Browsing by Author "Erlank, Erica"

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    Malaria parasite metabolite and mosquito vector dynamics
    (2021) Erlank, Erica
    Plasmodium falciparum makes its human host more attractive for its vector companion, the Anopheles mosquito. Once in the host, the malaria parasite synthesizes isoprenoids via the 2-C-methyl-D-erythritol 4-phosphate pathway. The precursor for isoprenoids in this pathway is known as (E)-4-hydroxy-3-methyl-but-2- enyl pyrophosphate (HMBPP). HMBPP activates red blood cells to release volatile organic compounds that acts as an attractant to the mosquito to stimulate blood feeding. Only a few anopheline mosquito species are known to transmit the human malaria parasite. These mosquitoes can be classified as either major or minor vectors, depending on their impact on malaria transmission. The main African malaria vectors are responsible for 95% of malaria cases while minor vectors contribute to the remaining 5%. During this study, the aim was to evaluate if HMBPP influences P. falciparum susceptibility, feeding rate and attraction in major, minor and non-vector mosquito species. The standard membrane feeding assay was used to artificially infect mosquitoes and evaluate feeding rate, whereas attraction assays was conducted with a dual choice chamber. Results revealed that both the major vector, An. gambiae s.s., and the minor vector, An. merus, had an increase in both prevalence and intensity of parasite oocysts. An increase in feeding rate and attraction was also observed for some vectors, in the presence of HMBPP. These findings could play an important role in understanding the role of parasite volatiles in malaria transmission.
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    The importance of morphological identification of African anopheline mosquitoes (Diptera: Culicidae) for malaria control programmes
    (BioMed Central (BMC), 2018-01) Erlank, Erica; Koekemoer, Lizette L.; Coetzee, Maureen
    Background: The correct identification of disease vectors is the first step towards implementing an effective control programme. Traditionally, for malaria control, this was based on the morphological differences observed in the adults and larvae between different mosquito species. However, the discovery of species complexes meant that genetic tools were needed to separate the sibling species and today there are standard molecular techniques that are used to identify the two major malaria vector groups of mosquitoes. On the assumption that species-diagnostic DNA polymerase chain reaction (PCR) assays are highly species-specific, experiments were conducted to investigate what would happen if non-vector species were randomly included in the molecular assays. Methods: Morphological keys for the Afrotropical Anophelinae were used to provide the a priori identifications. All mosquito specimens were then subjected to the standard PCR assays for members of the Anopheles gambiae complex and Anopheles funestus group. Results: One hundred and fifty mosquitoes belonging to 11 morphological species were processed. Three species (Anopheles pretoriensis, Anopheles rufipes and Anopheles rhodesiensis) amplified members of the An. funestus group and four species (An. pretoriensis, An. rufipes, Anopheles listeri and Anopheles squamosus) amplified members of the An. gambiae complex. Conclusions: Morphological identification of mosquitoes prior to PCR assays not only saves time and money in the laboratory, but also ensures that data received by malaria vector control programmes are useful for targeting the major vectors.