correctly, an important and strong attribute of our LC-MS/MS-based method, opening the door to using proteomics in countries where Chagas disease is endemic and resources are limited. Even though expertise and resources of research labs differ in locations across the globe, herein is described how LC-MS/MS is a valuable additional tool for fighting neglected tropical diseases. Ultimately, hemoglobin-based LC-MS/MS vector blood meal identification is a complementary technique to available molecular methods and can confidently identify Chagas vector blood meal sources to aid in understanding vector biology and ecology, and aid in developing appropriate Ecohealth vector control measures.