Hundreds of thousands of people die annually from malaria; a protozoan of the genus Plasmodium is responsible for this mortality. The Plasmodium parasite undergoes several life stages within the mosquito vector, the transition between which require passage across the lumen of the mosquito midgut. It has been observed that in about 15% of parasites that develop ookinetes in the mosquito abdomen, sporozoites never develop in the salivary glands, indicating that passage across the midgut lumen is a significant barrier in parasite development (Gamage-Mendis et al., 1993). We aim to investigate a possible correlation between passage through the midgut lumen and drug-resistance trends in Plasmodium falciparum parasites. This study contains a total of 1024 Anopheles mosquitoes: 187 Anopheles gambiae and 837 Anopheles funestus samples collected in high malaria transmission areas of Mozambique between March and June of 2016. Sanger sequencing will be used to determine the prevalence of known resistance alleles for anti-malarial drugs: chloroquine resistance transporter (pfcrt), multidrug resistance (pfmdr1) gene, dihydropteroate synthase (pfdhps) and dihydrofolate reductase (pfdhfr). We compare prevalence of resistance between abdomen and head/thorax in order to determine whether drug resistant parasites are disproportionately hindered during their passage through the midgut lumen. A statistically significant difference between resistance alleles in the two studied body sections supports the efficacy of new anti-malarial gene surveillance strategies in areas of high malaria transmission.

There are many challenges in designing neuroprostheses and one of them is to maintain proper axon selectivity in all situations. This project is based on an electrode that is implanted into a fascicle in a peripheral nerve and used to provide tactile sensory feedback of a prosthetic arm. This fascicle can undergo mechanical deformation during every day motion. This work aims to characterize the effect of fascicle deformation on axon selectivity and recruitment when electrically stimulated using hybrid modeling. The main framework consists of combining finite element modeling (FEM) and simulation environment NEURON. A suite of programs was developed to first populate a fascicle with axons followed by deforming the fascicle and rearranging axons accordingly. A model of the fascicle with an implanted electrode is simulated to find the electrical potential profile through FEM. The potential profile is then used to compare which axons are activated in the two conformations of the fascicle using NERUON.

Mosquitoes are estimated to kill roughly 700,000 people each year through the transmission of vector-borne diseases. Vector control via insecticides is a widely used method in order to combat the spread of mosquito populations; however, this comes at a cost. Resistance to insecticides has the potential to increase vector-borne disease rates. Aedes aegypti is an invasive mosquito species in Arizona and is a known potential vector for a variety of infectious diseases including dengue, chikungunya, Zika, and yellow fever. In contrast to many other mosquito species Ae. aegypti mosquito eggs can undergo quiescence, an active state of dormancy, over long periods of time. Variation in quiescent periods correlates to climatic rainfall alterations and can ultimately influence hatching and mating between multiple generations. I have studied the effect of quiescence on larvicide (i.e., temephos) susceptibility using mosquito eggs collected from a susceptible lab strain and stored under optimal temperature and humidity conditions. After undergoing various quiescent periods (3, 7, 14, 28, 84, and 182 days), the experimental eggs as well as 7-day quiescent control eggs were hatched and reared to 3rd instar larvae. Temephos susceptibility was tested using the WHO bioassay procedure at lethal concentration (LC) 20, LC50, LC80, diagnostic dose (twice LC99), plus an untreated control. Each concentration dose was replicated four times with 20 larvae each. The 3-day experimental group was excluded from analysis because the mortality was significantly lower than the 7-day for both the experimental and control groups. The 3 day experimental eggs displayed decreased mortality which did not align with the hypothesis, as the quiescence period elongates under optimal conditions, susceptibility to insecticides decreases, and this could have likely resulted from unintentional selection for increased fitness and faster developing eggs because the larvae that developed to 3rd instar first were those used for larvicide testing. ANOVA testing demonstrates variability in the LC80 experimental group which suggests the need for further investigation into high dose temephos concentrations. For the experimental LC20 linear regression, there were significant differences in mortality. The results indicate mortality gradually decreases when the quiescence period elongates, therefore there are significant differences in insecticide susceptibility when quiescence is 182 days (or longer), compared to when quiescence is 7 days. Further investigation into field mosquito’s genetic diversity, insecticide resistance profile, and environmental conditions should be considered.

Vector-borne diseases, such as Zika, chikungunya, dengue, and yellow fever, cause a significant portion of the global infectious disease problem, thereby representing an enormous public health threat worldwide. The threat has become more concerning as Aedes aegypti, who serve as primary vectors for these infectious diseases, continue to thrive in highly populated, urban environments. To solve this problem, insecticides have commonly been used, but this has brought forward additional issues. The overreliance on insecticides has resulted in insecticide resistant individuals emerging within once susceptible populations. Insecticide resistance in Ae. aegypti is a worldwide problem because it compromises the ability to control Ae. aegypti populations, thus increasing the spread of vector-borne diseases. With pyrethroids being commonly used worldwide, the mechanisms behind the knock-down resistance (kdr) are essential to investigate. Investigating the fitness of kdr resistant Ae. aegypti is essential in order to better understand their ability to reproduce and survive in a natural environment. Kdr resistant mutations are known to come with fitness costs: a highly energetic cost or a significant disadvantage that diminishes an aspect of the individual’s fitness. Although it is known that resistance comes with a cost, many research gaps remain. Still, it is unknown whether resistant genotypes differ in larval development times, immature survival, and adult qualities (body weight and wing length). As such, this study observed the impact of the larval development of Ae. aegypti genotypes with varying resistance at loci 1016 and 1534 of the voltage gated sodium channels. The 1016 kdr mutation results in a valine to isoleucine amino acid substitution at position 1016 (V1016I), and the 1534 kdr mutation results in a phenylalanine to cysteine amino acid substitution at position 1534 (F1534C). All strains included in this study were homozygous resistant for the 1534 mutation, while genotype varied at the 1016 locus. Mosquito strains were named after their genotype and are VVCC, VICC, and IICC. Mosquito larvae of each genotype were placed at three temperatures (22℃, 27℃, 32℃) and time to pupation, emergence, immature mortality, sex ratio, dry weight, and wing length was measured. In congruence with previous data, larval pupation and emergence occurred at a faster rate in hotter temperatures (32℃) than in colder temperatures (22℃) for all genotypes. Furthermore, the observed data shows that male mosquitos generally emerged before female mosquitos, regardless of temperature or strain. Interestingly, there were no significant differences between different genotypes in any of the fitness parameters, although the times to pupation suggest a potential trend of increased developmental time with increased resistivity. Ultimately, this data brings important implications to come up with better solutions in vector control programs in order to decrease the likelihood of adult mosquitoes becoming infected and delivering more infective bites. The study also brings light into on where future studies should take place, such as immature competition experiments, and reproductive fitness parameters in order to provide a more complete picture of the life history traits of Ae. aegypti with kdr mutations.