Efficacy of sulphadoxine/pyrimethamine for Plasmodium falciparum malaria in Malawian children under five years of age

Two decades of malaria control in Malawi: Geostatistical Analysis of the changing malaria prevalence from 2000-2022

Background

Malaria remains a public health problem in Malawi and has a serious socio-economic impact on the population. In the past two decades, available malaria control measures have been substantially scaled up, such as insecticide-treated bed nets, artemisinin-based combination therapies, and, more recently, the introduction of the malaria vaccine, the RTS,S/AS01. In this paper, we describe the epidemiology of malaria for the last two decades to understand the past transmission and set the scene for the elimination agenda.

Methods

A collation of parasite prevalence surveys conducted between the years 2000 and 2022 was done. A spatio-temporal geostatistical model was fitted to predict the yearly malaria risk for children aged 2-10 years (PfPR 2-10) at 1×1 km spatial resolutions. Parameter estimation was done using the Monte Carlo maximum likelihood method. District-level prevalence estimates adjusted for population are calculated for the years 2000 to 2022.

Results

A total of 2,595 sampled unique locations from 2000 to 2022 were identified through the data collation exercise. This represents 70,565 individuals that were sampled in the period. In general, the PfPR2_10 declined over the 22 years. The mean modelled national PfPR2_10 in 2000 was 43.93 % (95% CI:17.9 to 73.8%) and declined to 19.2% (95%CI 7.49 to 37.0%) in 2022. The smoothened estimates of PfPR2_10 indicate that malaria prevalence is very heterogeneous with hotspot areas concentrated on the southern shores of Lake Malawi and the country's central region.

Conclusions

The last two decades are associated with a decline in malaria prevalence, highly likely associated with the scale-up of control interventions. The country should move towards targeted malaria control approaches informed by surveillance data.

Transparent reporting of recruitment and informed consent approaches in clinical trials recruiting children with minor parents in sub-Saharan Africa: a secondary analysis based on a systematic review

Background

Standardised checklists of items to be addressed in clinical study protocols and publications are promoting transparency in research. However, particular specifications for exceptional cases, such as children with minor parents are missing. This study aimed to examine the level of transparency regarding recruitment and informed consent approaches in publications of clinical trials recruiting children with minor parents in sub-Saharan Africa. We thereby focused particularly on the transparency about consenting persons (i.e. proxy decision-makers) and assessed the need to expand reporting guidelines for such exceptional cases.

Methods

We conducted a secondary analysis of clinical trial publications previously identified through a systematic review. Multiple scientific databases were searched up to March 2019. Clinical trial publications addressing consent and potentially recruiting children with minor parents in sub-Saharan Africa were included. 44 of the in total 4382 screened articles met our inclusion criteria. A descriptive analysis was performed.

Results

None of the included articles provided full evidence on whether any recruited children had minor parents and how consent was obtained for them. Four proxy decision-maker types were identified (parents; parents or guardians; guardians; or caregivers), with further descriptions provided rarely and mostly in referenced clinical trial registrations or protocols. Also, terminology describing proxy decision-makers was often used inconsistently.

Conclusions

Reporting the minimum maternal age alongside maternal data provided in baseline demographics can increase transparency on the recruitment of children with minor mothers. The CONSORT checklist should require clinical trial publications to state or reference exceptional informed consent procedures applied for special population groups. A standardized definition of proxy decision-maker types in international clinical trial guidelines would facilitate correct and transparent informed consent for children and children with minor parents.

Study registration

CRD42018074220.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-11079-y.

Malaria medicines to address drug resistance and support malaria elimination efforts

INTRODUCTION

Antimalarial drugs are essential weapons to fight malaria and have been used effectively since the 17^th century. However, P.falciparum resistance has been reported to almost all available antimalarial drugs, including artemisinin derivatives, raising concerns that this could jeopardize malaria elimination. Areas covered: In this article, we present a historical perspective of antimalarial drug resistance, review current evidence of resistance to available antimalarial drugs and discuss possible mitigating strategies to address this challenge. Expert commentary: The historical approach to drug resistance has been to change the national treatment policy to an alternative treatment. However, alternatives to artemisinin-based combination treatment are currently extremely limited. Innovative approaches utilizing available schizonticidal drugs such as triple combination therapies or multiple first line treatments could delay the emergence and spread of drug resistance. Transmission blocking drugs like primaquine may play a key role if given to a substantial proportion of malaria infected persons. Deploying antimalarial medicines in mass drug administration or mass screening and treatment campaigns could also contribute to containment efforts by eliminating resistant parasites in some settings. Ultimately, response to drug resistance should also include further investment in the development of new antimalarial drugs.

Malaria research and its influence on anti-malarial drug policy in Malawi: a case study

Background

In 1993, Malawi changed its first-line anti-malarial treatment for uncomplicated malaria from chloroquine to sulfadoxine-pyrimethamine (SP), and in 2007, it changed from SP to lumefantrine-artemether. The change in 1993 raised concerns about whether it had occurred timely and whether it had potentially led to early development of Plasmodium falciparum resistance to SP. This case study examined evidence from Malawi in order to assess if the policy changes were justifiable and supported by evidence.

Methods

A systematic review of documents and published evidence between 1984 and 1993, when chloroquine was the first-line drug, and 1994 and 2007, when SP was the first-line drug, was conducted herein. The review was accompanied with key informant interviews.

Results

A total of 1287 publications related to malaria drug policy changes in sub-Saharan Africa were identified. Using the inclusion criteria, four articles from 1984 to 1993 and eight articles from 1994 to 2007 were reviewed. Between 1984 and 1993, three studies reported on chloroquine poor efficacy prompting policy change according to WHO’s recommendation. From 1994 to 2007, four studies conducted in the early years of policy change reported a high SP efficacy of above 80%, retaining it as a first-line drug. Unpublished sentinel site studies between 2005 and 2007 showed a reduced efficacy of SP, influencing policy change to lumefantrine-artemether. The views of key informants indicate that the switch from chloroquine to SP was justified based on local evidence despite unavailability of WHO’s policy recommendations, while the switch to lumefantrine-artemether was uncomplicated as the country was following the recommendations from WHO.

Conclusion

Ample evidence from Malawi influenced and justified the policy changes. Therefore, locally generated evidence is vital for decision making during policy change.

Anti-malarial drug formulations and novel delivery systems: a review

Artemisinin combination therapies have decreased malaria associated morbidity and mortality in several parts of the world. On the other hand, malaria cases have increased in sub-Saharan Africa largely due to falciparum resistance to the most frequently used drugs (chloroquine and sulphadoxine/pyrimethamine (SP) combination). Therapeutic failure has also been attributed in part to adverse effects of anti-malarial drugs and patients' non-compliance due to inconvenient dosing schedules. We consider that formulation and evaluation of novel drug delivery systems is not only less expensive than developing new drugs, but may also improve delivery of anti-malarials at the desired rates. In this review we evaluate the therapeutic efficacy of existing anti-malarial drugs and assess the feasibility of developing novel formulations and delivery systems.

Efficacy of chloroquine, amodiaquine and sulphadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria: revisiting molecular markers in an area of emerging AQ and SP resistance in Mali

Background

To update the National Malaria Control Programme of Mali on the efficacy of chloroquine, amodiaquine and sulphadoxine-pyrimethamine in the treatment of uncomplicated falciparum malaria.

Methods

During the malaria transmission seasons of 2002 and 2003, 455 children – between six and 59 months of age, with uncomplicated malaria in Kolle, Mali, were randomly assigned to one of three treatment arms. In vivo outcomes were assessed using WHO standard protocols. Genotyping of msp1, msp2 and CA1 polymorphisms were used to distinguish reinfection from recrudescent parasites (molecular correction).

Results

Day 28 adequate clinical and parasitological responses (ACPR) were 14.1%, 62.3% and 88.9% in 2002 and 18.2%, 60% and 85.2% in 2003 for chloroquine, amodiaquine and sulphadoxine-pyrimethamine, respectively. After molecular correction, ACPRs (cACPR) were 63.2%, 88.5% and 98.0% in 2002 and 75.5%, 85.2% and 96.6% in 2003 for CQ, AQ and SP, respectively. Amodiaquine was the most effective on fever. Amodiaquine therapy selected molecular markers for chloroquine resistance, while in the sulphadoxine-pyrimethamine arm the level of dhfr triple mutant and dhfr/dhps quadruple mutant increased from 31.5% and 3.8% in 2002 to 42.9% and 8.9% in 2003, respectively. No infection with dhps 540E was found.

Conclusion

In this study, treatment with sulphadoxine-pyrimethamine emerged as the most efficacious on uncomplicated falciparum malaria followed by amodiaquine. The study demonstrated that sulphadoxine-pyrimethamine and amodiaquine were appropriate partner drugs that could be associated with artemisinin derivatives in an artemisinin-based combination therapy.

Estimated financial and human resources requirements for the treatment of malaria in Malawi

Background

Malaria fever is a common medical presentation and diagnosis in Malawi. The national malaria policy supports self-diagnosis and self-medication for uncomplicated malaria with first line anti-malaria drugs. While a qualitative appreciation of the burden of malaria on the health system is recognized, there is limited quantitative estimation of the burden malaria exacts on the health system, especially with regard to human resources and financial burden on Malawi.

Methods

The burden of malaria was assessed based on estimated incidence rates for a high endemic country of which Malawi is one. Data on the available human resources and financial resources committed towards malaria from official Malawi government documents and programme reports were obtained. The amount of human and financial resources that would be required to treat 65% or 85% of symptomatic malaria cases as per the Roll Back Malaria partnership and the US President's Malaria Initiative targets.

Results

Based on a malaria incidence rate of 1.4 episodes per year per person it was estimated that there would be 3.71 million symptomatic episodes of malaria among children <5 years of age based on mid-2007 census projections. At 0.59 episodes each year per person there would be 2.13 million episodes in the 5 to 14 year age group and 1.02 million episodes in. There would be 761,848 malaria cases when HIV is not factored in among those 15 years of age or above; this figure rose to 2.2 million when the impact of HIV in increasing malaria incidence was considered. The prevalence of HIV has resulted in 42.3% increase in symptomatic malaria cases. Treating 65% to 85% of cases would result in using 8.9% to 12.2% of the national health budget or 22.2% to 33.2% of the national drug budget. Furthermore, having 65% to 85% of cases treated at a health facility would consume 55.5% to 61.1% of full-time equivalents of all the clinicians registered in the country. While this study's estimated time of 5 and 10 minutes per consultation may differ in actual practice, due to time constraints patients may not be seen for longer consultation in resources limited settings.

Conclusion

Malaria exacts a heavy toll on the health system in Malawi. The national recommendation of self-medication with first-line drug for uncomplicated malaria is justified as there are not enough clinicians to provide clinical care for all cases. The Malawi Ministry of Health's promotion of malaria drug prescription including other lower cadre health workers may be justified.

In-vivo parasitological response to sulfadoxine-pyrimethamine in pregnant women in southern Malawi

BACKGROUND

Malaria in pregnancy is a significant cause of maternal and infant morbidity and mortality. Malawi adopted intermittent preventive treatment with sulfadoxinepyrimethamine (SP) for the control of malaria in pregnancy in 1993. However there is little information on the in-vivo SP efficacy in pregnant women. This study was conducted to determine: prevalence of malaria and anaemia at the first antenatal visit and rate of parasitological failure to SP in pregnancy.

METHODS

A cross-sectional followed by a prospective cohort study was conducted in women attending antenatal care clinic at Montfort Hospital in Lower Shire Valley from June 2004 to February 2005. Women were screened for malaria and anaemia at the first antenatal visit. After taking SP under direct observation, women with malaria parasitaemia were followed up to day 14 to determine parasitological response.

RESULTS

Of 961 women screened, 9% had malaria, 77% had anaemia (HB<11.0g/dl), 24% had moderate anaemia (HB 7.0-8.9g/dl) and 6% had severe anaemia (HB<7.0g/dl). Malaria was significantly more frequent in primigravidae, the second trimester and in the post- rainy season (all p <0.05). Moderate anaemia (Hb < 9.0g/dl) was significantly more common in adolescents and primigravidae (both p <0.05). In the14-day follow up study, loss to follow up was 13%. Of the 74 women who completed the follow up, 89% cleared malaria parasites successfully and 11% had parasitological failure. Parasitological failures were all of the R1 type except for one with R2 failure.

CONCLUSION

Anaemia prevalence was high at first antenatal visit in this population. Rate of parasitological failure to SP in pregnancy increased from 5% in 1996 to 11% in 2004.

Rapid increase in resistance of Plasmodium falciparum to chloroquine-Fansidar in Uganda and the potential of amodiaquine-Fansidar as a better alternative

Combinations of chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) [CQSP] as the first line agents in Uganda have replaced CQ monotherapy. The idea of the combination is to delay the development of malaria resistance to either drug when used alone. We compared the clinical, parasitological and molecular findings of two studies with treatment arms of CQSP, amodiaquine (AQ) plus SP (AQSP) both done in 2003 with a study done 1 year earlier (2002) using SP alone. There was a notable decrease in adequate clinical response (ACR) by day 14 from 92.7% with SP to 80% with the combination CQSP, a year later. AQSP combination was found to have the best effect (94.3% ACR). There were no early treatment failures in the AQSP group. However, treatment failures were recorded at 20% on day 14 and 43% on day 28 for CQSP treatment and 5.7% by day 14 and 28.8% by day 28 in the AQSP group. The number of mutations that are associated with SP resistance increased from 2002 to 2003 at all loci monitored, from 83.8 to 100% at codon 108, 58.7 to 76% at codon 59 in the DHFR gene, and from 58.8 to 86% at codon 437 and 33 to 43% at codon 540 in the DHPS gene. We conclude that there has been a rapid development of resistance since the introduction of the new policy guidelines. AQSP was found to be a superior drug combination compared to CQSP and could be used as a low cost alternative at the moment.

Knowledge, attitudes and practices towards malaria among primary school pupils in Ndirande, Blantyre, Malawi

A qualitative cross-sectional study was conducted at Ndirande Primary School in the peri-urban area of Blantyre, Malawi in 2002. The aim was to describe the knowledge, attitudes and practices towards malaria among pupils. Forty pupils (20 boys and 20 girls) were recruited into four focus group discussions. There was very good knowledge about the role of the female Anopheles mosquito as an agent for transmission of malaria. Respondents were also aware of the clinical features of malaria and what measures could be taken to prevent the disease. However, the survey showed that many of the environmental modification measures were difficult to implement in the overcrowded peri-urban areas. Respondents did not believe that they could influence parents or other authorities in instituting environmental modification interventions. We conclude that children are unlikely to be effective change agents if the social environment does not offer them the opportunity to influence key community figures.

History, dynamics, and public health importance of malaria parasite resistance

Despite considerable efforts, malaria is still one of the most devastating infectious diseases in the tropics. The rapid spread of antimalarial drug resistance currently compounds this grim picture. In this paper, we review the history of antimalarial drug resistance and the methods for monitoring it and assess the current magnitude and burden of parasite resistance to two commonly used drugs: chloroquine and sulfadoxine-pyrimethamine. Furthermore, we review the factors involved in the emergence and spread of drug resistance and highlight its public health importance. Finally, we discuss ways of dealing with such a problem by using combination therapy and suggest some of the research themes needing urgent answers.

High prevalence of quintuple mutant dhps/dhfr genes in Plasmodium falciparum infections seven years after introduction of sulfadoxine and pyrimethamine as first line treatment in Malawi

Malawi changed its national policy for malaria treatment in 1993, becoming the first country in Africa to replace chloroquine by sulfadoxine and pyrimethamine combination (SP) as the first-line drug for uncomplicated malaria. Seven years after this change, we investigated the prevalence of dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) mutations, known to be associated with decreased sensitivity to SP, in 173 asymptomatic Plasmodium falciparum infections from Salima, Malawi. A high prevalence rate (78%) of parasites with triple Asn-108/Ile-51/Arg-59 dhfr and double Gly-437/Glu-540 dhps mutations was found. This 'quintuple mutant' is considered as a molecular marker for clinical failure of SP treatment of P. falciparum malaria. A total of 11 different dhfr and dhps combinations were detected, 3 of which were not previously reported. Nineteen isolates contained the single Glu-540 mutant dhps, while no isolate contained the single Gly-437 mutant dhps, an unexpected finding since Gly-437 are mostly assumed to be one of the first mutations commonly selected under sulfadoxine pressure. Two isolates contained the dhps single or double mutant coupled with dhfr wild-type. The high prevalence rates of the three dhfr mutations in our study were consistent with a previous survey in 1995 in Karonga, Malawi, whereas the prevalences of dhps mutations had increased, most probably as a result of the wide use of SP. A total of 52 P. falciparum isolates were also investigated for pyrimethamine and sulfadoxine/pyrimethamine activity against parasite growth according to WHO in vitro standard protocol. A pyrimethamine resistant profile was found. When pyrimethamine was combined with sulfadoxine, the mean EC(50) value decreased to less than one tenth of the pyrimethamine alone level. This synergistic activity may be explained by sulfadoxine inhibition of dhps despite the double mutations in the dhps genes, which would interact with pyrimethamine acting to block the remaining folate despite dhfr mutations in the low p-aminobenzoic acid and low folic acid medium mixed with blood.

Malaria: a rising incidence in the United States

Malaria is frequently a deadly disease, particularly in tropical countries of the world where this protozoan infection is endemic. While physicians in tropical countries are familiar with the presentation, those who do not practice in endemic regions of the world may neglect to add tropical diseases to their differential diagnosis of fever. Epidemiologic data from the CDC show the number of cases of malaria being diagnosed in the United States in the last decade has risen sharply. With international travel continuing to rise, there is strong reason to consider malaria as a source of fever.

Sulphadoxine/pyrimethamine: an appropriate first-line alternative for the treatment of uncomplicated falciparum malaria in Ghanaian children under 5 years of age

OBJECTIVE

To assess whether chloroquine (CQ) still is an appropriate first-line drug for the treatment of uncomplicated falciparum malaria in Ghana and whether sulphadoxine/pyrimethamine (SP) could be a good alternative.

METHOD

The parasitological, clinical and haematological responses to CQ and SP were studied in children < 5 years of age according to a modified WHO 28-day in vivo protocol. A total of 142 children attending the outpatients department meeting the inclusion criteria were randomly assigned to the CQ (n=72) or SP (n=70) group.

RESULTS

In the CQ group, 15 children (20.8%) exhibited early clinical failure (within 3 days) compared with only 1 (1.4%) in the SP group (P < 0.01). The clinical failure rate before day 14 (early treatment failure plus late treatment failure before day 14) also showed a marked advantage in favour of the SP group (1.4 against 29.2%). The median time to clinical failure was 11.5 days in the CQ group and 26 days in the SP group (P < 0.01). Of the 72 children treated with CQ, 9 (12.5%) had RIII resistance and 19 (26.4%) had RII resistance. A total of 36 (50.0%) were sensitive to CQ. From the 70 children treated with SP, none had RIII or RII resistance. There was no difference in haematological response between the two treatment groups.

CONCLUSION

Although there is little concordance on when to change treatment policy, the high resistance to CQ in this study supports the change to another first-line drug for children under 5 years of age. SP seems to be a good alternative, although a high RII and RIII resistance against this drug has already been reported in the coastal zones of Ghana.

Controlling malaria: challenges and solutions

Antimalarial drug resistance is a major public health challenge and the principal reason for the erosion of efficacious treatments. Cost and the limited number of antimalarial drugs in current use impose considerable constraints on malaria control, especially in sub-Saharan Africa. The paper describes a multilateral, multidisciplinary research project on artemisinin-based combination therapy, which offers a new and potentially highly effective way to prevent or retard the development of drug resistance.

Therapeutic efficacy of sulphadoxine/pyrimethamine and susceptibility in vitro of P. falciparum isolates to sulphadoxine-pyremethamine and other antimalarial drugs in Malawian children

Since 1993 sulphadoxine/pyrimethamine (SP) has been used as the first-line drug for uncomplicated Plasmodium falciparum malaria in Malawi. To investigate the current efficacy of SP and other antimalarial drug resistance, we studied in vivo and in vitro responses to SP, chloroquine (CQ), mefloquine (MF), quinine (QN), and halofantrine (HF) in Salima, central Malawi. In a follow-up of 14 days, nine (13.8%) of 65 children under five showed RII/RIII parasitological resistance, and in in vitro microtests 18 (62.1%) of 29 isolates showed < 90% inhibition of schizont maturation at pyrimethamine 75 nmol/l blood medium mixture, indicating resistance. The discrepancy between in vivo and in vitro results might be partially explained by acquired immunity in this holoendemic area. In vitro one (3.4%) of 29 isolates failed schizont inhibition at 1.6 micromol/l blood of CQ, indicating resistance. Compared with an in vitro study conducted in 1988 in another region of Malawi using the same cut-off point, the proportion of resistant isolates had decreased significantly (P < 0.01). Although 31% of isolates were borderline, showing schizont maturation at 0.8 micromol/l blood but no schizonts at 1.6 micromol/l in our study, the results suggest possible recovery of CQ sensitivity after long-term absence of drug pressure. Resistance remains a major problem in malaria control. Monitoring resistance patterns in vitro provides early warning signs of impending loss of therapeutic efficacy of the standard treatment, and may detect changing patterns in alternative drug resistance.

The comparative efficacy of chloroquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria in Kampala, Uganda

Chloroquine (CQ) remains the first-line treatment for uncomplicated malaria in much of Africa despite the growing problem of resistance to this drug. Sulfadoxine-pyrimethamine (SP) is often used after CQ treatment failure and has replaced CQ as the first-line treatment in parts of Africa. To compare the efficacy of these 2 regimens, we evaluated, in March-August 1999, clinical and parasitological responses over 28 days in 214 children and adults from Kampala, Uganda, with uncomplicated falciparum malaria. Compared to SP, significantly more patients treated with CQ developed early or late clinical failure (54% vs 11%, P < 0.001) and parasitological failure (72% vs 30%, P < 0.001) during 14 days of follow-up. The risk of treatment failure occurring after day 14 was similar between the 2 treatment groups. Among those treated with CQ, children aged < 5 years were at higher risk of clinical failure than older individuals (76% vs 28%, P < 0.001), an association not seen with SP (11% vs 10%, P = 0.91). Although early parasite clearance was significantly better in the SP group (P = 0.001), fever clearance at day 3 was the same (CQ 85%, SP 86%). These and other recent findings suggest that consideration be given to replacing CQ as the first-line therapy for uncomplicated malaria in Uganda, particularly in young children.

Chemoresistance of Plasmodium falciparum in the urban region of Yaounde, Cameroon. Part 2: Evaluation of the efficacy of amodiaquine and sulfadoxine-pyrimethamine combination in the treatment of uncomplicated Plasmodium falciparum malaria in Yaounde, Cameroon

The spread of chloroquine resistance or its stabilization at a high level calls for a change in the therapeutic strategy, including a possible replacement of chloroquine. We assessed and compared the efficacy of amodiaquine and sulfadoxine-pyrimethamine in Yaoundé. Of 140 adults and children > 5 years enrolled in the study, 59 in the amodiaquine and 58 in the sulfadoxine-pyrimethamine treatment group were followed until day 14. The efficacy of amodiaquine was 100%, whereas 12.1% of the patients treated with sulfadoxine-pyrimethamine responded with an early treatment failure. Side effects in both treatment groups were mild and did not require any specific treatment. We did in vitro drug assays for monodesethylamodiaquine (active metabolite of amodiaquine) and pyrimethamine and measured plasma levels of monodesethylamodiaquine, sulfadoxine, and pyrimethamine. Unlike amodiaquine, the results of the in vitro drug sensitivity test for pyrimethamine were not concordant with the clinical response. A wide inter-individual variation in the plasma drug levels was observed. Unlike chloroquine, the mean plasma concentrations did not vary with age. There was no significant difference in the plasma concentrations of sulfadoxine and pyrimethamine between patients responding with an adequate clinical response and those responding with treatment failure. Amodiaquine has several advantages over sulfadoxine-pyrimethamine combination and may be considered to be an effective drug in an endemic zone with a moderate level of chloroquine resistance.

Comparative efficacy of chloroquine plus chlorpheniramine and pyrimethamine/sulfadoxine in acute uncomplicated falciparum malaria in Nigerian children

The efficacy of pyrimethamine/sulfadoxine (PS) and chloroquine plus chlorpheniramine, a histamine H1 receptor blocker which reverses chloroquine insensitivity in Plasmodium falciparum in vitro, was evaluated in 100 consecutive children with acute symptomatic uncomplicated falciparum malaria. Parasitaemia on day 3 following initiation of treatment, fever and symptom clearance times were significantly lower in the chloroquine/chlorpheniramine (CQ/CP) combination group than in the PS group. The cure rate was also significantly higher in the combination group. The combination cured all children who had failed PS treatment. Gametocytaemia and the gametocyte carrier rate following therapy were significantly lower in the combination group than in those receiving PS. Both treatments were well tolerated but adverse drug reactions were commoner in the children given PS. CQ/CP is effective in PS treatment failure in Nigerian children and may be useful for this condition in African children in general.

Drug resistance among malaria and other parasites

Recent decades have witnessed the emergence and spread of parasites resistant to standard drug therapies, particularly malaria. Chloroquine-resistant Plasmodium falciparum has now spread to most malarial areas, and resistance to other antimalarial drugs, including mefloquine and sulfadoxine-pyrimethamine, have become significant problems in some parts of Southeast Asia and South America. Chloroquine-resistant P. vivax is well established in Papua New Guinea and Indonesia and has been reported in other areas. Trichomonas and Giardia infections resistant to metronidazole have also been documented. This article reviews the current status of drug resistance among parasites, particularly malaria, and offers strategies for managing patients with these infections.

Parasitological and haematological responses to treatment of Plasmodium falciparum malaria with sulphadoxine-pyrimethamine in southern Malawi

In 1993, Malawi introduced sulphadoxine-pyrimethamine (SP) for the treatment of uncomplicated, Plasmodium falciparum malaria and became the first country in Africa to abandon chloroquine for first-time therapy. This decision produced an urgent need to monitor local P. falciparum for resistance to SP and to establish both clinical and parasitological criteria for drug failure. The parasitological and haematological responses to treatment of malaria in southern Malawi with SP have now been investigated. Children, aged 6-59 months, who attended health-care facilities with uncomplicated infections of P. falciparum alone were enrolled in the study. Each received standard treatment with SP and paracetamol and was followed-up on days 3, 7, 14, 21 and 28 post-treatment. Haemoglobin (Hb) was measured on days 0, 14 and 28. Zinc erythroprotoporphyrin (ZP) was estimated once during follow-up, as an indicator of iron status. Of 107 children enrolled, 84 children (78.5%) were followed for 14 days or until clinical failure. The parasitological success rate amongst the latter was 90.5% (76/84). One child showed poor parasite clearance (with a parasitaemia at day 3 > 25% of that at day 0), one had a low level of persistent parasitemia, and six were parasitaemic on day 14 after being parasite free on day 7. A 14-day follow-up increased the detection of parasitological failure by 7.2%. Haematological recovery on day 14 was not significantly different for parasitological successes or failures. The geometric mean parasite density (GMPD) was significantly lower in children classified as iron deficient (ZP > or = 3.0 micrograms/g Hb) and these children were significantly more likely to be severely anaemic (Hb < 8 g/dl) at day 0. Parasitological responses and haemoglobin levels 28 days after SP treatment were independent of ZP levels. These results show that, 2 years after the introduction of SP in Malawi for the treatment of uncomplicated, P. falciparum malaria, the drug combination remains effective in 90.5% of cases. Iron status did not affect parasitological recovery. Although iron-deficient children were at greater risk of severe anaemia they did not show significantly reduced recovery from malarial anaemia.