Diversity, distribution, and drivers of Polychromophilus infection in Malagasy batsMalaria Journal - Tập 20 Số 1
Mercia Rasoanoro, Steven M. Goodman, Milijaona Randrianarivelojosia, Mbola Rakotondratsimba, Koussay Dellagi, Pablo Tortosa, Beza Ramasindrazana
Abstract
Background
Numerous studies have been undertaken to advance knowledge of apicomplexan parasites infecting vertebrates, including humans. Of these parasites, the genus Plasmodium has been most extensively studied because of the socio-economic and public health impacts of malaria. In non-human vertebrates, studies on malaria or malaria-like parasite groups have been conducted but information is far from complete. In Madagascar, recent studies on bat blood parasites indicate that three chiropteran families (Miniopteridae, Rhinonycteridae, and Vespertilionidae) are infected by the genus Polychromophilus with pronounced host specificity: Miniopterus spp. (Miniopteridae) harbour Polychromophilus melanipherus and Myotis goudoti (Vespertilionidae) is infected by Polychromophilus murinus. However, most of the individuals analysed in previous studies were sampled on the western and central portions of the island. The aims of this study are (1) to add new information on bat blood parasites in eastern Madagascar, and (2) to highlight biotic and abiotic variables driving prevalence across the island.
Methods
Fieldworks were undertaken from 2014 to 2016 in four sites in the eastern portion of Madagascar to capture bats and collect biological samples. Morphological and molecular techniques were used to identify the presence of haemosporidian parasites. Further, a MaxEnt modelling was undertaken using data from Polychromophilus melanipherus to identify variables influencing the presence of this parasite
Results
In total, 222 individual bats belonging to 17 species and seven families were analysed. Polychromophilus infections were identified in two families: Miniopteridae and Vespertilionidae. Molecular data showed that Polychromophilus spp. parasitizing Malagasy bats form a monophyletic group composed of three distinct clades displaying marked host specificity. In addition to P. melanipherus and P. murinus, hosted by Miniopterus spp. and Myotis goudoti, respectively, a novel Polychromophilus lineage was identified from a single individual of Scotophilus robustus. Based on the present study and the literature, different biotic and abiotic factors are shown to influence Polychromophilus infection in bats, which are correlated based on MaxEnt modelling.
Conclusions
The present study improves current knowledge on Polychromophilus blood parasites infecting Malagasy bats and confirms the existence of a novel Polychromophilus lineage in Scotophilus bats. Additional studies are needed to obtain additional material of this novel lineage to resolve its taxonomic relationship with known members of the genus. Further, the transmission mode of Polychromophilus in bats as well as its potential effect on bat populations should be investigated to complement the results provided by MaxEnt modelling and eventually provide a comprehensive picture of the biology of host-parasite interactions.
Integrated malaria prevention in low- and middle-income countries: a systematic reviewMalaria Journal - Tập 22 - Trang 1-37 - 2023
David Musoke, Edwinah Atusingwize, Carol Namata, Rawlance Ndejjo, Rhoda K. Wanyenze, Moses R. Kamya
As many countries aim to eliminate malaria, use of comprehensive approaches targeting the mosquito vector and environment are needed. Integrated malaria prevention advocates the use of several malaria prevention measures holistically at households and in the community. The aim of this systematic review was to collate and summarize the impact of integrated malaria prevention in low- and middle-income countries on malaria burden. Literature on integrated malaria prevention, defined as the use of two or more malaria prevention methods holistically, was searched from 1st January 2001 to 31st July 2021. The primary outcome variables were malaria incidence and prevalence, while the secondary outcome measures were human biting and entomological inoculation rates, and mosquito mortality. A total of 10,931 studies were identified by the search strategy. After screening, 57 articles were included in the review. Studies included cluster randomized controlled trials, longitudinal studies, programme evaluations, experimental hut/houses, and field trials. Various interventions were used, mainly combinations of two or three malaria prevention methods including insecticide-treated nets (ITNs), indoor residual spraying (IRS), topical repellents, insecticide sprays, microbial larvicides, and house improvements including screening, insecticide-treated wall hangings, and screening of eaves. The most common methods used in integrated malaria prevention were ITNs and IRS, followed by ITNs and topical repellents. There was reduced incidence and prevalence of malaria when multiple malaria prevention methods were used compared to single methods. Mosquito human biting and entomological inoculation rates were significantly reduced, and mosquito mortality increased in use of multiple methods compared to single interventions. However, a few studies showed mixed results or no benefits of using multiple methods to prevent malaria. Use of multiple malaria prevention methods was effective in reducing malaria infection and mosquito density in comparison with single methods. Results from this systematic review can be used to inform future research, practice, policy and programming for malaria control in endemic countries.
Prevalence of polymorphisms in glucose-6-phosphate dehydrogenase, sickle haemoglobin and nitric oxide synthase genes and their relationship with incidence of uncomplicated malaria in Iganga, UgandaMalaria Journal - Tập 16 - Trang 1-9 - 2017
Catherine Nassozi Lwanira, Fred Kironde, Mark Kaddumukasa, Göte Swedberg
Host genetics play an important role in Plasmodium falciparum malaria susceptibility. However, information on host genetic factors and their relationships with malaria in the vaccine trial site of Iganga, Uganda is limited. The main objective of this study was to determine the prevalence of selected host genetic markers and their relationship to malaria incidence in the vaccine trial site of Iganga, Uganda. In a 1-year longitudinal cohort study, 423 children aged below 9 years were recruited and their malaria episodes were investigated. Host genetic polymorphisms were assessed by PCR–RFLP, haemoglobin electrophoresis and DNA sequencing. Using a multivariate negative binomial regression model, estimates of the impact of human genetic polymorphisms on malaria incidence were performed. In all statistical tests, a P value of <0.05 was considered as significant. The prevalences of sickle cell haemoglobin trait, G6PD c.202 G>A (rs 1050828) and NOS2 −954 G>C (rs 1800482) variants were 26.6, 22.7 and 17.3%, respectively. Inducible nitric oxide synthase 2 (NOS2 −954 G>C; rs 1800482) heterozygosity was associated with lower incidence of malaria in all age groups {Adjusted incident rates ratio (aIRR) 0.59; 95% CI [0.386–0.887]; P = 0.012)}. About 4% of study subjects had co-existence of sickle cell Hb trait and G6PD deficiency. Sickle cell Hb heterozygotes (Hb AS) aged less than 1 year experienced significantly more malaria episodes annually than children with normal haemoglobin (Hb AA) {aIRR = 1.98; 95% CI [1.240–3.175]; P = 0.004}. There was no significant influence of the sickle cell trait on malaria incidence among older children of 1–9 years. Mutation (NOS2 −954 G>C; rs 1800482) of nitric oxide synthase 2 gene promoter was associated with a lower incidence of acute malaria. The normal haemoglobin (wild genotype; HbAA) was associated with reduced malaria incidence rates during the first year of life. More understanding of the interplay between host genetics and malaria susceptibility is required.
Comparison of coverage with insecticide-treated nets in a Tanzanian town and villages where nets and insecticide are either marketed or provided free of chargeMalaria Journal - Tập 5 - Trang 1-6 - 2006
CA Maxwell, RT Rwegoshora, SM Magesa, CF Curtis
There is much emphasis on social marketing as a means of scaling up coverage with insecticide-treated nets and the question has arisen whether nets provided free-of-charge will be looked after by householders. Over several years questionnaires and surveys of usage and condition of nets were carried out throughout a town and 15 villages in north-east Tanzania, where nets and insecticide have to be purchased and in 24 other villages where over 15000 nets had been donated and annual re-treatment is provided free-of-charge. There was very high population coverage in the town but, in the villages where nets have to be purchased, only 9.3% of people used nets which were intact and/or had been insecticide-treated and could, therefore, provide protection. However, where nets had been provided free, over 90% of the nets were still present and were brought for re-treatment several years later. In this part of Tanzania, social marketing has performed well in a town but very poorly in villages. However, the study showed that people look after and bring for re-treatment nets which had been provided free-of-charge.
Molecular surveillance of chloroquine resistance in Plasmodium vivax isolates from malaria cases in Yunnan Province of China using pvcrt-o gene polymorphismsMalaria Journal - Tập 22 - Trang 1-12 - 2023
Hongyun Ding, Ying Dong, Yan Deng, Yanchun Xu, Yan Liu, Jing Wu, Mengni Chen, Canglin Zhang, Li Liu, Yingkun Lin
The efficacy of chloroquine treatment for vivax malaria has been rarely evaluated due to a lack of an appropriate testing method. The objective of this study was to conduct molecular monitoring of chloroquine resistance in Plasmodium vivax strains from vivax malaria patients in Yunnan Province, focusing on the analysis of polymorphism in the P. vivax chloroquine resistance transporter protein orthologous gene (pvcrt-o). In accordance with the principles of a cohort study, blood samples were collected from malaria cases diagnosed with a P. vivax mono-infection in Yunnan Province from 2020 to 2022. Segmental PCR was used to amplify the whole pvcrt-o gene in the blood samples and their products were subsequently sequenced. The sequencing data were arranged to obtain the full coding DNA sequence (CDS) as well as the gene’s promoter region sequences. The CDSs were aligned with the reference sequence (XM_001613407.1) of the P. vivax SalI isolate to identify the mutant loci. From a total of 375 blood samples taken from vivax malaria cases, 272 both whole gene CDSs (1272–1275 bp) and promoter DNA sequences (707 bp) of pvcrt-o gene were obtained. Among the whole CDSs, there were 7 single nucleotide polymorphic sites in which c.7 A>G was the minor allele frequency (MAF) site with 4.4% (12/272) detection rate. The mutation detection rate showed a significant decrease from 9.8% (10/102) in 2020 to 1.1% (1/92) in 2021 and 1.3% (1/78) in 2022, indicating statistical significance (χ2 = 11.256, P < 0.05). Among the identified 12 haplotypes, the majority of which were wild type (75.7%; 206/272). These four mutant haplotypes (Hap_3, Hap_5, Hap_9, and Hap_10) were classified as “K10 insertion type” and accounted for 12.1% (33/272). The detection rate of Hap_3 increased from 1.0% (1/102) in 2020 to 13.0% (12/92) in 2021 and 14.1% (11/78) in 2022, indicating statistical significance. A total of 23.8% (65/272) of the samples exhibited 14 bp (bp) deletions in the promoter region, occurring most frequently in the wild type haplotype (Hap_1) samples at a rate of 28.6% (59/206). In recent years in Yunnan Province, a notable proportion of vivax malaria patients are infected by P. vivax strains with a “K10 insertion” and partial sequence deletions in the promoter region of the pvcrt-o gene, necessitating vigilance.
Development of a new version of the Liverpool Malaria Model. II. Calibration and validation for West AfricaMalaria Journal - Tập 10 - Trang 1-19 - 2011
Volker Ermert, Andreas H Fink, Anne E Jones, Andrew P Morse
In the first part of this study, an extensive literature survey led to the construction of a new version of the Liverpool Malaria Model (LMM). A new set of parameter settings was provided and a new development of the mathematical formulation of important processes related to the vector population was performed within the LMM. In this part of the study, so far undetermined model parameters are calibrated through the use of data from field studies. The latter are also used to validate the new LMM version, which is furthermore compared against the original LMM version. For the calibration and validation of the LMM, numerous entomological and parasitological field observations were gathered for West Africa. Continuous and quality-controlled temperature and precipitation time series were constructed using intermittent raw data from 34 weather stations across West Africa. The meteorological time series served as the LMM data input. The skill of LMM simulations was tested for 830 different sets of parameter settings of the undetermined LMM parameters. The model version with the highest skill score in terms of entomological malaria variables was taken as the final setting of the new LMM version. Validation of the new LMM version in West Africa revealed that the simulations compare well with entomological field observations. The new version reproduces realistic transmission rates and simulated malaria seasons are comparable to field observations. Overall the new model version performs much better than the original model. The new model version enables the detection of the epidemic malaria potential at fringes of endemic areas and, more importantly, it is now applicable to the vast area of malaria endemicity in the humid African tropics. A review of entomological and parasitological data from West Africa enabled the construction of a new LMM version. This model version represents a significant step forward in the modelling of a weather-driven malaria transmission cycle. The LMM is now more suitable for the use in malaria early warning systems as well as for malaria projections based on climate change scenarios, both in epidemic and endemic malaria areas.
A national policy for malaria elimination in Swaziland: a first for sub-Saharan AfricaMalaria Journal - Tập 10 - Trang 1-4 - 2011
Simon Kunene, Allison A Phillips, Roly D Gosling, Deepika Kandula, Joseph M Novotny
Swaziland is working to be the first country in mainland sub-Saharan Africa to eliminate malaria. The highest level of Swaziland's government recently approved a national elimination policy, which endorses Swaziland's robust national elimination strategic plan. This commentary outlines Swaziland's progress towards elimination as well as the challenges that remain, primarily around securing long-term financial resources and managing imported cases from neighbouring countries.
IL35 modulation altered survival, cytokine environment and histopathological consequences during malaria infection in miceMalaria Journal - Tập 18 - Trang 1-23 - 2019
Ramatu Omenesa Bello, Maizaton Atmadini Abdullah, Roslaini Abd Majid, Voon Kin Chin, Mohammed Faruq Abd Rachman Isnadi, Zaid Osama Ibraheem, Mohd Khairi Hussain, Mohammed Garba Magaji, Rusliza Basir
The immune modulating potential of IL-35 in multiple human disorders has been reported. Consequent upon the recognition of inflammatory cytokine activation and its preponderance for mediating pathology during malaria infection, the study aimed to characterize the expression and functional contribution(s) of IL-35 in Plasmodium berghei (strain ANKA) infected mice. Plasmodium berghei infection in male ICR mice was used as the rodent model of choice. The time course of IL-35 expression in the systemic circulation and tissues of P. berghei infected mice as well as their healthy control counterparts was assessed by enzyme linked immunosorbent assay and immunohistochemistry respectively. The effect of modulating IL-35 by recombinant IL-35 protein or neutralizing anti-Epstein-Barr virus-induced gene 3 antibody on the cytokine environment during P. berghei infection was assessed by flow cytometry. Furthermore, the influence of modulating IL-35 on histopathological hallmarks of malaria and disease progression was evaluated. Interleukin-35 was significantly up regulated in serum and tissues of P. berghei infected mice and correlated with parasitaemia. Neutralization of IL-35 significantly enhanced the release of IFN-γ, decreased the expression of IL-6 and decreased parasitaemia patency. Neutralization of IL-35 was also associated with a tendency towards increased survival as well as the absence of pathological features associated with malaria infection unlike recombinant IL-35 protein administration which sustained a normal course of infection and unfavourable malaria associated histological outcomes in P. berghei infected mice. These results indicate the involvement of IL-35 in P. berghei induced malaria infection. IL-35 neutralization strategies may represent viable therapeutic modalities beneficial for the resolution of malaria infection.
The effect of light and ventilation on house entry by Anopheles arabiensis sampled using light traps in Tanzania: an experimental hut studyMalaria Journal - Tập 21 - Trang 1-11 - 2022
Arnold S. Mmbando, John Bradley, Deogratius Kazimbaya, Robert Kasubiri, Jakob Knudsen, Doreen Siria, Lorenz von Seidlein, Fredros O. Okumu, Steve W. Lindsay
In sub-Saharan Africa, house design and ventilation affects the number of malaria mosquito vectors entering houses. This study hypothesized that indoor light from a CDC-light trap, visible from outside a hut, would increase entry of Anopheles arabiensis, an important malaria vector, and examined whether ventilation modifies this effect. Four inhabited experimental huts, each situated within a large chamber, were used to assess how light and ventilation affect the number of hut-entering mosquitoes in Tanzania. Each night, 300 female laboratory-reared An. arabiensis were released inside each chamber for 72 nights. Nightly mosquito collections were made using light traps placed indoors. Temperature and carbon dioxide concentrations were measured using data loggers. Treatments and sleepers were rotated between huts using a randomized block design. When indoor light was visible outside the huts, there was an 84% increase in the odds of collecting mosquitoes indoors (Odds ratio, OR = 1.84, 95% confidence intervals, 95% CI 1.74–1.95, p < 0.001) compared with when it was not. Although the odds of collecting mosquitoes in huts with closed eaves (OR = 0.54, 95% CI 0.41–0.72, p < 0.001) was less than those with open eaves, few mosquitoes entered either type of well-ventilated hut. The odds of collecting mosquitoes was 99% less in well-ventilated huts, compared with poorly-ventilated traditional huts (OR = 0.01, 95% CI 0.01–0.03, p < 0.001). In well-ventilated huts, indoor temperatures were 1.3 °C (95% CI 0.9–1.7, p < 0.001) cooler, with lower carbon dioxide (CO2) levels (mean difference = 97 ppm, 77.8–116.2, p < 0.001) than in poorly-ventilated huts. Although light visible from outside a hut increased mosquito house entry, good natural ventilation reduces indoor carbon dioxide concentrations, a major mosquito attractant, thereby reducing mosquito-hut entry.
Evaluation of a novel real-time PCR assay for the detection, identification and quantification of Plasmodium species causing malaria in humansMalaria Journal - Tập 20 Số 1 - 2021
Kim van Bergen, Toon Stuitje, Robert C. Akkers, Eric Vermeer, Rob Castel, T. G. Mank
Abstract
Background
The entry of PCR-based techniques into malaria diagnostics has improved the sensitivity and specificity of the detection of Plasmodium infections. It has been shown that humans are regularly infected by at least six different Plasmodium species. The MC004 real-time PCR assay for malaria diagnosis is a novel single-tube assay that has been developed for the purpose of simultaneously detecting all Plasmodium species known to infect humans, and discrimination between Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale wallikeri, Plasmodium ovale curtisi, Plasmodium knowlesi (including differentiation of three strains) and Plasmodium cynomolgi (including differentiation of three strains). Detection and identification of Plasmodium species relies on molecular beacon probe-based melting curve analysis. In addition, this assay might be used to quantify the parasitaemia of at least P. falciparum by calculating the level of parasitaemia directly from the Cq-value.
Methods
The samples used in this study comprised reference samples, patient samples, and synthetic controls. The following analytical performance characteristics of the MC004 assay were determined: analytical specificity, limit of detection, the ability to detect mixed infections, and the potential to determine the level of parasitaemia of P. falciparum, including assessment of within-run and between-run precisions.
Results
No false positive or false negative results were observed. The limit of detection of P. falciparum was 1 × 10–3 IU/mL (WHO standard). Mixed infections with P. falciparum and non-falciparum species were correctly identified. A calibration curve could be established to quantify the parasitaemia of at least P. falciparum. The within-run and between-run precisions were less than 20% CV at the tested parasitaemia levels of 0.09%, 0.16%, 2.15% and 27.27%.
Conclusion
Based upon the analytical performance characteristics that were determined, the MC004 assay showed performance suitable for use in clinical settings, as well as epidemiological studies.
