Clin Infect Dis. 2021 Jul 3:ciab610. doi: 10.1093/cid/ciab610. Online ahead of print.
ABSTRACT
BACKGROUND: The effect of primaquine in preventing P. vivax relapses from dormant stages is well established. For P. ovale, the relapse characteristics and the use primaquine is not as well studied. We set to evaluate the relapsing properties of these two species, in relation to primaquine use among imported malaria cases in a non-endemic setting.
METHODS: We performed a nationwide retrospective study of malaria diagnosed in Sweden 1995-2019, by reviewing medical records of 3254 cases. All episodes of P. vivax (n=972) and P. ovale (n=251) were selected for analysis.
RESULTS: First time relapses were reported in 80/857 (9.3%) P. vivax and 9/220 (4.1%) P. ovale episodes, respectively (p<0.01). Without primaquine, the risk for relapse was higher in P. vivax, 20/60 (33.3%), compared to 3/30 (10.0%) in P. ovale (HR 3.5, 95% CI 1.0-12.0). In P. vivax, patients prescribed primaquine had a reduced risk of relapse compared to episodes without relapse preventing treatment, 7.1% vs 33.3%, (HR 0.2, 95%CI 0.1-0.3). In P. ovale, the effect of primaquine on the risk of relapse did not reach statistical significance, with relapses seen in 2.8% of the episodes compared to 10.0% in patients not receiving relapse preventing treatment (HR 0.3, 95% CI 0.1-1.1).
CONCLUSION: The risk of relapse was considerably lower in P. ovale than in P. vivax infections indicating different relapsing features between the two species. Primaquine was effective in preventing P. vivax relapse. In P. ovale, relapse episodes were few and the supportive evidence for primaquine remains limited.
PMID:34216464 | DOI:10.1093/cid/ciab610
