Comparison of routine clinical profiles of patients with imported P. falciparum malaria and co-infection with Plasmodium ovale wallikeri or Plasmodium ovale curtisi

Highligts
• Co-infection with P. ovale curtisi or P. ovale wallikeri does not alter the clinical course of P. falciparum malaria.
• Co-infection with P. ovale spp influences certain laboratory parameters of uncertain significance.
• There appears to be a negative interaction that limits P. ovale curtisi co-infections.

Abstract
Current molecular diagnostic methods have revealed a high prevalence of mixed Plasmodium infections in endemic areas. There is currently very little information on mixed infections with Plasmodium ovale spp. and P. falciparum. A retrospective multicentre cohort study analysed 28 imported mixed Plasmodium ovale wallikeri/Plasmodium falciparum cases and 11 Plasmodium ovale curtisi/Plasmodium falciparum infections compared to 117 matched P. falciparum mono-infections diagnosed by PCR. Results revealed no significant differences in clinical presentation, severity, or hospitalization rates. However, in P. ovale wallikeri co-infections, total leukocyte counts were higher (median 6.25 vs 4.85 × 10⁹/L; p = 0.010) and the parasitemia index was lower (median 0.6 % vs 1.0 %; p = 0.025) with similar absolute parasitemia (2462 vs 3046/µL; p = 0.384). In P. ovale curtisi co-infections, ALT levels were lower (18.0 vs 27.3 IU/L; p = 0.022) and thrombocytopenia was more frequent (100 % vs 51 % <150 × 10⁹/L; p = 0.003) with lower platelet counts (105 vs 148 × 10⁹/L; p = 0.036). The diagnostic, clinical, or prognostic significance of these findings remains uncertain or limited at this time. The predominance of P. ovale wallikeri over P. ovale curtisi in mixed cases suggests a negative interaction between P. falciparum and P. ovale curtisi.