Assessment of fourteen days primaquine treatment efficacy in plasmodium vivax malaria at primary and tertiary care centers in Southwestern India

Abstract

Background: Acquaintance is scanty on PQ efficacy and P. vivax relapse in Udupi district, Karnataka, India. We assessed the efficacy of 14 days PQ treatment for preventing recurrence of P. vivax infection. Methods & Materials: Microscopy and PCR proven P. vivax infected adults (≥18 years) from one tertiary and five primary health centres, pre-enrolled in a chloroquine-primaquine (CQ-PQ) combined therapeutic trial, upon convalescence on 28th day were requested to participate in another 15 months long follow up study. Participants were treated previously with CQ 25 mg/kg body weight over 3 days and PQ 0.25 mg/kg body weight daily for 2 weeks upon confirmation of G6PD levels. A complete adherence for the prescribed CQ-PQ regimens was noted. A peripheral blood smear examination was performed with every participant within 1–2 months duration. A positive P. vivax case was considered as relapse/reinfection and retreated with CQ-PQ. Data were analysed by independent t-test or Mann Whitney U test, χ2 test or Fisher's exact test and Cox regression using SPSS v15.0, South Asia, Bangalore, India. Results: Of total 323 participants in CQ-PQ therapeutic trial, 114 participated in 15 months long follow up study. Of 114 participants, 28 (24.56%) recurred subsequently, including two participants with two recurrences and one participant with three recurrences. One patient did present with P. falciparum malaria after 3 months. The median duration of first recurrence was 3.14 months (IQR, 2.23 – 6.03) which ranged from 1.22 to 15.07 months. There were no clinical dissimilarities (p>0.05) among recurrence and non-recurrence groups. Participants with past history of P. vivax malaria had significantly higher odds of recurrence [HR (95% CI): 2.62 (1.24-5.54), p = 0.012]. The severity of disease (11.40%, 13/114) was not associated (p=1.00) with recurrence. Of 28 recurrent cases, 3 (10.71%) had severe malaria initially, however, none developed severe malaria during recurrences. Conclusion: Despite complete adherence to 14 days PQ regimen, P. vivax results in substantial recurrences in Udupi taluk. Further, molecular investigations are required to determine the true relapse/reinfection proportion and their determinants. Patients with past history of P. vivax malaria are at high risk of recurrences.