Efficacy of Primaquine in Preventing Short- and Long-Latency Plasmodium vivax Relapses in Nepal.
BACKGROUND
Plasmodium vivax is the main cause of malaria in Nepal. Relapse patterns have not been characterized previously.


METHODS
Patients with P. vivax malaria were randomized to receive chloroquine (CQ; 25 mg base/kg given over 3 days) alone or together with primaquine (PQ; 0.25 mg base/kg/day for 14 days) and followed intensively for 1 month, then at 1- to 2-month intervals for 1 year. Parasite isolates were genotyped.


RESULTS
One hundred and one (49%) patients received CQ and 105 (51%) received CQ + PQ. In the CQ + PQ arm, there were 3 (4.1%) recurrences in the 73 patients who completed 1 year of follow-up compared with 22 of 78 (28.2%) in the CQ-only arm (risk ratio, 0.146 [95% confidence interval, .046-.467]; P < .0001). Microsatellite genotyping showed relatively high P. vivax genetic diversity (mean heterozygosity, 0.843 [range 0.570-0.989] with low multiplicity of infection (mean, 1.05) reflecting a low transmission preelimination setting. Of the 12 genetically homologous relapses, 5 (42%) occurred in a cluster after 9 months, indicating long latency.


CONCLUSIONS
Although there may be emerging CQ resistance, the combination of CQ and the standard-dose 14-day PQ regimen is highly efficacious in providing radical cure of short- and long-latency P. vivax malaria in Nepal.
['Rijal|Komal Raj|KR|', 'Adhikari|Bipin|B|', 'Ghimire|Prakash|P|', 'Banjara|Megha Raj|MR|', 'Das Thakur|Garib|G|', 'Hanboonkunupakarn|Borimas|B|', 'Imwong|Mallika|M|', 'Chotivanich|Kesinee|K|', 'Day|Nicholas P J|NPJ|', 'White|Nicholas J|NJ|', 'Pukrittayakamee|Sasithon|S|']
D000293:Adolescent D000328:Adult D000962:Antimalarials D002738:Chloroquine D002908:Chronic Disease D004359:Drug Therapy, Combination D005260:Female D005500:Follow-Up Studies D005838:Genotype D006801:Humans D008137:Longitudinal Studies D016780:Malaria, Vivax D008297:Male D008875:Middle Aged D009390:Nepal D010966:Plasmodium vivax D011319:Primaquine D011446:Prospective Studies D012008:Recurrence D055815:Young Adult
primaquine Plasmodium vivax relapse Nepal chloroquine