The 2024/25 application process is now CLOSED
Visit the MRC DTP/CASE at LSTM pages for further information.
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Abstract |
Dengue virus (DENV) is transmitted by Aedes mosquitoes and the disease it causes in humans is now endemic in >100 countries. Cases of dengue reported to the World Health Organisation have increased substantially in the last two decades, increasing from 505 430 in 2000 to 5.2 million in 2019. Despite research toward a vaccine, reducing Aedes populations remains the main strategy for DENV control. In some countries, Ae. aegypti-infected Wolbachia have been released to successfully reduce DENV incidence, but this relies on this species being necessary and sufficient for transmission. Therefore, it is essential to confirm the relative contribution of both Ae. aegypti and Ae. albopictus to transmission when considering this control method in new areas. More generally, vector control efforts are rarely applied evenly across a region and therefore locations of highest transmission risk also need to be identified. Cross-sectional household surveys quantifying immature or adult Aedes abundance are often used by researchers and control practitioners to implicate species and guide where to focus control efforts. Cromwell et al. (2017) however showed that even adult Aedes abundance was not a sufficient proxy for human DENV infection risk. This is likely in part because human factors, including movement, also influence contact between susceptible humans and infectious mosquitoes and vice versa. Indeed, between households and public sites, the level of repeated bites on the same individuals versus bites on different individuals may vary considerably with important implications for transmission risk across locations. Despite this, when dengue transmission risk is compared between locations, Aedes abundance, is usually the only indicator used. Failure to account for other heterogeneities when identifying high risk areas and vector species may have contributed to the current lack of support for vector control as effective against DENV. Although there have not been any reported outbreaks of dengue in Ghana, recent studies have revealed evidence of DENV-2 (Dengue virus serotype-2) antibodies in people suspected to have malaria or visiting the hospital with acute fever symptoms (Narkwa et al., 2016; Ofosu-Appiah et al., 2018, Manu et al. 2019). Also, a recent study in Accra (Amoako et al., (2018)) detected DENV-2 viral RNA among two children which was closely related with DENV-2 involved in a 2016 outbreak in Burkina Faso. This project will quantify DENV transmission risk in public sites, including schools, hospitals and work places, compared with households in Greater Accra. Data will be collected on: i) adult Aedes aegypti and Ae. albopictus abundance using aspirators and odour-baited traps – including trial of a new heat trap that is as effective as a human-landing catch but without the inherent risks to the collector; ii) the number of different human DNA sequences in mosquito blood meals using nanopore sequencing as a proxy for the host population size accessible to Aedes; and iii) the proportion of adult mosquitoes infected with DENV using RT-qPCR and potentially nanopore sequencing. These data will be used, in combination with data on the vector competence of Ae. aegypti and Ae. albopictus from Greater Accra to parametrize mathematical models to quantify the relative transmission risk associated with location and species, accounting for variation in the number of humans available to Aedes populations, and the nonlinear dynamics of transmission. This will also allow analysis of the relationships between adult Aedes abundance and DENV infection prevalence in Aedes populations over time. Designing surveillance strategies informed by DENV transmission dynamics and greater focus on drivers of variation in the transmission process would improve the subsequent targeting of vector control which could be assessed using resulting models. We envisage the project would be suitable for a student familiar with the Ghanian context. |
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Where does the project lie on the Translational Pathway? |
T1 – Basic Research T4 Practice to Policy / Population |
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Expected Outputs |
This project will produce high quality REF returnable 3*/ 4* papers reporting the field data results and potentially vector competence experiments and then bringing these results together in a paper using modelling to determine the relative contribution of vector species and location to transmission risk. This project will also generate data to be used in collaborative applications to MRC for further Aedes-borne virus research in Ghana. |
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Training Opportunities |
The student will receive a unique combination of skills in: i) medical entomology; ii) nanopore sequencing and bioinformatics; iii) working at CL3/ arthropod infections and with support will gain exposure to the application of mathematical modelling in infectious disease epidemiology. In general we will encourage the student to identify internal/external training of interest and support attendance. |
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Skills Required |
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Key Publications associated with this project |
Longbottom et al. (2023) Aedes albopictus invasion across Africa: the time is now for cross-country collaboration and control |
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