Acta Tropica 76 (2000) 265 – 270 www.elsevier.com/locate/actatropica
In vivo sensitivity of Plasmodium falciparum to chloroquine and sulfadoxine-pyrimethamine among schoolchildren in rural Uganda: a comparison between 1995 and 1998 Richard Ndyomugyenyi a, Pascal Magnussen b,* b
a Vector Control Di6ision, Kampala, Uganda Danish Bilharziasis Laboratory, Jaegersborg Alle´ 1 D, DK-2920 Charlottenlund, Denmark
Received 17 February 1999; received in revised form 23 March 2000; accepted 18 May 2000
Abstract Sensitivity of Plasmodium falciparum to chloroquine and sulfadoxine-pyrimethamine was tested among asymptomatic school children in 1995 and 1998 using a modified in vivo test with examination for parasitaemia on day 0, 2 and 7. Sensitivity (S/RI) to chloroquine in ‘urban’ areas was found in 42% in 1995 and 62% in 1998 with resistance at the RII/RIII level observed in 58 and 38%, respectively (PB 0.01). In ‘rural’ areas, sensitivity to chloroquine was 76% in 1995 and 72% in 1998 (P =0.6) with resistance at the RII/RIII level observed in 24 and 18%, respectively (P=0.4). Sensitivity to sulfadoxine-pyrimethamine was found in 98 and 99% in 1995 and 1998, respectively. The apparent improvement in sensitivity to chloroquine in ‘urban’ areas might be due to a different school being included in the two studies. It is concluded that the pattern of sensitivity of P. falciparum to chloroquine and sulfadoxinepyrimethamine has not changed over a period of 2.5 year. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Plasmodium falciparum; Drug resistance; Chloroquine; Sulfadoxine-pyrimethamine; Uganda
1. Introduction Provision of prompt and effective treatment is a fundamental component of the global strategy for malaria control (World Health Organization, 1993). However, this strategy has become more complex due to multiple drug resistance of Plasmodium falciparum. Chloroquine has been the * Corresponding author. Tel.: +45-77-327732; fax: + 4577-327733. E-mail address:
[email protected] (P. Magnussen).
drug of choice for malaria treatment and chemoprophylaxis in sub-Saharan Africa but its effectiveness has been questioned due to drug resistance (Brabin et al., 1990). Resistance to sulfadoxine-pyrimethamine in the East African region is also on the increase (Vleugels et al., 1982; Rønn et al., 1996). Despite chloroquine and sulfadoxine-pyrimethamine resistance to P. falciparum the two drugs remain the first and second choice for malaria treatment in many African countries. A study conducted in Hoima district in 1995 (Ndyomugyenyi and Magnussen, 1997) and other
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studies in a number of districts in Uganda have reported chloroquine resistance at the RII and RIII level (Sezi et al., 1991; Kamugisha et al., 1994). However, no recent studies have been conducted to assess the current level of sensitivity of chloroquine and sulfadoxine-pyrimethamine in Uganda. Regular surveillance is important to determine changes in levels of drug resistance so as to introduce alternative drugs for malaria treatment when necessary. To assess the current level of sensitivity of P. falciparum to chloroquine and sulfadoxinepyrimethamine in the Hoima District, a study was conducted in 1998, i.e. 2.5 years after the first study.
2. Material and methods
2.1. Study area and population Details of the study area in Hoima District in Western Uganda are described elsewhere (Ndyomugyenyi and Magnussen, 1997). Briefly, the district is hyperendemic for malaria and transmission occurs throughout the year with peaks during rainfall in April – June and September – November. The annual rainfall ranges between 700 and 1000 mm. Malaria is the leading cause of out-patient morbidity in the district (Health Information System Annual Report 1995, Hoima District) and more than 98% of malaria infections in the area are caused by P. falciparum (Ndyomugyenyi and Magnussen, 1997). The 1995 sensitivity study was conducted in October and the 1998 study in April. Five schools were used for both studies (Rwemisanga, Kitana, Lwanga-Mpanga, Kibengeya and Tontema), while Hoima Public, Kabwoya and St. Bernadette were new schools in 1998. Buseruka school, which was used in 1995, was excluded in 1998 due to the unstable security situation in the area, while Kikonda was excluded due to lack of consent by the head teacher. Consent was solicited from the district authorities and head teachers who wrote to the parents of the children in the study schools requesting them to allow their children to participate. In both studies schools
within a radius of 5 km from a trading centre were categorized as ‘urban’ and those more than 5 km away as ‘rural’. Children fulfilling the following criteria for in vivo assessment of P. falciparum sensitivity to chloroquine and sulfadoxine-pyrimethamine (World Health Organization, 1973) were included: (1) no history of antimalarial drug use during the preceding 4 weeks, (2) a blood film positive for asexual forms of P. falciparum alone, (3) parasite count \ 1000/ml of blood and (4) absence of chloroquine and pyrimethamine in the urine.
2.2. Methods The methods used in the two studies have been described previously (Ndyomugyenyi and Magnussen, 1997). Briefly, thick smears were examined for parasites on days 0, 2 and 7. Parasites were counted against 200 leukocytes and counts were expressed as asexual parasites per ml of blood, assuming a total white cell count of 8000 per ml of blood. Children who met the inclusion criteria received either chloroquine or sulfadoxine-pyrimethamine treatment as follows. Chloroquine base 25 mg/kg in three divided doses (10 mg/kg day 0, 10 mg/kg day 1 and 5 mg/kg day 2) or two tablets of sulfadoxine 500 mg+ pyrimethamine 25 mg. All participants swallowed the drugs under direct supervision. The WHO classification (World Health Organization, 1973) was used to assess levels of sensitivity and resistance: (1) infections which resolved after treatment and remained negative on day 7 were classified as sensitive, (2) infections which resolved after 48 h and recurred at day 7 were classified as early RI, (3) infections which did not resolve completely, but had a decrease in parasitaemia ]75% on day 7 were classified as RII, (4) Infections in which the parasitaemia decreased B 75% were classified as RIII. Children who had a parasitaemia but did not meet other inclusion criteria received 25 mg/ kg chloroquine treatment in three divided doses. Children, who met the inclusion criteria and received chloroquine treatment were treated with sulfadoxine-pyrimethamine if they were found to be parasitaemic on day 7.
R. Ndyomugyenyi, P. Magnussen / Acta Tropica 76 (2000) 265–270
2.3. Data analysis For the analysis sensitive and RI, RII and RIII have been joined. Differences in proportions were tested with the x 2 test and a value of P B 0.05 was considered significant.
2.4. Ethical clearance Permission to carry out the study was obtained from the Ministry of Health in Uganda and Hoima District authorities. The project was reviewed by the Central Ethics Committee in Denmark and recommended.
3. Results
3.1. Sensiti6ity of P. falciparum to chloroquine and sulfadoxine-pyrimethamine in 1995 The sensitivity status of P. falciparum to chloroquine and sulfadoxine-pyrimethamine in 1995 has been described previously in detail (Ndyomugyenyi and Magnussen, 1997). Briefly, 725 school children, aged between 7 and 10 years, in seven primary schools from four sub-counties in the Hoima District, were screened. Four hundred and eighty seven (67%) had parasitaemia, 307 of those met the inclusion criteria and 280 completed the study (Table 1). Sensitivity (S/RI) to chloroquine in ‘urban’ areas was found in 41% and chloroquine resistance at the RII/RIII level was observed in 59%. However, in ‘rural’ areas sensitivity to chloroquine was found in 76% with resistance at the RII/RIII level found in 24%. Sensitivity to sulfadoxine-pyrimethamine was found in 98% and only 2% were resistant at the RII/RIII level.
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tions with P. falciparum and P. malariae were found in ten children. Two-hundred and twelve children were included in the study. Of these, 111 children received chloroquine and 101 children received sulfadoxine-pyrimethamine. In the chloroquine group, 102 (92%) and in the sulfadoxine-pyrimethamine group 92 (91%) completed day 7 follow-up, respectively. In the chloroquine treatment group 68 (61%) had cleared their parasitaemia by day 2. Reduction in parasitaemia ranged from 50–95% among those who were still parasitaemic by day 2. In the sulfadoxine-pyrimethamine group, parasitaemia cleared by day 2 in 99%. One child was still parasitaemic by day 7, with a reduction B 25% and, therefore, classified as RIII. Sixty-eight children (67%) receiving chloroquine had cleared parasitaemia by day 7. Sensitivity (S/RI) to chloroquine was found in 62% of children in ‘urban’ areas and 72% in ‘rural’ areas. In 1995 sensitivity (S/RI) of P. falciparum to chloroquine (‘urban’ and ‘rural’ combined) was found in 60% of children compared to 67% in 1998 (P= 0.3). The level of sensitivity of P. falciparum to chloroquine in the two schools used in both studies (Rwemisanga and Kitana) was not significantly different (P = 0.5 and 0.2, respectively). There was no difference in sensitivity to sulfadoxine-pyrimethamine in the two studies. The frequency of resistance at the RII/RIII level in ‘urban’ areas of 59 and 38% in 1995 and 1998, respectively was significantly different (P= 0.01). However, there was no difference in the frequency of resistance at the RII/RIII level in ‘rural’ areas in the two studies (P= 0.9).
4. Discussion
3.2. Sensiti6ity of P. falciparum to chloroquine and sulfadoxine- pyrimethamine in 1998 Children (782) aged between 4 and 10 years in standard one and two were examined and 445 (57%) were found to be infected (Table 2). All children were asymptomatic and P. falciparum accounted for 98% of the infections. Mixed infec-
In 1995 a satisfactory response to chloroquine (S/RI) of 42 and 76% was found in ‘urban’ and ‘rural’ areas, respectively. Sensitivity to sulfadoxine-pyrimethamine was found in 98% of the children (Ndyomugyenyi and Magnussen, 1997). The results 2.5 years later in the same area has shown sensitivity to chloroquine (S/RI) in 62% of chil-
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School
Buseruka (‘urban’)
Treatment Chloroquine Screened 155 children Parasitaemia 136 (88) (%) No. who 33 completed the study GMPD per mla 1396 S/RI (%) 14 (42) RII/RIII (%) 19 (58) a
Kitana* (‘urban’)
Rwemisanga (‘rural’)
Lwanga-Mpanga Buseruka (‘rural’) (‘urban’)
Kikonda (‘urban’)
Tontema (‘rural’)
Kibegenya (‘rural’)
Chloroquine 101
Chloroquine 102
Chloroquine 99
SP 100
SP 73
SP 95
83 (82)
49 (49)
51 (52)
31
37
31
1385 13 (42) 18 (58)
Geometric mean parasite density of the positives.
1286 26 (70) 11 (30)
1516 26 (84) 5 (16)
SP 155 136 (88) 45
1943 45 (100) 0
46 (46)
56 (77)
66 (70)
32
37
34
1400 32 (100) 0
1912 37 (100) 0
1600 31 (91) 3 (9)
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Table 1 In vivo sensitivity of P. falciparum parasites to chloroquine and sulfadoxine-pyrimethamine (SM) in school children from ‘rural’ and ‘urban’ areas in the Hoima District, Uganda, in 1995
School
Rwemisanga (‘rural’)
Treatment Chloroquine Screened 105 children Parasitaemia 41 (39) (%) No. who 16 completed the study GMPD per mla 1500 S/RI (%) 10 (62) RII/RIII (%) 6 (38) a
Hoima Public (‘urban’)
Kabwoya (‘rural’)
Kitana* (‘urban’)
Lwanga-Mpanga Kibegenya (‘rural’) (‘rural’)
St. Bernadette (‘urban’)
Tontema (‘rural’)
Chloroquine 193
Chloroquine 79
Chloroquine 75
SP 90
SP
SP 126
60 (31)
53 (67)
47 (63)
76 (84)
61 (68)
30
31
25
36
19
1241 19 (63) 11 (37)
Geometric mean parasite density of the positives.
1377 24 (77) 7 (23)
1556 15 (60) 10 (40)
2455 36 (100) 0
SP 90
1626 17 (99) 1 (5)
8 14 (58) 8
1778 8 (100) 0
93 (74) 29
1233 29 (100) 0
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Table 2 In vivo sensitivity of P. falciparum parasites to chloroquine and sulfadoxine-pyrimethamine in school children from ‘rural’ and ‘urban’ areas in the Hoima District, Uganda, in 1998
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dren in ‘urban’ areas and 72% in ‘rural’ areas. The apparent improvement in the sensitivity to chloroquine in the ‘urban’ areas from the 1995 to 1998 studies could be due to the fact that different schools were used in the two studies. Only two schools were used for assessment of sensitivity of P. falciparum to chloroquine in both studies. Sensitivity to chloroquine in Kitana primary school, which is an ‘urban’ area, was higher in 1998 than that observed in 1995, but not significantly. The sensitivity of P. falciparum to chloroquine was comparable in ‘rural’ areas in both studies and the sensitivity to chloroquine in the new schools used in 1998 (‘urban’ and ‘rural’) was comparable to the sensitivity observed in ‘rural’ areas in 1995. This indicates that chloroquine is still effective in both ‘urban’ and ‘rural’ areas in the Hoima District, and could remain the first choice for treatment for malaria. Possible reasons for the higher level of chloroquine resistance in ‘urban’ areas compared to ‘rural’ areas observed in both studies could be easy access and inadequate use of chloroquine from informal sources in ‘urban’ areas. The sensitivity of P. falciparum to chloroquine over the 2.5 years had not declined and is comparable to earlier findings in other districts of Uganda (Sezi et al., 1991; Kamugisha et al., 1994). Resistance to sulfadoxine-pyrimethamine has been observed at the RIII level in other parts of East African Region. In Tanzania sulfadoxine-pyrimethamine failed to clear parasitaemia among children within 7 days in 74% (Rønn et al., 1996). Sulfadoxine-pyrimethamine is still very effective in the Hoima District but the finding of a number of cases of resistance at the RII and RIII level, could imply that uncontrolled use of sulfadoxine-pyrimethamine may quickly lead to an increase in resistance to this drug. There has been no change in malaria treatment policy in Uganda and chloroquine remains the first line drug. However, Uganda has started to monitor resistance levels in different sites across the country.
.
5. Conclusion Chloroquine is still effective as a treatment for P. falciparum infections in ‘rural’ areas of the Hoima district and should remain the first line drug for treatment of malaria. The sensitivity of P. falciparum to chloroquine and sulfadoxinepyrimethamine in the study area had not declined between 1995 and 1998 and cases of RII/RIII resistance are still very few. This drug should be used as a second line for treatment of malaria in cases of chloroquine failure. However, resistance may propagate fast if the use of sulfadoxinepyrimethamine is not controlled. References Brabin, B.J., Ginny, M., Alpers, M., Brabin, L., Eggelte, T., Van Der Kaay, H.J., 1990. Failure of chloroquine prophylaxis for falciparum malaria in pregnant women in Madang, Papua New Guinea. Ann. Trop. Med. Parasitol. 84, 1 – 9. Health Information System Annual Report 1995, Hoima District, Uganda. Kamugisha, J., Kipp, W., Burnham, G., 1994. In vivo sensitivity of Plasmodium falciparum to chloroquine, amodiaquine and sulfadoxine-pyrimethamine in Western Uganda. Trop. Geogr. Med. 46, 364 – 365. Ndyomugyenyi, R., Magnussen, P., 1997. In vivo sensitivity of Plasmodium falciparum to chloroquine and sulfadoxinepyrimethamine in school children in Hoima district, Western Uganda. Acta Trop. 66, 137 – 143. Rønn, M.A., Msangeni, H.A., Mhina, J., Wernsdorfer, W.H., Bygbjerg, I.C., 1996. High level of resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine in children in Tanzania. Trans. R. Soc. Trop. Med. Hyg. 90, 179 – 181. Sezi, C.L., Nevill, C., Ochen, K., Munafu, C., Bek’Obita, D., 1991. The response of Plasmodium falciparum to 4-aminoquinolines and sulfadoxine-pyrimethamine in 6 sites scattered throughout Uganda. Uganda Med. J. 8, 33 – 36. Vleugels, M.P.H., Wetsteyn, J.C.F.M., Meuwissen, J.H.E.T., 1982. Fansidar-resistant Plasmodium falciparum infection from Tanzania. Trop. Geogr. Med. 34, 263 – 265. World Health Organization, 1973. Chemotherapy of Malaria and resistance to antimalarials: report of the World Health Organization Scientific group. WHO Tech. Rep. Ser. 529, 30 – 39. World Health Organization, 1993. A Global Strategy for Malaria Control. World Health Organization, Geneva.
