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Efficacy of chloroquine in the treatment of uncomplicated Plasmodium falciparum infection in East Timor, 2000
Acta Tropica 88 (2003) 87 /90 www.elsevier.com/locate/actatropica
Short communication
Efficacy of chloroquine in the treatment of uncomplicated Plasmodium falciparum infection in East Timor, 2000 Nadine Ezard a,*, Matthew Burns a, Caroline Lynch a, Qin Cheng b, Michael D. Edstein b a b
Medical Emergency Relief International, 5-13 Trinity Street, London SE1 1DB, UK Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Qld. 4052, Australia
Received 20 December 2002; received in revised form 12 April 2003; accepted 28 April 2003
Abstract Access to an efficacious antimalarial drug is one of the cornerstones of the Roll Back Malaria initiative to decrease malaria morbidity and mortality. This is particularly important in emergency and post-emergency settings where access to treatment in the event of therapeutic failure may be restricted. In the aftermath of violence securing the independence of East Timor (1999), chloroquine continued to be used as first line therapy for the treatment of malaria. However, reliable data on the efficacy of chloroquine was not available. This paper represents the first attempt to document treatment failure with chloroquine in East Timor. The study was conducted using modified WHO guidelines in a rural hospital outpatient department in an area where there is seasonal transmission of both Plasmodium vivax and Plasmodium falciparum . 48 subjects presenting with fever and microscopically confirmed P. falciparum monoinfection were given supervised oral treatment with quality controlled chloroquine (25 mg/kg over 3 days) and followed clinically and parasitologically for 28 days. 32 of the 48 subjects had recurrent parasitaemia, and PCR confirmed that 28 of these were likely to be due to recrudescent parasites. The corrected treatment failure was, therefore, 58.3% (28/48), with all but one (2.1%) defined as late treatment failures (7 /28 days after treatment). Further research into appropriate chemotherapy, including sulphadoxine /pyrimethamine and combination therapy for example with artemesinin or its derivatives, should be undertaken to select the most appropriate first line therapy for the management of uncomplicated malaria in East Timor. # 2003 Elsevier B.V. All rights reserved. Keywords: Chloroquine; Complex emergency; Drug resistance; East Timor; Malaria; Plasmodium falciparum
1. Introduction
* Corresponding author. Present address: Roll Back Malaria, World Health Organization, Wazir Akbar Khan, Kabul, Afghanistan. Tel.: /93-702-8-1127. E-mail address: [email protected] (N. Ezard).
Access to an efficacious antimalarial drug is one of the cornerstones of the Roll Back Malaria initiative to decrease morbidity and mortality due to malaria (World Health Organization, 2000). This is particularly important in emergency and
0001-706X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0001-706X(03)00161-X
88
N. Ezard et al. / Acta Tropica 88 (2003) 87 /90
post-emergency settings, where access to treatment may be decreased in the event of treatment failure. East Timor was devastated by violence following a referendum securing independence from Indonesia in September 1999. Chloroquine continues to be used as first-line therapy for uncomplicated Plasmodium falciparum malaria in post-emergency East Timor, despite evidence of resistance from earlier in vitro (Pribadi, 1992) and regional studies (Baird et al., 1997; Fryauff et al., 1998). We describe herein the first attempt at documenting in vivo efficacy of chloroquine in East Timor. The study was conducted in Los Palos subdistrict in eastern East Timor, with a population of approximately 21 000. A cross-sectional household study conducted in July 2000, in the late wet season, indicated that malaria is meso-endemic in this area, with 35.4% prevalence of parasitaemia (n /243, 95%CI 55.9 /76.3%). P. falciparum accounted for 66.7% (95%CI 55.9 /76.3%), Plasmodium vivax 26.7% (95%CI 17.9 /37.0%), mixed P. falciparum and P. vivax 5.6% (95%CI 1.8 /12.5%), and 1.1% unknown (95%CI 1.1 /6.0%). The prevalence of splenomegaly was 36.3% in children 2/ 9 years of age (95%CI 28.6 /46.2%) and 37.1% in adults over 15 years (95%CI 28.6 /46.2%).
2. Patients and methods The efficacy of chloroquine treatment was assessed in 48 patients presenting from May to July 2000 to the outpatient department of Los Palos hospital, a fixed primary health care facility for the subdistrict. A 28 day in vivo efficacy study was conducted using modified WHO protocol (World Health Organization, 1996). Potential participants were screened initially by rapid HRP2 antigen detection tests and P. falciparum infections were confirmed by microscopy. Enrolled patients were between 8 months and 29 years (mean age 10 years) and 56% were female. Inclusion criteria were: history of fever in the past 12 h; over 6 months of age; Giemsa stained slide positive P. falciparum mono-infection with parasite density of 1000/30 000 parasites/ml; live within 1-h’s car journey of hospital; and informed consent. Exclusion criteria were: any sign of severe disease;
pregnancy; currently in treatment for malaria; and febrile disease other than malaria. Pre-treatment with chloroquine on self-report was not considered an exclusion criterion. Patients were weighed, given three doses of chloroquine at 24 hourly intervals (10 mg/kg chloroquine base on day 0 and day 1 and 5 mg/ kg on day 2, dose given according to dose charts range 25/30 mg/kg over 3 days), and were observed for 30 min following each dose. Parasitological and clinical follow-up occurred on days 3, 7, 14, 21, 28 and any other day the patient complained of symptoms. Slides were crosschecked on site. Blood samples were taken for hemoglobin estimation (using the electronic HemoCue† photometer) on days 0, 14 and 28 or day of treatment failure. PCR genotyping was carried out on day 0 and follow-up samples using polymorphic markers of msp1 and msp2.
3. Results One third of patients, with initial parasitaemia ranging from 1222 to 29 440 asexual parasites/mcl (geometric mean 5998 per ml), were successfully cured (Table 1). Of the two thirds of patients who failed treatment, only one treatment failure (1/48, 2.1%, 95%CI 0.1 /12.5%) occurred during the first 3 days, with asexual parasitaemia on day 3 greater than 25% of day 0. All the remaining treatment failures were classified as Late Treatment Failures (31/48, 64.6%, 95%CI 49.4 /77.5%), with recurrent parasitaemia on days 7/28 after initial treatment, including one patient with parasitaemia on day 7 less than 1% of day 0 and subsequently negative for parasites on days 14 and 28. The median day of treatment failure was day 16. PCR analysis revealed that of the treatment failures, 28/32 (87.5%) were due to recrudescence and the remaining were new P. falciparum infections. The corrected failure is, therefore, 28/48 (58.3%, 95%CI 46.1 /70.5%). A mutation correlated with choloroquine resistance was detected in all pre- and posttreatment samples (Chen et al., 2002) regardless of the clinical response to chloroquine. No significant correlation was observed between treatment response and sex, age-group, reported
N. Ezard et al. / Acta Tropica 88 (2003) 87 /90
antimalarial use in the previous 2 months, paracetamol treatment, splenomegaly on day 0, or hemoglobin less than 10 g/dl on day of enrolment. Patients failing treatment were significantly more likely to have hemoglobin less than 10 g/dl on day of exit from the study (50.0%, 16/32) compared with patients cured at day 28 (18.8%, 3/16) (x2 / 4.36 df /1 P /0.03688). The 32 patients who failed chloroquine treatment were given a single supervised dose of sulphadoxine /pyrimethamine (sulphadoxine 25 mg/kg and pyrimethamine 1.25 mg/kg) and reviewed 14 days later. Two were withdrawn due to new infections with P. vivax , one was lost to follow-up, and 29 were asymptomatic with no parasitaemia on day 14 after treatment with sulphadoxine /pyrimethamine.
4. Discussion
89
Table 1 Summary statistics of a 28 day chloroquine clinical efficacy study for uncomplicated P. falciparum malaria, Los Palos, East Timor, May /August 2000 Number screeneda Subjects included Subjects withdrawn (intercurrent illness, new P. vivax infections) Loss to follow-up Subjects included and followed for up to 28 days Follow-up success rate Parasitaemia/ml day 0b Parasite clearance by day 3
439 53 4 1 48 98.2% 5998 (1222 / 29 440) 62.5% (30/48)
Cumulative incidence of treatment failure (parasitological evidence )c Day 3 2.1% (/1) Day 7 12.5% (/5) Day 14 39.6% (/13) Day 21 64.6% (/12) Day 28 66.7% (/1) a
Our findings provide the first documented evidence of in vivo P. falciparum resistance to chloroquine in East Timor. More than one half of the patients studied failed to be cured with the standard chloroquine treatment regime, indicating considerable chloroquine resistance in this region of East Timor. Nearly all of these treatment failures were, however, late (7 /28 days after treatment). Our study suggests that sulphadoxine /pyrimethamine may be efficacious in the treatment of falciparum malaria. However further studies of sulphadoxine /pyrimethamine efficacy are required, without systematic pre-treatment with chloroquine. Should sulphadoxine /pyrimethamine be shown to be efficacious, it may be an appropriate candidate for combination antimalarial therapy. Combination chemotherapies may offer the advantage of delaying the development of resistance to the individual compounds (White et al., 2001). Studies on combination chloroquine and sulphadoxine /pyrimethamine for the treatment of P. falciparum malaria suggest that where there is some degree of resistance to chloroquine but not to sulphadoxine /pyrimethamine, the addition of chloroquine results in more prompt symptom
Subjects screened with Quorum† rapid HRP-2 antigen detection kits with microscopically confirmed malaria infections. b Geometric mean (range). c Subjects categorized as a treatment failure on a nonscheduled visit to the hospital were classed to the nearest scheduled follow-up; numbers in parentheses indicate newly detected therapeutic failures on that day; see text for definition of treatment failure.
resolution, but not more prompt parasite clearance, than sulphadoxine /pyrimethamine alone (McIntosh and Greenwood, 1998; Darlow et al., 1982; Bojang et al., 1998). We have shown that chloroquine is no longer efficacious for the treatment of P. falciparum malaria, and thus would not be an appropriate choice for combination chemotherapy targeting P. falciparum . Nevertheless chloroquine remains first line therapy for P. vivax malaria, which is prevalent in this area and responds poorly to sulphadoxine /pyrimethamine. As an interim step, therefore, the combination of sulphadoxine /pyrimethamine plus chloroquine may be appropriate as first-line treatment in East Timor when uncomplicated malaria can only be diagnosed on clinical grounds alone. The search for appropriate combination therapies that are efficacious in the treatment of both P.
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N. Ezard et al. / Acta Tropica 88 (2003) 87 /90
falciparum and P. vivax infections should continue.
Acknowledgements This study received support from AusAID. MERLIN’s activities in East Timor were supported by WHO/RBM. We would like to thank Edmundo Vieira, Joa˜zinho da Cruz, Julio Pereira, Rumaldo Bosco, Julio dos Santos, the staff of the Los Palos hospital and laboratory, Yilma Robelle, and the participants. We would also like to thank Pascal Ringwald and Karl Rieckmann for their comments.
References Baird, J.K., Wiady, I., Fryauff, D.J., Sutanihardja, M.A., Leksana, B., et al., 1997. In vivo resistance to chloroquine by Plasmodium vivax and Plasmodium falciparum at Nabire, Irian Jaya, Indonesia. Am. Soc. Trop. Med. Hyg. 56, 627 / 631. Bojang, K.A., Schneider, G., Forck, S., Obaro, S.K., Jaffar, S., Pinder, M., Rowley, J., Greenwood, B.M., 1998. A trial of Fansidar† plus chloroquine and Fansidar† alone for the treatment of uncomplicated malaria in Gambia. Trans. R. Soc. Trop. Med. Hyg. 92, 73 /76. Chen, N., Baker, J., Ezard, N., Burns, M., Edstein, M., Cheng, Q., 2002. Molecular evaluation of the efficacy of chloro-
quine treatment of uncomplicated Plasmodium falciparum malaria in East Timor. Am. J. Trop. Med. Hyg. 67 (1), 64 / 66. Darlow, B., Vrbova, H., Gibney, S., Jolley, D., Stace, J., Alpers, M., 1982. Sulphadoxine /pyrimethamine for the treatment of acute malaria in children in Papua New Guinea. Am. J. Trop. Med. Hyg. 31 (1), 1 /9. Fryauff, D.J., Soekartono, T.S., Leksana, B., Suradi, T.S., Baird, J., 1998. Survey of resistance in vivo to chloroquine of Plasmodium falciparum and P. vivax in North Sulawesi, Indonesia. Trans. R. Soc. Trop. Med. Hyg. 92, 82 /83. McIntosh, H.M., Greenwood, B.M., 1998. Chloroquine or amodiaquine combined with sulfadoxine /pyrimethamine as a treatment for uncomplicated malaria, a systematic review. Ann. Trop. Med. Par. 92 (3), 265 /270. Pribadi, W., 1992. In vitro sensitivity of Plasmodium falciparum to chloroquine and other antimalarials in East Timor and east Kalimantan, Indonesia. SEAJ Trop. Med. Pub. Health 23 (suppl 4), 143 /148. White, N.J., Nosten, F., Looareesuwan, S., Watkins, W.M., Marsh, K., Snow, R.W., Kokwaro, G., Ouma, J., Hien, T.T., Molyneux, M.E., Taylor, T.E., Newbold, C.I., Ruebush, T.K., II, Danis, M., Greenwood, B.M., Anderson, R.M., Olliaro, P., 2001. Averting a malaria disaster. Lancet 353, 1965. World Heath Organization, 1996. Assessment of the therapeutic efficacy of antimalarial drugs for uncomplicated falciparum malaria for areas of intense transmission (WHO/ MAL/96.1077). WHO, Geneva, Switzerland. World Health Organization, 2000. African summit on Roll Back Malaria, Abuja, Nigeria, April 25 2000 (WHO/CDS/ RBM/2000.17). WHO, Geneva, Switzerland.
Short communication
Efficacy of chloroquine in the treatment of uncomplicated Plasmodium falciparum infection in East Timor, 2000 Nadine Ezard a,*, Matthew Burns a, Caroline Lynch a, Qin Cheng b, Michael D. Edstein b a b
Medical Emergency Relief International, 5-13 Trinity Street, London SE1 1DB, UK Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Qld. 4052, Australia
Received 20 December 2002; received in revised form 12 April 2003; accepted 28 April 2003
Abstract Access to an efficacious antimalarial drug is one of the cornerstones of the Roll Back Malaria initiative to decrease malaria morbidity and mortality. This is particularly important in emergency and post-emergency settings where access to treatment in the event of therapeutic failure may be restricted. In the aftermath of violence securing the independence of East Timor (1999), chloroquine continued to be used as first line therapy for the treatment of malaria. However, reliable data on the efficacy of chloroquine was not available. This paper represents the first attempt to document treatment failure with chloroquine in East Timor. The study was conducted using modified WHO guidelines in a rural hospital outpatient department in an area where there is seasonal transmission of both Plasmodium vivax and Plasmodium falciparum . 48 subjects presenting with fever and microscopically confirmed P. falciparum monoinfection were given supervised oral treatment with quality controlled chloroquine (25 mg/kg over 3 days) and followed clinically and parasitologically for 28 days. 32 of the 48 subjects had recurrent parasitaemia, and PCR confirmed that 28 of these were likely to be due to recrudescent parasites. The corrected treatment failure was, therefore, 58.3% (28/48), with all but one (2.1%) defined as late treatment failures (7 /28 days after treatment). Further research into appropriate chemotherapy, including sulphadoxine /pyrimethamine and combination therapy for example with artemesinin or its derivatives, should be undertaken to select the most appropriate first line therapy for the management of uncomplicated malaria in East Timor. # 2003 Elsevier B.V. All rights reserved. Keywords: Chloroquine; Complex emergency; Drug resistance; East Timor; Malaria; Plasmodium falciparum
1. Introduction
* Corresponding author. Present address: Roll Back Malaria, World Health Organization, Wazir Akbar Khan, Kabul, Afghanistan. Tel.: /93-702-8-1127. E-mail address: [email protected] (N. Ezard).
Access to an efficacious antimalarial drug is one of the cornerstones of the Roll Back Malaria initiative to decrease morbidity and mortality due to malaria (World Health Organization, 2000). This is particularly important in emergency and
0001-706X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0001-706X(03)00161-X
88
N. Ezard et al. / Acta Tropica 88 (2003) 87 /90
post-emergency settings, where access to treatment may be decreased in the event of treatment failure. East Timor was devastated by violence following a referendum securing independence from Indonesia in September 1999. Chloroquine continues to be used as first-line therapy for uncomplicated Plasmodium falciparum malaria in post-emergency East Timor, despite evidence of resistance from earlier in vitro (Pribadi, 1992) and regional studies (Baird et al., 1997; Fryauff et al., 1998). We describe herein the first attempt at documenting in vivo efficacy of chloroquine in East Timor. The study was conducted in Los Palos subdistrict in eastern East Timor, with a population of approximately 21 000. A cross-sectional household study conducted in July 2000, in the late wet season, indicated that malaria is meso-endemic in this area, with 35.4% prevalence of parasitaemia (n /243, 95%CI 55.9 /76.3%). P. falciparum accounted for 66.7% (95%CI 55.9 /76.3%), Plasmodium vivax 26.7% (95%CI 17.9 /37.0%), mixed P. falciparum and P. vivax 5.6% (95%CI 1.8 /12.5%), and 1.1% unknown (95%CI 1.1 /6.0%). The prevalence of splenomegaly was 36.3% in children 2/ 9 years of age (95%CI 28.6 /46.2%) and 37.1% in adults over 15 years (95%CI 28.6 /46.2%).
2. Patients and methods The efficacy of chloroquine treatment was assessed in 48 patients presenting from May to July 2000 to the outpatient department of Los Palos hospital, a fixed primary health care facility for the subdistrict. A 28 day in vivo efficacy study was conducted using modified WHO protocol (World Health Organization, 1996). Potential participants were screened initially by rapid HRP2 antigen detection tests and P. falciparum infections were confirmed by microscopy. Enrolled patients were between 8 months and 29 years (mean age 10 years) and 56% were female. Inclusion criteria were: history of fever in the past 12 h; over 6 months of age; Giemsa stained slide positive P. falciparum mono-infection with parasite density of 1000/30 000 parasites/ml; live within 1-h’s car journey of hospital; and informed consent. Exclusion criteria were: any sign of severe disease;
pregnancy; currently in treatment for malaria; and febrile disease other than malaria. Pre-treatment with chloroquine on self-report was not considered an exclusion criterion. Patients were weighed, given three doses of chloroquine at 24 hourly intervals (10 mg/kg chloroquine base on day 0 and day 1 and 5 mg/ kg on day 2, dose given according to dose charts range 25/30 mg/kg over 3 days), and were observed for 30 min following each dose. Parasitological and clinical follow-up occurred on days 3, 7, 14, 21, 28 and any other day the patient complained of symptoms. Slides were crosschecked on site. Blood samples were taken for hemoglobin estimation (using the electronic HemoCue† photometer) on days 0, 14 and 28 or day of treatment failure. PCR genotyping was carried out on day 0 and follow-up samples using polymorphic markers of msp1 and msp2.
3. Results One third of patients, with initial parasitaemia ranging from 1222 to 29 440 asexual parasites/mcl (geometric mean 5998 per ml), were successfully cured (Table 1). Of the two thirds of patients who failed treatment, only one treatment failure (1/48, 2.1%, 95%CI 0.1 /12.5%) occurred during the first 3 days, with asexual parasitaemia on day 3 greater than 25% of day 0. All the remaining treatment failures were classified as Late Treatment Failures (31/48, 64.6%, 95%CI 49.4 /77.5%), with recurrent parasitaemia on days 7/28 after initial treatment, including one patient with parasitaemia on day 7 less than 1% of day 0 and subsequently negative for parasites on days 14 and 28. The median day of treatment failure was day 16. PCR analysis revealed that of the treatment failures, 28/32 (87.5%) were due to recrudescence and the remaining were new P. falciparum infections. The corrected failure is, therefore, 28/48 (58.3%, 95%CI 46.1 /70.5%). A mutation correlated with choloroquine resistance was detected in all pre- and posttreatment samples (Chen et al., 2002) regardless of the clinical response to chloroquine. No significant correlation was observed between treatment response and sex, age-group, reported
N. Ezard et al. / Acta Tropica 88 (2003) 87 /90
antimalarial use in the previous 2 months, paracetamol treatment, splenomegaly on day 0, or hemoglobin less than 10 g/dl on day of enrolment. Patients failing treatment were significantly more likely to have hemoglobin less than 10 g/dl on day of exit from the study (50.0%, 16/32) compared with patients cured at day 28 (18.8%, 3/16) (x2 / 4.36 df /1 P /0.03688). The 32 patients who failed chloroquine treatment were given a single supervised dose of sulphadoxine /pyrimethamine (sulphadoxine 25 mg/kg and pyrimethamine 1.25 mg/kg) and reviewed 14 days later. Two were withdrawn due to new infections with P. vivax , one was lost to follow-up, and 29 were asymptomatic with no parasitaemia on day 14 after treatment with sulphadoxine /pyrimethamine.
4. Discussion
89
Table 1 Summary statistics of a 28 day chloroquine clinical efficacy study for uncomplicated P. falciparum malaria, Los Palos, East Timor, May /August 2000 Number screeneda Subjects included Subjects withdrawn (intercurrent illness, new P. vivax infections) Loss to follow-up Subjects included and followed for up to 28 days Follow-up success rate Parasitaemia/ml day 0b Parasite clearance by day 3
439 53 4 1 48 98.2% 5998 (1222 / 29 440) 62.5% (30/48)
Cumulative incidence of treatment failure (parasitological evidence )c Day 3 2.1% (/1) Day 7 12.5% (/5) Day 14 39.6% (/13) Day 21 64.6% (/12) Day 28 66.7% (/1) a
Our findings provide the first documented evidence of in vivo P. falciparum resistance to chloroquine in East Timor. More than one half of the patients studied failed to be cured with the standard chloroquine treatment regime, indicating considerable chloroquine resistance in this region of East Timor. Nearly all of these treatment failures were, however, late (7 /28 days after treatment). Our study suggests that sulphadoxine /pyrimethamine may be efficacious in the treatment of falciparum malaria. However further studies of sulphadoxine /pyrimethamine efficacy are required, without systematic pre-treatment with chloroquine. Should sulphadoxine /pyrimethamine be shown to be efficacious, it may be an appropriate candidate for combination antimalarial therapy. Combination chemotherapies may offer the advantage of delaying the development of resistance to the individual compounds (White et al., 2001). Studies on combination chloroquine and sulphadoxine /pyrimethamine for the treatment of P. falciparum malaria suggest that where there is some degree of resistance to chloroquine but not to sulphadoxine /pyrimethamine, the addition of chloroquine results in more prompt symptom
Subjects screened with Quorum† rapid HRP-2 antigen detection kits with microscopically confirmed malaria infections. b Geometric mean (range). c Subjects categorized as a treatment failure on a nonscheduled visit to the hospital were classed to the nearest scheduled follow-up; numbers in parentheses indicate newly detected therapeutic failures on that day; see text for definition of treatment failure.
resolution, but not more prompt parasite clearance, than sulphadoxine /pyrimethamine alone (McIntosh and Greenwood, 1998; Darlow et al., 1982; Bojang et al., 1998). We have shown that chloroquine is no longer efficacious for the treatment of P. falciparum malaria, and thus would not be an appropriate choice for combination chemotherapy targeting P. falciparum . Nevertheless chloroquine remains first line therapy for P. vivax malaria, which is prevalent in this area and responds poorly to sulphadoxine /pyrimethamine. As an interim step, therefore, the combination of sulphadoxine /pyrimethamine plus chloroquine may be appropriate as first-line treatment in East Timor when uncomplicated malaria can only be diagnosed on clinical grounds alone. The search for appropriate combination therapies that are efficacious in the treatment of both P.
90
N. Ezard et al. / Acta Tropica 88 (2003) 87 /90
falciparum and P. vivax infections should continue.
Acknowledgements This study received support from AusAID. MERLIN’s activities in East Timor were supported by WHO/RBM. We would like to thank Edmundo Vieira, Joa˜zinho da Cruz, Julio Pereira, Rumaldo Bosco, Julio dos Santos, the staff of the Los Palos hospital and laboratory, Yilma Robelle, and the participants. We would also like to thank Pascal Ringwald and Karl Rieckmann for their comments.
References Baird, J.K., Wiady, I., Fryauff, D.J., Sutanihardja, M.A., Leksana, B., et al., 1997. In vivo resistance to chloroquine by Plasmodium vivax and Plasmodium falciparum at Nabire, Irian Jaya, Indonesia. Am. Soc. Trop. Med. Hyg. 56, 627 / 631. Bojang, K.A., Schneider, G., Forck, S., Obaro, S.K., Jaffar, S., Pinder, M., Rowley, J., Greenwood, B.M., 1998. A trial of Fansidar† plus chloroquine and Fansidar† alone for the treatment of uncomplicated malaria in Gambia. Trans. R. Soc. Trop. Med. Hyg. 92, 73 /76. Chen, N., Baker, J., Ezard, N., Burns, M., Edstein, M., Cheng, Q., 2002. Molecular evaluation of the efficacy of chloro-
quine treatment of uncomplicated Plasmodium falciparum malaria in East Timor. Am. J. Trop. Med. Hyg. 67 (1), 64 / 66. Darlow, B., Vrbova, H., Gibney, S., Jolley, D., Stace, J., Alpers, M., 1982. Sulphadoxine /pyrimethamine for the treatment of acute malaria in children in Papua New Guinea. Am. J. Trop. Med. Hyg. 31 (1), 1 /9. Fryauff, D.J., Soekartono, T.S., Leksana, B., Suradi, T.S., Baird, J., 1998. Survey of resistance in vivo to chloroquine of Plasmodium falciparum and P. vivax in North Sulawesi, Indonesia. Trans. R. Soc. Trop. Med. Hyg. 92, 82 /83. McIntosh, H.M., Greenwood, B.M., 1998. Chloroquine or amodiaquine combined with sulfadoxine /pyrimethamine as a treatment for uncomplicated malaria, a systematic review. Ann. Trop. Med. Par. 92 (3), 265 /270. Pribadi, W., 1992. In vitro sensitivity of Plasmodium falciparum to chloroquine and other antimalarials in East Timor and east Kalimantan, Indonesia. SEAJ Trop. Med. Pub. Health 23 (suppl 4), 143 /148. White, N.J., Nosten, F., Looareesuwan, S., Watkins, W.M., Marsh, K., Snow, R.W., Kokwaro, G., Ouma, J., Hien, T.T., Molyneux, M.E., Taylor, T.E., Newbold, C.I., Ruebush, T.K., II, Danis, M., Greenwood, B.M., Anderson, R.M., Olliaro, P., 2001. Averting a malaria disaster. Lancet 353, 1965. World Heath Organization, 1996. Assessment of the therapeutic efficacy of antimalarial drugs for uncomplicated falciparum malaria for areas of intense transmission (WHO/ MAL/96.1077). WHO, Geneva, Switzerland. World Health Organization, 2000. African summit on Roll Back Malaria, Abuja, Nigeria, April 25 2000 (WHO/CDS/ RBM/2000.17). WHO, Geneva, Switzerland.