High risk of Plasmodium vivax malaria following splenectomy in Papua, Indonesia.

Background: Splenectomy increase the risk of severe and fatal infections, however the risk of Plasmodium vivax malaria is unknown. We quantified the Plasmodium species-specific risks of malaria and other outcomes following splenectomy in patients attending a hospital in Papua, Indonesia.

Methods: Records of all patients attending Mitra-Masyarakat Hospital 2004-2013 were reviewed, identifying those who underwent splenectomy. Subsequent risks of specific clinical outcomes within 12 months for splenectomized patients were compared to non-splenectomized patients from their first recorded hospital admission. In addition, patients splenectomized for trauma between 2015-2016 were followed prospectively for 14 months.

Results: Of the 10,774 non-pregnant patients aged 12-60 years hospitalized during 2004-2013, 67 underwent splenectomy. Compared to non-splenectomized inpatients, patients undergoing splenectomy had a 5-fold higher rate of malaria presentation within 12 months (Adjusted Hazard Ratio (AHR)=5.0 [95%CI:3.4-7.3], p<0.001). The rate was greater for P. vivax (AHR=7.8 [95%CI:5.0-12.3], p<0.001) compared to P. falciparum (AHR=3.0 [95%CI:1.7-5.4], p<0.001). Splenectomized patients had greater risk of being hospitalized for any cause (AHR=1.8 [95%CI:1.0-3.0], p=0.037) and, diarrheal illness (AHR=3.5 [95%CI:1.3-9.6], p=0.016). In the prospective cohort, 8 of 11 splenectomized patients had 18 episodes of malaria over 14 months, 12 episodes of P. vivax in 8 patients and 6 episodes of P. falciparum in 6 patients.

Conclusions: Splenectomy is associated with a high risk of malaria, greater for P. vivax than P. falciparum. Eradication of P. vivax hypnozoites using primaquine (radical cure) and subsequent malaria prophylaxis is warranted in patients following splenectomy in malaria-endemic areas, particularly in the early post-operative period.