Malaria diagnosis in most settings is largely dependent on the demonstration of parasites in stained blood films by conventional microscopy. This enables parasite detection, identification of Plasmodium species and estimation of parasite densities. Accurate identification of the infecting Plasmodium species relies on detailed examination of parasite morphological characteristics such as size, shape, pigmentation, besides the size and shape of the parasitized red blood cells and the inclusions therein [1, 2]. Medical text books, reference literature and atlases that describe morphological features of Plasmodium species already exist to aid microscopic diagnosis of malaria infections .
Plasmodium species traditionally associated with human infections are Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale. However, Plasmodium knowlesi associated with long tailed macaque monkeys has of late crossed over to humans and is now considered by some to be the fifth human malaria [3, 4]. Since Plasmodium species differ with respect to their biology, clinical symptoms, and treatment requirements [5, 6]; accurate identification of Plasmodium infections is of critical importance with regard to formulation and deployment of effective intervention strategies in endemic regions .
Plasmodium falciparum is the most prevalent malaria infection in Africa and accounts for the largest proportion of clinical cases [7, 8]. Plasmodium malariae infections are frequently found in sympatry with P. falciparum infections [7, 9–11], but cases go undetected unless molecular methods are used for diagnosis . The burden of P. ovale is thought to be highest in sub-Saharan Africa. However, its prevalence is deemed to be lower compared to P. malariae[11, 12]. The near absence of Duffy positive phenotype in the local populations seems to exclude transmission of P. vivax in sub-Saharan Africa [13, 14] except in countries such as Djibouti, Eritrea, Ethiopia, Somalia, and Sudan .
This work explores misclassification of four Plasmodium species by conventional microscopy relative to the proficiency of microscopists and morphological characteristics of the parasites on Giemsa stained blood films.