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Title: Comparing different diagnostic methods and detection platforms for schistosomiasis, giardiasis and malaria in Uganda and the Kingdom of Saudi Arabia
Author: Al-shehri, Hajri
ISNI:       0000 0004 7964 2013
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Introduction: Where access to sanitation is incomplete and environmental water contact high, water-borne diseases such as schistosomiasis can be com-mon in children and occur alongside other parasitic diseases. Parasitological diagnosis based upon microscopy of parasite ova or larvae underestimates true infection prevalence, and as NCPs reduce the intensity of infection(s) with pre-ventive chemotherapy, the diagnostic sensitivity also declines. In Uganda and the Kingdom of Saudi Arabia, for example, school-based disease control has been ongoing over the past decade, and there is a need to develop more sensi-tive methods of parasite detection and disease surveillance. Against this two-country backdrop, the application of novel diagnostics was investigated to re-veal the current status of infections in school children. Parasitological- and se-rological-based methods were compared against the implementation of real-time PCR methods to detect DNA from faecal or dried blood spot specimens. Diagnostic performance was then compared, and its epidemiological signifi-cance discussed for each country setting. Method: In Uganda, Buliisa District, a total of 271 children were enrolled. Stool, urine and blood were collected and examined for schistosomiasis, giardiasis and malaria using a selection of commercially available RDTs in the field, then compared against real-time PCR methods with TaqMan® probes in the la-boratory. In the Kingdom of Saudi Arabia, Al-Majardah District, a total of 163 children were enrolled for this study. As faecal samples could not be collected, blood and urine samples were inspected. Children were interviewed by ques-tionnaire and collection of intermediate snail hosts made. In the following up, all children positive for schistosomiasis where re-examined one year later. Results: In Uganda, Buliisa District, the overall prevalence of S. mansoni was: 44.1% by microscopy of duplicate KK smears from two consecutive stools, 56.9% by urine-CCA dipstick, 67.4% by DNA-TaqMan® and 75.1% by antibodies to SEA- ELISA. Giardiasis was 41.6% by QUIK CHEK™ RDT, and up to 87.0% of children were excreting Giardia DNA. The prevalence of heavy infection by real-time PCR assay (Ct = 19) was 19.5%. Notably, giardiasis was positively associated with egg-patent schistosomiasis and two Giardia assem-blages, A and B, were found. Co-infections thereof varied by school and by age. A total of 138 (55.8%) cases of malaria were diagnosed for P. falciparum (PfHRP-2-detecting RDTs), and 45 samples (18.2%) were positive for pan-Plas-modium species (PfHRP-2 and pan-pLDH test lines). Upon analysis of dried blood spots with real-time PCR, a total of 198 (80.1 %) cases for any Plasmo-dium spp. was detected and compared to real-time PCR of faecal samples. In the Kingdom of Saudi Arabia, Al-Majardah District, using urine-CCA strip assessment and SEA-ELISA, the prevalence of S. mansoni was 15.3% and combined S.mansoni/haematobium was 34.3%, respectively. Molecular DNA analysis using the CO1 gene alongside morphological identification of collected snails demonstrated the presence of Bulinus forskalii in this area and the local absence of Biomphalaria at the time of the survey. Conclusion: Using a combination of diagnostic methods, vital contemporary epidemiological information on schistosomiasis, giardiasis and malaria was re-vealed and then compared across the two countries using the ASSURED crite-rion. Foremost, whilst real-time PCR methods with TaqMan® probes have the greatest potential in Uganda, in Saudi Arabia however, owing to the difficulties in obtaining a stool, this method is inappropriate. Nonetheless, DNA-based di-agnostic platforms will be essential in future public health settings where prev-alence and intensity of infections continue to fall, as improved sensitivity is re-quired. Furthermore, the ability to simultaneously co-detect several infectious and parasitic diseases will boost disease surveillance efficiency and capacity.
Supervisor: Stothard, Russell ; LaCourse, James Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral