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. 2022 Apr 9;74(7):1199-1207.
doi: 10.1093/cid/ciab610.

Relapse of Plasmodium vivax and Plasmodium ovale Malaria With and Without Primaquine Treatment in a Nonendemic Area

Andreas Wångdahl  1   2 , Klara Sondén  1   3 , Katja Wyss  1   3 , Christine Stenström  4 , David Björklund  1 , Jessica Zhang  1 , Helena Hervius Askling  1   3 , Christina Carlander  2   5 , Urban Hellgren  3   5 , Anna Färnert  1   3
Affiliations

Relapse of Plasmodium vivax and Plasmodium ovale Malaria With and Without Primaquine Treatment in a Nonendemic Area

Andreas Wångdahl et al. Clin Infect Dis. .

Abstract

Background: The effect of primaquine in preventing Plasmodium vivax relapses from dormant stages is well established. For Plasmodium ovale, the relapse characteristics and the use of primaquine is not as well studied. We set to evaluate the relapsing properties of these 2 species, in relation to primaquine use among imported malaria cases in a nonendemic 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 < .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 (hazard ratio [HR] 3.5, 95% confidence interval [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 .1-.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 .1-1.1).

Conclusions: 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.

Keywords: P. ovale; P. vivax; malaria; primaquine; relapse.

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Figures

Figure 1.
Figure 1.
Chart of study population.
Figure 2.
Figure 2.
Kaplan-Meier analysis comparing the occurrence of relapse in all first diagnosed P. vivax (blue solid line) and P. ovale (red dashed line).
Figure 3.
Figure 3.
Plot visualizing the smoothed hazard function for relapse in P. vivax (left) and P. ovale (right) in episodes with (red dashed line) and without primaquine prescription (blue solid line). Long-term chloroquine is not included in the graph.
See this image and copyright information in PMC

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