Recurrence in Plasmodium vivax malaria: a prospective cohort study with long follow-up from a coastal region in South-West India.

Background:  India is endemic for Plasmodium vivax (Pv) malaria. Despite a decrease in incidence, its elimination is hampered by recurrences. This study aimed to characterize recurrences in Pv malaria and study its association with primaquine (PQ) usage. Methods:  Symptomatic adult Pv patients were followed-up for up to 23 months for recurrences. The time to recurrence was compared by the PQ dosage they received using a log-rank test. Results: Of the 294 malaria patients, 206 (70%) patients had Pv infection during the study period. A total of 20 (9.7%) recurrences were seen in 17 (8.2%) patients of Pv . The percentage of first-time recurrences were highest in the no PQ group (25%), followed by the weekly PQ group (20%), low dose daily PQ (8.2%) group, and high dose daily PQ group (3.1%). Conclusions: Recurrence in Pv malaria is common, especially in those who receive an inappropriate prescription of primaquine.