High efficacy of anti DBL4ɛ-VAR2CSA antibodies in inhibition of CSA-binding Plasmodium falciparum-infected erythrocytes from pregnant women

Malaria during pregnancy is a major cause of intra-uterine growth-retardation and infant death in sub-Saharan Africa. Ideally, this could be prevented by a vaccine delivered before the first pregnancy. Antibodies against domain DBL4ɛ from VAR2CSA has been shown to inhibit adhesion of laboratory isolates to the placental receptor chondroitin sulfate A. In this study, the binding inhibitory efficacy of IgG elicited by two different DBL4ɛ recombinant proteins was tested on a panel of fresh clinical isolates from pregnant women living in Benin and Tanzania. The most promising recombinant protein elicited antibodies with similar efficacy as pooled plasma from immune multi-gravid African women.

Malaria incidence and prevalence among children living in a peri-urban area on the coast of benin, west Africa: a longitudinal study

Clinical malaria incidence was determined over 18 months in a cohort of 553 children living in a peri-urban area near Cotonou. Three cross-sectional surveys were also carried out. Malaria incidence showed a marked seasonal distribution with two peaks: the first corresponding to the long rainy season, and the second corresponding to the overflowing of Lake Nokoue. The overall Plasmodium falciparum incidence rate was estimated at 84/1,000 person-months, and its prevalence was estimated at over 40% in the two first surveys and 68.9% in the third survey. Multivariate analysis showed that girls and people living in closed houses had a lower risk of clinical malaria. Bed net use was associated with a lower risk of malaria infection. Conversely, children of families owing a pirogue were at higher risk of clinical malaria. Considering the high pyrethroids resistance, indoor residual spraying with either a carbamate or an organophospate insecticide may have a major impact on the malaria burden.

Towards the rational design of a candidate vaccine against pregnancy associated malaria: conserved sequences of the DBL6epsilon domain of VAR2CSA

BACKGROUND

Placental malaria is a disease linked to the sequestration of Plasmodium falciparum infected red blood cells (IRBC) in the placenta, leading to reduced materno-fetal exchanges and to local inflammation. One of the virulence factors of P. falciparum involved in cytoadherence to chondroitin sulfate A, its placental receptor, is the adhesive protein VAR2CSA. Its localisation on the surface of IRBC makes it accessible to the immune system. VAR2CSA contains six DBL domains. The DBL6epsilon domain is the most variable. High variability constitutes a means for the parasite to evade the host immune response. The DBL6epsilon domain could constitute a very attractive basis for a vaccine candidate but its reported variability necessitates, for antigenic characterisations, identifying and classifying commonalities across isolates.

METHODOLOGY/PRINCIPAL FINDINGS

Local alignment analysis of the DBL6epsilon domain had revealed that it is not as variable as previously described. Variability is concentrated in seven regions present on the surface of the DBL6epsilon domain. The main goal of our work is to classify and group variable sequences that will simplify further research to determine dominant epitopes. Firstly, variable sequences were grouped following their average percent pairwise identity (APPI). Groups comprising many variable sequences sharing low variability were found. Secondly, ELISA experiments following the IgG recognition of a recombinant DBL6epsilon domain, and of peptides mimicking its seven variable blocks, allowed to determine an APPI cut-off and to isolate groups represented by a single consensus sequence.

CONCLUSIONS/SIGNIFICANCE

A new sequence approach is used to compare variable regions in sequences that have extensive segmental gene relationship. Using this approach, the VAR2CSA DBL6 domain is composed of 7 variable blocks with limited polymorphism. Each variable block is composed of a limited number of consensus types. Based on peptide based ELISA, variable blocks with 85% or greater sequence identity are expected to be recognized equally well by antibody and can be considered the same consensus type. Therefore, the analysis of the antibody response against the classified small number of sequences should be helpful to determine epitopes.

[Management of malaria in Benin: evaluation of the practices of healthcare professionals following the introduction of artemisinin derivatives]

In 2004 the policy for malaria management in Benin changed when the National Malaria Coordination Program (NMCP) introduced artemisinin-based combination therapy (ACT) for treatment of uncomplicated malaria. Up to that time, chloroquine had been used for first-line therapy against uncomplicated malaria and sulfadoxine pyrimethamine had been used in case of failure. Artemisinin derivatives have been used for monotherapy in Benin since 2002. The purpose of this transverse study carried out among public and private centers in Cotonou from March 16 to May 17, 2005 was to determine the impact of the switch to ACT on the practices of healthcare professionals. Medical centers were randomly selected from each stratum after identification and stratification of all facilities in the healthcare pyramid. A survey questionnaire was sent to healthcare workers. A total of 690 health workers responded to the questionnaire. Most responders (95.5%) were familiar with artemisinin but a lower percentage (89.6%) prescribed them. Responders were less knowledgable about ACT drugs and Coartem was the best known combination in the minds of prescribers. Biological diagnosis was available for 50% of patients. Artemisinine (derivates) were mainly prescribed as a second choice treatment and as monotherapy whether for severe or uncomplicated malaria. They were prescribed to pregnant women in 34.6% of the cases. Dosage was incorrect in 26.1% of cases in adults and 20.9% of cases in children. These findings indicate that more effort is needed to inform healthcare workers. This is especially urgent since the country is now considering revising its malaria management policy to make ACT available at all levels of the healthcare system. An effective information campaign must be set up to ensure that health workers and drug retailers throughout the country are duly informed of the new malaria treatment policy.

Intermittent treatment for the prevention of malaria during pregnancy in Benin: a randomized, open-label equivalence trial comparing sulfadoxine-pyrimethamine with mefloquine

BACKGROUND

In the context of the increasing resistance to sulfadoxine-pyrimethamine (SP), we evaluated the efficacy of mefloquine (MQ) for intermittent preventive treatment during pregnancy (IPTp).

METHODS

A multicenter, open-label equivalence trial was conducted in Benin from July 2005 through April 2008. Women of all gravidities were randomized to receive SP (1500 mg of sulfadoxine and 75 mg of pyrimethamine) or 15 mg/kg MQ in a single intake twice during pregnancy. The primary end point was the proportion of low-birth-weight (LBW) infants (body weight, <2500 g; equivalence margin, 5%).

RESULTS

A total of 1601 women were randomized to receive MQ (n=802)or SP (n=799).In the modified intention-to-treat analysis, which assessed only live singleton births, 59 (8%) of 735 women who were given MQ and 72 (9.8%) of 730 women who were given SP gave birth to LBW infants (difference between low birth weights in treatment groups, -1.8%; 95% confidence interval [CI], -4.8% to 1.1%]), establishing equivalence between the drugs. The per-protocol analysis showed consistent results. MQ was more efficacious than SP in preventing placental malaria (prevalence, 1.7% vs 4.4% of women; P = .005),clinical malaria (incidence rate, 26 cases/10,000 person-months vs. 68 cases/10,000 person-months; P = .007) and maternal anemia at delivery (as defined by a hemoglobin level <10 g/dL) (prevalence, 16% vs 20%; marginally significant at P = .09). Adverse events (mainly vomiting, dizziness, tiredness, and nausea) were more commonly associated with the use of MQ (prevalence, 78% vs 32%; P < 10(-3)) One woman in the MQ group had severe neuropsychiatric symptoms.

CONCLUSIONS

MQ proved to be highly efficacious--both clinically and parasitologically--for use as IPTp. However, its low tolerability might impair its effectiveness and requires further investigations.

Comparison of sulfadoxine-pyrimethamine, unsupervised artemether-lumefantrine, and unsupervised artesunate-amodiaquine fixed-dose formulation for uncomplicated plasmodium falciparum malaria in Benin: a randomized effectiveness noninferiority trial

BACKGROUND

We compared sulfadoxine-pyrimethamine (SP) with unsupervised artemether-lumefantrine (AL) and unsupervised amodiaquine-artesunate (ASAQ) fixed-dose formulation for the treatment of uncomplicated malaria in children in Benin.

METHODS

This open-label, noninferiority comparative trial included children aged 6-60 months. The follow-up period was 6 weeks, and the primary objective was a comparison of polymerase chain reaction (PCR)-adjusted effectiveness rates at day 28.

RESULTS

The study included 240 children (48 received SP, and 96 each received AL and ASAQ). The intention-to-treat analysis showed effectiveness rates on day 28 of 20.8%, 78.1%, and 70.5% for SP, AL, and ASAQ, respectively. After adjustment for PCR results, these rates were 27.1%, 83.3%, and 87.4%, respectively. The per-protocol analysis (217 patients) showed effectiveness rates on day 28 of 21.7%, 88.0%, and 76.1% for SP, AL, and ASAQ, respectively. After adjustment for PCR results, these rates were 28.3%, 94.0%, and 93.2%, respectively. SP was less effective than the other drugs in the PCR-adjusted analysis, whereas AL and ASAQ were equally effective. The rate of new infection was higher among children treated with ASAQ than among those treated with AL.

CONCLUSIONS

This was the first trial, to our knowledge, to compare unsupervised AL with unsupervised ASAQ fixed-dose formulation; both treatments provided high PCR-adjusted day 28 effectiveness rates. Efficacy rates for SP were surprisingly low. Clinical trials registration. NCT00460369.

Freshwater snail diversity in Benin (West Africa) with a focus on human schistosomiasis

The aim of this study was to conduct a large-scale freshwater snail survey in Benin to assess the malacological diversity and the larval trematode infections with a focus on Schistosoma genus. We conducted 82 freshwater snail surveys in 35 sites ranked in 4 types and belonging to 9 out of 12 departments. Among 19,200 collected snails, 11 species of freshwater snails were identified. Four species of human schistosome transmitting snails, Bulinus forskalii, B. globosus, B. truncatus and Biomphalaria pfeifferi and seven species of non-human schistosome transmitting snails. Although B. forskalii and B. globosus were the most largely distributed snails, none of the Bulinus snails were found naturally infected by schistosomes. B. pfeifferi was found naturally infected by S. mansoni only in one site with a 0.56% prevalence. The most risky areas were Borgou and the four coastal departments. Preliminary contempory information on human schistosomiasis was provided from three different sites. Schistosoma haematobium was found with 57.1%, 96% and 100% prevalences (two of which were new records for this species in Benin) while S. mansoni was restricted to one site (Toho-Todougba) with 74.3% prevalence. Our data showed that both schistosomiasis haematobium and mansoni prevalences increased during the last nineteen years in Toho-Todougba site.

Extended high efficacy of the combination sulphadoxine-pyrimethamine with artesunate in children with uncomplicated falciparum malaria on the Benin coast, West Africa

BACKGROUND

A study carried out in 2003-2005 in Southern Benin showed a day-28 sulphadoxine-pyrimethamine (SP) monotherapy failure rate greater than 40%, while for SP combined with artesunate (SP-AS) the failure rate was 5.3%. Such a large difference could be explained by the relatively short 28-day follow-up period, with a substantial number of recurrent infections possibly occurring after day 28. This paper reports the treatment outcome observed in the same study cohort beyond the initial 28-day follow-up.

METHODS

After the 28-day follow-up, children treated with either chloroquine alone (CQ), SP or SP-AS, were visited at home twice a week until day 90 after treatment. A blood sample was collected if the child had fever (axillary temperature > or =37.5 degrees C). Total clinical failure for each treatment group was estimated by combining all the early treatment failures and late clinical failures that occurred over the whole follow-up period, i.e. from day 0 up to day 90. Pre-treatment randomly selected blood samples were genotyped for the dhfr gene (59) and the dhps gene (437 and 540) point mutations related to SP resistance.

RESULTS

The PCR-corrected clinical failure at day 90 was significantly lower in the SP-AS group (SP-AS: 2.7%, SP alone: 38.2%; CQ: 41.1%) (Log-Rank p < 0,001). The most prevalent haplotype was dhfr Arg-59 with the dhps Gly-437 mutant and the dhps 540 wild type (85.5%). The dhps 540 mutation could be found in only three (8.3%) samples.

CONCLUSION

Combining artesunate to SP dramatically increased the treatment efficacy, even when extending the follow-up to day 90 post-treatment, and despite the high percentage of failures following treatment with SP alone. Such a good performance may be explained by the low prevalence of the dhps 540 mutation, by the rapid parasite clearance with artesunate and by the level of acquired immunity.

[Report of the 3rd International Conference on Envenomations in Africa]

The 3rd International Conference on Envenomations was held in Brazzaville from 15 to 17 November; 2007. At this meeting, updating of epidemiological and treatment information on envenomations in Africa were presented. A round table concluded the conference drawing contributors' main recommendations. One of these recommendation pointed out the need to treat the problem of envenimations at a regional level by creating a group of experts in charge of considering the priorities as well as identifying relevant strategies of management, ensuring the plea and finding the financing.

Efficacy of intermittent preventive treatment versus chloroquine prophylaxis to prevent malaria during pregnancy in Benin

BACKGROUND

In West Africa, treatment for the prevention of malaria during pregnancy has recently changed from chloroquine (CQ) prophylaxis to intermittent preventive treatment (IPTp). We assessed the benefits of IPTp with respect to those of CQ, using a before-after study.

METHODS

CQ efficacy was evaluated during a cross-sectional survey conducted in Benin between April 2004 and April 2005. IPTp efficacy was assessed using data from an ongoing clinical trial to compare sulfadoxine-pyrimethamine with mefloquine that began in the same maternity clinics during July 2005; the present analysis is limited to women who delivered between November 2005 and November 2006. Treatment assignments were not unblinded. We compared the efficacy of the 2 strategies against low birth weight and placental infection by performing multiple logistic regressions.

RESULTS

A total of 1699 women (1090 in the CQ group and 609 in the IPTp group) who delivered live singletons were analyzed. Characteristics of women in the CQ group were similar to those of women in the IPTp group. We showed that women in the IPTp group had a significantly decreased risk of delivering an infant with a low birth weight (adjusted odds ratio [aOR], 0.54; 95% confidence interval [CI], 0.38-0.78) and placental infection (aOR, 0.15; 95% CI, 0.09-0.24).

CONCLUSION

We clearly evidenced that IPTp is substantially more beneficial than CQ for the prevention of malaria during pregnancy.

Ethics committees in western and central Africa: concrete foundations

The involvement of developing countries in international clinical trials is necessary for the development of appropriate medicines for local populations. However, the absence of appropriate structures for ethical review represents a barrier for certain countries. Currently there is very little information available on existing structures dedicated to ethics in western and central Africa. This article briefly describes historical milestones in the development of networks dedicated to capacity building in ethical review in these regions and outlines the major conclusions of two workshops on this issue, which were held in September and October 2002 in Libreville, Gabon, and Paris, France. The workshops were the culmination of collaboration between the African Malaria Network Trust (AMANET) and the Pan African Bioethics Initiative (PABIN). They produced an update on ethics organizations with regard to mission, function, activities, members, and contact people, in eight countries within the regions discussed. As a result of the commitment of mandated delegates, a further prominent outcome followed these workshops: the creation of national structures, where none existed before, dedicated to the ethical review of clinical trials.

Adding artesunate to sulphadoxine-pyrimethamine greatly improves the treatment efficacy in children with uncomplicated falciparum malaria on the coast of Benin, West Africa

Background

Benin has recently shifted its national antimalarial drug policy from monotherapies to combinations containing artemisinin derivatives. When this decision was taken, the available information on alternatives to chloroquine and sulphadoxine-pyrimethamine, the first- and second-line treatment, was sparse.

Methods

In 2003 – 2005, before the drug policy change, a randomized, open-label, clinical trial was carried out on the efficacy of chloroquine, and sulphadoxine-pyrimethamine alone or combined with artesunate, with the aim of providing policy makers with the information needed to formulate a new antimalarial drug policy. Children between six and 59 months of age, with uncomplicated malaria and living in the lagoon costal area in southern Benin, were randomly allocated to one of the three study arms and followed up for 28 days.

Results

Treatment failure (PCR corrected) was significantly lower in the artesunate + sulphadoxine-pyrimethamine group (4/77, 5.3%) than in chloroquine group(51/71, 71.8%) or the sulphadoxine-pyrimethamine alone group (30/70, 44.1%) (p < 0.001). Despite high sulphadoxine-pyrimethamine failure, its combination with artesunate greatly improved treatment efficacy.

Conclusion

In Benin, artesunate + sulphadoxine-pyrimethamine is efficacious and could be used when the recommended artemisinin-based combinations (artemether-lumefantrine and amodiaquine-artesunate) are not available. However, because sulphadoxine-pyrimethamine is also used in pregnant women as intermittent preventive treatment, its combination with artesunate should not be widely employed in malaria patients as this may compromise the efficacy of intermittent preventive treatment.

Intermittent preventive treatment for the prevention of malaria during pregnancy in high transmission areas

Malaria in pregnancy is one of the major causes of maternal morbidity and adverse birth outcomes. In high transmission areas, its prevention has recently changed, moving from a weekly or bimonthly chemoprophylaxis to intermittent preventive treatment (IPTp). IPTp consists in the administration of a single curative dose of an efficacious anti-malarial drug at least twice during pregnancy - regardless of whether the woman is infected or not. The drug is administered under supervision during antenatal care visits. Sulphadoxine-pyrimethamine (SP) is the drug currently recommended by the WHO. While SP-IPTp seems an adequate strategy, there are many issues still to be explored to optimize it. This paper reviewed data on IPTp efficacy and discussed how to improve it. In particular, the determination of both the optimal number of doses and time of administration of the drug is essential, and this has not yet been done. As both foetal growth and deleterious effects of malaria are maximum in late pregnancy women should particularly be protected during this period. Monitoring of IPTp efficacy should be applied to all women, and not only to primi- and secondigravidae, as it has not been definitively established that multigravidae are not at risk for malaria morbidity and mortality. In HIV-positive women, there is an urgent need for specific information on drug administration patterns (need for higher doses, possible interference with sulpha-based prophylaxis of opportunistic infections). Because of the growing level of resistance of parasites to SP, alternative drugs for IPTp are urgently needed. Mefloquine is presently one of the most attractive options because of its long half life, high efficacy in sub-Saharan Africa and safety during pregnancy. Also, efforts should be made to increase IPTp coverage by improving the practices of health care workers, the motivation of women and their perception of malaria complications in pregnancy. Because IPTp is not applicable in early pregnancy, which is a period when malaria may also be deleterious for women and their offspring, there is a necessity to integrate this strategy with other preventive measures which can be applied earlier in pregnancy such as insecticide-treated nets.

Clinical trial of an F(ab')2 polyvalent equine antivenom for African snake bites in Benin

We report the results of a trial designed to measure the safety and efficacy of African Antivipmyn, a new freeze-dried polyvalent equine F(ab')(2)-based antivenom. We tested 289 envenomations. After treatment, 19% of treated patients had undesirable events, all benign. A possible adverse effect was attributed to this antivenom in 11% of the patients. Bleeding was observed in 48% of the patients; it stopped within 2 hours after treatment with antivenom in 60% of the patients. Blood incoagulability was observed in 80% of the patients. Restoration of coagulation was attained within 4 hours in 60% of the patients. Nine patients died; 6 arrived at the hospital in the final stage of complications and 5 arrived at the hospital more than 60 hours after the bite. The value of blood coagulation tests in diagnosis of envenomation and bleeding as an indicator of renewal of treatment are emphasized.

Dramatically decreased therapeutic efficacy of chloroquine and sulfadoxine-pyrimethamine, but not mefloquine, in southern Benin

OBJECTIVE

To evaluate the in vivo therapeutic efficacy of chloroquine (CQ), sulfadoxine-pyrimethamine (SP) and mefloquine (MQ) in children presenting with uncomplicated malaria in Benin.

METHODS

Drug efficacy was tested according to the WHO in vivo 28-day protocol. For failures that occurred after 7 days of follow-up, paired pre- and post-treatment blood samples were genotyped at msp1 and msp2 loci to distinguish new infections and recrudescent strains. Children enrolled were randomly assigned to a therapeutic group (CQ, n=14; SP, n=42; MQ, n=44). The number of CQ treatment was intentionally restricted after 1 month, as its use was considered to constitute a danger for children.

RESULTS

Chloroquine and SP showed very high failure rates (85.7% and 50%, respectively), whereas MQ treatment was successful in 97.5%. The molecular tool allowed to re-evaluate two new infections previously considered as failures.

CONCLUSIONS

Chloroquine should no longer be used to treat children presenting with Plasmodium falciparum malaria in Benin.

Is chloroquine chemoprophylaxis still effective to prevent low birth weight? Results of a study in Benin

Background

In areas of stable transmission, malaria during pregnancy is associated with severe maternal and foetal outcomes, especially low birth weight (LBW). To prevent these complications, weekly chloroquine (CQ) chemoprophylaxis is now being replaced by intermittent preventive treatment with sulfadoxine-pyrimethamine in West Africa. The prevalence of placental malaria and its burden on LBW were assessed in Benin to evaluate the efficacy of weekly CQ chemoprophylaxis, prior to its replacement by intermittent preventive treatment.

Methods

In two maternity clinics in Ouidah, an observational study was conducted between April 2004 and April 2005. At each delivery, placental blood smears were examined for malaria infection and women were interviewed on their pregnancy history including CQ intake and dosage. CQ was measured in the urine of a sub-sample (n = 166). Multiple logistic and linear regression were used to assess factors associated with LBW and placental malaria.

Results

Among 1090 singleton live births, prevalence of placental malaria and LBW were 16% and 17% respectively. After adjustment, there was a non-significant association between placental malaria and LBW (adjusted OR = 1.43; P = 0.10). Multiple linear regression showed a positive association between placental malaria and decreased birth weight in primigravidae. More than 98% of the women reported regular chemoprophylaxis and CQ was detectable in 99% of urine samples. Protection from LBW was high in women reporting regular CQ prophylaxis, with a strong duration-effect relationship (test for linear trend: P < 0,001).

Conclusion

Despite high parasite resistance and limited effect on placental malaria, a CQ chemoprophylaxis taken at adequate doses showed to be still effective in reducing LBW in Benin.

Bringing antivenoms to Sub-Saharan Africa

To reduce unacceptably high death rates from snakebite envenomation, sub-Saharan Africa must adopt not only a new generation of multivalent biotech antivenoms, but also an infrastructure to deliver them.

[The re-emergence of the human African trypanosomiasis in Kerou, Benin]

Located in the northern part of Bénin, the district of Kérou is an historical HTA focus of the 60s formerly called the "Atacora focus". This survey was conducted in 2001 to determine the prevalence of HAT in Kérou. The methodology consisted in a cross-sectional survey based on random sampling with two levels of stratification. 3367 persons were included (i=5%). After a screening based on CATT test with total blood test, the examination of trypanosomae was performed with QBC on the subjects that have some persistent antibodies above serum dilution at 1/4, followed by lumbar puncture. For 3367 surveyed subjects, the CATT seroprevalence test with total blood sample is 4.2% and it is 2.4% with serum dilution at 1/8. The research of trypanosomae with QBC is positive in 48 patients and the prevalence is 1.4%. The community survey conducted among 106 positive persons with CATT test serum at 1/4 dilution has revealed that 71 (67%) persons have never left the area since their birth. The HAT is actually emerging in Atacora district in the north of Bénin, especially in Kérou.

Round table of November 20th, 2004: recommendations for improving the management of envenomations

The round table underlines the necessity to follow the epidemiological and clinical surveys in order to precise the incidence and severity of snakebites and inform the health authorities that could thus arrange to take in charge envenomation accidents. Simple therapeutic protocols adapted to epidemiological and clinical data will be elaborated according to each level of health pyramid. They will be included in the health staff training and integrate traditional practitioners whose role must be clearly defined. An experimental and clinical validation must confirm its appropriateness with countries and victims needs. Some microeconomic surveys are necessary to identify adapted funding and thus improve their accessibility

Prevalence and risk-factors for Helicobacter pylori infection in urban and rural Beninese populations

In total, 446 healthy individuals (240 in urban and 206 in rural environments, respectively) were selected from 96 households, based on cluster sampling of residential location. Demographic, sociological and environmental data were collected by face-to-face interviews using a standard questionnaire. Infection with Helicobacter pylori was assessed by detection of anti-H. pylori IgG serum antibodies. The prevalence of H. pylori antibodies was 75.4% in the urban population and 72.3% in rural (village) residents (p 0.459). No association was found between infection and age, gender, education level, size of household, economic activity or source of drinking water. The infection rate was higher in children whose parents were both infected, and also in children whose mother was infected (p < 0.001). By logistic regression analysis, the density of occupation of sleeping accommodation (more than three persons sharing a room; 95% odds ratio (OR) = 9.82 (4.13-23.31), p < 0.001), and the mother's status within the household (95% OR = 3.85 (1.53-9.67), p 0.003), were independent predictors for H. pylori infection. The 74% seroprevalence of H. pylori infection found in healthy Beninese individuals is similar to that reported previously from other parts of sub-Saharan Africa. Family contact with infected persons and crowded living conditions were associated with increased risk of infection. These findings are consistent with intra-familial H. pylori transmission and suggest that improvement of living conditions should be protective against infection.

[Monitoring and assessment indicators in 2001 of "Roll Back Malaria" initiative in Benin]

Within the context of WHO/CDS/RBM/2000, a survey was conducted in 2001 by the National Malaria Control Program of Benin. Following a well-thought-out choice, the survey took place simultaneously in health areas corresponding to epidemiological regions. Morbidity due to malaria is very high among children under five years admitted in external clinic (44.3% of cases) and (46.5%) for hospitalization. The crude rate of mortality is 129%. The use of non-impregnated bednet is usually met in three health areas, where 47.4% of the household have at least one non-impregnated bednet versus 5.4% of household with impregnated bednets. Percentage of pregnant women sleeping under an impregnated bednet and following chemoprophylaxis is respectively 43.3% and 3.8%. Results obtained at the end of this database survey in 2001 have facilitated the definition of indicators of the process, results and impact which remain very useful for the implementation of the monitoring and assessment system of "Roll Back Malaria" in Benin.

[Limits and weaknesses of intermittent treatment in malaria prevention]

WHO proposal of a new strategy for the control of malaria, intermittent treatment using sulfadoxine-pyrimethamine, encounters various conceptual and logistic problems. First, the treatment is dedicated only to a very small part of the population which is not representative of the population at risk. Secondly, it largely underestimates the risks of this type of drugs. At last, the difficulties of its management should lead to hamper this strategy. It would be preferable to study the real causes of the current strategy failure and to take it into account for a new strategy.

A randomized, double-blind study on the efficacy and safety of a practical three-day regimen with artesunate and mefloquine for the treatment of uncomplicated Plasmodium falciparum malaria in Africa

A randomized, double-blind, parallel-group study in 104 hospitalized patients with acute, uncomplicated Plasmodium falciparum malaria was performed in West and Central Africa from March to July 2001. Patients were randomized to receive simultaneous dosing (artesunate 200 mg/d plus mefloquine 250 mg/d from the first to the third day [investigational group]) or sequential dosing (artesunate 200 mg/d for 3 d plus mefloquine 250 mg on the second and 500 mg on the third day [reference group]). Patients were followed-up for 28 d, and clinical and parasitological outcomes were assessed. The 14-d cure rate was 100% in the investigational group and 98% in the reference group with no recrudescence until day 28. Mean times to fever and parasite clearance were similar between the 2 groups (32 h vs. 26 h and 45 h vs. 48 h) and tolerability was good in both groups. The number of patients with vomiting was statistically significantly lower in the investigational group compared to the reference group (3.8% vs. 19.2%, P = 0.014). A 3-d once-daily co-administration of artesunate and mefloquine starting on day one offers a practical dosing regimen, which is highly effective and well tolerated in patients with uncomplicated P. falciparum malaria.

[Geoclimatology and severity of snake bite envenomations in Benin]

Envenomations following snakebite are common in Benin where they constitute, particularly in certain areas, a significant problem for the local populations and health workers. The present epidemiological study describes the snakebite envenomations which occurred in 18 medical centres of the country (6 departmental hospitals and 12 provincial hospitals). The studied variables were: prevalence, length of hospitalisation, major complications, quality of therapeutic management and development of the disease according to area. The study covered a period from April 2000 to March 2001. 486 cases of snakebite necessitating hospitalisation were notified including 413 (85%) in the two northern departments: Atacora and Borgou. Males were largely predominant (90%) and patients under 40 years were the most numerous (82%). The dry season seemed a period of higher risk (75% of the cases). The delay between the bite and admission to hospital, studied for 120 patients in the area of Atacora (North-West Benin), was relatively long: the average was 4 days, with extremes ranging from 10 hours to 21 days. This delay explained the severity of the complications diagnosed. They can be listed according to decreasing frequency: shock, coagulopathy, acute renal failure, respiratory distress. Less than 20% of the patients could benefit from antivenom. Management in emergency care units was impossible in most cases, none of the medical centres (except in Porto-Novo, the capital) having an intensive care unit with artificial ventilation available. Average mortality was 22%. Poisonous snakebites remain serious in Benin, mainly in the northern part of the Country. Access to health care and the quality of the management must be improved. This will require significant efforts from health workers, medical authorities as well as the local population. It is urgent to plan a national therapeutic consensus to reduce the high mortality due to snakebites.

[Epidemiological data on snake bite cases reported in Benin from 1994 to 2000]

Snake bites constitute a frequent occupational injury, mainly occuRring during agricultural activities in Benin as in the majority of tropical countries. The present study was performed within the scope of a periodic epidemiological analysis of occupational injuries over the past 15 years. It is a retrospective study based on the snake bites reported by the Ministry of Public Health from 1994 to 2000. The data collected through the medical centre registers showed that, with a total of 30,273 cases declared during these 7 years, snakebites represent less than 1% of the whole causes of admission. Although the prevalence was weak, the lethality was very high (15%). Envenomations involved more deaths than malaria and acute respiratory infections together. One third of cases occurred in adults and teenagers. Lethality in infants was not negligible. The two departments of northern Benin accounted for 314 of the envenomations. Lethality does not appear to be decreasing. The routine management of cases should be improved by appropriate training for health care workers and the introduction of a therapeutic strategy at every level of the medical system.

Round table and synthesis of the meeting

Our knowledge of the epidemiology of scorpion stings and snakebites remains fragmentary but sufficient, nevertheless, to be able to confirm that envenomations constitute a real public health problem throughout Africa. In order for the health authorities to be able to improve management of this problem, data collection must be enhanced. The objective should be to determine what kinds of intervention are necessary (quantity of antivenom serum and drugs, in particular) and where they should be applied. Specialists must come to a rapid consensus for a simple therapeutic protocol to be used in peripheral health centres where means are often scarce. Training for health personnel is also insufficient. Appropriate courses must be organised for medical doctors and nurses within both their basic and on-going training. These courses must necessarily involve health personnel from rural zones must affected by envenomations. The availability of antivenom serum--the only specific, efficacious drug--must be improved as soon as possible. If quantitative and geographic needs can be determined by epidemiological studies, then distribution must be developed by original means (grouping orders at national level, direct orders) and diversified financial support (purchase on the open market, local authority grants, community participation). The symposium attendees agreed to meet again within two years' time to evaluate progress in the area.

[The risk of malaria transmission by blood transfusion at Cotonou, Benin]

The risk of transmission of infectious agents by blood transfusion is a permanent preoccupation for diseases that we do not know how to cure, such as hepatitis B, hepatitis C and AIDS. However, few studies have been carried out concerning the risks of transmitting curable infectious diseases, such as malaria. We carried out a cross-sectional study of 355 healthy blood donors in the rainy season, in which we used thick and thin blood film smears to screen for malaria. We found that 33.5% of donors harbored trophozoites and were therefore capable of transmitting malaria via blood donation. There were 1,000 to 4,760 parasites per microliter of blood and there was no relationship between the load of parasitized red blood cells and clinical malaria. Plasmodium falciparum was the most common species identified (96.63% of cases). The results confirm that it is vital, in this age of resistance to anti-malaria drugs and HIV, to screen blood donations systematically. Patients receiving transfusions should be given anti-malaria treatment and donors should be encouraged to sleep under treated mosquito nets.

[Preliminary evaluation of morbidity due to S. haematobium and S. mansoni in the area of the future Adjarala Dam in Benin]

The aim of this study was to provide a preliminary assessment of morbidity due to schistosomiasis in the area of the future Adjarala Dam in Benin. We included 412 schoolchildren from five villages in the study. The mean age of the children was 9.4 +/- 2.3 years and the sex ratio (F/M) was 0.94. These children underwent parasitological examination. The children provided urine samples, which were examined by eye, filtered and tested for blood and protein. Stool samples were examined using Kato's technique and an ultrasound scan of the urinary tract was performed. We carried out a survey of snails at the possible transmission sites of all the villages, with a view to identifying the intermediate hosts. We detected S. mansoni and S. haematobium in the area. Urinary schistosomiasis was mesoendemic (prevalence of 19.7%) whereas schistosomiasis due to S. mansoni was hypoendemic (prevalence of 3. 9%). Ultrasound scans showed that 28% of the children had bladder lesions and that 2.5% were carriers of hydronephrosis. We compared the diagnostic performances of the various indirect indicators of morbidity. We found that a history of hematuria was the most sensitive indicator (88%) but that the sensitivity of this indicator differed significantly according to the sex of the child. Hematuria >= 1+ was the most effective indicator. Snail surveys showed that Biomphalaria pfeifferi and Bulinus globosus were present in the area.

Molecular characterisation of Plasmodium reichenowi apical membrane antigen-1 (AMA-1), comparison with P. falciparum AMA-1, and antibody-mediated inhibition of red cell invasion

Apical membrane antigen 1 is a candidate vaccine component for malaria. It is encoded by a single copy gene and has been characterised in a number of malaria species as either an 83-kDa de novo product (Plasmodium falciparum; Pf AMA-1) or a 66-kDa product (all other species). All members of the AMA-1 family are expressed during merozoite formation in maturing schizonts and are initially routed to the rhoptries. Processed forms may subsequently be associated with the merozoite surface. Because of the unique occurrence of the 83-kDa form in P. falciparum we were interested to determine whether the phylogenetically closely related chimpanzee malaria Plasmodium reichenowi shared characteristics with Pf AMA-1. Here we show that the molecular structure, the localisation and processing are similar to that of Pf AMA-1 and that in vitro growth inhibitory mAbs reactive with Pf AMA-1 also inhibit P. reichenowi growth in an in vitro assay. Polymorphism in the 83-kDa AMA-1 family was analysed through comparison of Pr ama-1 with Pf ama-1 alleles, which showed the most significant evidence for selection maintaining polymorphism in Domains I-III of AMA-1 in P. falciparum. The most substantial divergence between Pr AMA-1 and Pf AMA-1 sequences was in the N-terminal region unique to the 83-kDa form of AMA-1. It was confirmed that the specific Pr ama-1-type allele was not present among P. falciparum parasites in an African population, and an allele coding for lysine at amino acid 187 was uniquely associated with field isolates in this population.

[Granulomatous peritonitis from ascariasis: apropos of 1 case in a Benin child]

We report a case of granulomatous peritonitis in a child, due to Ascaris lumbricoïdes eggs. A 6 year-old child was admitted to the emergency ward with acute abdomen pain. Upon performing a laparotomy, severe adhesive inflammation and adenopathies were found and abdominal tuberculosis was diagnosed. Specific treatment was administered. Later, the acurage diagnosis of Ascaris ova peritonitis was made by histopathological examination of tissue removed during the operation. The pathogenesis is briefly discussed.

[Epidemiological observations on the first case of human paragonimiasis and potential intermediate hosts of Paragonimus sp. in Benin]

Parasitological investigations were carried out for four months in 1998 in two Beninese centres of pneumo-phtisiology (Akpakpa, at Cotonou, and Akron, at Porto-Novo) to detect the patients harbouring eggs of Paragonimus sp. amongst the persons consulting for tuberculosis and showing a broncho-pneumopathy without mycobacteria. Eggs of Paragonimus sp. were detected in the sputum of a single patient out of 369 persons examined (prevalence, 0.2%). This patient had eaten crabs in the months preceding the date of diagnosis. A treatment using praziquantel has improved clinical symptomatology and biological signs found in this patient. These studies have been completed by visiting markets located in the coastal plain of Benin to identify the crabs that were sold and to find metacercariae of Paragonimus sp. Negative results were obtained when 126 Cardisoma armatum ("hole crab") were dissected. In contrast, the dissection of 176 Callinectes marginatus ("swimming crab") was successful, with 5% of crabs harbouring metacercariae of probably Paragonimus sp. Further studies are necessary to confirm these first results and to determine the global prevalence of Paragonimus infection in these definitive and intermediary hosts.

Lymphatic filariasis in a hyperendemic region: a ten-year, follow-up panel survey

The present study is a long-term panel survey of a population living in a previously identified Wuchereria bancrofti-endemic area of Benin. Unexpectedly, a marked decrease in the prevalence of microfilaremia (from 9.4% to 0.48%; P < 0.001) occurred over a 10-year period in the absence of chemotherapy or vector control measures. The percentage of patients with chronic pathology remained stable during the study period. The decrease in the prevalence of parasitemia could not be explained by environmental or sociologic changes in the region, or by differences between the two study populations. These data suggest that the epidemiology of lymphatic filariasis in an endemic region may change independently of recognized modulating factors.

Strong IgG isotypic antibody response in sowdah type onchocerciasis

Persons exposed to Onchocerca volvulus express differences in manifestations of onchocerciasis ranging from hyporeactive (generalized) to hyperreactive (sowdah) forms; absence of disease is seen in endemic normal persons. Analysis of the IgG isotypic antibody response to O. volvulus extracts and nonparasite ubiquitous antigens in 92 West Africans revealed highest anti-O. volvulus IgG1 and IgG2 responses in sowdah, high levels in the generalized form, and low antibody levels in endemic normal persons. Nonexposed persons had no antibodies. A significant IgG3 antibody response was detected only in sowdah, while high IgG4 levels occurred in both polar groups but were absent in both control groups. Isotypic responses to antigens unrelated to O. volvulus were similar in all groups but showed higher IgG1 and IgG2 levels in sowdah. Sowdah patients had high levels of Ro/SS-A antibodies, circulating immune complexes, and eosinophil cationic protein. These results document a strong B cell response in African sowdah and indicate variations in immune responsiveness.

Gamma delta T cells in the peripheral blood of individuals from an area of holoendemic Plasmodium falciparum transmission

gamma delta T cells bearing V gamma 9 T cell receptors from unexposed Caucasian donors make large responses to Plasmodium falciparum in vitro. This finding, together with observations of others showing high levels of V gamma 9+ T cells in the blood of infected non-immune individuals, led us to hypothesize that the response of these cells might contribute to the pathology of P. falciparum malaria. Acquisition of immunity to disease in people naturally exposed to infection may therefore be due in part to down-regulation or alteration of the function of gamma delta T cells. Supporting this view, and in contrast to infection in non-immune individuals, V gamma 9+ T cells are not elevated in peripheral blood of children or adults living in an endemic area despite constant exposure to P. falciparum. After in vitro stimulation with P. falciparum, however, the expansion of V gamma 9+ cells from the African donors is of similar magnitude to that observed for non-exposed Europeans. Thus, although these cells are not elevated in peripheral blood, they are still able to respond to P. falciparum antigens. In adult European donors the major gamma delta T cell population in peripheral blood is V gamma 9+ (approximately 70% of all gamma delta cells), whereas in the majority of adult Africans V delta 1+ V gamma 9- T cells predominated (approximately 70% of total gamma delta cells).

Albendazole in human loiasis: results of a double-blind, placebo-controlled trial

To assess the filaricidal activity and clinical safety of albendazole in human loiasis, a double-blind, placebo-controlled study was conducted in an endemic area in Benin, Africa. Twenty-three men with microfilaremia (100-30,000/mL) were randomly assigned to receive albendazole (200 mg; n = 11) or placebo (n = 12) twice daily for 21 days; 1 patient from each group withdrew from the study. There were no clinical adverse effects and no observed hepatotoxicity, renal toxicity, or hematologic abnormalities attributable to the drug. In the albendazole group, microfilarial levels began to decrease at day 14 after treatment and by 6 months had fallen to a geometric mean of 20% of pretreatment levels (vs. 84.8% in the placebo group). Blood eosinophil levels and anti-filarial IgG and IgG4 also fell significantly in response to albendazole. Taken together, these data suggest that albendazole has a primary (possibly embryotoxic) effect on the adult parasite, resulting in a slow decrease in microfilaremia.

Epidemiological studies of onchocerciasis in southern Benin

We studied the prevalence of human onchocerciasis in four geographically different regions of the southern part of Benin in West Africa. In a total of thirteen villages 1596 individuals were examined for clinical and parasitological signs of onchocerciasis. Prevalence of microfilariae of Onchocerca volvulus in skin snips was 29% in region I (lower Oueme river), 64% in region II (Mono river), 56% in region III (upper Oueme river) and 70% in region IV (Okpara river). Based on endemicity criteria of the WHO regions II and IV were found to be hyperendemic, region III mesoendemic and region I hypoendemic for onchocerciasis. The community microfilarial load ranged from 4 mf/mg skin in the hypoendemic region to 10.5 mf/mg skin in the hyperendemic regions. The prevalence of nodules was 21% in region I, 30% in region II, 17% in region III and 41% in region IV. The overall prevalence of chronic onchocercal dermatitis was 12%. Of 689 individuals infected with O. volvulus 388 were treated with a single dose of ivermectin.

[Rotavirus gastroenteritis in a pediatric service at the National University Hospital Center of Cotonou (Benin)]

The authors are reporting results from rotavirus research in diarrhoeal stools among 220 children under 5 years of age in Cotonou C.N.H.U. (Bénin). Among them, 64 (29%) are rotavirus carriers.

[Clinical evaluation and epidemiology of dracunculosis in Benin]

A clinical and epidemiological longitudinal survey was made from 1985 to 1989 in four villages of a dracunculiasis hyper endemic region of Benin to identify indices usable in evaluation of prevalence or incidence of dracunculiasis. 720 patients were examined. 93.5% presented a typical eruption of one or more worms. Inflammatory, infectious or mechanical complications were observed in 57.5% of cases and induced disabilities in 44.7% of patients. Although retrospective surveys are easier, authors do not recommend such studies. Cross-sectional surveys would be performed at the peak of transmission. The index would be the number of disabled seen in the village at the moment of investigators' passage. This index represents about 20% of annual dracunculosis cases. Longitudinal surveys would be made by village health workers. The best index is the number of worm eruptions corrected by a reducing factor: from 0.4 to 0.67 according to transmission pattern of the region and knowledge of the local transmission model.

Loiasis in endemic and nonendemic populations: immunologically mediated differences in clinical presentation

To define the clinical spectrum of loiasis more precisely and to begin to assess the immunologic basis for the difference in clinical manifestations between visitors to endemic areas and natives of these areas, 51 West African patients with loiasis were evaluated and compared with 42 infected expatriates. Microfilaremia was present in 90% and Calabar swellings in only 16% of the endemic patients. Conversely, only 10% of the expatriates were microfilaremic while 95% complained of Calabar swellings. The endemic population showed significantly decreased levels of peripheral blood eosinophils, parasite-specific IgG, and lymphocyte proliferation to parasite antigens compared with the nonendemic population. These findings support the hypothesis that differences in the modulation of the immune response to parasite antigen are responsible for the observed differences in clinical presentation between expatriate and endemic populations with loiasis.

Seroepidemiology of human T-cell lymphotropic virus type I/II in Benin (West Africa)

In 1988-1989, a national survey was conducted in Benin to determine the distribution of HTLV-I infection in a representative sample of adult individuals. This study comprised 2625 healthy subjects recruited in the six provinces of Benin and 1300 blood donors from Cotonou and from the other five provinces. Sera were screened for HTLV-I antibody by both immunofluorescence (IF) and enzyme immunoassay (EIA). Sera positive or doubtful by at least one technique were further analyzed by Western blot and radioimmunoprecipitation assay (RIPA) when indeterminate. Samples were considered as positive if they reacted with two gene products. No blood donor was positive. Over the 2625 subjects, 39 (1.5%) were positive. We observed a statistical difference between male and female (1%, 2%, p less than 0.05). A difference was also observed according to the areas studied: the HTLV-I antibody rate increased from coastal (0.3%) to northern (5.4%) provinces. HTLV-I seroprevalence increased significantly with age. This survey shows that HTLV-I infection exists in Benin but varies according to regions.

[In vivo amodiaquine sensitivity of Plasmodium falciparum in the town of Cotonou and in the vicinity (Bénin)]

In the coastal area of Benin, where chloroquine resistant Plasmodium falciparum strains occur, 152 children in the Guezo military camp (Cotonou) and 448 children in a fishermen village (Ekpe), on the southern bank of lake Nokoue, are examined. The falciparum malaria infected children (29 and 135 respectively) have received 35 mg/kg body weight of amodiaquine (Flavoquine) divided in three consecutive daily doses. Only one child among the 69 treated having a parasitemia higher than 1,000/mm3 failed to be cured. The amodiaquine tolerance is excellent for, respectively, 64% and 72% of the children. Minor side-effects are rapidly regressive. The frequency of conjonctival hyperhemia as an amodiaquine side-effect is nevertheless relatively high (14.7%) in the children regularly treated with this drug, e.g. those of the military camp, while it is rare (0.8%) in others, e.g. in the fishermen village children where amodiaquine is unusual as an antimalarial medicine.