Chantal Van Overmeir

Human Plasmodium knowlesi infections in young children in central Vietnam

BackgroundConsidering increasing reports on human infections by Plasmodium knowlesi in Southeast Asian countries, blood samples collected during two large cross-sectional malariometric surveys carried out in a forested area of central Vietnam in 2004 and 2005 were screened for this parasite.MethodsBlood samples collected at the 2004 survey and positive for Plasmodium malariae were randomly selected for PCR analysis detecting P. knowlesi. Blood samples collected in 2005 from the same individuals were screened again for P. knowlesi. Positive samples were confirmed by sequencing. Family members of positive cases who participated in both surveys were also screened.ResultsNinety-five samples with P. malariae mono- or mixed infections identified by species-specific PCR were screened for P. knowlesi. Among the five (5.2%) positive samples by PCR, three were confirmed to be P. knowlesi infections by sequencing, two young children (<5 years old) and a young man, all asymptomatic at the time of the survey and for the next six months after the survey. One of the two children was still positive one year later. No infection was found among the family members.ConclusionPlasmodium knowlesi infections in humans can be found in central Vietnam. A small child was positive for P. knowlesi in both surveys at one year interval, though it is unclear whether it was the same or a new infection.

HIV-1 Immune Suppression and Antimalarial Treatment Outcome in Zambian Adults with Uncomplicated Malaria

BACKGROUND Human immunodeficiency virus (HIV)-1 infected adults with low CD4 cell count have a higher risk of malaria infection and clinical malaria. We assessed the influence that HIV-1 immune suppression has on the efficacy of antimalarial treatment in adults with uncomplicated malaria. METHODS This clinical trial included 971 Zambian adults with uncomplicated malaria. Patients were tested for HIV-1, and, if positive, a CD4 cell count was assessed. The primary outcome was recurrent parasitemia corrected by molecular genotyping within 45 days after treatment. RESULTS HIV-1 infection was detected in 33% (320/971) of adult patients with malaria. Treatment failure was not associated with HIV-1 infection (relative risk [RR], 1.12 [95% confidence interval {CI}, 0.82-1.53]; P=.45). HIV-1-infected patients with a CD4 cell count <300 cells/microL had an increased risk of recurrent parasitemia, compared with those with a CD4 cell count >or=300 cells/microL (RR, 2.24 [95% CI, 1.20-4.14]; P=.01). After genotyping, the risk of recrudescence was higher in HIV-1-infected patients with a CD4 cell count <300 cells/microL than in the other patients with malaria (RR, 1.67 [95% CI, 1.13-2.47]; P=.02). CONCLUSION HIV-1-infected patients with malaria with a CD4 cell count <300 cells/microL have a higher risk of experiencing a recrudescent infection, compared with those with a CD4 cell count >or=300 cells/microL or without HIV-1 infection. Trial registered at http://www.clinicaltrials.gov/; reference number NCT00304980.

High Complexity of Plasmodium vivax Infections in Symptomatic Patients from a Rural Community in Central Vietnam Detected by Microsatellite Genotyping

Fourteen published and three newly identified polymorphic microsatellites were used to genotype 69 Plasmodium vivax samples obtained from 39 patients detected over a period of two years who lived in a rural community of central Vietnam. All samples were polyclonal with an average expected heterozygosity of 0.86. Among the 39 patients, 16 experienced 1–5 recurrent episodes of P. vivax malaria, most of them (83%) with a different genotype profile compared with previous infections. The minimal set of microsatellites required for differentiating the genotype profiles of the recurrent infections compared with the full set of 17 microsatellites was explored. A combination of five markers was sufficient to identify all recurrent infections with an unrelated or different genotype profile compared with all previous episodes.

Is amodiaquine failing in Rwanda? Efficacy of amodiaquine alone and combined with artesunate in children with uncomplicated malaria

We investigated the safety and efficacy of amodiaquine alone (AQ) and combined with artesunate (AQ + AS) in 308 Rwandan children 6–59 months old with uncomplicated Plasmodium falciparum malaria attending three sentinel sites. The two treatment regimes were well tolerated and no serious adverse events were recorded. After excluding new infections, children treated with AQ + AS had fewer clinical failures at day 28 after treatment than those treated with AQ alone: OR = 0.20 [95% CI: 0.06–0.57 (P = 0.001)]. Total (parasitological and clinical) failure was also significantly less frequent in the AQ + AS group: OR = 0.34 [95% CI: 0.17–0.67 (P = 0.001)]. When adjusting for study site, the hazard ratio for treatment failure was 0.37 [95% CI: 0.20–0.68 (P = 0.001)]. Combining AQ with AS increases the efficacy of the treatment but the apparent increase of AQ resistance observed in just a 1‐year period is worrying and casts doubts on the suitability of implementing AQ + AS as first‐line treatment in Rwanda. Alternative treatments should be identified and tested.

Safety and efficacy of lumefantrine-artemether (Coartem ® ) for the treatment of uncomplicated Plasmodium falciparum malaria in Zambian adults

BackgroundIn Zambia, unacceptably high resistance to commonly used antimalarial drugs prompted the choice of artemether-lumefantrine (AL) as first line treatment for uncomplicated Plasmodium falciparum malaria. Although the safety and efficacy of AL have been extensively documented, no clinical trials had been carried out in Zambia.MethodsNine hundred seventy one adult patients with uncomplicated malaria were randomized to either sulfadoxine-pyrimethamine (SP)(486) or AL (485) and followed up for 45 days. Outcome of treatment was defined according to the standard WHO classification. Recurrent parasitaemia were genotyped to distinguish between recrudescence and new infection.ResultsFever at day 3 was significantly lower (AL: 0.9%; 4/455; SP: 3,5%; 15/433; p = 0.007) and the mean haemoglobin at day 45 significantly higher (AL: 134 g/l; SP 130 g/l; p = 0.02) in the AL group. Almost all clinical symptoms cleared faster with AL. Early treatment failure was significantly higher in the SP (25/464) than in the AL (2/463) (OR: 13.1 95% CI: 3.08–55.50; P < 0.001). The rate of new infections was similar in both groups (18 with SP and 19 with AL). Late clinical failure (OR: 2.55; 95% CI: 1.34–4.84; P = 0.004) and late parasitological failure (OR:3.18; 95% CI: 1.25–8.09; P = 0.02) were significantly higher in the SP group. Total treatment failure was significantly higher in the SP group (96/393; 19.3%) as compared to the AL (22/403; 5.4%) group (OR: 4.15; 95% CI: 2.52–6.83; P < 0.001).ConclusionIn Zambia, the new first line regimen AL is far more efficacious than SP in treating uncomplicated P. falciparum malaria in adults. Data on safety and efficacy of AL in pregnant women are urgently needed.

Varying efficacy of artesunate+amodiaquine and artesunate+sulphadoxine-pyrimethamine for the treatment of uncomplicated falciparum malaria in the Democratic Republic of Congo: a report of two in-vivo studies

BackgroundVery few data on anti-malarial efficacy are available from the Democratic Republic of Congo (DRC). DRC changed its anti-malarial treatment policy to amodiaquine (AQ) and artesunate (AS) in 2005.MethodsThe results of two in vivo efficacy studies, which tested AQ and sulphadoxine-pyrimethamine (SP) monotherapies and AS+SP and AS+AQ combinations in Boende (Equatorial province), and AS+SP, AS+AQ and SP in Kabalo (Katanga province), between 2003 and 2004 are presented. The methodology followed the WHO 2003 protocol for assessing the efficacy of anti-malarials in areas of high transmission.ResultsOut of 394 included patients in Boende, the failure rates on day 28 after PCR-genotyping adjustment of AS+SP and AS+AQ were estimated as 24.6% [95% CI: 16.6–35.5] and 15.1% [95% CI: 8.6–25.7], respectively. For the monotherapies, failure rates were 35.9% [95% CI: 27.0–46.7] for SP and 18.3% [95% CI: 11.6–28.1] for AQ. Out of 207 patients enrolled in Kabalo, the failure rate on day 28 after PCR-genotyping adjustment was 0 [1-sided 95% CI: 5.8] for AS+SP and AS+AQ [1-sided 95% CI: 6.2]. It was 19.6% [95% CI: 11.4–32.7] for SP monotherapy.ConclusionThe finding of varying efficacy of the same combinations at two sites in one country highlights one difficulty of implementing a uniform national treatment policy in a large country. The poor efficacy of AS+AQ in Boende should alert the national programme to foci of resistance and emphasizes the need for systems for the prospective monitoring of treatment efficacy at sentinel sites in the country.

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.

Marked age-dependent prevalence of symptomatic and patent infections and complexity of distribution of human Plasmodium species in central Vietnam.

In Vietnam, Plasmodium falciparum and P. vivax are responsible for most malaria infections, and P. malariae and P. ovale infections are rarely reported. Nevertheless, species-specific polymerase chain reaction analysis on 2,303 blood samples collected during a cross-sectional survey conducted in a forest area of central Vietnam identified 223 (9.7%) P. falciparum, 170 (7.4%) P. vivax, 95 (4.1%) P. malariae, and 19 (0.8%) P. ovale mono-infections and 164 (7.1%) mixed infections. Of the 671 Plasmodium-positive samples by polymerase chain reaction, only 331 were detected by microscopy. Microscopy poorly diagnosed P. malariae, P. ovale, and mixed infections. Clinical and sub-clinical infections occurred in all age groups. The risk for infection and disease decreased with age, probably because of acquired partial immunity. The common occurrence of sub-patent infections seems to indicate that the malaria burden is underestimated and that diagnostic and therapeutic policies should be adapted accordingly.

Development, validation and evaluation of a rapid PCR-nucleic acid lateral flow immuno-assay for the detection of Plasmodium and the differentiation between Plasmodium falciparum and Plasmodium vivax

BackgroundMolecular tools are very sensitive and specific and could be an alternative for the diagnosis of malaria. The complexity and need for expensive equipment may hamper implementation and, therefore, simplifications to current protocols are warranted.MethodsA PCR detecting the different Plasmodium species and differentiating between Plasmodium falciparum and Plasmodium vivax was developed and combined with a nucleic acid lateral flow immuno-assay (PCR-NALFIA) for amplicon detection. The assay was thoroughly evaluated for the analytical sensitivity and specificity in the laboratory, the robustness and reproducibility in a ring trial and accuracy and predictive value in a field trial.ResultsThe analytical sensitivity and specificity were 0.978 (95% CI: 0.932–0.994) and 0.980 (95% CI: 0.924-0.997), respectively, and were slightly less sensitive for the detection of P. vivax than for P. falciparum. The reproducibility tested in three laboratories was very good (k = 0.83). This evaluation showed that the PCR machine used could influence the results. Accuracy was evaluated in Thailand and compared to expert microscopy and rapid diagnostic tests (RDTs). The overall and P. falciparum-specific sensitivity and specificity was good ranging from 0.86-1 and 0.95-0.98 respectively, compared to microscopy. Plasmodium vivax detection was better than the sensitivity of RDT, but slightly less than microscopy performed in this study.ConclusionPCR-NALFIA is a sensitive, specific and robust assay able to identify Plasmodium species with good accuracy. Extensive testing including a ring trial can identify possible bottlenecks before implementation and is therefore essential to perform in additon to other evaluations.

Susceptibility of Grammomys surdaster thicket rats to Trypanosoma brucei gambiense infection.

Human African Trypanosomiasis is caused by Trypanosoma brucei gambiense and T. b. rhodesiense. Historically, a treatment relapse rate of about 5% is observed in patients treated with melarsoprol, an arsenical derivative used for treatment of both gambiense and rhodesiense second stage sleeping sickness. More recently, relapse rates up to 30% are noted in gambiense sleeping sickness foci in Angola, Sudan and Uganda. Therefore, WHO established a Network on Treatment Failure and Drug Resistance in Sleeping Sickness. One of its objectives is to improve isolation of T. b. gambiense from relapsing cases for research on drug resistance mechanisms. Trypanosoma b. gambiense isolation techniques suffer from low success rates and long periods needed to adapt the parasite to its new host. Usually, rodents are inoculated with patients blood or cerebrospinal fluid and sub‐passaged until the strain becomes sufficiently adapted to yield high parasitaemia within few days after inoculation. Until now, the best recipient for T. b. gambiense is Mastomys natalensis, with a success rate of about 50%. In this study, Grammomys surdaster (former Thamnomys surdaster) was investigated as a potential recipient for isolation of T. b. gambiense. Comparative experimental infections of Swiss mice, Wistar rats and G. surdaster thicket rats with T. b. gambiense clearly show that this trypanosome grows faster in G. surdaster. Inoculation of the same rodent species with patients blood and cerebrospinal fluid in Kinshasa (R.D. Congo) confirms the observation that the thicket rats are more susceptible to T. b. gambiense infection than typical laboratory rodents.