Comparison of mosquito nets, proguanil hydrochloride, and placebo to prevent malaria

Comparative effectiveness of malaria prevention measures: a systematic review and network meta-analysis

Background

Malaria causes significant morbidity and mortality worldwide. There are several preventive measures that are currently employed, including insecticide-treated nets (ITNs, including long-lasting insecticidal nets and insecticidal-treated bed nets), indoor residual spraying (IRS), prophylactic drugs (PD), and untreated nets (UN). However, it is unclear which measure is the most effective for malaria prevention. We therefore undertook a network meta-analysis to compare the efficacy of different preventive measures on incidence of malaria infection.

Methods

A systematic literature review was undertaken across four medical and life sciences databases (PubMed, Cochrane Central, Embase, and Web of Science) from their inception to July 2016 to compare the effectiveness of different preventive measures on malaria incidence. Data from the included studies were analysed for the effectiveness of several measures against no intervention (NI). This was carried out using an automated generalized pairwise modeling (GPM) framework for network meta-analysis to generate mixed treatment effects against a common comparator of no intervention (NI).

Results

There were 30 studies that met the inclusion criteria from 1998–2016. The GPM framework led to a final ranking of effectiveness of measures in the following order from best to worst: PD, ITN, IRS and UN, in comparison with NI. However, only ITN (RR: 0.49, 95% CI: 0.32–0.74) showed precision while other methods [PD (RR: 0.24, 95% CI: 0.004–15.43), IRS (RR: 0.55, 95% CI: 0.20–1.56) and UN (RR: 0.73, 95% CI: 0.28–1.90)] demonstrating considerable uncertainty associated with their point estimates.

Conclusion

Current evidence is strong for the protective effect of ITN interventions in malaria prevention. Even though ITNs were found to be the only preventive measure with statistical support for their effectiveness, the role of other malaria control measures may be important adjuncts in the global drive to eliminate malaria.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2783-y) contains supplementary material, which is available to authorized users.

Malaria in school-age children in Africa: an increasingly important challenge

School-age children have attracted relatively little attention as a group in need of special measures to protect them against malaria. However, increasing success in lowering the level of malaria transmission in many previously highly endemic areas will result in children acquiring immunity to malaria later in life than has been the case in the past. Thus, it can be anticipated that in the coming years there will be an increase in the incidence of both uncomplicated and severe malaria in school-age children in many previously highly endemic areas. In this review, which focuses primarily on Africa, recent data on the prevalence of malaria parasitaemia and on the incidence of clinical malaria in African school-age children are presented and evidence that malaria adversely effects school performance is reviewed. Long-lasting insecticide treated bednets (LLIN) are an effective method of malaria control but several studies have shown that school-age children use LLINs less frequently than other population groups. Antimalarial drugs are being used in different ways to control malaria in school-age children including screening and treatment and intermittent preventive treatment. Some studies of chemoprevention in school-age children have shown reductions in anaemia and improved school performance but this has not been the case in all trials and more research is needed to identify the situations in which chemoprevention is likely to be most effective and, in these situations, which type of intervention should be used. In the longer term, malaria vaccines may have an important role in protecting this important section of the community from malaria. Regardless of the control approach selected, it is important this is incorporated into the overall programme of measures being undertaken to enhance the health of African school-age children.

Plasmodium infection, anaemia and mosquito net use among school children across different settings in Kenya

OBJECTIVE

To investigate risk factors, including reported net use, for Plasmodium infection and anaemia among school children and to explore variations in effects across different malaria ecologies occurring in Kenya.

METHODS

This study analysed data for 49 975 school children in 480 schools surveyed during a national school malaria survey, 2008-2010. Mixed effects logistic regression was used to investigate factors associated with Plasmodium infection and anaemia within different malaria transmission zones.

RESULTS

Insecticide-treated net (ITN) use was associated with reduction in the odds of Plasmodium infection in coastal and western highlands epidemic zones and among boys in the lakeside high transmission zone. Other risk factors for Plasmodium infection and for anaemia also varied by zone. Plasmodium infection was negatively associated with increasing socio-economic status in all transmission settings, except in the semi-arid north-east zone. Plasmodium infection was a risk factor for anaemia in lakeside high transmission, western highlands epidemic and central low-risk zones, whereas ITN use was only associated with lower levels of anaemia in coastal and central zones and among boys in the lakeside high transmission zone.

CONCLUSIONS

The risk factors for Plasmodium infection and anaemia, including the protective associations with ITN use, vary according to malaria transmission settings in Kenya, and future efforts to control malaria and anaemia should take into account such heterogeneities among school children.

Assessment of the effect of insecticide-treated nets and indoor residual spraying for malaria control in three rural kebeles of Adami Tulu District, South Central Ethiopia

Background

In the Adami Tulu District, indoor residual spraying (IRS) and insecticide-treated nets (ITNs) has been the main tool used to control malaria. The purpose of this study was to assess the effect of IRS and ITNs control strategies in Aneno Shisho kebele (lowest administrative unit of Ethiopia) compared with Kamo Gerbi (supplied ITN only) and Jela Aluto (no IRS and ITNs), with regards to the prevalence of malaria and mosquito density.

Methods

Cross-sectional surveys were conducted after heavy rains (October/November, 2006) and during the sporadic rains (April, 2007) in the three kebeles of Adami Tulu District. Malaria infection was measured by means of thick and thin film. Monthly collection of adult mosquitoes from October-December 2006 and April-May 2007 and sporozoite enzyme-linked immunosorbent assay (ELISA) on the collected mosquitoes were detected. Data related to the knowledge of mode of malaria transmission and its control measures were collected. Data collected on parasitological and knowledge, attitude and practice (KAP) surveys were managed and analysed using a statistical computer program SPSS version 13.0. A P-value <0.05 was considered to be statistically significant.

Results

The overall prevalence of malaria was 8.6% in Jela Aluto, 4.4% in Kamo Gerbi and 1.3% in Aneno Shisho in the two season surveys. The vector, Anopheles gambiae s.l., Anopheles pharoensis and Anopheles coustani were recorded. However, sporozoite ELISA on mosquito collections detected no infection. The difference in overall malaria prevalence and mosquito density between the three kebeles was significant (P<0.05).

Conclusions

The present study has provided some evidence for the success of ITNs/IRS combined malaria control measures in Aneno Shisho kebele in Adami Tulu District. Therefore, the combined ITNs/IRS malaria control measures must be expanded to cover all kebeles in the District of Ethiopia.

Intermittent preventive treatment for malaria in children living in areas with seasonal transmission

BACKGROUND

In malaria endemic areas, pre-school children are at high risk of severe and repeated malaria illness. One possible public health strategy, known as Intermittent Preventive Treatment in children (IPTc), is to treat all children for malaria at regular intervals during the transmission season, regardless of whether they are infected or not.

OBJECTIVES

To evaluate the effects of IPTc to prevent malaria in preschool children living in endemic areas with seasonal malaria transmission.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register (July 2011), CENTRAL (The Cochrane Library 2011, Issue 6), MEDLINE (1966 to July 2011), EMBASE (1974 to July 2011), LILACS (1982 to July 2011), mRCT (July 2011), and reference lists of identified trials. We also contacted researchers working in the field for unpublished and ongoing trials.

SELECTION CRITERIA

Individually randomized and cluster-randomized controlled trials of full therapeutic dose of antimalarial or antimalarial drug combinations given at regular intervals compared with placebo or no preventive treatment in children aged six years or less living in an area with seasonal malaria transmission.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed eligibility, extracted data and assessed the risk of bias in the trials. Data were meta-analysed and measures of effects (ie rate ratio, risk ratio and mean difference) are presented with 95% confidence intervals (CIs). The quality of evidence was assessed using the GRADE methods.

MAIN RESULTS

Seven trials (12,589 participants), including one cluster-randomized trial, met the inclusion criteria. All were conducted in West Africa, and six of seven trials were restricted to children aged less than 5 years.IPTc prevents approximately three quarters of all clinical malaria episodes (rate ratio 0.26; 95% CI 0.17 to 0.38; 9321 participants, six trials, high quality evidence), and a similar proportion of severe malaria episodes (rate ratio 0.27, 95% CI 0.10 to 0.76; 5964 participants, two trials, high quality evidence). These effects remain present even where insecticide treated net (ITN) usage is high (two trials, 5964 participants, high quality evidence).IPTc probably produces a small reduction in all-cause mortality consistent with the effect on severe malaria, but the trials were underpowered to reach statistical significance (risk ratio 0.66, 95% CI 0.31 to 1.39, moderate quality evidence).The effect on anaemia varied between studies, but the risk of moderately severe anaemia is probably lower with IPTc (risk ratio 0.71, 95% CI 0.52 to 0.98; 8805 participants, five trials, moderate quality evidence).Serious drug-related adverse events, if they occur, are probably rare, with none reported in the six trials (9533 participants, six trials, moderate quality evidence). Amodiaquine plus sulphadoxine-pyrimethamine is the most studied drug combination for seasonal chemoprevention. Although effective, it causes increased vomiting in this age-group (risk ratio 2.78, 95% CI 2.31 to 3.35; two trials, 3544 participants, high quality evidence).When antimalarial IPTc was stopped, no rebound increase in malaria was observed in the three trials which continued follow-up for one season after IPTc.

AUTHORS' CONCLUSIONS

In areas with seasonal malaria transmission, giving antimalarial drugs to preschool children (age < 6 years) as IPTc during the malaria transmission season markedly reduces episodes of clinical malaria, including severe malaria. This benefit occurs even in areas where insecticide treated net usage is high.

Costs and cost-effectiveness of delivering intermittent preventive treatment through schools in western Kenya

BACKGROUND

Awareness of the potential impact of malaria among school-age children has stimulated investigation into malaria interventions that can be delivered through schools. However, little evidence is available on the costs and cost-effectiveness of intervention options. This paper evaluates the costs and cost-effectiveness of intermittent preventive treatment (IPT) as delivered by teachers in schools in western Kenya.

METHODS

Information on actual drug and non-drug associated costs were collected from expenditure and salary records, government budgets and interviews with key district and national officials. Effectiveness data were derived from a cluster-randomised-controlled trial of IPT where a single dose of sulphadoxine-pyrimethamine and three daily doses of amodiaquine were provided three times in year (once termly). Both financial and economic costs were estimated from a provider perspective, and effectiveness was estimated in terms of anaemia cases averted. A sensitivity analysis was conducted to assess the impact of key assumptions on estimated cost-effectiveness.

RESULTS

The delivery of IPT by teachers was estimated to cost US$ 1.88 per child treated per year, with drug and teacher training costs constituting the largest cost components. Set-up costs accounted for 13.2% of overall costs (equivalent to US$ 0.25 per child) whilst recurrent costs accounted for 86.8% (US$ 1.63 per child per year). The estimated cost per anaemia case averted was US$ 29.84 and the cost per case of Plasmodium falciparum parasitaemia averted was US$ 5.36, respectively. The cost per case of anaemia averted ranged between US$ 24.60 and 40.32 when the prices of antimalarial drugs and delivery costs were varied. Cost-effectiveness was most influenced by effectiveness of IPT and the background prevalence of anaemia. In settings where 30% and 50% of schoolchildren were anaemic, cost-effectiveness ratios were US$ 12.53 and 7.52, respectively.

CONCLUSION

This study provides the first evidence that IPT administered by teachers is a cost-effective school-based malaria intervention and merits investigation in other settings.

Chemoprophylaxis and intermittent treatment for preventing malaria in children

BACKGROUND

Malaria causes repeated illness in children living in endemic areas. Policies of giving antimalarial drugs at regular intervals (prophylaxis or intermittent treatment) are being considered for preschool children.

OBJECTIVES

To evaluate prophylaxis and intermittent treatment with antimalarial drugs to prevent malaria in young children living in malaria-endemic areas.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (August 2007), CENTRAL (The Cochrane Library 2007, Issue 3), MEDLINE (1966 to August 2007), EMBASE (1974 to August 2007), LILACS (1982 to August 2007), mRCT (February 2007), and reference lists of identified trials. We also contacted researchers.

SELECTION CRITERIA

Individually randomized and cluster-randomized controlled trials comparing antimalarial drugs given at regular intervals (prophylaxis or intermittent treatment) with placebo or no drug in children aged one month to six years or less living in a malaria-endemic area.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed methodological quality. We used relative risk (RR) or weighted mean difference with 95% confidence intervals (CI) for meta-analyses. Where we detected heterogeneity and considered it appropriate to combine the trials, we used the random-effects model (REM).

MAIN RESULTS

Twenty-one trials (19,394 participants), including six cluster-randomized trials, met the inclusion criteria. Prophylaxis or intermittent treatment with antimalarial drugs resulted in fewer clinical malaria episodes (RR 0.53, 95% CI 0.38 to 0.74, REM; 7037 participants, 10 trials), less severe anaemia (RR 0.70, 95% CI 0.52 to 0.94, REM; 5445 participants, 9 trials), and fewer hospital admissions for any cause (RR 0.64, 95% CI 0.49 to 0.82; 3722 participants, 5 trials). We did not detect a difference in the number of deaths from any cause (RR 0.90, 95% CI 0.65 to 1.23; 7369 participants, 10 trials), but the CI do not exclude a potentially important difference. One trial reported three serious adverse events with no statistically significant difference between study groups (1070 participants). Eight trials measured morbidity and mortality six months to two years after stopping regular antimalarial drugs; overall, there was no statistically significant difference, but participant numbers were small.

AUTHORS' CONCLUSIONS

Prophylaxis and intermittent treatment with antimalarial drugs reduce clinical malaria and severe anaemia in preschool children.

Malaria in adolescence: burden of disease, consequences, and opportunities for intervention

The problem of malaria in adolescence has largely been overshadowed by the huge burden of disease in young children. A substantial number of adolescents are at risk from malaria infection, but the burden of disease and consequences of infection in this age-group have rarely been studied. Our understanding of specific risk factors and beneficial interventions for adolescents is also limited. Data show that, from an adolescent viewpoint, malaria is a common cause of clinical illness and a preventable cause of death, even in areas of stable malaria transmission. Younger adolescents might be at a higher risk than older adolescents, because of immunological and hormonal factors. There are limited data about the adverse consequences of malaria in non-pregnant adolescents. However, in pregnant adolescents, the consequences of malaria are of great concern and simple interventions might lead to a substantial benefit. Malaria infection in adolescents is an under-recognised problem, and the prevention, diagnosis, and treatment of malaria should have a high priority within adolescent health programmes.

Chemoprophylaxis and intermittent treatment for preventing malaria in children

BACKGROUND

Malaria causes repeated illness in children living in endemic areas. Policies of giving antimalarial drugs at regular intervals (prophylaxis or intermittent treatment) are being considered for preschool children.

OBJECTIVES

To evaluate chemoprophylaxis and intermittent treatment with antimalarial drugs to prevent malaria in young children living in malaria endemic areas.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (April 2005), CENTRAL (The Cochrane Library Issue 1, 2005), MEDLINE (1966 to April 2005), EMBASE (1974 to April 2005), LILACS (1982 to April 2005), and reference lists of identified trials. We also contacted researchers.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing antimalarial drugs given at regular intervals (prophylaxis or intermittent treatment) with placebo or no drug in children aged one month to six years or less living in an area where malaria is endemic.

DATA COLLECTION AND ANALYSIS

We independently extracted data and assessed methodological quality. We used relative risk (RR) or weighted mean difference with 95% confidence intervals (CI) for meta-analyses. Where we detected heterogeneity and considered it appropriate to combine the trials, we used the random-effects model (REM).

MAIN RESULTS

Nineteen trials (14,393 participants) met the inclusion criteria. Children receiving antimalarial drugs as prophylaxis or intermittent treatment had fewer clinical malaria episodes (RR 0.52, 95% CI 0.35 to 0.77, REM; 4051 participants, 8 trials), and severe anaemia was less common (RR 0.54, 95% CI 0.42 to 0.68; 2727 participants, 8 trials). We did not detect a difference in the number of deaths from any cause (RR 0.82, 95% CI 0.65 to 1.04; 7929 participants, 9 trials), but the confidence intervals do not exclude a potentially important difference. None of the trials reported serious adverse events. Three trials measured morbidity and mortality six months to two years after stopping regular antimalarial drugs; overall, there was no statistically significant difference, but participant numbers were small.

AUTHORS' CONCLUSIONS

Prophylaxis and intermittent treatment with antimalarial drugs reduce clinical malaria and severe anaemia in preschool children. There is insufficient evidence to detect an effect on mortality.

Insecticide-treated bed nets and curtains for preventing malaria

BACKGROUND

Malaria is an important cause of illness and death in many parts of the world, especially in sub-Saharan Africa. There has been a renewed emphasis on preventive measures at community and individual levels. Insecticide-treated nets (ITNs) are the most prominent malaria preventive measure for large-scale deployment in highly endemic areas.

OBJECTIVES

To assess the impact of insecticide-treated bed nets or curtains on mortality, malarial illness (life-threatening and mild), malaria parasitaemia, anaemia, and spleen rates.

SEARCH STRATEGY

I searched the Cochrane Infectious Diseases Group trials register (January 2003), CENTRAL (The Cochrane Library, Issue 1, 2003), MEDLINE (1966 to October 2003), EMBASE (1974 to November 2002), LILACS (1982 to January 2003), and reference lists of reviews, books, and trials. I handsearched journals, contacted researchers, funding agencies, and net and insecticide manufacturers.

SELECTION CRITERIA

Individual and cluster randomized controlled trials of insecticide-treated bed nets or curtains compared to nets without insecticide or no nets. Trials including only pregnant women were excluded.

DATA COLLECTION AND ANALYSIS

The reviewer and two independent assessors reviewed trials for inclusion. The reviewer assessed trial methodological quality and extracted and analysed data.

MAIN RESULTS

Fourteen cluster randomized and eight individually randomized controlled trials met the inclusion criteria. Five trials measured child mortality: ITNs provided 17% protective efficacy (PE) compared to no nets (relative rate 0.83, 95% confidence interval (CI) 0.76 to 0.90), and 23% PE compared to untreated nets (relative rate 0.77, 95% CI 0.63 to 0.95). About 5.5 lives (95% CI 3.39 to 7.67) can be saved each year for every 1000 children protected with ITNs. In areas with stable malaria, ITNs reduced the incidence of uncomplicated malarial episodes in areas of stable malaria by 50% compared to no nets, and 39% compared to untreated nets; and in areas of unstable malaria: by 62% for compared to no nets and 43% compared to untreated nets for Plasmodium falciparum episodes, and by 52% compared to no nets and 11% compared to untreated nets for P. vivax episodes. When compared to no nets and in areas of stable malaria, ITNs also had an impact on severe malaria (45% PE, 95% CI 20 to 63), parasite prevalence (13% PE), high parasitaemia (29% PE), splenomegaly (30% PE), and their use improved the average haemoglobin level in children by 1.7% packed cell volume.

REVIEWERS' CONCLUSIONS

ITNs are highly effective in reducing childhood mortality and morbidity from malaria. Widespread access to ITNs is currently being advocated by Roll Back Malaria, but universal deployment will require major financial, technical, and operational inputs.

The cost of not treating bednets

For centuries, bednets have been used as a physical barrier against biting insects. Recent epidemiological investigations into their protective effects against malaria were quickly overtaken by studies focusing on the benefits of impregnating bednets with insecticide. The operational problems encountered in re-treating bednets with insecticide are often cited as an impediment to wide-scale implementation. The evidence for a protective effect of untreated nets against malaria is presented here alongside an analysis of how well untreated nets would need to work in order to compete with treated nets within a cost-effectiveness framework.

Do untreated bednets protect against malaria?

Bednets are thought to offer little, if any, protection against malaria, unless treated with insecticide. There is also concern that the use of untreated nets will cause people sleeping without nets to receive more mosquito bites, and thus increase the malaria risk for other community members. Regular retreatment of nets is therefore viewed as critical for malaria control. However, despite good uptake of nets, many control programmes in Africa have reported low re-treatment rates. We investigated whether untreated bednets had any protective benefit (in October and November 1996) in The Gambia where nets, although widely used, are mostly untreated. Cross-sectional prevalence surveys were carried out in 48 villages and the risk of malaria parasitaemia was compared in young children sleeping with or without nets. Use of an untreated bednet in good condition was associated with a significantly lower prevalence of Plasmodium falciparum infection (51% protection [95% CI 34-64%], P < 0.001). This finding was only partly explained by differences in wealth between households, and children in the poorest households benefited most from sleeping under an untreated net (62% protection [14-83%], P = 0.018). There was no evidence that mosquitoes were diverted to feed on children sleeping without nets. These findings suggest that an untreated net, provided it is in relatively good condition, can protect against malaria. Control programmes should target the poorest households as they may have the most to gain from using nets.

Insecticide-treated bednets and curtains for preventing malaria

BACKGROUND

Malaria is an important cause of illness and death in many parts of the world, especially in Africa. There has been a renewed emphasis on preventive measures, both at community and at individual level. Insecticide treated bednets and curtains are a promising preventive measure.

OBJECTIVES

The objective of this review was to assess the effects of insecticide-treated bednets or curtains in preventing malaria

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group trials register, Medline, Embase and the reference lists of articles. We handsearched journals, contacted researchers, funding agencies and net and insecticide manufacturers.

SELECTION CRITERIA

Randomized and quasi-randomized trials of insecticide-treated bednets or curtains with a sufficient dose of a suitable insecticide compared with nets without insecticide or no nets at all. Studies including pregnant women were excluded.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed and data extracted by the reviewer. Trial inclusions/exclusions were reviewed by two independent individuals.

MAIN RESULTS

Of 65 identified studies, 18 were included. Of these, 11 were randomized by cluster rather than individually. Mortality in children under five was measured in four trials. When impregnated nets were compared with plain nets or no nets, the summary relative risk was 0. 83. This translates to an estimate of protective efficacy of 17%. For treated nets compared with untreated nets, the relative risk of child mortality was 0.77. About six lives can be saved each year for every 1000 children protected with insecticide-treated nets. Insecticide-treated nets also reduced the incidence of mild malarial episodes by 48% (controls=no nets) and 34% (controls=untreated nets).

REVIEWER'S CONCLUSIONS

Insecticide-treated nets appear to be effective in reducing childhood mortality and morbidity from malaria. Widespread access to insecticide-treated nets will require major financial, technical and operational inputs.

Illness in Journalists and Relief Workers Involved in International Humanitarian Assistance Efforts in Somalia, 1992-93

Background: Journalists and relief workers participating in international relief efforts in Somalia following the intervention of outside armed forces in late 1992, were faced with a number of threats to their health. Principally these threats were from endemic infectious diseases and trauma. Methods: In-patient, emergency clinic, and laboratory records of U.S. military field hospitals, which provided the only available sophisticated medical care in Somalia during most of the study period (December 15, 1992, to February 15, 1993), were reviewed to determine the number of workers evaluated and the causes of their illnesses. In addition, two questionnaire surveys were conducted to elucidate risk factors for illness in these groups. Results: One hundred and thirty-eight journalists and relief workers, primarily from Europe and North America, were evaluated at a hospital for a variety of common travel-associated health problems, including diarrhea (33%), acute respiratory infection (21%), other febrile illnesses (11%), hepatitis (2%), major trauma (6%), and minor trauma (13%). Documented infectious disease pathogens included Plasmodium falciparum (7 cases), Shigella sp (3 cases), enterotoxigenic Escherichia coli (ETEC) (3 cases), dengue virus-2 (2 cases), and hepatitis E virus (3 cases). Two relief workers were killed by gunshot wounds. In the questionnaire surveys of 104 journalists and 98 relief workers, 84% of respondents reported that they had received some pretravel medical advice, but only 70% sought a medical consultation in person. Thirty-four percent were not receiving a recommended antimalarial chemoprophylaxis regimen, and only 10% obtained a fluoroquinolone antimicrobial drug for self treatment of diarrhea. Sixty-four percent of both groups combined, reported having had diarrhea, and 26% experienced a nondiarrheal febrile illness. Sixty-eight percent reported that their work performance was adversely affected by illness. In multivariate logistic regression analyses, factors associated with an increased risk of diarrhea were age < 35 years (OR 1.5, 95% CI 1.1-1.9); residence in Somalia for more than 21 days (OR 1.7, 95% CI 1.3-2.1); and regular consumption of local food and water (OR 3.8, 95% CI 3.4-4.2). Factors associated with nondiarrheal febrile illness were age < 35 years (OR 1.4, 95% CI 1.1-1.8); residence in Somalia for more than 21 days (OR 1.8, 95% CI 1.4-2.2); and not having had an in-person pretravel medical consultation (OR 2.0, 95% CI 1.5-3.0). Conclusions: These data indicate that journalists and relief workers who traveled to Somalia in response to the massive humanitarian crisis themselves experienced substantial health problems. Improved pretravel medical preparation might prevent or limit illness in these unique groups and improve the efficiency of future disaster response efforts. (J Travel Med 2:70-76, 1995)

Metabolic disposition of proguanil in extensive and poor metabolisers of S-mephenytoin 4'-hydroxylation recruited from an Indonesian population

1. The metabolism of proguanil (PG) was studied by measuring PG, cycloguanil (CG) and 4-chlorophenylbiguanide (CPB) in plasma and urine samples after an oral 200 mg dose of PG hydrochloride administered to 14 extensive (EMs) and 10 poor hydroxylators (PMs) of S-mephenytoin of Indonesian origin. 2. The mean ( +/- s.d.) values of the elimination half-life (t 1/2) and AUC of PG were significantly (P < 0.01) greater in the PM than in the EM group (20.6 +/- 3.1 vs 14.6 +/- 3.5 (95% confidence intervals of difference 3.1 to 8.9) h; and 5.43 +/- 1.89 vs 3.68 +/- 0.83 (0.58 to 2.91) micrograms ml-1 h). 3. Plasma concentrations of CG, an active metabolite, could not be detected in all PMs, and those of CPB were sufficiently high to determine a time-course in only four PMs. Mean AUC(0,24 h) values of CPB were significantly (P < 0.05) lower in the PM (n = 4) than in the EM group (n = 14) (0.47 +/- 0.13 vs 0.88 +/- 0.50 (-0.14 to 0.96) micrograms ml-1 h). 4. Log10 percentage urinary recovery of 4'-hydroxymephenytoin correlated significantly (P < 0.05) with the t 1/2 (rs = -0.661) and AUC (rs = -0.652) of PG. 5. PG, CG and CPB were detectable in urine at 12 h in all subjects. Log10 percentage urinary recovery of 4'-hydroxymephenytoin correlated significantly (P < 0.01) with urinary PG/CG (rs = -0.876), PG/CPB (rs = -0.833) and PG/(CG + CPB) (rs = -0.831) metabolic ratios.(ABSTRACT TRUNCATED AT 250 WORDS)

Economic aspects of the use of impregnated mosquito nets for malaria control

The use of pyrethroids to impregnate mosquito nets has had a good impact on the incidence of morbidity and mortality from malaria. These nets are therefore likely to be used on a large scale as an important strategy of malaria control in the future. Published information on the cost and effectiveness of mosquito nets is presented and analysed. In two examples, from Malawi and Cameroon, the per household expenditure to purchase and use impregnated mosquito nets compares favourably with the costs of malaria. Thus, we expect that the economic losses from malaria would be reduced by 37.3% over a 3-year period in Malawi. Even if the impact of malaria on productivity is not taken into account, the introduction of nets will result in gains, as shown in Cameroon; savings of 9.3% and 11.2% in two places resulted as a consequence of a diminished need for case treatment. The role of government programmes in the promotion of bednets is indirect and concerned mainly with facilitation and the dissemination of information. Much depends on the capability of the private sector and the willingness of the target population to buy the nets for a programme to be effective. Specific studies by health economists on this subject are lacking.

Imported falciparum malaria in British troops returning from Kenya

The objective of this study was to report on a breakthrough of Plasmodium falciparum infection following a military exercise in central Kenya and the treatment regimens used. A series of case reports are presented from the three UK hospitals involved. Among 150 British soldiers who had been on exercises for five weeks in central Kenya, taking proguanil/chloroquine anti-malarial prophylaxis, seven developed symptomatic falciparum malaria. Initial symptoms, which started between 2 and 10 days before their return to England, included faintness, sweating, shivering, diarrhoea, headache and myalgia. Diagnosis was delayed from between 5 and 13 days after the first symptom. One patient was severely ill with 50% parasitaemia: he required intensive care, exchange blood transfusion and haemofiltration for acute renal failure. Compliance with chemoprophylaxis was not measured and anti-mosquito measures were not generally practised. However, British Army policy was amended in June 1993 so that mefloquine will be used in future rather than proguanil/chloroquine. It was concluded therefore that even in an educated and motivated population simple preventive measures are not observed. Chemoprophylactic compliance could be improved by changing to a simpler regime. Falciparum malaria is a medical emergency that requires urgent admission for confirmation of diagnosis, supportive and curative treatment. Its presence should be suspected in any ill traveller.

Malaria and pregnancy: epidemiology, pathophysiology and control options

Extensive research on the epidemiology, pathophysiology, and control of malaria during pregnancy has led to new developments and some controversies. Meanwhile, malaria remains a major environmental factor causing serious pregnancy complications, whose incidence and severity depend on gestational age, parity, and the level of malaria endemicity. There is no cohesive explanation for pregnancy-related immunosuppression, though several pathophysiological hypotheses have been proposed. Furthermore, the emergence and rapid spread of chloroquine resistance has complicated the epidemiology, and the policy on alternative chemoprophylaxis. Chemoprophylaxis is probably the only available option for the control of malaria during pregnancy in Africa. However, the best delivery strategy still has to be established. Daily proguanil is the best chemoprophylactic drug at hand. Its deployment should include constant monitoring for the emergence of proguanil resistance, as well as controlled supervision of the distribution of the drug. New control options, such as the use of insecticide-impregnated bed nets, and intermittent targeted mass chemotherapy, require more operational research before they can be broadly recommended.

Daily chlorproguanil is an effective alternative to daily proguanil in the prevention of Plasmodium falciparum malaria in Kenya

To test the efficacy of chlorproguanil prophylaxis, 156 malaria-free schoolchildren in the coastal region of Kenya were allocated at random to receive either 7.5 mg chlorproguanil daily, 50 mg chlorproguanil weekly, 100 mg proguanil daily, or 100 mg calcium lactate weekly (placebo). The children were followed up daily for 169 d, by which time Plasmodium falciparum parasitaemia had occurred in 92% of the placebo group, 31% of the daily proguanil group, 38% of the daily chlorproguanil group and 55% of the weekly chlorproguanil group. There was significant reduction (P < 0.001) in the risk of parasitaemia in all the groups receiving chemoprophylaxis. Daily chlorproguanil and daily proguanil were equally effective, and significantly more effective than weekly high dose chlorproguanil. No significant toxicity was reported or observed. Thus daily chlorproguanil 20 mg/60 kg is a cheap and effective alternative to proguanil for chemoprophylaxis.

Variability in the metabolism of proguanil to the active metabolite cycloguanil in healthy Kenyan adults

Extensive metabolizers (EM) and poor metabolizers (PM) of the malaria chemoprophylactic drug proguanil have been identified by measuring the proguanil/cycloguanil ratio in urine following a single dose of the pro-drug. The pharmacokinetic characteristics of proguanil were similar in 8 EM and 8 PM subjects, but there were significant differences between the 2 groups with respect to cycloguanil pharmacokinetics. In none of the PM subjects could cycloguanil be detected in whole blood samples at any time after proguanil dosage. Plasma cycloguanil was measureable in only 2 of 8 PM subjects, despite an analytical sensitivity in the high-performance liquid chromatographic assay of 1 ng/ml cycloguanil. A comparatively high proportion of Black Kenyan adults appear to metabolize proguanil poorly, possibly because they lack the specific mixed function oxidase which will accept proguanil as substrate.

Malaria in an urban and a rural area of Zambia

Children in Lusaka and in a rural area in central Zambia were examined during November 1984 and April 1985 to assess the effect of urbanization on malaria transmission. Of 423 urban children examined in November, 2.4% had scanty parasitaemia, and low titres of malarial antibodies were found in 46%. These proportions increased in April to a parasite rate of 10.3% and malaria antibodies were detected by indirect fluorescent antibody tests (IFAT) in 62%. The presence of malaria antibodies was positively associated with journeys outside the main towns. Examination of paired sera from the 2 periods showed an association between a history of malaria and an increased antibody titre, but failed to show an association between travel outside the main towns and conversion from a negative to a positive IFAT. The spleen rate in children under 15 years old in Lusaka was 3%, indicating hypoendemic malaria. In rural children the parasite rate was 10% and 27% in the 2 seasons, respectively, and over 97% of the children had malaria antibodies. The spleen rate was 20%, indicating mesoendemic malaria. It is concluded that there is only low transmission of malaria in Lusaka so that many people do not develop resistance and are therefore at risk of severe attacks if they do become infected. Possible measures to protect the urban population are discussed.

Prevention of malaria

With the increased spread of chloroquine-resistant Plasmodium falciparum malaria and mounting evidence of lack of efficacy and toxicity of alternative drugs, it has become extremely difficult to propose simple, widely applicable and uniformly acceptable recommendations for malaria chemoprophylaxis. With regard to specific drugs, it is clear that because of its toxicity amodiaquine should no longer be used for chemoprophylaxis, and that pyrimethamine/sulfadoxine should, for the most part, be used only as a presumptive therapy. The pyrimethamine/dapsone combination is promising, but data on its efficacy are limited. Although proguanil (chloroguanide) is recommended by several sources because of its safety, disturbing reports of chemoprophylaxis failure in Africa and a well-documented lack of efficacy in South East Asia would suggest that its usefulness may be limited. However, a recent study has documented the efficacy of a proguanil-sulphonamide combination in Thailand, an area of high grade chloroquine resistance. Although long term studies of drug safety are not yet available, doxycycline and mefloquine appear to be the drugs of choice in areas where P. falciparum shows multidrug resistance. Regardless of the drug regimen recommended for chemoprophylaxis, travellers must be informed that no present-day antimalarial agent guarantees protection against malaria.

Malaria chemoprophylaxis among European tourists in tropical Africa: use, adverse reactions, and efficacy

In order to determine knowledge, attitudes and practices towards malaria prophylaxis, as well as its side-effects and efficacy, a self-administered questionnaire was distributed to European travellers on return flights from tropical Africa to Europe. Between 1985 and 1988 the questionnaire was completed by 44,472 passengers (80.1% of those on board) on 242 flights. A follow-up questionnaire was completed by 42,202 (94.9%) of the same travellers 3 months later. Almost all knew about the risk of malaria, but 10% relied solely on advice from nonmedical sources. While 55.6% had taken at least one measure against mosquito bites, only 4.5% adopted three such measures (used repellents and insecticides and wore long clothing after dusk). Compliance with chemoprophylaxis use was reported by 57.0% of travellers who spent less than 3 months in Africa, compared with 29.2% who stayed 3-12 months. Depending on the antimalaria regimen taken, 11-44% of the travellers experienced adverse effects, while four deaths were attributed to the chemoprophylaxis. The incidence of malaria per month of exposure for travellers who took no chemoprophylaxis was 15.2 per 1000 in East Africa and 24.2 per 1000 in West Africa. In East Africa, the prophylactic efficacy of the currently recommended antimalaria regimens (relative to that of no chemoprophylaxis) was zero for a chloroquine dosage of 300 mg base per week (4 malaria fatalities), 64.1% for a chloroquine dosage of 600 mg base per week (P = 0.03), and 94.0% for mefloquine (P = 0.003).

Infectious disease and the Unesco basic education initiative

As part of a Basic Education for All campaign, Unesco is exploring ways to improve health and nutrition in school-age children in order to help them take advantage of the only schooling they may ever receive. At the first international Unesco working meeting on health, nutrition and school performance, intestinal helminths were identified as more appropriate immediate targets than malaria and other infectious diseases. Prevalence and intensity of infection in school-age children, the schools as vehicles of intervention, and the availability of interventions contributed to this choice. However, there are still many gaps in our knowledge of the effects of infectious diseases in schoolchildren. Through the improvement of understanding in this area, the parasitology community may be able to contribute to the Unesco project.

Tropical obstetrics and gynaecology. 1. Anaemia in pregnancy in tropical Africa

Major causes of anaemia in pregnancy in tropical Africa are malaria, iron deficiency, folate deficiency and haemoglobinopathies: now there is added also the acquired immune deficiency syndrome (AIDS). Anaemia is often multifactorial, with the different causes interacting in a vicious cycle of depressed immunity, infection and malnutrition. Anaemia progresses through 3 stages: compensation, with breathlessness on exertion only; decompensation, with breathlessness at rest and haemoglobin (Hb) below about 70 g/litre; cardiac failure, with Hb below about 40 g/litre. Without treatment, over half of the women with haematocrit less than 0.13 and heart failure die. Maternal anaemia, malaria and deficiencies of iron and folate cause intrauterine growth retardation, premature delivery and, when severe, perinatal mortality. Surviving infants have low birthweights, immune deficiency and poor reserves of iron and folate. They have entered already the vicious cycle of infection, malnutrition and impaired immunity. Treatment with blood transfusions is even more hazardous since the advent of AIDS, and should be limited to saving the life of the mother. Treatment of malaria is complex as chloroquine-resistant strains are now common. Prevention remains relatively easy with proguanil and supplements of iron and folic acid and is highly cost-effective in the improvement of maternal and infant health; it is more important than ever as it avoids the unnecessary exposure of women and infants to HIV transmitted through blood transfusion.

Malaria prophylaxis in travellers from Britain

A short questionnaire about malarial prophylaxis was completed by 376 travellers departing from Gatwick Airport to destinations in Asia, Africa, Australasia and South or Central America. Only 263 (70%) had sought advice, 80% of them from a general practitioner. Of travellers born in Britain, 81% had sought advice compared to 38% of those born abroad (P less than 0.001). Advice about protective measures to reduce mosquito bites had been given to 52% travellers. Although 264 were travelling to areas where prophylaxis is advised, only 167 (63%) were taking antimalarials, while 22% travelling to malaria-free destinations were taking unnecessary prophylaxis. Many British travellers do not take effective antimalarial chemoprophylaxis. This has undoubtedly contributed to the recent increase in incidence of the disease in the U.K. General practitioners should ensure that they give correct advice and the immigrant population need to understand the risk of malaria when they return home.

Efficacy of drug prophylaxis

With the spread of chloroquine resistant Plasmodium falciparum the control of malaria has become increasingly complex. In recent years, particular concern has arisen over how best to prevent malaria in non-immune international travellers. Prior to the recognition of the potential toxicity of some antimalarial drugs, malaria preventive guidelines switched from chloroquine to the newer compound antimalarial drugs and to amodiaquine; this adjustment was made when sentinel cases alerted clinicians that breakthrough infections occurred in travellers to East Africa taking chloroquine prophylaxis. Changes were also supported by data derived from field studies illustrating the effectiveness of these drugs for therapy in indigenous populations. However, international studies have now documented serious adverse reactions to pyrimethamine/dapsone, pyrimethamine/sulphadoxine, and amodiaquine, and caution is required with their use. Rates in British users concur with international estimates. Specialists preparing malaria preventive guidelines have, therefore, preferred to recommend the use of relatively safe antimalarial drugs, like chloroquine and proguanil, provided they offer non-immune travellers adequate protection against P. falciparum infections. Substantial difficulty has arisen, however, in the definition of 'adequate protection'. Field studies in indigenous communities with partial immunity can provide concise biological measures of parasite resistance to drugs. Unfortunately, these data cannot be used directly to determine the expected efficacy of chemoprophylactic drugs in non-immune populations. The transmission of malaria and the degree and intensity of resistance vary even within small geographical areas. Comprehensive patterns of resistance cannot be mapped out on a countrywide or regional basis for logistic reasons, and are restricted focally to discrete study locations.(ABSTRACT TRUNCATED AT 250 WORDS)