Therapeutic efficacy of chloroquine and primaquine for Plasmodium vivax malaria treatment in southeast Iran

Background

Plasmodium vivax is the main cause of malaria infection in Asian, Central and South American countries [1]. It accounts for more than 90% annually of the reported malaria cases in Iran [2]. Plasmodium vivax resistant to chloroquine has emerged in some regions of Asia and resistance or tolerance to primaquine has been demonstrated in several countries [3, 4]. The aim of this study was to determine the therapeutic efficacy of chloroquine and primaquine for Plasmodium vivax malaria treatment in southeast Iran.

Material and methods

A total of randomly selected 270 patients with confirmed P. vivax infection participated in 28-day in vivo study that extended for 2 years for detecting relapse infection. Chloroquine and primaquine were administrated during 3 days and 8 weeks respectively in 2010. The thick and thin film blood smears were screened for malaria parasites by microscopy. The nested PCR was applied using the Plasmodium 18 subunit ribosomal ribonucleic (Ssr RNA) genes for detecting mixed infections and diagnosis of parasites in the samples with low parasite on days monitoring the drug resistance.

Results

Fever resolved on the first day in all subjects. Microscopy findings showed that P. vivax was cleared in 15%, 50%, 95%, and 100% of patients on days 1, 2, 3 and 4, respectively. All 270 subjects showed ~120 Bp band in the nested PCR which was indicative of P. vivax malaria on the zero days. Six patients (2.2%) had specific P. vivax band in nested PCR on day 5. No recurrence was observed on days 7, 14 and 28 in thick blood smear and nested PCR. Mean (±standard deviation) parasite clearance time was 2.41 (±0.8) days. Two patients had P. vivax malaria clinical and parasitological infection following 8 and 12 months after primary P. vivax malaria infection.

Conclusions

The findings of this study showed susceptibility of P. vivax to chloroquine in South east Iran. This finding is compatible with results of neighboring countries Pakistan and Afghanistan. Nested PCR was a suitable assay to determine exact malaria parasite clearance time in our study. The further investigation is being conducted in two reinfection cases by PCR -Single strand conformational polymorphism method to differentiate between relapse and new P. vivax infection.