Browsing by Author "Tambo, Munyaradzi"

Now showing 1 - 6 of 6
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    Association of Human Papiloma Virus (HPV) 16 and 18 in breast cancer biopsies in Namibia
    (University of Namibia, 2018) Mumbengegwi, Davis R.; Van Kent, Samuelia; Tambo, Munyaradzi
    Cancer is a growing global health concern due to increased exposure to risk factors including infection by viruses such as human papillomavirus (HPV). HPV is associated with several cancers and may be an etiological agent contributing to increasing breast cancer cases in Namibia. This study investigated the association between HPV infection and breast cancer cases in Namibia. DNA was isolated from 47 breast tumour biopsies, (22 breast cancer positive and 25 negative) and analysed for HPV 16 and 18 sequences using PCR. HPV 16 and 18 were detected in 86.3 % and 81.8 % respectively, of breast cancer positive samples, whilst only 36 % and 48 % respectively, were found in breast cancer negative samples. In total 95.5 % of breast cancer positive samples were infected by at least either of HPV 16 or 18 compared to only 52 % of breast cancer negative samples. Infection with HPV 16 or 18 increases the risk of cervical cancer and possibly breast cancer, hence the results suggest that HPV may contribute to the increasing breast cancer statistics in Namibia. This is the first study in Namibia linking HPV and breast cancer, but a larger sample size will be required to power the study to make the findings statistically significant.
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    Evaluation of Loop-mediated isothermal DNA amplification as a diagnostic tool for malaria in reactive case detection in Namibia
    (University of Namibia, 2015) Tambo, Munyaradzi
    Malaria, the disease, is a clinical diagnosis that is caused by Plasmodium parasites and is spread through the bites by infected female Anopheles mosquitoes. Malaria is a health concern in temperate tropical areas, but a scale up of control interventions resulted in reduction and elimination of the disease in developed countries. In 2010 Namibia adopted a strategy to eliminate malaria within its borders by the year 2020 as a result of the reduction in malaria cases. However, as malaria case incidences are reduced the number of low parasite density sub-patent infections increases posing a challenge for diagnosis. Therefore, in Namibia which is a low prevalence setting, malaria cases could be going undetected due to difficulty in detection of low parasite density infections with the routinely used Rapid Diagnostic Tests (RDTs). This study evaluated the use of reactive case detection to trace malaria cases, symptomatic and asymptomatic and compared the routinely used RDTs with a highly sensitive molecular tool, Loop-mediated isothermal amplification (LAMP). All reported cases in the Engela Health District of Namibia were traced back to their place of residence and everyone in the same household as the reported case and the four surrounding households was tested for malaria with RDTs. In addition, Dry Blood Spots (DBS) were also collected from all persons tested. RDT and DBS samples were collected from 2790 individuals. DNA was extracted from all the DBS and RDT samples and was used to test for malaria with LAMP. All positive Pan-LAMP samples and 10% of the negative LAMP samples were tested by nested PCR (nPCR) as the reference technique. In addition, all positive Pan-LAMP samples were tested with Pf-LAMP specific kits in order to determine the presence of P. falciparum and cytochrome B digestion was done on all n-PCR positive samples for species determination. RDTs detected a total of 37 malaria infections; only 2.7% were from control neighbourhoods with a sensitivity of 56.06% at 95% CI. LAMP detected a total of 66 malaria infections; only 3% of the infections were from control neighbourhoods with a sensitivity of 100% at 95% CI. A total of 64 of the LAMP positive samples were also nPCR positive and all LAMP negative samples were also nPCR negative. N-PCR, the reference standard, had a sensitivity of 96.97% at 95% CI. Both RDTs and LAMP determined that all the malaria infections were caused by P. falciparum and this was confirmed by n-PCR. The number of malaria infections detected doubled with the use of LAMP as compared to RDTs. In addition, LAMP with n-PCR as a reference, detected 4 times more secondary cases than RDTs. The majority of the malaria infections, 97%, were from case neighbourhoods. This indicates that individuals in proximity to malaria infections are more likely to be infected by malaria. Therefore, reactive case detection is an important surveillance tool in order to detect all cases around reported cases that are usually asymptomatic as a step towards malaria elimination. LAMP detected 4 times more secondary cases than RDTs with n-PCR as the reference. This shows that RDTs have short comings in the detection of low parasite density infections and a highly sensitive tool such as LAMP is required to detect all malaria cases as a step towards malaria elimination.
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    Evaluation of loop‑mediated isothermal amplification as a surveillance tool for malaria in reactive case detection moving towards elimination
    (2018) Tambo, Munyaradzi; Auala, Joyce R.; Sturrock, Hugh J.; Kleinschmidt, Immo; Bock, Ronnie; Smith, Jennifer L.; Gosling, Roland; Mumbengegwi, Davis R.
    Background: As malaria transmission decreases, the proportion of infections that are asymptomatic at any given time increases. This poses a challenge for diagnosis as routinely used rapid diagnostic tests (RDTs) miss asymptomatic malaria cases with low parasite densities due to poor sensitivity. Yet, asymptomatic infections can contribute to onward transmission of malaria and therefore act as infectious reservoirs and perpetuate malaria transmission. This study compared the performance of RDTs to loop-mediated isothermal amplification (LAMP) in the diagnosis of malaria during reactive active case detection surveillance. Methods: All reported malaria cases in the Engela Health District of Namibia were traced back to their place of residence and persons living within the four closest neighbouring houses to the index case (neighbourhood) were tested for malaria infection with RDTs and dried blood spots (DBS) were collected. LAMP and nested PCR (nPCR) were carried out on all RDTs and DBS. The same procedure was followed in randomly selected control neighbourhoods. Results: Some 3151 individuals were tested by RDT, LAMP and nPCR. Sensitivity of RDTs and LAMP were 9.30 and 95.50%, respectively, and specificities were 99.27 and 99.92%, respectively, compared to nPCR. LAMP carried out on collected RDTs showed a sensitivity and specificity of 95.35 and 99.85% compared to nPCR carried out on DBS. There were 2 RDT samples that were negative by LAMP but the corresponding DBS samples were positive by PCR. Conclusion: The study showed that LAMP had the equivalent performance as nPCR for the identification of Plasmodium falciparum infection. Given its relative simplicity to implement over more complex and time-consuming methods, such as PCR, LAMP is particularly useful in elimination settings where high sensitivity and ease of operation are important.
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    Population genetics and transmission dynamics of Plasmodium falciparum in the Kavango East and Zambezi regions of Namibia
    (University of Namibia, 2019) Tambo, Munyaradzi
    In 2010, Namibia, declared a goal to eliminate malaria within its borders, this was revised in 2017 to 2022 due to new challenges in achieving elimination. Some of the key challenges associated with malaria control and elimination are; 1) a lack of comprehensive data including malaria case distribution and resources especially in Africa where the burden is highest 2) there is no accurate classification of imported and local malaria cases or quantification of the level of importation 3) a lack of validated tools to supplement transmission estimates. Malaria positive samples tested with rapid diagnostic tests (RDTs) and dried blood spots (DBS) were collected with corresponding epidemiological data from health districts in the Kavango East and Zambezi regions of Namibia. DNA was extracted using the chelex DNA extraction method, the parasite DNA was genotyped with capillary electrophoresis using a 26 microsatellite marker set to determine P. falciparum genetic structure in the Kavango East and Zambezi regions of Namibia The study through population genetics analysis showed that the genetic structure of P. falciparum in Namibia follows the pattern of a high transmission setting, there are high levels of genetic diversity, low genetic relatedness, random mating and population admixture. Secondly, there are high levels of importation contributing to local transmission. Lastly, population genetic matrices are good surrogate markers for measuring malaria transmission intensity and importation.
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    Spatial clustering of patent and sub-patent malaria infections in northern Namibia: Implications for surveillance and response strategies for elimination
    (2017) Smith, Jennifer L.; Auala, Joyce R.; Tambo, Munyaradzi; Haindongo, Erastus H.; Katokele, Stark; Uusiku, Petrina; Gosling, Roly; Kleinschmidt, Immo; Mumbengegwi, Davis R.; Sturrock, Hugh J.
    Reactive case detection (RACD) around passively detected malaria cases is a strategy to identify and treat hotspots of malaria transmission. This study investigated the unproven assumption on which this approach is based, that in low transmission settings, infections cluster over small scales.
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    Study protocol for a cluster randomised controlled factorial design trial to assess the effectiveness and feasibility of reactive focal mass drug administration and vector control to reduce malaria transmission in the low endemic setting of Namibia
    (2017) Medzihradsky, Oliver F.; Kleinschmidt, Immo; Mumbengegwi, Davis R.; Roberts, Kathryn W.; McCreesh, Patrick; Dufour, Mi-Suk Kang; Uusiku, Petrina; Katokele, Stark; Bennet, A.; Smith, Jennifer L.; Sturrock, Hugh J.; Prach, Lisa M.; Nkutu, Henry; Tambo, Munyaradzi; Didier, Bradley; Greenhouse, Bryan; Gani, Zaahira; Aerts, Ann; Gosling, Roly; Hsiang, M.
    Introduction To interrupt malaria transmission, strategies must target the parasite reservoir in both humans and mosquitos. Testing of community members linked to an index case, termed reactive case detection (RACD), is commonly implemented in low transmission areas, though its impact may be limited by the sensitivity of current diagnostics. Indoor residual spraying (IRS) before malaria season is a cornerstone of vector control efforts. Despite their implementation in Namibia, a country approaching elimination, these methods have been met with recent plateaus in transmission reduction. This study evaluates the effectiveness and feasibility of two new targeted strategies, reactive focal mass drug administration (rfMDA) and reactive focal vector control (RAVC) in Namibia. Methods and analysis This is an open-label cluster randomised controlled trial with 2×2 factorial design. The interventions include: rfMDA (presumptive treatment with artemether-lumefantrine (AL)) versus RACD (rapid diagnostic testing and treatment using AL) and RAVC (IRS with Acellic 300CS) versus no RAVC. Factorial design also enables comparison of the combined rfMDA+RAVC intervention to RACD. Participants living in 56 enumeration areas will be randomised to one of four arms: rfMDA, rfMDA+RAVC, RACD or RACD+RAVC. These interventions, triggered by index cases detected at health facilities, will be targeted to individuals residing within 500 m of an index. The primary outcome is cumulative incidence of locally acquired malaria detected at health facilities over 1 year. Secondary outcomes include seroprevalence, infection prevalence, intervention coverage, safety, acceptability, adherence, cost and costeffectiveness.