Biology subjects

Bargul, J. L.

Publications and source records attributed to Bargul, J. L..

4 recordsLinked to original sources

bioRxiv2025

Convenient screening for drug resistance mutations from historical febrile malaria samples across Kenya

BackgroundHistorically, chloroquine resistance emerged that was driven by mutations in the chloroquine resistance transporter (Pfcrt) gene. This led to the global withdrawal of chloroquine in 1998 and its subsequent replacement with sulfadoxine-pyrimethamine, whose efficacy was compromised by a high prevalence of mutations in the dihydrofolate reductase and the dihydropteroate synthase genes by 2004. Consequently, artemisinin-based combination therapies (ACTs) were introduced in 2006. Since then, thirteen mutations in the kelch 13 (Pfk13) propeller domain have emerged and validated by the World Health Organization (WHO) as markers of partial artemisinin resistance. This study aimed to characterize temporal trends in both established, Pfcrt and Pfk13 and less well-described potential markers, cysteine desulfurase (Pfnfs) and Pfcoronin, using febrile malaria samples collected across diverse regions of Kenya between 2013 and 2022. MethodsThe temporal trend of these markers of resistance were assessed by screening archived P. falciparum positive dried blood spots (DBS). A total of 1,750 DBS samples collected from Therapeutic Efficacy Studies (TES) conducted in: Kwale (2013, n=350), Kisumu (2015, n=314), Busia (2016, n=334), Kisii (2017, n=314), Kwale (2018, n=150), and a hrp2 study conducted Kisii (2022, n=288). Parasite genomic DNA was extracted using the Chelex-saponin method and confirmed by a Pf 18S RT-PCR. Pfk13, Pfcrt, Pfnfs and Pfcoronin PCR amplicons were sequenced using capillary electrophoresis, Illumina Miseq or the Oxford Nanopore (GridION) platform. ResultsThe prevalence of Pfcrt mutations declined over time and no WHO validated Pfk13 mutations associated with artemisinin resistance were detected. However, synonymous substitutions at WHO-validated codons C469C and P553P were identified. In the PfCoronin gene, non-synonymous mutations distinct from those reported in West Africa were observed at high frequencies (>75%). Notably, the Pfnfs-K65Q mutation, previously associated with reduced lumefantrine sensitivity in West Africa, was detected in over 80% of samples. Our findings reveal differences in some antimalarial resistance genetic markers between observations made in The Gambia and Senegal (West Africa) and Kilifi (East Africa). Based on the convenient sample set, there were no WHO validated k13 mutations up until 2022, suggesting continued ACT efficacy in Kenya. This study underscores the importance of continued molecular surveillance and suggests that resistance may evolve through different pathways in East compared to West Africa and Southeast Asia.

genomics↗

bioRxiv2024

Stomoxys flies (Diptera, Muscidae) are competent vectors of multiple livestock hemopathogens

Stomoxys flies are widely distributed and economically significant vectors of various livestock pathogens of veterinary importance. However, the role of Stomoxys spp. in pathogen transmission is poorly understood. Therefore, we studied the feeding patterns of these blood feeders collected from specific locations in Kenya, to identify various vertebrate hosts they fed on, and the livestock hemopathogens they carried, to elucidate their role in pathogens transmission. Our findings show that field-collected Stomoxys flies carried several pathogens including Trypanosoma spp., Anaplasma spp., and Theileria spp. that were also found in the blood of sampled livestock, namely camels and cattle. The findings on blood meal analysis show that Stomoxys flies fed on a variety of domestic and wild vertebrate hosts. We further determined whether Stomoxys spp. are vectors of hemopathogens they harbored by studying the vector competence of S. calcitrans, S. niger niger, and S. boueti species complex, through laboratory and natural experimental in vivo studies. We show that in the process of blood feeding Stomoxys spp. complexes can transmit T. evansi (8.3%) and T. vivax (30%) to Swiss white mice. In addition, field-collected Stomoxy spp. were exposed to healthy mice for blood meal acquisition, and in the process of feeding, they transmitted Theileria mutans and Anaplasma spp. to Swiss white mice (100% infection in the test mice group). All mice infected with both trypanosomes via stomoxys bite died while those infected with Theileria and Anaplasma species did not, demonstrating virulence difference between pathogens. The key finding of this study showing broad feeding host range, cosmopolitan, plethora of pathogens harboured, and efficient vector competence in spreading multiple pathogens suggests profound role of Stomoxys on pathogen transmission and infection prevalence in livestock. Author summaryStomoxys flies are highly adaptable to several ecological settings, including metropolitan areas. In contrast, tsetse flies (genus Glossina), the main biological vectors of African trypanosomes, have a limited distribution to parks and other conservation areas. Stomoxys flies could play a significant role in the spread of animal African trypanosomes, among other hemopathogens, particularly in areas with or without tsetse infestation. Although there have been speculations about the potential role of Stomoxys flies in the transmission of various pathogens, there is lack of data to link hemopathogens occurring in both bloodmeal hosts of Stomoxys and in the flies, and further in vivo experimental studies to confirm the vector competence of Stomoxyine flies. Here, we explored a host and pathogens network, and investigated species diversity at various ecologies, and demonstrated that Stomoxys flies feed on diverse vertebrate hosts and are infected with a plethora of pathogens. We also showed experimentally that they could transmit some of these hemopathogens to mice, for instance, T. vivax, T. evansi, Theileria mutans, and Anaplasma spp. with varying infection success rates. Stomoxys flies could play a significant role in transmitting and spreading various hemopathogens of veterinary importance and possibly maintaining their circulation in livestock, which could explain the occurrence of animal African trypanosomes in the regions outside the tsetse belts.

pathology↗

bioRxiv2020

Molecular characterization of pathogenic African trypanosomes in biting flies and camels in surra-endemic areas outside the tsetse fly belt in Kenya

BackgroundAfrican animal trypanosomosis is becoming prevalent beyond its traditionally defined geographical boundaries and is a threat to animals beyond the tsetse belts in and outside Africa. However, knowledge of infections with clinically important trypanosome species and their diversity among field-collected hematophagous biting flies and domestic animals is limited mainly to tsetse and their mammalian hosts in tsetse-infested areas. This study aimed to examine the presence of trypanosomes in both biting flies and domestic animals outside the tsetse belt in northern Kenya, potential mechanical vector species, and their host-feeding profiles. MethodsWe screened for pathogenic African trypanosomes in blood samples from domestic animals and field-trapped flies by microscopy and sequencing of internal transcribed spacer (ITS1) gene PCR products. We sequenced kinetoplast maxicircle genes to confirm Trypanosoma brucei detection and the RoTat 1.2 and kinetoplast minicircle genes to differentiate type-A and type-B Trypanosoma evansi, respectively. Further, we identified the hosts that field-trapped flies fed on by PCR-HRM and sequencing of 16S rRNA genes. ResultsHippobosca camelina, Stomoxys calcitrans, Tabanus spp., and Pangonia rueppellii are potential vectors of trypanosomes outside the tsetse belt in Marsabit County, northern Kenya. We identified Trypanosoma spp., including Trypanosoma vivax, T. evansi, T. brucei, and T. congolense in these biting flies as well as in camels (Camelus dromedarius). Trypanosomes detected varied from single up to three trypanosome species in H. camelina and camels in areas where no tsetse flies were trapped. Similar trypanosomes were detected in Glossina pallidipes collected from a tsetse-infested area in Shimba Hills, coastal Kenya, showing the wide geographic distribution of trypanosomes. Furthermore, we show that these biting flies acquired blood meals from camels, cattle, goats, and sheep. Phylogenetic analysis revealed diverse Trypanosoma spp. associated with variations in virulence and epidemiology in camels, which suggests that camel trypanosomosis may be due to mixed trypanosome infections rather than only surra (T. evansi), as previously thought.

pathology↗

bioRxiv2019

Three-gene PCR and high-resolution melting analysis for differentiating vertebrate species mitochondrial DNA for forensic and biodiversity research pipelines

Reliable molecular identification of vertebrate species from morphologically unidentifiable tissue is critical for the prosecution of illegally-traded wildlife products, conservation-based biodiversity research, and identification of blood-meal hosts of hematophagous invertebrates. However, forensic identification of vertebrate tissue relies on the sequencing of mitochondrial cytochrome oxidase I (COI) barcode genes, which remains costly for purposes of screening large numbers of unknown samples during routine surveillance. Here, we adopted a rapid, low-cost approach to differentiate 10 domestic and 24 wildlife species that are common in the East African illegal wildlife products trade based on their unique high-resolution melting profiles from COI, cytochrome b, and 16S ribosomal RNA gene PCR products. Using the approach, we identified (i) giraffe among covertly sampled meat from Kenyan butcheries, and (ii) forest elephant mitochondrial sequences among savannah elephant reference samples. This approach is being adopted for high-throughput pre-screening of potential bushmeat samples in East African forensic science pipelines.

molecular biology↗