Comparison of ImportedPlasmodium ovale curtisiandP. ovale wallikeriInfections among Patients in Spain, 2005–2011

Abstract

Sequencing data from Plasmodium ovale genotypes co-circulating in multiple countries support the hypothesis that P. ovale curtisi and P. ovale wallikeri are 2 separate species. We conducted a multicenter, retrospective, comparative study in Spain of 21 patients who had imported P. ovale curtisi infections and 14 who had imported P. ovale wallikeri infections confirmed by PCR and gene sequencing during June 2005–December 2011. The only significant finding was more severe thrombocytopenia among patients with P. ovale wallikeri infection than among those with P. ovale curtisi infection (p = 0.031). However, we also found nonsignificant trends showing that patients with P. ovale wallikeri infection had shorter time from arrival in Spain to onset of symptoms, lower level of albumin, higher median maximum core temperature, and more markers of hemolysis than did those with P. ovale curtisi infection. Larger, prospective studies are needed to confirm these findings.

Clinical significance of molecular methods in the diagnosis of imported malaria in returning travelers in Serbia

“…The low performance of our PCR for the detection of P. ovale reflects the limitations of the primers and probe used in distinguishing between the two P. ovale subspecies, P. ovale curtisi and P. ovale wallikeri. 19,21,22 Since the primers we used for the detection of P. ovale detect only P. ovale curtisi, we indirectly confirmed that the four detected cases were P. ovale curtisi and the other two undetected ones were P. ovale wallikeri. Overall, the introduction of molecular diagnostics demonstrated a remarkably higher share (13.3%) of P. ovale among the Plasmodium species imported into Serbia than considered before the introduction of qPCR (1%).…”

“…This may have been due to the poor quality of the long stored blood samples and DNA degradation, or the inhibition of PCR amplification. 3,19 However, as this sample was positive by species-specific qPCR and RDT for P. falciparum, a technical error is more likely. The false-positive results obtained for a few patients in samples collected after antimalarial treatment may be attributed to the persistence of gametocytes (although sexual stages of Plasmodium were not detected independently of asexual parasites), circulating DNA from therapy-damaged parasites, 20 or to cross-reactivity with homologous DNA of other eukaryotic species.…”

“…7 Generally, P. ovale was underestimated before the PCR era in terms of both geographical distribution and severity. 19,21 Microscopic errors mostly occur between P. ovale and P. vivax, because of the highly similar morphology of these two species. 3,9 Fortunately, the misidentification of one of these species for the other does not have clinical ramifications since the therapeutic approach is the same for both.…”

Parasitological correlates of Plasmodium ovale curtisi and Plasmodium ovale wallikeri infection

“…As previously noted, P. ovale wallikeri cases appeared to increase more so than P. ovale curtisi in the past five years, and if this trend were to continue, the lack of Schüffner’s stippling may further hinder interpretation of microscopy and RDT results. The lack of Schüffner’s stippling among P. ovale wallikeri isolates joins other findings that the sub-species have distinguishing clinical characteristics, such as latency and degree of thrombocytopaenia, in addition to their genotype [9, 10]. That said, molecular techniques are still the most accurate and specific method for determining sub-species of P. ovale .…”

“…First recognized in 2010, these two sub-species are believed to have diverged one to two million years ago [7, 9]. Clinical differences between the two sub-species have not been clearly elucidated, although there have been differences found in latency period [9] and thrombocytopaenia [10]. At present, it is unknown if the performance of malaria diagnostic tests may differ between the sub-species, causing infection.…”