Abstract
BackgroundWith 75% of the Ethiopian population at risk of malaria, accurate diagnosis is crucial for malaria treatment in endemic areas where Plasmodium falciparum and Plasmodium vivax co-exist. The present study evaluated the performance of regular microscopy in accurate identification of Plasmodium spp. in febrile patients visiting health facilities in southern Ethiopia.MethodsA cross-sectional study design was employed to recruit study subjects who were microscopically positive for malaria parasites and attending health facilities in southern Ethiopia between August and December 2011. Of the 1,416 febrile patients attending primary health facilities, 314 febrile patients, whose slides were positive for P. falciparum, P. vivax or mixed infections using microscopy, were re-evaluated for their infection status by PCR. Finger-prick blood samples were used for parasite genomic DNA extraction. Phylogenetic analyses were performed to reconstruct the distribution of different Plasmodium spp. across the three geographical areas.ResultsOf the 314 patients with a positive thick blood smear, seven patients (2%) were negative for any of the Plasmodium spp. by nested PCR. Among 180 microscopically diagnosed P. falciparum cases, 111 (61.7%) were confirmed by PCR, 44 (24.4%) were confirmed as P. vivax, 18 (10%) had mixed infections with P. falciparum and P. vivax and two (1.1%) were mixed infections with P. falciparum and P. malariae and five (2.8%) were negative for any of the Plasmodium spp. Of 131 microscopically diagnosed P. vivax cases, 110 (84%) were confirmed as P. vivax, 14 (10.7%) were confirmed as P. falciparum, two (1.5%) were P. malariae, three (2.3%) with mixed infections with P. falciparum and P. vivax and two (1.5%) were negative for any of the Plasmodium spp. Plasmodium falciparum and P. vivax mixed infections were observed. Plasmodium malariae was detected as mono and mixed infections in four individuals.ConclusionFalse positivity, under-reporting of mixed infections and a significant number of species mismatch needs attention and should be improved for appropriate diagnosis. The detection of substantial number of false positive results by molecular methodologies may provide the accurate incidence of circulating Plasmodium species in the geographical region and has important repercussions in understanding malaria epidemiology and subsequent control.
Highlights
With 75% of the Ethiopian population at risk of malaria, accurate diagnosis is crucial for malaria treatment in endemic areas where Plasmodium falciparum and Plasmodium vivax co-exist
Malaria is caused by parasites of the genus Plasmodium, with four different species infecting humans (Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae) and parasites of non-human primates, such as Plasmodium knowlesi, infecting humans occasionally
Plasmodium falciparum accounts for 60-70% and P. vivax accounts for 30-40% of malaria cases in Ethiopia, these proportions might fluctuate on the spatial and temporal scale [6]
Summary
With 75% of the Ethiopian population at risk of malaria, accurate diagnosis is crucial for malaria treatment in endemic areas where Plasmodium falciparum and Plasmodium vivax co-exist. Malaria is one of the major causes of mortality and morbidity in tropical and subtropical countries with an estimated 655,000 malaria deaths in 2010, and 91% of these cases were in sub-Saharan Africa [1]. Malaria is caused by parasites of the genus Plasmodium, with four different species infecting humans (Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae) and parasites of non-human primates, such as Plasmodium knowlesi, infecting humans occasionally. Plasmodium falciparum is the most virulent species contributing to a larger extent to malarial deaths in Africa, including Ethiopia. Anopheles arabiensis is the main vector widely distributed in Ethiopia, while Anopheles pharoensis, Anopheles funestus and Anopheles nili contribute as secondary vectors [7]
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