MalariaWorld journal最新文献

Background: Falciparum malaria in endemic areas continues to occur in asymptomatic cases, which contribute to the persistence of transmission as well as the size of the parasite reservoirs. Recent successes in malaria control have resulted in renewed interest in malaria eradication and identification of the human infectious reservoir is essential for this. In this study, we evaluated prevalence of microscopic and submicroscopic gametocytes that were obtained from asymptomatic primary school children from Bagamoyo rural in Tanzania.

Materials and methods: Samples were collected from 501 asymptomatic primary school children (6-14 years of age) from 7 villages in Bagamoyo district. Participants were screened for malaria in the field using RDT, and samples were brought to the laboratory for microscopy and molecular analysis. Parasite density was determined by microscopy, and gametocyte carriage identification was performed by RT-qPCR targeting gametocyte-specific genes.

Results: Asymptomatic infection was found to be 45.1% (95% : CI=40.7-49.6) by RT-qPCR, followed by RDT, 14.2% (95%: CI=11.2-17.5) and microscopy 6.8% (95%: CI=4.7-9.4). Parasite prevalence by microscopy was 12% (23/191) in boys compared to 3.6% (11/310) in girls (p<0.001). Gametocytes were detected in 12.6% (226/501) of the asymptomatic school children by RT-qPCR compared to only 0.8% (4/501) of the children by microscopy (P=0.008).

Conclusions: Asymptomatic infection and submicroscopic gametocyte carriage were high in the study area. The detection of asymptomatic cases with circulating submicroscopic P. falciparum gametocytes in school children indicates that these form a substantive gametocyte reservoir that sustains malaria transmission. Asymptomatic carriers and submicroscopic infections should therefore be considered when implementing elimination strategies of the disease.

Background: Rapid diagnostic tests (RDTs) and microscopy are routinely used for the diagnosis of malaria in Ghana. DNA-based polymerase chain reaction (PCR) is not yet used routinely. We compared diagnostic methods and tested the sensitivities of different malaria diagnostic methods against PCR.

Materials and methods: Study participants from four hospitals with a suspicion of malaria donated finger -prick blood for RDT and blood film examination. In addition, a blood spot was collected for PCR analysis, prior to treatment. Retrospective species-specific PCR was performed on all samples collected.

Results: Using PCR we found an overall malaria prevalence of 39% among the 211 evaluable blood spots (83/211) and this ranged between 6-61% across the four hospitals. Of the 164 participants with RDT data, malaria prevalence was 57% (94/164), ranging from 3-100% from the four hospitals. Microscopy was the least sensitive with a parasite prevalence of 21% (25/119) of the evaluable 119 participants, varying from 9 to 35% across three health facilities. By comparison, we found the sensitivities and specificities of RDT results when compared to PCR to be slightly higher than microscopy compared to PCR. These were 56.4% versus 41.7% and 90% versus 81.9%, respectively, but generally lower than expected. Ninety-five percent of the PCR-detected infections were P. falciparum, while 4% were mixed species infections of P. falciparum and P. malariae, with the remaining being a mono-infection of P. malariae.

Conclusions: While using PCR as a gold standard, we found RDT to be more reliable in diagnosing malaria than microscopy. In addition, a majority of malaria-treated cases were not supported by PCR diagnosis, leading to possible overtreatment. Pragmatic strategies are needed to ensure suspected malaria cases are accurately diagnosed before treatment.

Background: A study was carried out on students of the University of Dschang, Cameroon, to examine the relationship between ABO blood group, rhesus factor and prevalence of Plasmodium falciparum infection.

Materials and methods: Blood group and rhesus factor were typed by agglutination using antisera while malaria infection was determined using Rapid Diagnostic Test CareStart malaria HRP2 pf. Out of 620 students 582 were screened for ABO blood group and Rhesus factor, and 276 were tested for P. falciparum infection.

Results: Faculty of Science (FS) members and male students were highly represented, with 356 (61.2% ) and 303 (52.1%) participants, respectively. Blood group O was most common (48.8%), followed by blood group A (25.8%), B (23.0%) and AB (2.4%). Total percentage of rhesus positive was 92.4%, and its distribution varied across ABO blood groups. Of the 276 students examined for malaria infection, 27 were found positive (9.8%). Except for blood group AB individuals, of which none were infected, malaria infection did not vary among blood groups.

Conclusion: Rhesus factor and blood group did not impact on malaria infection in the hypo-endemic highland area of Dschang, Cameroon.

Background: Malaria in pregnancy is one of the major causes of mater nal morbidity and mortality as well as of poor pregnancy outcomes. We studied the knowledge, attitude and practices of pregnant women on malaria prevention, assessed their knowledge of sulfadoxine-pyrimethamine (SP) for intermittent preventive therapy in pregnancy (IPTp-SP), and used the outcomes to create awareness on malaria prevention with IPTp-SP.

Materials and methods: A structured questionnaire on malaria prevention and SP utilisation was administer ed to 450 pregnant women attending antenatal clinics in both government and private health facilities in Badagry, Lagos State, Nigeria.

Results: 355 (78.8% ) of the pregnant women perceived malaria as a serious illness. Other responses by the respondents included: parasitic disease (13; 2.9%); caused by mosquito (5; 1.9%), while 77 (17%) said they did not know. The signs and symptoms of malaria mentioned included headache (109; 24.2%), weakness (77; 17.1%), fever (77; 17.1%) and body pains (44; 10%). 174 (58%) women indicated that they would go to a hospital when having malaria, 54 (17%) indulged in self-medication, while 32 (11%) took herbs. 43 (14%) did nothing. Malaria prevention was performed by taking herbs (134; 30%); artemisinin-based combination therapy (ACT) (123; 27%); daraprim (104; 23%); blood tonic (51; 11%); paracetamol (21; 5%) and SP (17; 4%). Mosquito control was mainly carried out by the use of insecticide spray (215; 47.7%), followed by anti-mosquito coils (95; 21%). Out of the 450 pregnant women interviewed, 350 (84.5%) said that SP was for the treatment of malaria, while 69 (15.2%) said that it was for malaria prevention. Knowledge of SP was influenced by both education (P<0.05) and parity (P<0.001).

Conclusion: The majority of the pregnant women had knowledge of SP but did not know that it is used for malaria prevention. Most of the respondents took malaria-preventive measures by taking herbs but preferred to go to the hospital when suspecting that they had malaria.

Background: Communities' knowledge, attitudes and practices on malaria disease often remain unobserved during malaria control efforts. In Tanzania, many studies focus on increasing community knowledge and awareness on malaria prevention but the potential participation and contribution of schoolchildren towards knowledge, attitudes and practices on malaria has received little attention. We investigated the knowledge and understanding of primary school children on malaria transmission, recognition of symptoms, treatment seeking behaviour, preventive measures and practices in order to potentially include this group in Tanzania's malaria control efforts.

Materials and methods: 125 children were recruited from three purposively selected primary schools in Bagamoyo district, Tanzania. A semi-structured interview guide, including both closed and open-ended questions, was used to collect information from the participants to obtain their knowledge and understanding on malaria transmission, treatment and prevention.

Results: More than half of the school children (79/125; 63.2% ) had knowledge on malaria as a disease and its transmission; 101/125 (80.8%) of the respondents reported that going to the hospital was their immediate care-seeking behaviour once they felt malaria symptoms, while 14/125 (11.2%) opted for self-medication. With regard to malaria prevention and control, 115/125 (92.0%) of the respondents reported using bednets as their main malaria prevention strategy, while 6/125 (4.8%) preferred the use of medicine, mostly artemether lumefantrine, as prophylaxis. Narratives obtained were able to explain clearly the rationale behind different options children took to treat and to protect themselves against malaria.

Conclusions: Findings indicated that primary school children in Bagamoyo district are aware of malaria, its symptoms and preventive measures, although some had misconceptions and could not associate the disease with its transmission. We conclude that inclusion of school children on malaria control educational programmes could yield substantial benefits towards malaria elimination.

Background: Until about 2010, the majority of data collected on malaria in Côte d'Ivoire were based on presumptive cases, particularly in the northern part of the country, where parasitological research had rarely been carried out. Recently, WHO recommended restricting treatment to confirmed malaria cases only. Thus, the purpose of this study determine the actual malaria prevalence amongst presumptive cases admitted to one of the general hospitals in the Northern part of the country, where malaria diagnosis is suboptimal.

Materials and methods: A cr oss-sectional study was conducted in the general medicine, maternity and paediatric wards between January and August 2010. Patients of all ages, suspected of having malaria, were included after giving their informed oral consent. Several parameters were investigated: the presence of Plasmodium using thick blood film, HIV/ Plasmodium co-infection, signs of severity, aspects of malaria treatment and other associated factors.

Results: Of 379 patients included, with a median age of 4 yrs [range 1 month - 71 yrs], 9% were HIV-positive, 74% were ≤ 15 yrs of age, 60% were urbanised and 23% were using long-lasting insecticide-treated nets. Malaria prevalence was 67.5% and was significantly associated with the rainy season (p < 0.001), age ≤ 5 yrs (p = 0.004) and no cotrimoxazole chemoprophylaxis in HIV-infected patients (p = 0.04). Only P. falciparum was detected, with a mean density of 12,523 trophozoites/μl of blood, but with 12,610 trophozoites/μl of blood in HIV-positive patients and 7,055 trophozoites/μl of blood in HIV-negative patients (p < 0.001). Severe malaria accounted for 77% of cases. Prescribed antimalarial drugs were: IM artemether (56%), quinine (28%), artemether + lumefantrine (10%) and artesunate + amodiaquine (6%). Apyrexia and parasite clearance were observed at day 2-3 post treatment in 87% of patients. Adverse events were reported among 60 patients (17%). The outcome was marked by: a healing rate of 90%, a rate of 5% lost to follow-up and a 7% lethality for severe malaria, significantly associated with the age ≤ 5 yrs (p=0.02), hyperparasitaemia >20% (p=0.004), neurological disorders (p < 0.001) and respiratory distress (p=0.007).

Conclusions: Malaria prevalence in the general hospital of Tanda remains high, with a predominance of sever e malaria affecting children under the age of 5 yrs.

Background: In many tropical countries, malaria remains a major health problem. Effective control of in -house mosquitoes, due to entry prevention, takes advantage of the behavioural preferences of endophagy and endophily of mosquitoes. Insecticide-treated nets (ITN) adopt this, but is burdened with challenges, which result in dwindling adoption of the methodology in the tropics. An alternative is prevention of vector-human contact through house modifications, which adopts S/O channel/grip devices that form attachments to existing windows. Inverted S/O channel/grip frame (ISOWF) was therefore devised as an integrated window frame, which could be used for direct net attachment and housing shutters. The ISOWF is a lightweight material weighing 1/6 of the equivalent size of wood.

Materials and methods: Appropriate dies were employed to form channels from thin iron sheets in the prefer red shape and size of a laterally inverted letter 'S' (ƨ). The upper half was minimised to form and facilitate the 'O' griping of nets, while the remaining half was bloated to house window shutters. Net hoisting or de-hoisting periods were determined by timing. A room screened with a net was attached to the device and situated next to a mosquito breeding room. The room was charged with adequate carbon dioxide attractant for mosquitoes and protected with ISOWF screen. This was used to evaluate the effectiveness of the method. The time taken to hoist the net was measured. The frame was constructed like a metal/ wooden frame, except that the anterior view had two steps.

Results: The average time taken to hoist or de-hoist a net across a 60 cm x 120 cm window, formed by the frame, was 5.96 and 1.68 minutes, respectively. The nets retained their integrity. Mixed mosquito populations numbering 1,341 in total could not gain access to a room with carbon dioxide attractant, and the ISOWF screen prevented passage.

Conclusion: The ISOWF acts as a potential mosquito entry-prevention device, which further provides reinforcement to house screening. It forms an effective mosquito control device, which brands house screening as a sustainable environment for mosquito control, and subsequently, malaria control. This will also control the overall indoor densities of nuisance mosquitoes and other insect vectors.

Background: The evolution of insecticide resistance can lead to an increase in the entomological indicators of malaria transmission, such as mosquito survival and blood feeding rates, thus threatening efforts to control malaria. Yet, there is little evidence from the field that malaria control programmes are failing due to insecticide resistance. One explanation for this apparent contradiction is the growing evidence that insecticide resistance declines with mosquito age. Once a mosquito is first infected by Plasmodium parasites, it will not be able to transmit those parasites until they have undergone development, which lasts around 10 days. Thus, although the evolution of resistance in a population will enhance the survival of young mosquitoes, the insecticide may still kill old, and thus potentially infectious, mosquitoes, and thereby maintaining its efficacy in controlling malaria.

Materials and methods: The current evidence for age-related insecticide resistance is reviewed. A mathematical model is then described that predicts how the decline of resistance with the age of a mosquito will affect the intensity of transmission of malaria. The model combines the behavioural response of the mosquitoes to insecticides with an epidemiological model of malaria.

Results: It was found that phenotypic resistance decreases between 1.37% to 9.71% per day, independent of the mosquito species or strain. The models suggest that a decline in resistance within this range strongly diminishes the predicted impact of insecticide resistance on the effectiveness of malaria transmission-controlling interventions.

Conclusions: Our model can be used to assess the threat of insecticide-resistance for the control of malaria. The model confirms observations from the field suggesting that, even where genetically insecticide-resistant mosquitoes dominate populations, insecticides can substantially reduce the transmission of malaria.

Background: As part of efforts to monitor the impact of vector control strategies so that they can be improved and more targeted, we collected baseline data on aspects of the bionomics of endophilic anophelines in southern Ghana.

Materials and methods: Indoor resting anophelines were collected using mouth aspirators and pyrethroid spray catch. Anopheles females were identified to species level using morphological characteristics and sibling species were distinguished by PCR. The presence of the L1014F mutation, conferring resistance to insecticides, was determined in An. gambiae s.s. and An. coluzzii samples using TaqMan real-time PCR. Host blood meal sources were determined by PCR, and the presence of Plasmodium falciparum circumsporozoite proteins determined by ELISA.

Results: A total of 892 female Anopheles (31% An. gambiae, 41% An. coluzzii and 28% An. funestus) were collected from six villages. The L1014F mutation was almost fixed in all populations studied (allele frequencies: 0.87-1.00). Both An. gambiae s.l. and An. funestus fed mainly on humans, with a human blood index of 1, although some animal feeding was recorded in An. gambiae. P. falciparum was detected in all ecological zones and in all three major vector species, being 4.9% in An. funestus, 3.8% in An. gambiae s.s. and 1.1% in An. coluzzii.

Conclusions: These findings suggest that the three major vectors of malaria are present in all ecological zones of southern Ghana and contribute to disease transmission. The near fixation of the L1014F mutation in southern Ghana poses a great threat to vector control, thus highlighting the urgent need to implement measures to maintain the efficacy of current control tools and to develop novel control strategies.

Background: A series of outbreaks of fever has previously been reported in the DR Congo. The occurrence of similar outbreaks in Mweka district presented the opportunity to investigate these occurrences.

Materials and methods: Health facilities and communities were visited. Permission was obtained to access to health records and a questionnaire was competed in the community. Blood samples for malaria, salmonellosis, Chikungunya, dengue and filovirus testing were obtained both in health facilities and the communities. Capture of mosquitoes and larvae in breeding sites was done and used bednets were collected. Excel, SPSS and Stats Direct were used for analyses of epidemiological data and malaria case management, with the Chi-square test and Fisher's Exact test used for assessing relationships resulting from contingency table analyses.

Results: An increase in the number of malaria cases beyond the expected number for the study period was observed in the two health districts located in the savannah zone (p<0.05) and in one health centre among sixteen located in the forest zone (p<0.05). In the health facilities and households visited (653 people), 141 persons had fever of which 82.2% was attributed to Plasmodium falciparum malaria. An incidence of 5.87% was recorded in the first half of 2013. Hundred and sixty patients (6.9%) died among 2,304 admitted for severe malaria in the three referral hospitals, 118 of them were children of under five years old. PCR testing of the blood samples obtained during home visits revealed malaria parasites in 63 (73.3%) of the 86 analysed samples. The test was negative for other parasites and bacteria and one dengue virus case was detected. Anopheles gambiae from Mweka were found to be resistant to permethrin using the WHO susceptibility test, with a knock down rate of ≤ 50% and mortality of ≤ 30%.

Conclusion: These investigations confirmed epidemic outbreaks in Mweka District caused by malaria with a high mortality rate in children below five years of age.