| 1. |
- Amodu, O. K., et al.
(author)
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Association of the sickle cell trait and the ABO blood group with clinical severity of malaria in southwest Nigeria
- 2012
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 123:2, s. 72-77
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Journal article (peer-reviewed)abstract
- In regions of high Plasmodium falciparum malaria endemicity, certain erythrocyte polymorphisms confer resistance to severe disease. In this study, we evaluate the role of the sickle cell trait (HbS) and ABO blood groups in the clinical manifestations of childhood malaria in Southwest Nigeria. The subjects comprised 3100 children (53% males, median age 39 months), including 1400 children with uncomplicated malaria, 1000 children with asymptomatic malaria and 700 with severe malaria. Haemoglobin (Hb) types were determined using electrophoresis and serum agglutination techniques were used to determine ABO blood groups. Blood group O was the commonest ABO blood group (47.7%) in the study population, the others were A (22.5%), B (25.2%) and AB (4.6%). The frequencies of the HbAS and HbAC were 14.4% and 5.8%, respectively. In regression models adjusting for age, gender, parasite density and blood group, HbAS was associated with a reduced risk of severe malaria OR=0.46 (CI95%: 0.273-0.773). Among severe malaria subjects, HbAS was associated with significantly lower parasite densities. The protective effect of blood group 0 was demonstrated with a decreased risk of severe malaria OR=0.743 (CI95%: 0.566-0.976) after adjusting for age, gender and parasite density and Hb genotype. Blood group B was associated with increased risk of severe malaria OR=1.638 (CI95%: 1.128-2.380) after adjusting for age, gender, packed cell volume, parasite density and Hb genotype. We have confirmed from this large study of Nigerian children the major protective effective of the sickle cell heterozygous state against both cerebral malaria and severe malarial anaemia. We also show that the B blood group is associated with an increased risk of severe malaria. In conclusion, the sickle cell haemoglobin type and ABO groups modulate the risk of severe malaria in Nigerian children.
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| 2. |
- Arrighi, Romanico B. G., et al.
(author)
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Plasmodium falciparum GPI toxin : A common foe for man and mosquito
- 2010
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 114:3, s. 162-165
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Journal article (peer-reviewed)abstract
- The glycosylphosphatidylinositol (GPI) anchor of the malaria parasite, Plasmodium falciparum, which can be regarded as an endotoxin, plays a role in the induced pathology associated with severe malaria in humans. However, it is unclear whether the main mosquito vector, Anopheles gambiae, can specifically recognize, and respond to GPI from the malaria parasite. Recent data suggests that the malaria vector does mount a specific response against malaria GPI. In addition, following the strong immune response, mosquito fecundity is severely affected, resulting in a significant reduction in viable eggs produced. In this mini-review we look at the increased interest in understanding the way that malaria antigens are recognized in the mosquito, and how this relates to a better understanding of the interactions between the malaria parasite and both human and vector.
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| 3. |
- Balogun, Halima A., et al.
(author)
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Pattern of antibodies to the Duffy binding like domain of Plasmodium falciparum antigen Pf332 in Senegalese individuals
- 2014
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 130, s. 80-87
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Journal article (peer-reviewed)abstract
- Acquisition of antibodies against blood stage antigens is crucial in malaria immunity and the Plasmodium falciparum antigen Pf332, which is present in close association with the infected red blood cell membrane, is one such antigen. In this study, the antibody response to a Duffy binding like fragment of Pf332, termed Pf332-DBL was investigated in sera from naturally exposed individuals living in Dielmo village, Senegal, with regard to immunoglobulin classes (IgG, IgM, IgE) and IgG subclasses (IgG1-4). While the levels of IgM, IgG, IgG1 and IgG2 only displayed a moderate trend to increase with age, Pf332-DBL specific IgG3 levels increased significantly in the older villagers. In multivariate analysis, when controlling for confounding factors, and in a linear model with a Poisson distribution, anti-Pf332-DBL IgG3 as well as the ratio of cytophilic to non cytophilic anti-Pf332-DBL antibodies were found significantly associated with a reduced risk of malaria attack. This association was also present when the IgG3:IgG1 ratio was tested. Finally, two subgroups of villagers with the same mean age, were delineated by IgG3 concentrations either lower or higher than the median value. A total of 45.2% of the individuals with low anti-Pf332-DBL-IgG3 levels but only 21.4% of the villagers in the group with high levels of such antibodies had a clinical malaria attack during a period of 3 years of continuous follow-up after the blood sampling. In conclusion, Pf332-DBL induces naturally the acquisition of antibodies, and Pf332-DBL-specific IgG3 appears to be associated with protection against malaria in this endemic setting.
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| 6. |
- Kamugisha, Erasmus, et al.
(author)
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Large differences in prevalence of Pfcrt and Pfmdr1 mutations between Mwanza, Tanzania and Iganga, Uganda : a reflection of differences in policies regarding withdrawal of chloroquine?
- 2012
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 121:2, s. 148-151
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Journal article (peer-reviewed)abstract
- BACKGROUND: Malaria is still a major public health problem in the world and sub-Saharan Africa is one of the most affected areas. Efforts to control malaria are highly affected by drug resistance to commonly used antimalarials. The introduction of artemisinin based combination therapy (ACT) as a first line drug seems to be a major step in treatment of uncomplicated malaria, though search for drugs to combine with artemisinins still continues. There have been reports on increased prevalence of the wild type markers Pfcrt 76K and Pfmdr1 86N in some African countries and ideas of using chloroquine (CQ) in intermittent presumptive treatment for adults (IPTa) is coming up. The common combination of artemether and lumefantrine even selects for parasites that are wild type at these positions. This study is comparing prevalence of mutation at these two positions in two East African countries with ACT as their first line drug but following somewhat different drug policies regarding CQ. In Tanzania CQ was stopped in 2001 but in Uganda CQ was retained in combination with sulfadoxine-pyrimethamine (SP) and used in home based management of fever for some time. SP is still used in IPT for pregnant women. METHODS: Blood smears and dried blood spots on Whatman filter papers were collected from 100 patients with uncomplicated malaria in Mwanza, Tanzania and 100 patients from Iganga, Uganda. DNA was extracted from all samples using Tris EDTA method. PCR and RFLP were performed and sequencing done on Pfcrt amplification products. RESULTS: The prevalence of K76T mutations at Pfcrt in samples from Mwanza, Tanzania was 40.5% (34/84) and 100% (100/100) in samples from Iganga, Uganda. Prevalence of N86Y mutations in Pfmdr1 was 16.9% (13/77) and 77.7% (63/81) in samples from Mwanza and Iganga, respectively. The re-emergence of CQ sensitive isolates in Mwanza, Tanzania showed the haplotype CVMNK typical for wild type isolates. CONCLUSIONS: The prevalence of CQ resistant parasites in Mwanza, Tanzania is low compared to the existing high level of resistant parasites in Iganga, Uganda. This could be an indication that CQ may become useful in the future in Tanzania. This study shows clearly that there is a difference in mutations at these positions in these two countries implementing similar but somewhat different drug policies. In Uganda the drug resistance has reached fixation while in Tanzania the prevalence is going down.
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| 7. |
- Kaneko, Akira
(author)
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A community-directed strategy for sustainable malaria elimination on islands : Short-term MDA integrated with ITNs and robust surveillance
- 2010
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 114:3, s. 177-183
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Journal article (peer-reviewed)abstract
- In the Asia Pacific sites with low and unstable transmission, elimination should be feasible with existing tools. On Aneityum island, Vanuatu both Plasmodium falciparum and Plasmodium vivax malaria were eliminated in 1991 after implementation of a combined intervention package, including mass drug administration (MDA) and insecticide-treated bed nets (ITNs), with high degree of community involvement. Subsequently, community-based surveillance and vector control measures have kept. By reviewing the experiences of the Aneityum project, I intended to examine the roles of community in malaria elimination. To be successful, the program should transfer major intervention components from the external donor-directed initiative to the community-directed approach. Scaling up of community involvement from simple participation to social participation, where communities involve in health planning functions is necessary from malaria control to malaria elimination.
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| 10. |
- Lees, Rosemary Susan, et al.
(author)
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Review : Improving our knowledge of male mosquito biology in relation to genetic control programmes
- 2014
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 132, s. S2-S11
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Research review (peer-reviewed)abstract
- The enormous burden placed on populations worldwide by mosquito-borne diseases, most notably malaria and dengue, is currently being tackled by the use of insecticides sprayed in residences or applied to bednets, and in the case of dengue vectors through reduction of larval breeding sites or larviciding with insecticides thereof. However, these methods are under threat from, amongst other issues, the development of insecticide resistance and the practical difficulty of maintaining long-term community-wide efforts. The sterile insect technique (SIT), whose success hinges on having a good understanding of the biology and behaviour of the male mosquito, is an additional weapon in the limited arsenal against mosquito vectors. The successful production and release of sterile males, which is the mechanism of population suppression by SIT, relies on the release of mass-reared sterile males able to confer sterility in the target population by mating with wild females. A five year Joint FAO/IAEA Coordinated Research Project brought together researchers from around the world to investigate the pre-mating conditions of male mosquitoes (physiology and behaviour, resource acquisition and allocation, and dispersal), the mosquito mating systems and the contribution of molecular or chemical approaches to the understanding of male mosquito mating behaviour. A summary of the existing knowledge and the main novel findings of this group is reviewed here, and further presented in the reviews and research articles that form this Acta Tropica special issue.
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| 11. |
- Nyakeriga, Alice M., et al.
(author)
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Haptoglobin phenotypes and iron status in children living in a malaria endemic area of Kenyan coast
- 2013
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 126:2, s. 127-131
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Journal article (peer-reviewed)abstract
- Malaria infection may be affected by host genetic factors as well as nutritional status. Iron status and the phenotype of haptoglobin, a heme-binding acute phase reactant may be determinants of malaria parasitemia. A combination of cross sectional studies and longitudinal follow-up were used to describe the association between iron status, C-reactive protein, malaria infections and host genetic factors including; haptoglobin (Hp) phenotypes, in children below 9 years in a malaria endemic area in Coastal Kenya. The prevalence of 0.45 and 0.41, respectively for Hp 1-1 and Hp 2-1 phenotypes was significantly higher than 0.14 for Hp 2-2 phenotype (n = 162). Children with Hp 2-2 phenotype showed significantly higher iron storage compared to those with Hp 1-1 and Hp 2-1 phenotypes when children with malaria parasites and high C-reactive protein (>9 mg/L) were excluded from the analysis. There were no significant differences in malaria parasite densities among Hp phenotypes but children with Hp 2-2 had lower number of clinical malaria episodes (P=0.045). Taken together, this study shows that the presence of malaria may complicate the interpretation of iron status in children based on their Hp-phenotypes. Further studies will be required to address possible interactions among the various genetic factors and iron status in a malaria endemic setting.
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| 12. |
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| 13. |
- Pitts, R. Jason, et al.
(author)
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The roles of kairomones, synomones and pheromones in the chemically-mediated behaviour of male mosquitoes
- 2014
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 132:1, s. S26-S34
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Journal article (peer-reviewed)abstract
- Despite decades of intensive study of the chemical ecology of female mosquitoes, relatively little is known about the chemical ecology of males. This short review summarizes the current state of knowledge of the chemicals that mediate male mosquito behaviour. Various trophic interactions including insect plant, insect host, and insect insect responses are emphasized. The relevance of the chemical ecology of male mosquitoes in the context of vector control programmes is discussed.
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| 14. |
- Simone, Olivia, et al.
(author)
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TLRs innate immunereceptors and Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) CIDR1α-driven human polyclonal B-cell activation.
- 2011
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 119:2-3, s. 144-150
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Journal article (peer-reviewed)abstract
- Chronic malaria severely affects the immune system and causes polyclonal B-cell activation, as evidenced by the presence of hypergammaglobulinemia, elevated levels of autoantibodies, loss of B-cell memory and the frequent occurrence of Burkitt's lymphomas (BL) in children living in malaria endemic areas. Previous studies have shown that the cysteine-rich interdomain region 1α (CIDR1α) of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) of the FCR3S1.2 strain, subsequently named CIDR1α, interacts with B cells partially through the binding to the B-cell receptor (BCR). This interaction leads to an activated phenotype, increased survival, and a low degree of proliferation. CIDR1α preferentially activates the memory B-cell compartment, therefore PfEMP1 is considered to act as a polyclonal B-cell activator and its role in memory maintenance has been suggested. In this report, we extend the analysis of the PfEMP1-CIDR1α B-cell interaction and demonstrate that PfEMP1-CIDR1α increases the expression of TLR7 and TLR10 mRNA transcripts and sensitizes B cells to TLR9 signalling via the MyD88 adaptor molecule. Furthermore, despite its ability to bind to surface Igs, PfEMP1-CIDR1α-induced B-cell activation does not seem to proceed through the BCR, since it does not induce Lyn and/or phospho-tyrosine mediated signalling pathways. Rather PfEMP1-CIDR1α induces the phosphorylation of downstream kinases, such as ERK1/2, p38 and IKBα, in human B cells. These findings indicate that PfEMP1-CIDR1α induces a persistent activation of B cells, which in turn can contribute to the exhaustion and impairment of B-cell functions during chronic malaria infection.
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| 15. |
- Vongsombath, Chanda, et al.
(author)
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Keeping leeches at bay : Field evaluation of plant-derived extracts against terrestrial blood-sucking leeches (Haemadipsidae) in Lao PDR
- 2011
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In: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 119:2-3, s. 178-182
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Journal article (peer-reviewed)abstract
- Terrestrial blood-sucking leeches (Haemadipsidae) are common in the damp forests of the subtropical and tropical Indo-Pacific region. Members of the genus Haemadipsa are abundant in Laos and adjacent countries of Southeast Asia, and discomfort to people and livestock. Plant-derived repellents against arthropods and leeches are common in Lao PDR, and have been used by Lao ethnic groups for generations. Numerous studies have been conducted on the efficacy of traditional plant-derived repellents against mosquitoes but only a few on repellents against terrestrial blood-sucking leeches. Field experiments were conducted to evaluate the leech repellent activities of aqueous extracts of three traditionally used plant species, Sapindus rarak DC., Catunaregam spathulifolia Tirv. and Vernonia elaeagnifolia DC. Stockings impregnated with aqueous extracts exhibited moderate to high leech repellent activity, C spathulifolia (62.6%), V. elaeagmfolia (63.0%), and S. rarak (82.6%). The corresponding repellencies of deltamethrin and DEET were 73.1% and 88.4%, respectively. An aqueous extract of S. rarak applied on cloth at a concentration of 1.9 mg/cm(2) is an effective and practical prevention method significantly reducing the number of blood-feeding leeches recorded on stockings worn by humans. This plant species is common in Southeast Asia and can be obtained at limited or no cost.
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