Abstract
Plasmodium ovale can infect humans, causing malaria disease. We aimed to investigate the severity and mortality of severe P. ovale infection to increase the awareness of physicians regarding the prognosis of this severe disease and outcome-related deaths in countries in which this disease is endemic. Articles that were published in the PubMed, Scopus, and ISI Web of Science databases prior to January 5, 2020 and reported the prevalence of severe P. ovale infection were systematically searched and reviewed. Studies that mainly reported severe P. ovale infection according to the 2014 WHO criteria for the treatment of malaria were included. Two reviewers selected, identified, assessed, and extracted data from studies independently. The pooled prevalence of severe P. ovale mono-infections was estimated using the command “metaprop case population, random/fixed”, which yielded the pooled estimate, 95% confidence interval (CI) and the I2 value, indicating the level of heterogeneity. Meta-analyses of the proportions were performed using a random-effects model to explore the different proportions of severity between patients with P. ovale and those with other Plasmodium species infections. Among the eight studies that were included and had a total of 1,365 ovale malaria cases, the pooled prevalence of severe P. ovale was 0.03 (95% CI = 0.03–0.05%, I2 = 54.4%). Jaundice (1.1%), severe anemia (0.88%), and pulmonary impairments (0.59%) were the most common severe complications found in patients infected with P. ovale. The meta-analysis demonstrated that a smaller proportion of patients with P. ovale than of patients with P. falciparum had severe infections (P-value = 0.01, OR = 0.36, 95% CI = 0.16–0.81, I2 = 72%). The mortality rate of severe P. ovale infections was 0.15% (2/1,365 cases). Although severe complications of P. ovale infections in patients are rare, it is very important to increase the awareness of physicians regarding the prognosis of severe P. ovale infections in patients, especially in a high-risk population.
Highlights
Severe malaria results in the dysfunction of one or more vital organs [1]
Most of the Plasmodium spp. infections that were reported among the included studies were caused by P. falciparum (116,898 cases, 51%), P. vivax (78,282 cases, 34.1%), mixed infection (26,049 cases, 11.4%), P. malariae (6,428 cases, 2.8%), and P. ovale (1,365 cases, 0.6%)
The results showed that the age of the participants in six of the included studies did not confound the pooled prevalence of severe P. ovale infections
Summary
Plasmodium ovale, which causes tertian malaria, was first reported in 1922 as one of the five Plasmodium species that can infect humans [2]. The most recent retrospective cohort study conducted in Papua, Indonesia during 2004–2013 demonstrated a low prevalence of P. ovale infections (0.06%) among 68,361 patients [6]. P. ovale is detected and identified with the standard microscopic method. The sensitivity of RDTs to detect P. ovale is low (22.2%) [11]. Continuous efforts regarding PCR techniques have been made to develop new diagnostic techniques, such as Plasmodium species-specific PCR-restriction fragment length polymorphism (PCR-RFLP) [16], for identifying malaria parasites, nested PCR techniques with high sensitivity and specificity are needed
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