POS1408 AN ULTRASOUND NEGATIVE FOR SUBCLINICAL SYNOVITIS IN PATIENTS WITH ARTHRALGIA: IS IT HELPFUL IN IDENTIFYING THOSE WHO WILL NOT DEVELOP INFLAMMATORY ARTHRITIS? A LONGITUDINAL STUDY IN FOUR ARTHRALGIA COHORTS

Background

Ultrasound (US) has become an established method in the evaluation of joints and is often used in clinical practice to guide management decisions in arthralgia-patients. To date, studies on the prognostic value of MSUS in arthralgia focused on the positive predictive value of subclinical inflammation. However, also the absence of imaging-detected subclinical synovitis is now increasingly used in daily practice to exclude arthralgia-patients from further follow-up. Though, evidence on the value of a negative US in ruling out future IA development in arthralgia-patients (the negative predictive value) is mostly absent. According to the rules of Bayes, predictive values are highly dependent on the prior-risk of developing the disease. The NPV therefore, is strongly related to the prior-risk of not getting IA, which is quite considerable in arthralgia-patients.

Objectives

To investigate the negative predictive value (NPV) of musculoskeletal ultrasound (MSUS) in arthralgia patients at risk for developing inflammatory arthritis (IA).

Methods

An MSUS examination of hands and feet was performed in arthralgia-patients at risk for IA in four independent cohorts. Patients were followed for one-year on the development of IA. Subclinical synovitis was defined as greyscale≥2 and/or power Doppler≥1. NPVs were determined and compared with the prior risks of not developing IA. Outcomes were pooled using meta-analyses and meta-regression analyses. In sensitivity analyses, MSUS-imaging of tender joints only (rather than the full US-protocol) was analyzed and ACPA-stratification applied, the latter being in line with the use of US in daily care.

Results

After one-year 78%, 82%, 77% and 72% of patients in the four cohorts did not develop IA. The NPV of a negative US was 86%, 85%, 82% and 90%, respectively. The meta-analysis showed a pooled non-IA prevalence of 79%(95%CI: 75%-83%) and a pooled NPV of 86%(95%CI:81-89%) (Figure 1). Imaging tender joints only (as generally done in clinical practice) and ACPA-stratification showed similar results.

Figure 1.

Full US protocol; Prior risks of not developing IA (A) and negative predictive values of MSUS (B) in the four cohorts. For comparison, the pooled prior risk and confidence interval from A are depicted in the red column in B.

Conclusion

A negative US result in arthralgia has a high NPV for not developing IA, which is mainly due to the high a-priori risk of not developing IA. The added value of a negative US (<10% increase) was limited.

References

N.A.

Disclosure of Interests

Cleo Rogier: None declared, Giulia Frazzei: None declared, Marion Kortekaas: None declared, Marloes Verstappen: None declared, Sarah Ohrndorf: None declared, Elise van Mulligen: None declared, Ronald van Vollenhoven Speakers bureau: Speaker, for which institutional and/or personal honoraria were received: AbbVie, Galapagos, GSK, Janssen, Pfizer, UCB, Consultant of: Consultancy, for which institutional and/or personal honoraria were received: AbbVie, AstraZeneca, Biogen, Biotest, BMS, Galapagos, Gilead, Janssen, Pfizer, Sanofi, Servier, UCB, Vielabio, Grant/research support from:

Research Support (institutional grants): BMS, GSK, Lilly, UCB

Support for Educational programs (institutional grants): Pfizer, Roche

, Dirkjan van Schaardenburg: None declared, Pascal de Jong: None declared, Annette van der Helm-van Mil: None declared

POS0501 SEQUENTIAL ULTRASOUND IN ARTHRALGIA PATIENTS AT RISK FOR INFLAMMATORY ARTHRITIS; IS IT HELPFUL FOR RISK STRATIFICATION IN DAILY PRACTICE?

Background

Musculoskeletal Ultrasound (MSUS) is often used to assess the presence of subclinical joint inflammation in patients presenting with arthralgia suspicious for progression to inflammatory arthritis (IA). Even though evidence-based guidelines for these patients are still absent, presence or absence of subclinical joint inflammation often influences management decisions in daily clinical practice. Studies so far focused on MSUS results at presentation with arthralgia. However, it is unknown if and how MSUS results change over time, and whether repeating MSUS is helpful in demonstrating or ruling out impending RA with greater certainty.

Objectives

To investigate whether sequential imaging at 4-months, in addition to baseline evaluation, is helpful in the risk stratification of arthralgia-patients.

Methods

Arthralgia-patients suspicious for progression to IA were included in the Rotterdam clinically suspect arthralgia cohort. At baseline and at 4-months a bilateral MSUS-examination was performed of the joints and tendons in both hands and feet. Subclinical inflammation was defined as GS>1 and/or PD>0, this was scored according to the latest OMERACT- guidelines.(1, 2) Based on a large US study carried out in a symptom-free population, the cut-off value in MTP 2-3 was considered present if GS ≥3 and/or PD ≥1.(3) Patients were followed for one-year on development of IA, identified with joint examination by experienced rheumatologists. The value of MSUS was studied separately for patients with and without subclinical joint inflammation at baseline. In a sensitivity analysis, ACPA-stratification was applied.

Results

A total of 52 consecutive patients were studied; 29% developed IA after one year. At baseline, 25 patients had subclinical inflammation and 27 patients did not have subclinical inflammation. In these groups respectively 28% and 7% developed IA before the 4-month-visit and therefore did not have repeated MSUS (Figure 1 A/B). In the patients with a positive MSUS at baseline, 28% had a negative MSUS at four months, all these patients did not progress to IA, irrespective of tender joints count(Figure 1A). In the group of patients with a negative MSUS at baseline, 26% achieved a positive MSUS at 4-months. All patients with a negative MSUS at baseline and no tender joints at 4-months did not progress to IA, regardless of the MSUS results. Patients with a negative MSUS at baseline and tender joints at 4-months developed IA infrequently, without relevant differences between those that did or did not develop a positive MSUS at 4-monthts. Overall, only a minority of patients whose MSUS progressed from negative to positive indeed developed IA, whereas this repeated MSUS was falsely positive in most cases(Figure 1B). Despite the small numbers, ACPA-stratification was performed, this showed a similar trend.

Figure 1.

Sequential ultrasound at baseline and after 4-months of follow-up in arthralgia-patients at risk for inflammatory arthritis with subclinical inflammation at baseline (A) and without subclinical inflammation at baseline(B).

Conclusion

Within arthralgia patients with a positive MSUS at baseline, a negative MSUS after 4-months may be an incentive to exclude arthralgia-patients from further follow-up. Within the patients with a negative MSUS at baseline, repeating MSUS may induce more false positive than correct positive results.

References

[1]D’Agostino MA, Terslev L, Aegerter P et al. Scoring ultrasound synovitis in rheumatoid arthritis: a EULAR-OMERACT ultrasound taskforce-Part 1: definition and development of a standardised, consensus-based scoring system. RMD Open. 2017;3(1):e000428.

[2]Naredo E, D’Agostino MA, Wakefield RJ et al. Reliability of a consensus-based ultrasound score for tenosynovitis in rheumatoid arthritis. Ann Rheum Dis. 2013;72(8):1328-34.

[3]Padovano I, Costantino F, Breban M et al. Prevalence of ultrasound synovial inflammatory findings in healthy subjects. Ann Rheum Dis. 2016;75(10):1819-23.

Disclosure of Interests

None declared.

POS1418 REALIZING EARLY RECOGNITION OF ARTHRITIS IN TIMES OF INCREASED TELEMEDICINE: THE VALUE OF PATIENT-REPORTED SWOLLEN JOINTS

Background:

Early diagnosis and management of patients with inflammatory arthritis(IA) are critical to improve long-term patient-outcomes. Assessment of joint swelling at joint examination is the reference of IA-identification; early access clinics are constructed to promote this early recognition of IA. However, due to the COVID-19 pandemic the face-to-face capacity of such services is severely reduced. The accuracy of patient-reported swelling in comparison to joint examination has been extensively evaluated in established RA (ρ 0.31-0.67), but not in patients suspected for IA.[1]

Objectives:

To promote evidence based care in the era of telemedicine, we determined the accuracy of patient-reported joint swelling for actual presence of IA in persons suspected of IA by general practitioners(GP).

Methods:

Data from two Dutch Early Arthritis Recognition Clinics were studied. These are screening clinics (1.5-lines-setting) where GPs send patients in case of doubt on IA. At this clinic patients were asked to mark the presence of swollen joints on a mannequin with 52 joints. For this study the DIP joints and the metatarsal joints were excluded and, therefore, a total of 42 joints were assessed for self-reported joint swelling. Clinically apparent IA of ≥1 joint determined by the physician was the reference to calculate sensitivity, specificity, positive and negative likelihood ratios (LR+,LR-), and positive and negative predictive values (PPV, NPV) on patient-level. Pearson correlation coefficients(ρ) were determined. Predictive values depend on the prevalence of a disease in a population. Because the prevalence of IA in a 1.5-lines-setting will differ from a primary care setting, post-test probabilities of IA were estimated for two lower prior-test probabilities as example, namely 20% (estimated probability in patients GPs belief IA is likely) and 2% (prior-test probability with less preselection by GPs), using likelihood ratios and nomograms.

Results:

A total of 1637 consecutive patients were studied. Median symptom duration was 13 weeks. 76% of patients marked ≥1swollen joint at the mannequin. 41% of patients had ≥1swollen joint at examination by rheumatologists. ρ was 0.20(patient-level)-0.26(joint-level).

The sensitivity of patients-reported joint swelling was high, 87%, indicating that the majority of patients with IA had marked swelling on the mannequin. However the specificity was 31%, indicating that 69% of persons without IA had also done so. The LR+ was 1.25; the LR- 0.43. The PPV was 46%, the NPV 77%. Thus the PPV increased hardly (from 41% to 46%) and the NPV somewhat (from 59% to 77%). Also in settings with prior-test probabilities of 20% and 2%, estimated PPVs (from respectively 20% and 2% to 24% and 2%) and NPVs (from respectively 80% and 98% to 90% and 99%) hardly increased.

Conclusion:

Patient-reported joint swelling had little value in distinguishing patients with/without IA for different prior-test probabilities, and is less valuable in comparison to self-reported flare detection in established RA.

References:

[1]Barton JL, Criswell LA, Kaiser R, et al. Systematic review and metaanalysis of patient self-report versus trained assessor joint counts in rheumatoid arthritis. J Rheumatol 2009;36:2635-2641.

Disclosure of Interests:

None declared

AB1127 IS SHOULDER INVOLVEMENT IN CLINICALLY SUSPECT ARTHRALGIA AN EARLY FEATURE OF RHEUMATOID ARTHRITIS? -A LONGITUDINAL ULTRASOUND STUDY

Background:

Multiple studies have demonstrated that shoulder complaints are frequent in Rheumatoid arthritis (RA). Recently, it has been shown that shoulder involvement is predictive for RA development in patients with undifferentiated arthritis(UA) and its value is comparable to that of small joint involvement. The phase of clinically suspect arthralgia (CSA) precedes the phase of clinically apparent arthritis; in this phase subclinical tenosynovitis of the hands, is associated with the development of RA. Given the similarities in predictive values between the shoulder and small joints in UA, and the predictive value of tenosynovitis in CSA, we hypothesized that subclinical tenosynovitis of the bicep tendon is also associated with RA development. We examined the biceps tendon, since this is the only tendon of the shoulder that is enclosed by a synovial sheath as it passes through the bicipital groove.

Objectives:

Therefore, the aim of this study is to examine the predictive value of tenosynovitis of the bicep tendon by ultrasound (US) on developing inflammatory arthritis (IA) in CSA-patients.

Methods:

The SONAR (Sonographic evaluation of hands, shoulders and feet in patients presenting with inflammatory arthralgia to identify subclinical arthritis) is a multi-center observational cohort study in which patients were followed for the development of clinically apparent inflammatory arthritis (IA). Visits were done at baseline and 6 monthly thereafter. At baseline a US of both shoulders was made. 1-year follow-up data were used. IA was defined as having an arthritis verified by the treating physician. US abnormalities of (1) the biceps tendon, (2) the glenohumeral joint and (3) the subdeltoid bursa, were assessed for tenosynovitis, arthritis and bursitis.. Reference values for tendon thickness and effusion of the bursa were determined according to Schmidt et al.(1)

Results:

A total of 170 patients were included and underwent bilateral ultrasound (US) of the shoulder joint. Shoulder symptoms were infrequent (Table 1). After one year 37 patients developed IA (22%). ACPA positivity was associated with the development of IA (Table 1). As presented in Table 1, US abnormalities of the shoulder were found but none were associated with IA-development. In particular biceps tenosynovitis was not increased in the patients that developed IA.

Table 1.

Baseline characteristics and ultrasound abnormalities at baseline in patients with CSA.

Baseline characteristicsAll CSA-patientsn=170CSA-patients with IA(n=37)CSA-patients without IA (n=133)P valueGender, female, n (%)140 (82)30 (81)110 (83)0.82Age, years, mean (SD)45 (12)47 (12)44 (12)0.28Symptom duration, weeks median (IQR)30 (19-43)37 (23-43)28 (19-39)0.14TJC44, median (IQR)5 (3-8)5 (3-8)5 (3-8)0.81Shoulder pain, n (%)9 (5)0 (0)9 (6.8)0.10SJC44, median (IQR)0 (0-0)0 (0-0)0 (0-0)-ESR, median (IQR)10 (5-21)9 (5-22)11 (5-21)0.66RF-positive, n (%)46 (28)12 (34)34 (26)0.33ACPA-positive, n (%)26 (16)10 (29)16 (12)0.019US abnormalitiesof the shoulderAny USabnormalities, n (%)(n=170)50 (29)8 (22)42 (32)0.24Biceps tendon Tenosynovitis, n (%)(n=164)19 (12)5 (15)14 (11)0.48Biceps tendon thickness, n (%)(n=164)6 (4)0 (0)6 (5)0.19Subdeltoid bursa effusion, n (%)(n=159)29 (18)3 (9)26 (21)0.094Effusion joint, n (%)(n=157)0 (0)0 (0)0 (0)-

Abbreviations:IA: Inflammatory Arthritis, TJC44: Tender Joint Count in 44 joints, SCJ44: Swollen Joint Count in 44 joints,, ESR: Erythrocyte sedimentation rate, RF: Rheumatoid Factor, ACPA: Anti-citrullinated Protein Antibody

Conclusion:

Subclinical tenosynovitis of the shoulder is not an early feature of RA in patients with CSA.

Reference:

[1]Schmidt WA, Schmidt H, et al.Standard reference values for musculoskeletal ultrasonography.Ann Rheum Dis. 2004 Aug;63(8):988-94.

Acknowledgments:

*van der Helm- van Mil and de Jong contributed equal to this study

Disclosure of Interests:

None declared

SAT0071 SUBCLINICAL SYNOVITIS IN ARTHRALGIA: HOW OFTEN DOES IT RESULT IN CLINICAL ARTHRITIS? A LONGITUDINAL STUDY TO REFLECT ON STARTING POINTS FOR DMARD TREATMENT

Background:

Clinically apparent arthritis is mandatory for diagnosing and classifying RA. It is often used as endpoint in arthralgia cohorts and as a starting point for DMARD therapy in clinical practice. In recent literature subclinical synovitis, visualized with MRI or ultrasound, is increasingly used as a starting point for DMARD therapy in absence of clinically apparent arthritis. However, not all patients with a subclinical synovitis will develop clinically apparent arthritis, and thus may be overtreated. It has even been suggested to replace the entry-criterion of clinical arthritis by subclinical synovitis within the 2010 classification criteria for RA to diminish overtreatment. However this might lead to an overclassification of the disease. Because of aforementioned reasoning we aimed to evaluate the risk of overtreatment of these approaches and therefore performed a longitudinal study in three observational arthralgia cohorts.

Objectives:

To determine the frequency of non-progression to clinical arthritis in patients with subclinical synovitis, also after considering the 2010-criteria.

Methods:

Three individual cohorts of arthralgia patients without clinically apparent arthritis (n=166, 473 and 168) were followed for 1-year on the development of inflammatory arthritis (IA). At baseline subclinical synovitis in hands or feet was visualized with ultrasound (US) (defined as greyscale≥2 and/or power-doppler≥1) in cohort 1 and 3 and MRI (synovitis score ≥1 by two readers) in cohort 2. For all patients with subclinical synovitis the proportion of progressors (‘true positives’) and non-progressors (‘false positives’) were determined. The same analysis was done in the subgroup of patients that fulfilled the 2010 criteria for RA, if subclinical synovitis was used as entry criterion. Analyses were stratified for ACPA.

Results:

At baseline 36%, 41% and 31% of patients had subclinical synovitis. Of the ACPA-positive arthralgia patients with subclinical synovitis 46%, 56% and 29% respectively developed IA, whereas 54%, 44% and 71% did not progress. Within ACPA-negative arthralgia patients with subclinical synovitis 34%, 15% and 10% developed IA; whereas 66%, 85% and 90% did not progress (Figure 1A). Similar results were seen in the subgroup of patients that fulfilled the 2010 criteria with subclinical synovitis as entry criterion (Figure 1B).

Figure 1.

Percentage of arthralgia patients with subclinical synovitis that did and did not develop IA, in three independent cohorts:(A) Percentage of patients with subclinical synovitis that did and did not progress to IA after one-year follow-up, stratified for ACPA status. (B) Percentage of patients with subclinical synovitis and ≥6 points at baseline that did and did not progress to IA after one-year follow-up stratified for ACPA status.

Conclusion:

Replacing clinical arthritis by subclinical synovitis in arthralgia introduces a high false-positive rate: 44-71% (ACPA-pos) and 66-90% (ACPA-neg) of patients with subclinical synovitis did not develop clinically apparent arthritis within one year. Applying the 2010-criteria in this setting did not diminish the false positive rate. Starting DMARDs in patients without clinical synovitis may therefore introduce considerable overtreatment.

Acknowledgments *:

C Rogier and F Wouters contributed equal to this study

Disclosure of Interests:

None declared

Contribution of the French army health service in support of expertise and research in infectiology in Africa

Historically, infectious diseases have caused more casualties than battle. The French military health service therefore developed a range of research on vector-borne diseases such as malaria and arboviruses, antibiotic resistance, infectious agents that can be used as biological weapons and vaccines. The main objective is to control naturally acquired or provoked infectious diseases and limit their impact on armed forces as well as on civilian populations in France or abroad, particularly in Africa and anywhere French armies may be deployed. The expertise of the military health service teams in manipulating agents requiring high level of biosafety precautions and in organizing and providing medical care in unnatural conditions, including the battlefield, associated with complementarity staff experience (physicians, biologists, epidemiologists, researchers, pharmacists, logisticians), has been used in the management of the Ebola outbreak in Guinea.

Correction: Safety of Seasonal Malaria Chemoprevention (SMC) with Sulfadoxine-Pyrimethamine plus Amodiaquine when Delivered to Children under 10 Years of Age by District Health Services in Senegal: Results from a Stepped-Wedge Cluster Randomized Trial

[This corrects the article DOI: 10.1371/journal.pone.0162563.].

Safety of Seasonal Malaria Chemoprevention (SMC) with Sulfadoxine-Pyrimethamine plus Amodiaquine when Delivered to Children under 10 Years of Age by District Health Services in Senegal: Results from a Stepped-Wedge Cluster Randomized Trial

Background

It is recommended that children aged 3 months to five years of age living in areas of seasonal transmission in the sub-Sahel should receive Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine plus amodiaquine (SPAQ) during the malaria transmission season. The purpose of this study was to evaluate the safety of SMC with SPAQ in children when delivered by community health workers in three districts in Senegal where SMC was introduced over three years, in children from 3 months of age to five years of age in the first year, then in children up to 10 years of age.

Methods

A surveillance system was established to record all deaths and all malaria cases diagnosed at health facilities and a pharmacovigilance system was established to detect adverse drug reactions. Health posts were randomized to introduce SMC in a stepped wedge design. SMC with SPAQ was administered once per month from September to November, by nine health-posts in 2008, by 27 in 2009 and by 45 in 2010.

Results

After three years, 780,000 documented courses of SMC had been administered. High coverage was achieved. No serious adverse events attributable to the intervention were detected, despite a high level of surveillance.

Conclusions

SMC is being implemented in countries of the sub-Sahel for children under 5 years of age, but in some areas the age distribution of cases of malaria may justify extending this age limit, as has been done in Senegal. Our results show that SMC is well tolerated in children under five and in older children. However, pharmacovigilance should be maintained where SMC is implemented and provision for strengthening national pharmacovigilance systems should be included in plans for SMC implementation.

Trial Registration

ClinicalTrials.gov NCT 00712374

Is critical illness polyneuropathy associated with decreased heart rate variability?

INTRODUCTION

This pilot study assessed the association between critical illness polyneuropathy (CIP) and decreased heart rate variability (HRV) in intensive care patients.

METHODS

All patients admitted to the intensive care unit and expected to be ventilated for at least 72 hours were included and underwent weekly electromyograms and HRV analyses for three weeks. HRV was assessed by time domain analysis of 24h recording electrocardiograms, and alterations in HRV were assessed as the square root of the mean squared differences of successive RR intervals (RMSSD) ≤ 15.

RESULTS

We evaluated 26 patients, 12 men and 14 women, median age 64 years. During follow-up, 12 patients died and 9 developed CIP. CIP was not associated with age, sex, simplified acute physiology score II and treatment agents. Altered RMSSD tended to be associated with onset of CIP (P=0.06). Altered RMSSD occurred earlier or at the same time as electromyogram abnormalities in all CIP patients, but the difference was not significant.

CONCLUSION

Altered HRV, may be associated with the onset of CIP in ICU patients. Although not statistically significant (P=0.06), altered RMSSD may be a surrogate marker of CIP in ICU patients undergoing mechanical ventilation. The physiological pathway linking HRV and CIP remains uncertain.

The changes in mosquito vector behaviour and the emerging resistance to insecticides will challenge the decline of malaria

The preventive measures against malaria recommended by the WHO include anti-vector procedures such as indoor residual spraying, the use of long-lasting insecticide-treated bed-nets, and the destruction of larval breeding sites. The presence of insecticide-treated materials inside the mosquito habitat has consequences for the vector's population, reducing density, survival, contact with humans, and feeding frequency. However, the effectiveness of these tools is being challenged by the emergence of insecticide resistance. The evolution of resistance to insecticides in Anopheles threatens to thwart the goal of decreasing malaria transmission, in an arms race between malaria control programmes and the vector populations. Multiple mechanisms of resistance to insecticides have been observed in Anopheles populations, including target site mutation (knockdown resistance), increased metabolic detoxification, and remarkable behavioural adaptation. These disturbing observations all show the capacity of Anopheles to adapt to and circumvent strategies aimed at reducing malaria transmission. Thus, by using nets to protect ourselves, are we providing Anopheles with the entire arsenal needed to hit much harder?

Mosquito salivary gland protein preservation in the field for immunological and biochemical analysis

Mosquito salivary proteins are involved in several biological processes that facilitate their blood feeding and have also been reported to elicit an IgG response in vertebrates. A growing number of studies have focused on this immunological response for its potential use as a biological marker of exposure to arthropod bites. As mosquito saliva collection is extremely laborious and inefficient, most research groups prefer to work on mosquito salivary glands (SGs). Thus, SG protein integrity is a critical factor in obtaining meaningful data from immunological and biochemical analysis. Current methodologies rely on an immediate freezing of SGs after their collection. However, the maintenance of samples in a frozen environment can be hard to achieve in field conditions. In this study, SG proteins from two mosquito species (Aedes aegypti and Anopheles gambiae s.s.) stored in different media for 5 days at either +4°C or room temperature (RT) were evaluated at the quantitative (i.e., ELISA) and qualitative (i.e., SDS-PAGE and immunoblotting) levels. Our results indicated that PBS medium supplemented with an anti-protease cocktail seems to be the best buffer to preserve SG antigens for 5 days at +4°C for ELISA analysis. Conversely, cell-lysis buffer (Urea-Thiourea-CHAPS-Tris) was best at preventing protein degradation both at +4°C and RT for further qualitative analysis. These convenient storage methods provide an alternative to freezing and are expected to be applicable to other biological samples collected in the field.

[Molecular markers of Plasmodium falciparum drug resistance]

The main Plasmodium falciparum genes known to be associated with drug resistance are pfcrt, pfmdr1, pfdhfr pfdhps, pfcytb, pfmrp, pfnhe1, pfmdt, pfserca and pftetQ. Molecular markers for resistance to chloroquine, amodiaquine, mefloquine, sulfadoxine-pyrimethamine, cycloguanil and atovaquone have been validated and used to predict the parasitological and clinical efficacy of these drugs (i.e. based on in vivo tests). These molecular markers have numerous advantages. They allow evaluation of large series of samples in less time than in vivo tests. Collection, transport and storage of samples are much easier than for in vitro tests. These markers can be used for epidemiological monitoring of resistance for an entire country as well as for prediction of therapeutic outcome for a single individual. Development of high-throughput molecular biology techniques, availability of the nucleotidic sequences of P. falciparum genomes, and close collaboration between fundamental researcher workers, clinical practitioners, and officials in charge of the national malaria control programs are major assets in the research and development of molecular markers for P. falciparum resistance to antimalarial drugs.

[Distinguishing Plasmodium falciparum populations for clinical research]

The genetic diversity of Plasmodium falciparum is generally high. Study of this diversity is useful to differentiate the strains present in an individual before and after malaria treatment or to check if several individuals have been infected by the same parasites. Interpretation of the in vivo test recommended by the WHO to evaluate antimalarial drug efficacy requires distinguishing recrudescence from new infection when recurrent parasitemia suggests the possibility of therapeutic failure and antimalaria resistance. For this purpose, molecular biology techniques such as nested-PCRs are becoming increasingly available and can now be used in most endemic areas. An effort has been made to standardize P. falciparum genotyping carried out to distinguish recrudescence from new infection. Standardization has focused not only on genotyping methods but also on interpretation criteria. Compliance with these recommendations should improve the quality of clinical research and allow comparison of data from different centers.

[Methods for the phase IV evaluation of malaria vector control interventions: a case-control study of the effectiveness of long lasting impregnated bed nets after their deployment in Benin]

Vector-control measures are a component of integrated malaria control strategies. After evaluation in phase III pilot studies, these measures are currently being deployed in many endemic malaria zones. Their effectiveness must be evaluated under actual conditions of use but it is not ethically acceptable to use unexposed individuals for control groups. In a attempt to overcome this problem, a case-control study was undertaken to evaluate the effectiveness of long-lasting insecticide treated mosquito nets (LLITN) against clinical malaria attacks due to Plasmodium falciparum in an endemic area of southern Benin. During a 4-month period (July to October 2008), 35 clinically documented cases of uncomplicated malaria (fever + parasite density > 3000/microL) were diagnosed in children less than 5 years old from 6 villages in the Tori Bossito medical district. The parents of these children were interviewed at the same time as the parents of 181 children randomly selected from the same 6 villages. A total of 115 of the randomly selected children who had not been feverish during study period were used as controls. The proportion of children having consistently slept under LLITN throughout the study period was 46% in the case group and 78% in the control group (OR=0.32, 95%CI: 0.15-0.71). These data show that the LLITN provided a significant level of protection, i.e., 68% (IC95%: 29%-85%). This case-control study shows that vector control measures can be effectively evaluated after deployment in population. The limitations of this methodology are discussed.

[Guidelines for phase III evaluation of vector control methods against malaria]

Most new vector control methods against malaria involve the use of pesticides. Prior to release of these products for general use, their efficacy, persistence, and cross-resistance must be tested on mosquito colonies raised in the laboratory (phase I) then on wild mosquitoes in the field (small-scale), individual dwellings, or experimental huts (phase II). The goal of phase III studies is to evaluate the efficacy and effectiveness of the vector-control product or method against malaria in a population at regular risk for transmission. The main objective of phase III tests is to measure the epidemiologic impact, e.g. on the incidence or prevalence of malaria in humans. This article presents guidelines for carrying out phase III tests of vector-control methods against malaria (e.g. home insecticide spraying or insecticide-impregnated bednet use). It was written by participants in a workgroup formed to define recommendations for the WHOPES (WHO Pesticide Evaluation Scheme).

[Contribution of remote sensing to malaria control]

Despite national and international efforts, malaria remains a major public health problem and the fight to control the disease is confronted by numerous hurdles. Study of space and time dynamics of malaria is necessary as a basis for making appropriate decision and prioritizing intervention including in areas where field data are rare and sanitary information systems are inadequate. Evaluation of malarial risk should also help anticipate the risk of epidemics as a basis for early warning systems. Since 1960-70 civilian satellites launched for earth observation have been providing information for the measuring or evaluating geo-climatic and anthropogenic factors related to malaria transmission and burden. Remotely sensed data gathered for several civilian or military studies have allowed setup of entomological, parasitological, and epidemiological risk models and maps for rural and urban areas. Mapping of human populations at risk has also benefited from remotely sensing. The results of the published studies show that remote sensing is a suitable tool for optimizing planning, efficacy and efficiency of malaria control.

[Evaluation of the anopheline mosquito aggressivity and of malaria transmission risk: methods used in French Army]

Identification of the anopheline mosquito species involved in local transmission as well as knowledge of its biology and behavior is necessary for malaria vector control. To allow such study, two methods are usually used to capture adult mosquitoes, i.e., night catches on human volunteers and light-trap collections with human bait. The purpose of this article is to describe these two methods including their advantages and disadvantages as well as a method of surveying breeding sites as implemented by French Army personnel.

[Epidemiologic evaluation of malaria in endemic areas]

For decades malarial control has been implemented to control the impact of the disease on the health of populations living in endemic zones. The use of artemisinine combination therapy, intermittent preventive treatment for children and pregnant women, vector-control methods such as long-lasting insecticide-impregnated mosquito nets and indoor remanent insecticide spraying has proven to be effective. These practices have lead to such an extensive reduction of the malaria burden in some endemic areas that the objective of eradication that was unimaginable a few years ago is now back to the forefront. Regardless of the method chosen, careful evaluation and surveillance of its effectiveness in man is necessary. Achieving epidemiologic impact is the main goal of malaria control methods. The main measures for evaluation involve parasitological and clinical aspects of human malaria. The purpose of this article is to review methods used for epidemiologic evaluation of malaria burden.

Apoptosis: a potential triggering mechanism of neurological manifestation in Plasmodium falciparum malaria

Plasmodium falciparum infection can lead to a life threatening disease and the pathogenetic mechanisms of severe manifestations are not fully understood. Here, we investigated the capacity of P. falciparum-parasitized red blood cells (PRBC) from 45 children with clinical malaria to induce endothelial cell (EC) apoptosis. In all subjects, PRBC that cytoadhered to ECs could be found albeit to a variable degree. By contrast, PRBC that induce EC apoptosis were found only in nine (20%) subjects. Interestingly, children with neurological manifestations were significantly more likely to harbour apoptogenic strains. There was no quantitative relationship between the capacity of these isolates to cytoadhere and apoptosis induction. We hypothesize that P. falciparum-encoded molecules could be responsible for apoptosis induction and therefore suggest new insights in the pathogenesis of P. falciparum malaria. Further investigations are currently in progress to determine whether these results can be confirmed and to identify putative parasite apoptogenic factors.

Antibody responses to a C-terminal fragment of the Plasmodium falciparum blood-stage antigen Pf332 in Senegalese individuals naturally primed to the parasite

Previous studies have shown that antibodies from humans exposed continuously to malaria recognize the Plasmodium falciparum asexual blood-stage antigen Pf332. Here we analysed the antibody responses to a C-terminal fragment of Pf332, designated C231, in individuals from Senegal, by measuring the serum levels of immunoglobulin M (IgM), IgG class and subclass and IgE antibodies. IgG antibody reactivity with crude P. falciparum antigen was detected in all the donors, while many of the children lacked or had low levels of such antibodies against C231. The antibody levels increased significantly with age for both crude P. falciparum antigen and C231, and in the older age groups most of the donors displayed antibodies to C231. This was also true for IgM, IgE and IgG subclass reactivity against C231. Moreover, the ratio of IgG1/IgG2 was considerably lower for C231 than for crude P. falciparum antigen, and in age groups 10-14 and 15-19 years the levels of IgG2 against C231 even exceeded that of IgG1. The IgG2/IgG3 ratios suggest that C231 gives similar levels of IgG2 and IgG3, except for children aged 4-9 years, where IgG3 was higher. Raw IgM, IgG class and subclass and IgE antibody levels to C231 tended to be higher in those who did not experience a malaria attack, but following linear multivariate analysis the trends were not significant.

[Challenge of developing anti-parasite vaccines in the tropics]

Much effort has been devoted to developing anti-parasite vaccines. The main obstacles to overcome involve problems in cultivating parasites, variability in antigens of cultivated parasites, insufficient immune responses that do not provide full protection, lack of animal models and difficulty in evaluating immune protection acquired naturally or after vaccination in populations living in endemic areas. Numerous clinical trials have been conducted and several parasite antigens, in particular against malaria, have been tested in endemic areas. Up to now no candidate vaccine has shown sufficient, long-term efficacy to justify its inclusion in public health program. However trials using anti-parasite vaccination under both experimental and field conditions clearly demonstrate that a certain level of clinical immunity against malaria, bilharziasis, and leishmaniasis.

[Proteomic analysis and parasitosis: principles and applications]

O'Farrel described a method allowing two-dimensional (2D) protein separation more than 30 years ago. Since then the original technique has made enormous progress. This progress has been accompanied by advances in mass spectrometry technology as well as various genome-sequencing programs. Today 2D electrophoresis has become the workhorse of proteomics, allowing resolution of complex structures containing thousands of proteins and providing a global view of the state of a proteome. This article presents the different steps and limitations of proteomic analysis: preparation of biological material, 2D electrophoresis, protein detection systems, and available tools for protein identification. Alternative proteomic approaches to 2D electrophoresis are also presented. A few applications are described as examples to illustrate the utility of proteomic analysis for studying the mechanisms underlying virulence, resistance to antimalarial therapies and immune response against pathologic agents.

[Cyclines and malaria]

The emergence and rapid spread of Plasmodium falciparum resistance to various antimalarials compounds is gradually reducing the clinician's options for treating malaria and for adapting prophylaxis to each traveler and destination. In this context doxycycline is an increasingly useful alternative except in individuals with contraindications, mainly children under the age of eight and pregnant women. Already used successfully in association with quinine for treatment of malaria in areas with multiresistance, doxycline has also proven to be effective and well tolerated for prophylaxis of malaria. No resistance to doxycycline has been observed to date. Most reported prophylactic failures have been related to poor compliance during the month following return from the endemic zone. The mechanisms of action of doxycycline on the parasite are still unclear. Identification of the molecular targets of doxycycline would open the way for the design of more active structural analogues with longer half-life.

[Malaria vaccines: prospects and reality]

The development of a malaria vaccine has been accelerating in the last ten years. The number of clinical trials has increased and some malaria antigens have been tested in endemic areas. No potential vaccine has yet shown sufficient and lasting efficacy to justify its inclusion in a public health program. However, trials have unambiguously shown that some level of anti-malaria clinical immunity can be achieved by vaccination, both in experimental and in field conditions. Advances in malaria vaccine development are presented.

In vitro activity of iron-binding compounds against Senegalese isolates of Plasmodium falciparum

OBJECTIVES

The in vitro activities of FR160, a synthetic catecholate siderophore, and two iron-binding agents, desferrioxamine and doxycycline, were evaluated against Plasmodium falciparum isolates. Correlations between these compounds and standard antimalarial drugs (chloroquine, quinine, amodiaquine, pyronaridine, artemether, artesunate, atovaquone, cycloguanil and pyrimethamine) were assessed to determine any degree of cross-resistance.

METHODS

Between October 1997 and February 1998, and September and November 1998, 189 P. falciparum isolates were obtained in Dielmo and Ndiop (Dakar). Their susceptibilities were assessed using an isotopic, microwell format, drug susceptibility test.

RESULTS

The 137 inhibitory concentrations (IC(50)) values of FR160 ranged from 0.1 to 10 microM and the geometric mean IC(50) was 1.48 microM (95% CI = 1.29-1.68 microM). The geometric mean IC(50) of doxycycline for 121 isolates was 18.9 microM (95% CI = 16.8-21.3 microM) and that of desferrioxamine for 73 isolates was 20.7 microM (95% CI = 17.3-24.8 microM). FR160 was significantly less active against the chloroquine-resistant isolates (P < 0.0001). The mean IC(50)s of doxycycline were significantly higher for the chloroquine-susceptible isolates than for the resistant parasites (P = 0.0447). There was a weak correlation between the responses to FR160, desferrioxamine or doxycycline and those to the other antimalarial compounds (r(2) < 0.22).

CONCLUSIONS

The activities of FR160 and desferrioxamine, determined for P. falciparum clones, were confirmed against 137 isolates. The coefficients of determination between the responses to FR160, doxycycline or desferrioxamine and those to all the antimalarial drugs tested are too weak to suggest cross-resistance. FR160 could be a rationale partner to use in combination with doxycycline.

[Metallocenes and malaria: a new therapeutic approach]

Rapid development of significant resistance to antimalarial drugs has been a major force driving research to identify and develop new compounds. The use of synthetic organometallic complexes seems to be promising for treatment of malaria infections. Recent progress in identification and development of new drugs promises to lead to a much greater range of antimalarial agents. Organometallic complexes and metalloporphyrins have shown in vitro activity against Plasmodium falciparum. Ferroquine (ferrocenyl chloroquine) is more active than chloroquine against strains and isolates of P. falciparum and shows efficacy against murine parasites.

Genetic study of ICAM1 in clinical malaria in Senegal

Many genes have been implicated in the risk of severe malaria, generally based on candidate gene studies in case/control populations. Among these genes, there has been conflicting reports for the implication of a variant of the intercellular adhesion molecule 1 (ICAM1), ICAM1(Kilifi), in the risk of severe malaria, while in vitro studies provided independent support for a functional role of this variant. In order to explore the possible implication of ICAM1 in the susceptibility/resistance to malaria and to try to understand its clinical relevance in the disease process, we have conducted linkage and association studies of ICAM1 in two Senegalese villages located in regions of endemic malaria. We explored the full genetic variability of ICAM1, and tested it on several clinical malarial traits which are under genetic control, focusing principally on variables related to the parasite density and the number of malarial attacks. Our study provides no evidence for a role of ICAM1 variability on the malarial phenotypes studied.

Comment évaluer la morbidité attribuable au paludisme en zone d’endémie ?

There are no specific clinical signs or symptoms of malaria. Fever attacks, anemia, or signs of severity like coma or respiratory distress cannot easily be attributed to malaria in people who are infected most of the time. Ascribing clinical manifestations to malaria is problematic in populations that are regularly exposed to the transmission of human plasmodia. The more transmission is intense and regular, the higher the prevalence of asymptomatic infections. In areas of intense and perennial malaria transmission, more than 90% of the population may be infected and the simple detection of a plasmodial infection is not enough to attribute clinical manifestations to malaria. Naturally acquired anti-malaria immunity permitting asymptomatic infections is incomplete and temporary. It is an obstacle to the estimation of the malaria burden in endemic areas. The positive association between parasite density and fever allows the attribution of clinical attacks to malaria. The relationship between parasitaemia and the risk of fever is not continuous. An age- and endemicity-dependent threshold effect of parasite density has been demonstrated and can be used to distinguish clinical attacks due to malaria from others. Clinical diagnosis and evaluation of malaria are problematic in three situations: in public health to estimate the malaria burden for health services, in clinical research to evaluate treatments or prophylactic measures (drug, vaccine, anti-vectorial devices), and in basic research on pathophysiology, immunology or genetic susceptibility to clinical malaria. No one diagnostic definition nor procedure for detecting cases is adequate for all three purposes. Case detection may be passive (in health structures for example) or active (in population). The choice of methods for diagnosis and recruitment depends on the objectives and whether a "pragmatic" or "explicative" approach is used. The radical differences between these approaches are often unsuspected or ignored.

[Malaria modelling]

The purpose of this article is to describe various models used for the study of malaria. The type of models depends on the focus of study. Until now the most models have been designed to study malaria transmission. In addition to giving a basic description of a few classic models, we show how simulation can be useful despite the inherent simplicity of models. In our opinion it is urgent to develop models for use in public health based on recent advances in computer, automation, and mathematical techniques.

[Use of satellites for public health purposes in tropical areas]

The epidemiological hallmark of the new millennium has been the emergence or recrudescence of transmissible diseases with high epidemic potential. Disease tracking is becoming an increasingly global task requiring implementation of more and more sophisticated control strategies and facilities for sustainable development. A promising initiative involves the use of satellite technology to monitor and forecast the spread of disease. The Health Early Warning System (HEWS) was designed based on successful application of satellite data in food programs as well as in other areas (e.g. weather, farming and fishing). The HEWS integrates data from communications, remote-sensing and positioning satellites. The purpose of this review is to present the main studies containing satellite data on public health in tropical areas. Satellite data has allowed development of more reactive epidemiological tracking networks better suited to increasing population mobility, correlation of environmental factors (vegetation index, rainfall and ocean surface color) with human, animal and insect factors in epidemiological studies and assessment of the role of such factors in the development or reappearance of disease. Satellite technology holds great promise for more efficient management of public health problems in tropical areas.

[Pertinence of the 2000 WHO criteria in non-immune children with severe malaria in Dakar, Senegal ]

The relevance of World Health Organization (WHO) criteria for severe malaria has not been assessed in non-immune children. The objectives of this study were (i) to evaluate the significance of 1990 WHO definition reconsidered in 2000 on distribution and lethality of severe cases in children admitted with falciparum malaria, and (ii) to contribute to the study of relevance of the WHO severe criteria in Dakar, an hypoendemic area in Senegal.

PATIENTS AND METHODS

The 1990 WHO criteria, respiratory distress and platelet counts were prospectively collected in 1997-99 from children admitted to Hôpital Principal de Dakar, Senegal, with falciparum malaria diagnosed on a thick blood film. This method allowed also the definition of severe cases according to 2000 WHO criteria.

RESULTS

Among 311 patients (median age: 8 years old), according to the 2000 WHO criteria, the frequency of severe malaria cases was increased by 23% (75% versus 52%) and case-fatality rates thereof were decreased by 5% (17% versus 12%) compared with 1990 WHO definition. One death occurred among cases defined as severe on admission only according to criteria modified by WHO in 2000. A multivariate logistic regression model identified several independent prognostic factors: cerebral malaria, hypoglycaemia, respiratory distress, renal failure, collapse, abnormal bleedings, pupillary abnormalities and thrombocytopaenia defined as a platelet count below 100,000/mm3. A significant association (p < 0.001) was observed between platelet count increase and consciousness level improvement, evaluated on day of first platelet count control (time from admission: 1-7 d). Among survivors, a lesser improvement in coma score was associated with a decrease in platelet counts (p < 0.04).

CONCLUSIONS

The 1990 WHO criteria, which predicted death among malaria cases in children living under stable falciparum transmission, are relevant in this series of non-immune children living in a low and seasonal transmission. Nevertheless new WHO criteria showed poor prognostic significance. However, the 2000 WHO definition was highly sensitive to detect severe malaria cases. These findings should be considered for managing severe malaria in migrant children.

Sex ratio of Plasmodium falciparum gametocytes in inhabitants of Dielmo, Senegal

An epidemiological survey was conducted during a 4-month period of intense malaria transmission in Dielmo, a holoendemic Senegalese village. Two thick blood smears per inhabitant were collected weekly. The sex ratio of Plasmodium falciparum gametocytes (gamete precursors) was studied in 50 gametocyte carriers. All age classes were represented (mean 19.7 years; range: 2 months-75 years); 42 (84%) of them did not receive antimalarial treatment. Overall 668 thick smears were examined until 100 gametocytes had been counted or for 40 min. A total of 11204 gametocytes were observed with a mean sex ratio of 0.346 (95% CI 0.317-0.374), i.e. 2.89 females per 1 male. Among the 284 thick smears in which at least 10 gametocytes were observed, the mean percentage of male gametocytes was 27.8%, with a range of 0-82%. Great variability was observed between gametocyte carriers and also between thick smears from the same gametocyte carrier. A multivariate analysis was performed which highlighted the fact that only 2 variables had a significant effect on the sex ratio. Anaemia was associated with an increased percentage of males (Prevalence Rate Ratio [PPR] of male gametocytes was multiplied by 1.65 if haematocrit rate < 32%) and a wave of gametocytes was associated with an increased percentage of female gametocytes (PRR was multiplied by 0.48 during the peak of gametocytaemia and for the 2 weeks following this peak). The variables without significant effect on sex ratio were: age, sex, clinical status and sickle cell trait status of the gametocyte carrier, density of asexual parasites, quinine treatment, and gametocyte density (when taking account of its waves). These results are discussed in regard of possible differential production, mortality or sequestration of one gametocyte sex and selective advantages for the transmission of parasites.

Inland valley rice production systems and malaria infection and disease in the savannah of Côte d'Ivoire

In sub-Saharan Africa, lowlands developed for rice cultivation favour the development of Anopheles gambiae s. l. populations. However, the epidemiological impact is not clearly determined. The importance of malaria was compared in terms of prevalence and parasite density of infections as well as in terms of disease incidence between three agroecosystems: (i) uncultivated lowlands, 'R0', (ii) lowlands with one annual rice cultivation in the rainy season, 'R1' and (iii) developed lowlands with two annual rice cultivation cycles, 'R2'. We clinically monitored 2000 people of all age groups, selected randomly in each agroecosystem, for 40 days (in eight periods of five consecutive days scheduled every 6 weeks for 1 year). During each survey, a systematic blood sample was taken from every sick and asymptomatic person. The three agroecosystems presented a high endemic situation with a malaria transmission rate of 139-158 infective bites per person per year. The age-standardized annual malaria incidence reached 0.9 malaria episodes per person in R0, 0.6 in R1 and 0.8 in R2. Children from 0 to 9-year-old in R0 and R2 had two malarial attacks annually, but this was less in R1 (1.4 malaria episodes per child per year). Malaria incidence varied with season and agroecosystem. In parallel with transmission, a high malaria risk occurs temporarily at the beginning of the dry season in R2, but not in R0 and R1. Development of areas for rice cultivation does not modify the annual incidence of malarial attacks despite their seasonal influence on malaria risk. However, the lower malaria morbidity rate in R1 could be explained by socio-economic and cultural factors.

[Cohorts and bio-libraries for studying malaria in tropical areas]

The relationship between Plasmodii transmission, infection, morbidity, genetic susceptibility and acquisition of natural immunity is studied among two cohorts in the Senegalese villages of Dielmo (300 inhabitants) and Ndiop (350 inhabitants) where malaria is holoendemic (about 200 P. falciparum infective bites/person/year) and mesoendemic (about 20 P. falciparum infective bites/person/year), respectively. The populations are under a daily active clinical survey. Blood samples are collected at least once per month. Plasma and red blood cells are stored in bio-libraries that allow longitudinal studies of the immune responses against plasmodial antigens and the investigation of the natural history of P. falciparum infections by molecular genotyping methods.

[Malaria in military personnel: the case of the Ivory Coast in 2002-2003]

French troops were sent to the Ivory Coast on September 22, 2002 within the framework of Operation Unicorn in response to the political unrest. From September 22 to October 20, a total of 37 cases of malaria were reported, i.e., 35.7 cases per 1000 man-months. As of October 11, the central headquarters of the Armed Services Health Corps decided to use doxycycline as the exclusive agent for drug prophylaxis in military personnel on duty in the Ivory Coast and to enhance vector control measures. The incidence of malaria decreased to 2 cases per 1000 man-months at the sixth month. A recrudescence of malaria to 15 cases per 1000 man-months was observed with the rainy season in April. During this period one person presenting severe malaria with coma required emergency evacuation to France. In May 2003, several studies were undertaken to determine the factors that caused this recrudescence. These studies included surveys to evaluate awareness concerning malaria and monitor compliance with drug prophylaxis and tolerance of doxycycline, a case-control study to identify factors related to malarious episodes and an entomological study. Awareness of malaria was high with 75% of the 477 respondents stating that malaria could be transmitted by single mosquito bite. The case-control study showed a correlation between occurrence of malarious bouts and non-compliance with drug prophylaxis (p < 10(-5)). The odds-ratio was 3.05 (95% confidence interval, 1.52-6.14) for subjects claiming zero to one incident of non-compliance per week and 7.51 (IC95%, 3.24-17.40) for those claiming more than one incident of non-compliance per week. Tolerance of doxycyline was good since 72% of respondents reported no adverse effects. The main vector was Anopheles gambiae. The number of bites per man per night ranged from 25 to 2 and the number of infected bites ranged from 2 to 3 per week. Treatment was initiated promptly using quinine at a total dose of 25 mg/kg in 3 daily doses for 7 days by the intravenous then oral route. This experience shows that malaria remains a major concern for military forces, that standardization of preventive measures in emergency situations is needed, and that enhanced vector control, verification of compliance with drug prophylaxis and prompt treatment based on the presence of a physician in each emergency outpost is crucial. These recommendation must be applied to all French military personnel in the Ivory Coast.

[Childhood malaria in endemic areas: epidemiology, acquired immunity and control strategies]

Malaria is a major cause of childhood mortality and morbidity in endemic areas. The incidence and severity of malaria depends on various entomological, parasitological, environmental, and human factors. Clinical presentation and epidemiologic features vary according to genetic factors, personal behavior, and immune status. Populations exposed to frequent infection may develop partial labile protective malarial immunity at the price of high morbidity and mortality due to ineffectiveness of antimalarials. Malarial immunity affects not only mortality and severity of malaria but also uncomplicated malarial attacks and plasmodium infection. The number of determining factors involved in relatively limited but, like a game of chess, their possible combinations are numerous. A better understanding of malaria is necessary to plan and implement effective control strategies. That is the aim of this review.

Iron chelators as antimalarial agents: in vitro activity of dicatecholate against Plasmodium falciparum

The present study was undertaken to explore the antimalarial effect of a series of dicatecholate iron chelators. They may be made more or less lipophilic by increasing or reducing the length of the R substituent on the nitrogen. In vitro activity against the W2 and 3D7 clones of Plasmodium falciparum, toxicity on Vero cells and toxicity on uninfected erythrocytes by measure of the released haemoglobin were assessed for each compound. These findings were compared with the ability of iron(III), iron(II) and ferritin to reverse the inhibitory effect of catecholates. This study shows that increased lipid solubility of catecholate iron chelators does not lead to improved antimalarial activity. However, their activity is well correlated with their interaction with iron and with their toxicity against Vero cells. This study demonstrates a potent antimalarial effect of FR160 (R = C9H19) on five different strains of P. falciparum in vitro. FR160 inhibited parasite growth with an IC50 between 0.8 and 1.5 micro M. The effects of FR160 on mammalian cells were minimal compared with those obtained with malaria parasites. FR160 acted on parasites at considerably higher rates than desferrioxamine, and at all stages of parasite growth. The drug was more effective at the late trophozoite and young schizont stages, although FR160 affected rings and schizonts as well. Ascorbic acid, a free radical scavenger, reduced the activities of FR160 and artesunate. FR160 might induce formation of free radicals, which could explain why FR160 antagonized the effects of artesunate and dihydroartemisinin.