Status of chloroquine and sulphadoxine/pyrimethamine efficacy against Falciparum Malaria at Sennar, Sudan

This thesis was concerned with studying the resistance of P. falciparum malaria to antimalarial drugs, and was carried out in Sennar city during the rainy season (Sept-Nov.2001) mainly at El Galaa area.

The study was conducted to assess the response of chloroquine, and sulphadoxine/pyrimethamine and we used three methods to measure the antimalarial drugs resistance in vivo, in vitro and PCR.
Out of 1100 patients (1-65 yrs old) came to the clinic, 319 (29%) were diagnosed as malaria positive. Sixty-six 66 were treated with chloroquine and completed the follow-up period, 48 (72.7%) were classified as sensitive, and the treatment failure was observed in 18 (27.3%) patients. From them 11 (16.7%) were classified as resistant grade I (R1), and 6 (9.1%) classified as R II and one (1.5%)patient classified as R III.
In vitro testing was performed simultaneously with in vivo to assess the sensitivity of P. falciparum isolates to chloroquine. The in vitro response of the 32 isolates, which showed growth in the chloroquine plates, indicated that 12 (37.5%) were resistant to chloroquine, while 20 (62.5%) isolates were chloroquine sensitive.

The effective concentrations (EC50), in which 50% of the parasites failed to undergo maturation was found to be 4.8 pmol/well (0.96x10-6mol/l blood) for 32 isolates. The effective concentration EC95 (minimum concentration inhibiting) 95 % of the schizont maturation was found to be 49.4 pmol/well (9.9 x10-6mol/lblood) for all 32 isolates. The restriction fragment length polymorphism (RFLP) was used to detect the prevalence of the mutation in the P. falciparum genes (Pfcrt & Pfmdr) in chloroquine resistant malaria.

A Pfcrt polymorphic marker was examined in 66 P. falciparum positive samples, RFLP analysis revealed the presence of the mutant T76 allele in 42 (63.6%) isolates. The remaining 24 (36.4%) isolates carried the wild type k76 allele. The Pfmdr1 N86Y mutation was similarly detected by RFLP analysis. RLFP analysis revealed the presence of the mutant mdr1 Tyr- 86 in 33 (50%) isolates. The 26(39.4%) isolates carried (Asn-86) wild type, while 7 (10.6%) isolates had mix infection (Asn-86 plus Tyr-86).
Sulfadoxine/pyrimethamine were determined for 47 patients who completed the 14-day follow-up. Forty-four (93.6%) were sensitive to sulfadoxine/pyrimethamine, while 3 (6.4%) patients were resistant, 2 of them classified as RII and 1 RI according to the WHO protocol.

Forty-eight isolates of P. falciparum were tested in vitro against Sulphadoxine /Pyrimethamine. Successful growth was obtained in 33 isolates. The mean effective concentrations (EC50& EC90) in which the parasites failed to undergo maturation were found to be 21.6 pmol/well and 703.7 pmol/well respectively, while the minimum inhibitory concentration that inhibited 95% of the schizont maturation was found to be 1889.9 pmol/well for the 33 isolates.

RFLP analysis revealed the presence of the mutant Asn-108 allele in 35(72.9%) isolates. The remaining 7(14.6%) isolates carried the wild type Ser-108 allele, and 5 (10.4%) were had mixed alleles (Asn-108 + Ser-108).

The setting of the present study, chloroquine fail to treatment the infection with P.falciparum, sulfadoxine/pyrimethamine appear more effective than chloroquine, while quinine effective against chloroquine-resistant infection, and well tolerated by children with acute, uncomplicated, P.falciparum malaria. It may therefore be useful as an alternative to chloroquine in the areas of chloroquine resistance.