Malaria diagnosis and treatment administered by teachers in primary schools in Tanzania

A school health programme in Mwera Division, Pangani District included treatment of malaria attacks occurring in children during school time. A combination of symptoms (headache, muscle/joint pains, feeling feverish) and oral temperature > or = 37.5 degrees C was used for the diagnosis of malaria. Chloroquine (25 mg/kg given over 3 days) was used for treatment. Malariometric surveys on children aged 7-15 years (mean 10 years) were conducted once a year (1995-1997). Plasmodium falciparum accounted for 100% of infections and the parasite prevalence varied between 32.7 and 35.3% from 1995 to 1997. The number of malaria cases (cases/1000 registered school children) diagnosed and treated by school teachers was 159 (67) in 1995, 324 (124) in 1996, 348 (128) in 1997 and 339 (108) in 1998. Children in grades 1-4 (age 7-13) accounted for 64.6% of cases. Symptoms and oral temperature were recorded for 1258 children. Of those, 992 (78.9%) complained of fever and at least one other symptom when presenting to teachers, 98 (7.8%) had fever as their only complaint and 168 (13.5%) presented without a perception of fever, but with other symptoms. Of these children, 36 (21.4%) had a temperature > or =37.5 degrees C. The sensitivity of "feeling feverish" was 96.5% with a specificity of 54.5%. The positive predictive value of feeling feverish was 89.9% and the negative predictive value 78.6%. Blood slides were prepared from 55.3 and 37.2% of children diagnosed by teachers during 1995 and 1996, respectively, and 71.4% were found positive. Among children who fulfilled the algorithm criteria 75.0% had a positive blood slide. With little training and regular supervision it was feasible for school teachers to make a presumptive diagnosis of malaria. We conclude that teachers can play a major role in school health programmes and are willing to be involved in health matters as long as they are supported by health and educational authorities.     

The changing epidemiology of malaria in Ifakara Town, southern Tanzania

Between 1995 and 2000 there were marked changes in the epidemiology of malaria in Ifakara, southern Tanzania. We documented these changes using parasitological and clinical data from a series of community- and hospital-based studies involving children up to the age of 5 years. There was a right shift and lowering in the age-specific parasite prevalence in the community-based cohort studies. The incidence of clinical malaria in placebo-receiving infants in additional study cohorts dropped from 0.8 in 1995 to 0.43 episodes per infant per year in 2000, an incidence rate ratio of 0.53 (95% confidence interval: 0.404, 0.70, P<0.0001). At the same time, there was an increase in the total number of malaria admissions and a marked right shift in the age pattern of these admissions (median age in 1995 1.55 years vs. 2.33 in 2000, P<0.0001). However, the burden of malaria deaths remained in infants. We discuss how these dramatic changes in the epidemiology of malaria may have arisen from the use of currently available malaria control tools. Caution is required in the interpretation of hospital-based data as it is likely to underestimate the impact of anaemia on mortality in the community, where most paediatric deaths occur. Even in low/moderate malaria transmission settings, where older children suffer most malaria episodes, targeting effective malaria control at infants may produce important reductions in infant mortality caused by malaria.     

Risk factors for presentation to hospital with severe anaemia in Tanzanian children: a case-control study

In malaria endemic areas anaemia is a usually silent condition that nevertheless places a considerable burden on health services. Cases of severe anaemia often require hospitalization and blood transfusions. The objective of this study was to assess risk factors for admission with anaemia to facilitate the design of anaemia control programmes. We conducted a prospective case-control study of children aged 2-59 months admitted to a district hospital in southern Tanzania. There were 216 cases of severe anaemia [packed cell volume (PCV) < 25%] and 234 age-matched controls (PCV > or = 25%). Most cases [55.6% (n = 120)] were < 1 year of age. Anaemia was significantly associated with the educational level of parents, type of accommodation, health-seeking behaviour, the child's nutritional status and recent and current medical history. Of these, the single most important factor was Plasmodium falciparum parasitaemia [OR 4.3, 95% confidence interval (CI) 2.9-6.5, P < 0.001]. Multivariate analysis showed that increased recent health expenditure [OR 2.2 (95% CI 1.3-3.9), P = 0.005], malnutrition [OR 2.4 (95%CI 1.3-4.3), P < 0.001], living > 10 km from the hospital [OR 3.0 (95% CI 1.9-4.9), P < 0.001], a history of previous blood transfusion [OR 3.8 (95% CI 1.7-9.1), P < 0.001] and P. falciparum parasitaemia [OR 9.5 (95% CI 4.3-21.3), P < 0.001] were independently related to risk of being admitted with anaemia. These findings are considered in terms of the pathophysiological pathway leading to anaemia. The concentration of anaemia in infants and problems of access to health services and adequate case management underline the need for targeted preventive strategies for anaemia control.     

Introducing insecticide-treated nets in the Kilombero Valley, Tanzania: the relevance of local knowledge and practice for an information, education and communication (IEC) campaign

Since 1997 the WHO has been recommending an integrative strategy to combat malaria including new medicines, vaccines, improvements of health care systems and insecticide-treated nets (ITNs). After successful controlled trials with ITNs in the past decade, large-scale interventions and research now focus on operational issues of distribution and financing. In developing a social marketing approach in the Kilombero Valley in south-east Tanzania in 1996, a combination of qualitative and quantitative methods was employed to investigate local knowledge and practice relating to malaria. The findings show that the biomedical concept of malaria overlaps with several local illness concepts, one of which is called malaria and refers to mild malaria. Most respondents linked malaria to mosquitoes (76%) and already used mosquito nets (52%). But local understandings of severe malaria differed from the biomedical concept and were not linked to mosquitoes or malaria. A social marketing strategy to promote ITNs was developed on the basis of these findings, which reinforced public health messages and linked them with nets and insecticide. Although we did not directly evaluate the impact of promotional activities, the sharp rise in ownership and use of ITNs by the population (from 10 to > 50%) suggests that they contributed significantly to the success of the programme. Local knowledge and practice is highly relevant for social marketing strategies of ITNs.     

Polymorphisms in the dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) genes of Plasmodium falciparum and in vivo resistance to sulphadoxine/pyrimethamine in isolates from Tanzania

The efficacy of sulphadoxine/pyrimethamine (S/P) in treatment of uncomplicated falciparum malaria in Africa is increasingly compromised by development of resistance. The occurrence of mutations associated with the active site sequence in the Plasmodium falciparum genes coding for dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) is associated with in vitro resistance to pyrimethamine and sulphadoxine. This study investigates the occurrence of these mutations in infected blood samples taken from Tanzanian children before treatment with S/P and their relationship to parasite breakthrough by day 7. The results show that alleles of DHPS (436-alanine, 437-alanine and 540-lysine) were significantly reduced in prevalence on day 7 after S/P treatment. In this area, a DHPS with 436-serine, 437-glycine and 540-glutamate appears to play a major role in resistance to S/P in vivo . Evidence for the influence of mutations in the DHFR gene in this investigation is not clear, probably because of the high prevalence of 'resistance-related' mutations at day 0 in the local parasite population. For apparently the same reason, it was not possible to show a statistical association between S/P resistance and the presence of particular polymorphisms in the DHFR and DHPS genes before treatment.     

Use of proxy measures in estimating socioeconomic inequalities in malaria prevalence

Objectives To present and compare socioeconomic status (SES) rankings of households using consumption and an asset‐based index as two alternative measures of SES; and to compare and evaluate the performance of these two measures in multivariate analyses of the socioeconomic gradient in malaria prevalence. Methods Data for the study come from a survey of 557 households in 25 study villages in Tanzania in 2004. Household SES was determined using consumption and an asset‐based index calculated using Principal Components Analysis on a set of household variables. In multivariate analyses of malaria prevalence, we also used two other measures of disease prevalence: parasitaemia and self‐report of malaria or fever in the 2 weeks before interview. Results Household rankings based on the two measures of SES differ substantially. In multivariate analyses, there was a statistically significant negative association between both measures of SES and parasitaemia but not between either measure of SES and self‐reported malaria. Age of individual, use of a mosquito net, and wall construction were negatively and significantly associated with parasitaemia, whilst roof construction was positively associated with parasitaemia. Only age remained significant when malaria self‐report was used as the measure of disease prevalence. Conclusions An asset index is an effective alternative to consumption in measuring the socioeconomic gradient in malaria parasitaemia, but self‐report may be an unreliable measure of malaria prevalence for this purpose.     

Diagnostic accuracy and case management of clinical malaria in the primary health services of a rural area in south-eastern Tanzania

Malaria control continues to rely on the diagnosis and prompt treatment of both suspected and confirmed cases through the health care structures. In south-eastern Tanzania malaria is one of the leading causes of morbidity and mortality. The absence of microscopic examination in most of the health facilities implies that health workers must rely on clinical suspicion to identify the need of treatment for malaria. Of 1558 randomly selected paediatric consultations at peripheral health facilities throughout Kilombero District, 41.1% were diagnosed by the attending health worker as clinical malaria cases and 42.5% prescribed an antimalarial. According to our malaria case definition of fever or history of fever with asexual falciparum parasitaemia of any density, 25.5% of all children attending the health services had malaria. This yielded a sensitivity of 70.4% (IC95% = 65.9-74.8%) and a specificity of 68.9% (IC95% = 66.2-71.5%). Accordingly, 30.4% of confirmed cases left with no antimalarial treatment. Among malaria-diagnosed patients, 10% were underdosed and 10.5% were overdosed. In this area, as in many African rural areas, the low diagnostic accuracy may imply that the burden of malaria cases may be overestimated. Greater emphasis on the functioning and quality of basic health services in rural endemic areas is required if improved case management of malaria is to help roll back this scourge.     

A comparison of use of a pyrethroid either for house spraying or for bednet treatment against malaria vectors

In an intensely malarious area in north-east Tanzania, microencapsulated lambdacyhalothrin was used in four villages for treatment of bednets (provided free of charge) and in another four villages the same insecticide was used for house spraying. Another four villages received neither intervention until the end of the trial but were monitored as controls. Bioassays showed prolonged persistence of the insecticidal residues. Light traps and ELISA testing showed reduction of the malaria vector populations and the sporozoite rates, leading to a reduction of about 90% in the entomological inoculation rate as a result of each treatment. Collections of blood fed mosquitoes showed no diversion from biting humans to biting animals. Incidence of re-infection was measured by weekly monitoring of cohorts of 60 children per village, after clearing pre-existing infection with chlorproguanil-dapsone. The vector control was associated with a reduction in probability of re-infection per child per week by 54–62%, with no significant difference between the two vector control methods. Cross-sectional surveys for fever, parasitaemia, haemoglobin and weight showed association of high parasitaemia with fever and anaemia and beneficial effects of each intervention in reducing anaemia. However, passive surveillance by resident health assistants showed no evidence for reduced prevalence of fever or parasitaemia. Net treatment consumed only about one sixth as much insecticide as house spraying and it was concluded that the former intervention would work out cheaper and nets were actively demanded by the villagers, whereas spraying was only passively assented to.     

Economic burden of malaria in rural Tanzania: variations by socioeconomic status and season

OBJECTIVE: To determine the economic burden of malaria in a rural Tanzanian setting and identify any differences by socioeconomic status and season. METHODS: Interviews of 557 households in south eastern Tanzania between May and December 2004, on consumption and malaria-related costs. RESULTS: Malaria-related expenses were significantly higher in the dry, non-malarious season than in the rainy season. Households sought treatment more frequently and from more expensive service providers in the dry season, when they have more money. Malaria expenses did not vary significantly across socioeconomic status quintiles, but poorer households spent a higher proportion of their consumption in both seasons. CONCLUSION: Poorer households bear a greater economic burden from malaria relative to their consumption than better-off households. Households are particularly vulnerable to malaria in the rainy season, when malaria prevalence is highest but liquidity is lower. Alternative strategies to assist households to cope with seasonal liquidity issues, including insurance, should be investigated.     

Assessing the validity of health facility-based data on insecticide-treated bednet possession and use: comparison of data collected via health facility and household surveys--Lindi region and Rufiji district, Tanzania, 2005

Objective To assess the validity of health facility (HF)-based data on bednet and insecticide-treated bednet possession and use by children <5 years old. Methods We compared estimates based on data collected via HF surveys of under-5s attending well-child visits (e.g. immunizations) and sick-child visits vs. representative household surveys (a 'gold standard' method for measuring insecticide-treated net coverage). In Lindi region, Tanzania, we collected contemporaneous data on 637 under-5s via a HF survey (444 well-child visits and 193 sick-child visits), and on 305 households with an under-5 (including 354 children) via a household survey. In Rufiji district, Tanzania, we collected contemporaneous data on 1433 under-5s via a HF survey (911 well-child visits and 522 sick-child visits), and on 328 households with an under-5 (including 455 children) via a household survey. Results Possession of bednets by households with an under-5 was similar using HF data and household data in both Lindi region and Rufiji district. However, reported use of bednets was significantly higher in HF data than household data in both Lindi and Rufiji, as was reported use of insecticide-treated bednets. HF-based data accurately estimated community-level bednet possession in households with an under-5, but overestimated community-level bednet use by 9-35% and insecticide-treated bednet use by 15-21%. Conclusions Information bias rather than selection bias appears to be a key cause for the overestimation of bednet and insecticide-treated bednet use (e.g. social desirability bias: caretakers of under-5s attending health facilities might be more likely to report using bednets and insecticide-treated bednets). Additional studies of the validity, cost and utility of HF-based data to monitor insecticide-treated bednet use are needed before recommending this monitoring strategy for widespread use. Overestimating insecticide-treated bednet use could lead to inappropriate public health actions and missed opportunities for achieving local and global public health goals.     

黔桂疟疾联防区20年疟疾防治效果评价

黔桂疟疾联防区２４个县,是两省（区）的边陲山区,也是两省（区）最严重的恶性疟和间日疟混合流行的疟疾高发区。经过联防２０年的同步防治,疟疾发病率从１９７５年的１１１．９４降至１９９５年的１．８７,年带虫发病率也降至１．４７,已无当地感染的恶性疟病例,经考核有８个县达到卫生部《基本消灭疟疾标准》     

Socially marketed insecticide-treated nets improve malaria and anaemia in pregnancy in southern Tanzania

OBJECTIVES: To study the uptake of socially marketed insecticide-treated nets (ITNs) and their impact on malaria and anaemia in pregnancy; and to report on a discount voucher system which aimed to increase coverage in pregnancy. METHODS: A 12-month cross-sectional study of women in the second or third trimester of pregnancy. ITN use and other factors were assessed by questionnaire and a blood sample taken for malaria parasitaemia and anaemia. 'Non-users' of ITNs included both women not using any net and women using untreated nets. RESULTS: Fifty three per cent of pregnant women used ITNs. Women aged 15-19, primigravidae, unmarried women, and those with no access to cash had the lowest ITN use. Fewer ITN users were positive for malaria than ITN non-users (25 vs. 33%: P=0.06), and the protective efficacy (PE) for parasitaemia was 23% (CI 2-41). Multiparous ITN users had a twofold decrease in parasite density compared with multiparous non-ITN users (625 parasites/microl vs. 1173 parasited/microl: P=0.01). Fewer ITN users were anaemic (Hb < 11 g/dl) than ITN non-users (72 vs. 82%: P=0.01). ITNs had a PE of 12% (CI 2-21) against mild anaemia and a PE of 38% (CI 4-60) against severe anaemia (Hb < 8 g/dl). There was a trend in the prevalence of severe, mild and no anaemia, and of high density, low density and no malaria infection by ITN status. Recently treated nets were most effective at preventing malaria and anaemia (prevalence of mild anaemia was 68% compared with 82% for those without nets (P=0.002); prevalence of malaria was 22% compared with 33% for those without nets (P=0.02). Knowledge and reported use of the discount voucher system were low. Further qualitative research is ongoing. CONCLUSIONS: A modest impact of ITNs on pregnancy malaria and anaemia was shown in our high malaria transmission setting. The development of ITN programmes for malaria control should include pregnant women as a specific target group.     

Mosquito nets and the poor: can social marketing redress inequities in access?

Treated mosquito nets are a practical malaria control tool. However, implementation of efficient delivery mechanisms remains a challenge. We investigated whether social marketing of treated mosquito nets results in decreased equity in rural Tanzania, through household surveys before the start of a social marketing programme and 3 years later. About 12,000 household heads were asked about ownership of nets and other assets including a tin roof, radio, or bicycle. A socio-economic status score was developed for each household. Net ownership was calculated for households in each quintile of this score, from poorest to least poor. In 1997, about 20% of the poorest households and over 60% of the least poor households owned a mosquito net. Three years later, more than half of the poorest households owned a net, as did over 90% of the least poor: the ratio of net ownership among the poorest to least poor increased from 0.3 in 1997 to 0.6 in 2000. Social marketing in the presence of an active private sector for nets was associated with increased equity.     

In vivo efficacy study of amodiaquine and sulfadoxine/ pyrimethamine in Kibwezi, Kenya and Kigoma, Tanzania

We conducted two randomized clinical trials to determine the in vivo efficacy of amodiaquine and sulfadoxine/pyrimethamine in treating Plasmodium falciparum malaria. Seventy-five patients under the age of 10 years in Kibwezi, Kenya, and 171 patients in Kigoma, Tanzania, were enrolled for treatment. Due to loss of eight patients in Kibwezi and 37 in Kigoma to follow-up, we used best and worst case scenarios for the parasitological response. The in vivo sensitivity of Plasmodium falciparum to amodiaquine was 75% (no loss to follow-up) in Kibwezi and ranged from 85% in the best to 65% in the worst case scenario in Kigoma. The sensitivity to sulfadoxine/pyrimethamine was 70% to 88% in Kibwezi and 65% to 89% in Kigoma. R1 resistance to amodiaquine was 22% in Kibwezi and varied from 6% in the best to 26% for the worst case scenario in Kigoma. The R1 resistance to sulfadoxine/pyrimethamine was 5% to 23% in Kibwezi and 2% to 26% in Kigoma. R2 resistance was 3% for amodiaquine and 7% for sulfadoxine/pyrimethamine in Kibwezi and 9% in Kigoma for each treatment group. There was no statistically significant difference between treatment groups at either study site, except for a slight difference in R1 resistance in the best case scenario, Kibwezi, in favour of S/P. Although both amodiaquine and sulfadoxine/pyrimethamine resistance seems to be increasing, these antimalarials are still effective in parasite clearance.     

Retail supply of malaria-related drugs in rural Tanzania: risks and opportunities

OBJECTIVES: To characterize availability of fever and malaria medicines within the retail sector in rural Tanzania, assess the likely public health implications, and identify opportunities for policy interventions to increase the coverage of effective treatment. METHODS: A census of retailers selling drugs was undertaken in the areas under demographic surveillance in four Tanzanian districts, using a structured questionnaire. RESULTS: Drugs were stocked by two types of retailer: a large number of general retailers (n = 675) and a relatively small number of drug shops (n = 43). Almost all outlets stocked antipyretics/painkillers. One-third of general retailers stocking drugs had antimalarials, usually chloroquine alone. Almost all drug shops stocked antimalarials (98%): nearly all had chloroquine, 42% stocked quinine, 37% sulphadoxine-pyrimethamine and 30% amodiaquine. A large number of antimalarial brands were available. Population ratios indicate the relative accessibility of retail drug providers compared with health facilities. Drug shop staff generally travelled long distances to buy from drugs wholesalers or pharmacies. General retailers bought mainly from local general wholesalers, with a few general wholesalers accounting for a high proportion of all sources cited. CONCLUSIONS: Drugs were widely available from a large number of retail outlets. Potential negative implications include provision of ineffective drugs, confusion over brand names, uncontrolled use of antimalarials, and the availability of components of potential combination therapy regimens as monotherapies. On the other hand, this active and highly accessible retail market provides opportunities for improving the coverage of effective antimalarial treatment. Interventions targeted at all drug retailers are likely to be costly to deliver and difficult to sustain, but two promising points for targeted intervention are drug shops and selected general wholesalers. Retail quality may also be improved through consumer education, and modification of the chemical quality, packaging and price of products entering the retail distribution chain.     

The immunology of malaria—a view from the bush

During the past few years a great deal has been learnt about malaria parasites and the immune responses that they evoke in their hosts. However, this new knowledge has so far had little impact on the practical problems of malaria control in tropical developing countries where malaria is still responsible for much mortality and morbidity. In Africa the malaria situation is now more serious than it was 20 years ago. Exciting new developments in molecular biology suggest that this situation may change in a few years time but attempts should be made to put the advances that have been made to the best practical use as soon as possible rather than delaying until even better technologies have been developed. This approach will require close collaboration between immunologists in sophisticated laboratories in industrialised countries and smaller laboratories in the countries of the developing world where malaria is still a major problem.