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- All Subjects: Mosquito
- All Subjects: insecticide resistance mutation
- Creators: Bond, Angela
- Creators: Huijben, Silvie
- Creators: Paaijmans, Krijn
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
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.
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.