Rifampicin/Cotrimoxazole/Isoniazid versus mefloquine or quinine + sulfadoxine- pyrimethamine for malaria: a randomized trial

OBJECTIVES

Previous studies of a fixed combination including cotrimoxazole, rifampicin, and isoniazid (Cotrifazid) showed efficacy against resistant strains of Plasmodium falciparum in animal models and in small-scale human studies. We conducted a multicentric noninferiority trial to assess the safety and efficacy of Cotrifazid against drug-resistant malaria in Papua New Guinea.

DESIGN

The trial design was open-label, block-randomised, comparative, and multicentric.

SETTING

The trial was conducted in four primary care health facilities, two in urban and two in rural areas of Madang and East Sepik Province, Papua New Guinea.

PARTICIPANTS

Patients of all ages with recurrent uncomplicated malaria were included.

INTERVENTIONS

Patients were randomly assigned to receive Cotrifazid, mefloquine, or the standard treatment of quinine with sulfadoxine-pyrimethamine (SP).

OUTCOME MEASURES

Incidence of clinical and laboratory adverse events and rate of clinical and/or parasitological failure at day 14 were recorded.

RESULTS

The safety analysis population included 123 patients assigned to Cotrifazid, 123 to mefloquine, and 123 to quinine + SP. The Cotrifazid group experienced lower overall incidence of adverse events than the other groups. Among the efficacy analysis population (72 Cotrifazid, 71 mefloquine, and 75 quinine + SP), clinical failure rate (symptoms and parasite load) on day 14 was equivalent for the three groups (0% for Cotrifazid and mefloquine; 1% for quinine + SP), but parasitological failure rate (P. falciparum asexual blood-stage) was higher for Cotrifazid than for mefloquine or quinine + SP (9% [PCR corrected 8%] versus 0% and 3%, respectively [p = 0.02]).

CONCLUSION

Despite what appears to be short-term clinical equivalence, the notable parasitological failure at day 14 in both P. falciparum and P. vivax makes Cotrifazid in its current formulation and regimen a poor alternative combination therapy for malaria.

The sensitivity of the OptiMAL rapid diagnostic test to the presence of Plasmodium falciparum gametocytes compromises its ability to monitor treatment outcomes in an area of Papua New Guinea in which malaria is endemic

Using in vivo samples from treatment failure malaria cases, we demonstrate the high sensitivity of the parasite lactase dehydrogenase (pLDH)-based OptiMAL rapid diagnostic test in the detection of P. falciparum gametocytes. This high sensitivity limits the use of pLDH-based tests in the monitoring of treatment outcomes in circumstances where gametocytemia is common.

Parasitological and clinical efficacy of standard treatment regimens against Plasmodium falciparum, P. vivax and P. malariae in Papua New Guinea

Resistance of Plasmodium falciparum (Pf) and P. vivax (Pv) to standard antimalarials is widespread in Papua New Guinea (PNG). The objective of the study was to assess the rate of clinical treatment failure (TF) and parasite resistance to amodiaquine (AQ), chloroquine (CQ) and quinine+sulfadoxine/pyrimethamine (Q+SP) for malaria in a rural health centre of the East Sepik Province. 179 patients presenting with symptoms and signs of malaria and with Pf (144 patients), Pv (18 patients), P. malariae (Pm) (7 patients) or mixed infection (10 patients) were included. 86 were treated with AQ, 88 with CQ and 5 with Q+SP. 21/179 patients (12%) were not cured or had a recrudescence of symptoms associated with parasitaemia in the 28 days following treatment, 14% after AQ, 10% after CQ and 0% after Q+SP. The proportion of TF was higher (17%) when the analysis population included only the 108 subjects who had a complete follow-up, especially for failure with Pf following AQ treatment (26%). During the 28 days of follow-up, RII or RIII level of resistance in Pf was detected in 55% of the subjects treated with amodiaquine, 30% of those treated with chloroquine and 0% of those treated with quinine+SP. Of the Pv or Pm parasites only one Pv was found to be RII resistant to CQ in the 28-day test. In vitro resistance of Pf to CQ was higher than to AQ (50% versus 27% of 36 parasite samples that grew successfully). The level of TF and parasitological resistance to standard antimalarial drugs was lower in this area than in urban settings, where drugs are more easily available. AQ performed less well than CQ but the difference is likely to be due to the age of the users, ie, their level of immunity, AQ being the first-line drug for young children. These results provided support for the recent change in the policy for the standard treatment of uncomplicated malaria in PNG from AQ or CQ to the combination of AQ+SP or CQ+SP, a recommendation aimed at slowing down the spread of multidrug resistance.

Molecular analysis of Plasmodium falciparum from drug treatment failure patients in Papua New Guinea

A study was conducted in Papua New Guinea to analyze Plasmodium falciparum drug resistance polymorphisms in patients presenting with resistant malaria. One hundred ninety-nine P. falciparum-positive patients were recruited at two sites, Madang and Maprik. Exposure to the 4-aminoquinolines chloroquine and amodiaquine was uniformly high, at 84% overall. However, 59% of these were taken in various combinations of sulfadoxine/pyrimethamine and/or primaquine and/or quinine. Two markers for 4-aminoquinoline resistance, P. falciparum chloroquine resistance transporter 76T and P. falciparum multidrug resistance 1, were fixed in the population and two markers for pyrimethamine resistance, dihydrofolate reductase (dhps) 59R and 108N, were found at moderate to high levels, overall 60% and 75%, respectively. No polymorphisms in dhps associated with sulfadoxine resistance were present. Differences between the two sites are analyzed. The study period encompasses a change in standard malaria treatment policy. These findings stress the need for regular monitoring of the effects of standard drug treatment of uncomplicated malaria in Papua New Guinea.

Safety and immunogenicity of a three-component blood-stage malaria vaccine in adults living in an endemic area of Papua New Guinea

A Phase I safety and immunogenicity study with a three-component blood-stage malaria vaccine was conducted in adult male subjects living in an endemic area of Papua New Guinea. The preparations were recombinant proteins which corresponded to parts of the two merozoite surface proteins of Plasmodium falciparum (MSP1 and 2), and of the ring-infected erythrocyte surface antigen (RESA). The three proteins were emulsified with the adjuvant Montanide ISA720. Ten subjects were injected twice (four weeks apart) with the vaccine formulation and two with the adjuvant alone. Mild pain at the site of injection was reported by about half of the subjects but no systemic reaction related to the formulation occurred. There was a sharp rise in geometric mean stimulation index after the second dose compared to baseline for MSP1 and RESA, while the rise was small for MSP2. Geometric mean antibody titres increased for MSP1 during the study, whereas they hardly changed for MSP2 and RESA. The vaccine formulation was safe when used in an already immune population. The vaccine induced good cellular responses, especially for MSP1 and RESA. Boosting of humoral responses was weak, probably because of high baseline antibody levels.

Measurement of ovalocyte frequency in peripheral blood smears in defining ovalocytosis in Papua New Guinea

Red cell oval morphology is still the only accepted basis for the clinical or epidemiological diagnosis of ovalocytosis. Therefore it is important to know the errors when detecting and counting morphological ovalocytes. In all previous studies of ovalocytosis there was no assessment of the variation which may have occurred in classification due to smearing and staining techniques or the criteria for the diagnosis of ovalocyte morphology; nor was inter or intraobserver variation assessed. We report how different peripheral blood smear methods influence the diagnosis of ovalocytosis in populations in the Madang and East Sepik Provinces in Papua New Guinea. We also examined within and between observer variation in the quantitative assessment of ovalocytosis at x 40 and x 100 microscopy powers. A modified method of making a thin malaria blood smear gave the best preservation of red cell morphology and was adopted for the quantitative ovalocytosis studies. A special haematology smear is unnecessary. Ovalocyte frequency estimations were similar when x 40 and x 100 lenses were used, but x 40 was preferable for assessing morphology. Two observers were consistent in their findings and produced very similar results for the high-quality smears from the planned Madang survey, and rather different results for the smears from the unplanned routine Sepik survey. We conclude that measurement error for ovalocytosis assessment can be quite small and unimportant, minimized by careful planning and quality control. Otherwise measurement error is substantial and threatens validity of classification and grading of ovalocytosis.

Relation of anthropometry to malaria morbidity and immunity in Papua New Guinean children

The interaction between malnutrition and malaria is complex and there is evidence that malnutrition decreases the susceptibility to malaria. To investigate the relation between anthropometric measurements and subsequent malaria morbidity and to examine whether the effect observed was due to interaction with host immunity, we followed for 1 y a cohort of 136 children aged 10 to < 120 mo in Wosera, East Sepik Province, Papua New Guinea. At baseline, 21% were stunted, 10% were wasted, and 5% were both stunted and wasted. After adjustment for age and use of bed nets, height-for-age z score (HAZ) at baseline predicted the number of clinical episodes of falciparum malaria during the following year: incidence rate increased with increasing HAZ. Humoral responses to specific malarial antigens were lowest in the wasted children. The prevalence of lymphoproliferative responders was not significantly different between well-nourished and undernourished children. In contrast, the prevalence of cytokine producers was higher in the undernourished than in the well-nourished children. Our findings support the view that stunting but not wasting protects against falciparum malaria. The mechanism may be related to an improved ability of malnourished children to produce certain cytokines in response to stimulation by specific malarial antigens.

Assessment of the role of the humoral response to Plasmodium falciparum MSP2 compared to RESA and SPf66 in protecting Papua New Guinean children from clinical malaria

The prevalence and concentration of naturally acquired humoral response (IgG) to merozoite surface protein 2 (MSP2), RESA, SPf66 and crude schizont extract were measured in a population living in a malaria highly endemic area of Papua New Guinea. A prospective longitudinal study in 0.5-15 year old children was conducted for one year in order to examine the relationship between the humoral response to these antigens and subsequent susceptibility to clinical malaria using a series of clinical definitions. The prevalence and concentration of antibodies to all antigens increased with age. Such correlation with age was most marked for MSP2 recombinant proteins. When age and previous exposure were controlled for, only antibody levels to MSP2 recombinant proteins (3D7 and d3D7) and to RESA predicted a reduction in incidence rate of episodes of clinical malaria. Our results support the inclusion of the recombinant proteins of the 3D7 allelic family of merozoite surface antigen 2 and RESA into a subunit vaccine against malaria.

The epidemiology of malaria in the Wosera area, East Sepik Province, Papua New Guinea, in preparation for vaccine trials. II. Mortality and morbidity

Malaria mortality and morbidity were studied in a rural population of 4000 in the Wosera area, East Sepik Province, Papua New Guinea. Malaria accounted for 4.9% of the 162 deaths investigated by verbal autopsy and for 12.2% of the 49 deaths assessed through medical records. Malaria was the first cause of death in children aged 0.5-4 years. Of the 7795 subjects interviewed and bled during six cross-sectional community-based surveys, children of 1-4 years had the highest malaria-related morbidity. In this age group, point prevalences of fever, fever associated with parasitaemia, and fever plus Plasmodium falciparum (Pf) parasitaemia > or = 10,000 parasites/microliters blood were 5%, 4.1% and 1.5%, respectively. The corresponding figures for adults were 2%, 0.9% and 0.1%, respectively. The calculation of attributable fraction (AF) using a multiple logistic regression model showed that malaria accounted for 0.44 of all fevers in children of 1-4 years and 0.08 of the fevers in adults. Prevalence data derived from the AF estimate were compared with those calculated using different accepted density thresholds. The prevalences which best approximated the results from the logistic regression model were obtained using parasitaemia cut-offs of > or = 1000 Pf parasites/microliter in children aged 1-4 years and adults older than 19 years and of > or = 10,000 parasites/microliter in those aged 5-19 years. Prevalence of fever associated with parasitaemia was highly seasonal, with a peak at the beginning of the wet season. The geographical distribution of malaria morbidity was not uniform. The measurement of malaria-related morbidity, the identification of significant seasonal and local variation as well as the assessment of different methods of defining a clinical episode of Pf malaria are crucial for the design and evaluation of intervention studies, including field trials of antimalarial vaccines.

The use of untreated bednets and malaria infection, morbidity and immunity

The effect of bednet use was investigated, without undertaking a specific intervention, in four cross-sectional community-based surveys in 10 villages of a highly endemic area of Papua New Guinea. Over half (55%) of the villagers interviewed reported that they had used a bednet on the previous night. In general and after adjustment for age, village and housing characteristics, bednet users, particularly children, had lower parasite prevalences and spleen rates and less enlarged spleens than non-users. However, users were similar to non-users in terms of fever reported for the previous week, axillary temperature, parasite density and haemoglobin level. The prevalence of antibody to the ring erythrocyte surface antigen and the major merozoite surface antigen 2 was lower in users than non-users. The association with malariometric indices and immune responses remained significant when bednet users were compared with non-users in houses without bednets. Thus, untreated bednets do not reduce malaria transmission sufficiently to decrease morbidity. They might paradoxically increase the risk of clinical malaria by lowering the development of humoral immunity.

Failure of chloroquine prophylaxis for falciparum malaria in pregnant women in Madang, Papua New Guinea

Six hundred and twenty pregnant women, living under conditions of year-round transmission of malaria in a rural coastal area of Madang, Papua New Guinea (PNG), were followed while attending mobile antenatal clinics and receiving chloroquine prophylaxis (300 mg base weekly). Whole blood chloroquine concentrations measured by ELISA from samples collected at delivery indicated a high level of drug compliance in regular attenders. Susceptibility is increased in primigravidae to Plasmodium falciparum but not to other malaria species, with the peak prevalence occurring at nine to 16 weeks gestation. The incidence of P. falciparum infection per person-month was 20% for primigravidae, 25% for those gravida 2, 17% for those gravida 3 or greater, and 14% for non-pregnant nulliparae. Some 8.7% of primigravidae and 9.5% of those gravida 2 had persistent infections. Prophylactic chloroquine is required in this pregnant population because of altered host immunity during pregnancy, but is reduced in efficacy because of chloroquine resistance. Despite this, a missed clinic attendance resulted in a two-fold increase in incidence for all pregnant women, indicating that chloroquine was having some effect.

Consequences of maternal anaemia on outcome of pregnancy in a malaria endemic area in Papua New Guinea

The prevalence of anaemia during pregnancy was investigated in relation to parasite and spleen rates of pregnant women living in a defined study area in rural Madang, Papua New Guinea. The effects in pregnancy of anaemia, iron deficiency and malaria on the foetus were investigated. There is a high prevalence of anaemia in this population, with 44% of primigravidae and 29% of multigravidae having severe anaemia [haemoglobin (Hb) less than 8 g dl-1] after 28 weeks gestation. The odds ratio for severe anaemia at 0-16 weeks gestation in pregnant compared to non-pregnant women was 4.7 (P less than 0.0001). Forty-seven per cent of primigravidae and 32% of multigravidae had evidence of iron deficiency with high free erythrocyte protoporphyrin values (greater than 35 micrograms dl-1 whole blood) at antenatal booking. The risk of severe anaemia was significantly associated with splenomegaly and iron deficiency for all gravidae (splenomegaly P less than 0.05; iron deficiency, P less than 0.0002). Hb values at delivery were higher than at first attendance, with the greatest difference between groups malaria-positive at booking and malaria-negative at delivery (primigravidae 1.5 g dl-1, P less than 0.01; multigravidae, 0.7 g dl-1, P less than 0.01), indicating that malaria prophylaxis was an important factor in controlling anaemia. Two Hb groups were defined on the basis of the cut-off at 8 g dl-1, which corresponded to the lower quartile value at booking and delivery. A significantly increased risk of low birthweight was shown for primigravidae with values below 8 g dl-1 (65% v. 27%, P less than 0.025), but the prematurity rate was not significantly increased, indicating that the majority of babies were growth-retarded. Early pregnancy anaemia and iron deficiency were related to the risk of low birthweight in primigravidae. Current parasitaemia at delivery appeared a less important factor, although primigravidae with severe anaemia and parasitaemia at delivery had the lowest birthweights. The extent to which malaria control, using drug treatment and chemoprophylaxis, can reduce the risk of low birthweight will vary in relation to the prevalence and causes of anaemia in women.

Reduction in incidence and prevalence of Plasmodium falciparum in under-5-year-old children by permethrin impregnation of mosquito nets

The malaria incidence and prevalence rates among children who slept under permethrin-impregnated mosquito nets in four villages near Madang, Papua New Guinea, were compared with the rates among children who slept under unimpregnated nets in four paired control villages. Immediately following a parasitological survey in the eight villages, malaria parasites were cleared from the children with chemotherapy, and the mosquito nets in the four experimental villages were impregnated with permethrin. Follow-up parasitological surveys were performed 4 and 10 weeks later. Sporozoite rates in female mosquitos of the Anopheles punctulatus complex decreased significantly in two of the experimental villages after impregnation. Also, the incidence of Plasmodium falciparum between the 4-week and 10-week surveys was significantly lower among the 0-4-year olds in villages with impregnated nets than in those with unimpregnated nets, leading to reduced prevalence of P. falciparum in this age group. Use of permethrin-impregnated nets had no effect on the incidence or prevalence of P. falciparum among 5-9-year olds or on that of P. vivax among the 0-4- or 5-9-year olds.