Section 1: Construction and screening of a genomic library for the mosquito Aedes aegypti (Diptera, culicidae). A genomic library has been constructed for this important vector of arboviral disease. Total genomic DNA and various classes of RNA from Ae. aegypti were used to screen this library. The results obtained indicate that this species has a short period interspersion pattern of repeated sequences. Transcription of these repeats could not be detected using total cytoplasmic RNA, hnRNA or mRNA as hybridisation probes. Section 2: Sequence organisation of ribosomal DNA in Aedes aegypti. The Aedes aegypti genomic library was used to isolate clones containing the intact ribosomal DNA (rDNA) repeat of this species. This has been restriction mapped and the transcribed regions have been identified. The rDNA repeat is 9.0 Kb in length and is present as approximately 500 head-to-tail tandemly repeated copies. A low level of intraspecies polymorphism of Ae. aegypti rDNA is evident. Two restriction polymorphisms have been identified within the rDNA repeat. Section 3: Analysis of ribosomal DNA variation within Ae. aegypti'and between closely related species. Four variant rDNA clones have been isolated. One of these' may contain the end of a tandem array of ribosomal genes. Another variant contains a duplication of rDNA within the internal transcribed spacer region of the ribosomal repeat. Sequence analysis of this clone has identified regions at the 3' end of the 18S rRNA gene of Ae. aegypti which show very strong homology with the corresponding regions in other species. Some repeated sequences have been identified downstream of the 18S rRNA gene in this clone. Preliminary analysis of the two other rDNA variants indicates that one contains a duplication or insertion of DNA in the 28S rRNA coding region and one contains non-transcribed spacer homologous sequences which are not associated with rRNA coding regions. Section 4: DNA probes for species identification of mosquitoes in the Anopheles gambiae complex. DNA sequences have been isolated which distinguish four of the morphologically identical members of the An. gambiae species complex. Two sequence classes were obtained. Class 1 homologues are highly reiterated in the genomes of An. arabiensis and An. merus, present in low copy number in An. melas and were not detected in An. gambiae s. s. Class 1 sequences are male specific in An. arabiensis. Class 2 homologues are highly reiterated in the genomes of An. merus and An. melas and present in low to middle copy number in An. gambiae s. s, and An. arabiensis. Sex specificity of Class 2 homologues does not occur in the species tested (An. gambiae s. s. and An. arabiensis). Hybridisation of these species specific DNA sequences to mosquitoes squashed directly onto nitrocellulose provides a simplified method of species identification.

Aedes mosquitoes are responsible for the transmission of several arboviruses throughout tropical and subtropical regions of the world. In the Americas, Aedes aegypti is the most competent vector of dengue, chikungunya, Zika, and yellow fever. With up to 400 million cases globally each year, dengue fever is the fastest growing vector-borne disease in the world, and it has become an increasingly significant risk to global health. In the Western Hemisphere, dengue, and more recently chikungunya and Zika, exists throughout much of Latin America and the Caribbean. Both diseases are spread via Aedes mosquitoes and both constitute major health risks in Costa Rica. A dengue outbreak in Costa Rica in 2013 was the largest epidemic in the country since the return of the disease in 1993. Moreover, between 2014 and 2015 there was a 54.9% increase in dengue cases in Costa Rica, further demonstrating the relevancy of research on mosquito-borne diseases. Given this context, this study employs qualitative methods to critically investigate measures to combat Aedes mosquito-borne diseases in Costa Rica. Data were collected using household interviews (n = 80); semi-structured key informant interviews with public health officials, researchers, nonprofit organizations, and community leaders (n = 22); and a focus group discussion in each of two study areas. The results provide broad and place-specific information about mosquito control efforts and other actions deployed in Costa Rica to mitigate mosquito-borne diseases. The data reveal differences in perceptions and disease incidence among household interviewees as well as where households source information about mosquitoes and mosquito-borne diseases. Varying degrees of knowledge on mosquitoes and mosquito-borne diseases were uncovered across the study sites, as were differing attitudes among the general population regarding mosquito control techniques (e.g., fumigation, education campaigns, and household visits by public health officials). Additionally, data indicated a gap in knowledge regarding the ability of the public to report mosquito-related problems to health authorities. Households also exhibited discrepancies in knowledge pertaining to chikungunya transmission and details about the vector. / Master of Science

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