Profile of mixed species (Plasmodium vivax and falciparum) malaria in adults.

Objective: Studies on malaria due to co-existent P. falciparum and P. vivax infections are negligible in India. Therefore, this study was undertaken to find out the clinical profile, prognostic factors, and outcome of mixed species malaria and to compare it with P. falciparum malaria.

Methods: This prospective, comparative study has been conducted in a tertiary health care institution with high prevalence of malaria. A cohort of 888 patients of malaria was enrolled in this study. The diagnosis of malaria was made either by Giemsa stained peripheral blood smear or RDT. Mixed species (MS) malaria was diagnosed when both P. vivax and P. falciparum were detected either from peripheral blood smear or RDT. Patients with P. falciparum malaria were grouped in to Pf group. The differences in clinical presentation, biochemical and haematological findings, occurrence of severe malaria, and outcome were recorded, compared, and analyzed. The severity of complication was assessed and Malaria Severity Score (MSS) was calculated. All the patients were treated according to WHO guidelines.

Results: Of them MS and Pf malaria constituted 118 (13.2%) and 770 (86.7%) patients respectively. Severe malaria was found in 17.8% (21 of 118) patients of MS and 57.1% (440 of 770) patients Pf malaria. Pf constituted 440 (95.5%) cases where as MS constituted 21 (4.5%) respectively. The number of severe malaria was significantly (p < 0.001) more in Pf than MS. Out of 21 cases of severe malaria in MS infection, 14 (66.6%) had single complication and 7 (33.3%) cases had multiple complication. However, in Pf mono infection there were 200 (45.5%) patients with single and 240 (54.5%) with multiple complication. There were 4 independent risk factors for a patient of developing complicated malaria. They were: presenting without fever, high parasite count, Pf mono infection, and fever to treatment interval. Multiple complications and high MSS are associated with increased death in Pf malaria. The outcome of patients of MS was good.

Conclusion: In conclusion mixed species infection is not uncommon in the locality where both species coexists. Mixed species infection can complicate with severe malaria. However, its incidence and severity is less than severe falciparum malaria. In mixed infection, P.vivax malaria has a protective effect against the severity of falciparum malaria.