Samuel Baso

Haemoglobin (Hb) recovers slowly in malaria and may be influenced by naturally acquired immunity. Hb recovery was compared in malaria immune, indigenous Papuan and non-Papuan adults with limited malaria exposure. Hb concentrations were measured on Days (D) 0, 3, 7, and 28 in 57 Papuans and 105 non-Papuans treated with chloroquine, doxycycline or both drugs for acute, uncomplicated Plasmodium vivax (n?=?64) or Plasmodium falciparum (n?=?98). Mean (SD, range) D0 Hb was 12.7 (2.2, 7–21.3) g/dL and was similar in P. falciparum infected Papuans and non-Papuans: 12.2 vs. 12.8 g/dL (P?=?0.15) but significantly lower in: (i) P. vivax-infected Papuans vs. P. vivax-infected non-Papuans: 11.4 vs. 13.47 g/dL [∆?=?−2.07 (95% CI: –3.3 – –0.8), P?=?0.0018], (ii) all patients with splenomegaly (vs. those without splenomegaly): 12.16 vs. 13.01 g/dL [∆?=?−0.85 (−1.6– –0.085), P?=?0.029], and (iii) all females vs. all males: 10.18 vs. 13.01 g/dL [∆?=?−2.82 (−3.97 – –1.67), P?<?0.0001].Multiple regression identified female sex (P?=?0.000), longer illness duration (P?=?0.015) (P. falciparum patients) and Papuan ethnicity (P?=?0.017) (P. vivax patients) as significant factors for a lower D0 Hb. Mean D28 Hb increased to 13.6 g/dL [∆?=?1.01 (0.5-1.5) vs. D0 Hb, P?=?0.0001]. It was: (i) positively correlated with the D0 Hb (adjusted R2?=?0.24, P?=?0.000), and was significantly lower in P. vivax infected Papuans vs. non-Papuans: 12.71 vs. 14.46 g/dL [∆?=?−1.7 (−2.95– –0.5, P?=?0.006). Haemoglobin recovery was related to baseline Hb. Vivax-infected malaria immune Papuans had persistently lower Hb concentrations compared to non-Papuans with limited malaria exposure. This haematological disadvantage remains unexplained.