Epidemiological profile of Plasmodium ovale spp. imported from Africa to Anhui Province, China, 2012 – 2019

Abstract

Background Although autochthonous malaria cases are no longer reported in Anhui Province, China, imported malaria has become a major health concern. The proportion of reported malaria cases caused by Plasmodium ovale spp. increased to levels higher than expected during 2012 to 2019, and showed two peaks, 19.69% in 2015 and 19.35% in 2018. Methods We conducted a case-based retrospective study, using data collected from the China Information System for Disease Control and Prevention and Information System for Parasitic Disease Control and Prevention from 2012–2019, to describe the trends and differences between P. o. curtisi and P. o. wallikeri. Epidemiological characteristics were analyzed using descriptive statistics. Results P. ovale curtisi and P. ovale wallikeri were found simultaneously circulating in 14 African countries. Among 128 patients infected with P. ovale spp., the proportion of mixed infection cases was 10.16%. Six cases of co-infection by P. ovale and P. falciparum were observed, each presenting with two clinical attacks (the first attack was due to P. falciparum and the second was due to P. ovale spp.) at different intervals. Accurate identification of the infecting species was achieved in only 20.00% of cases with P. ovale infection. At the reporting units, 32.17% and 6.96% of P. ovale spp. cases were misdiagnosed as P. vivax and P. falciparum, respectively. Conclusion Our finding indicates that the ability of P. ovale spp. to co-infect with other malarial species has been previously underestimated and providing rational evidence for the existence of hypnozoites in P. ovale spp. P. o. curtisi and P. o. wallikeri circulate simultaneously in Africa, and the incidence of P. ovale spp. is probably also underestimated in these source countries where the disease is endemic. Given the low rate of species identification, more sensitive point-of-care detection methods need to be developed for P. ovale spp., and introduced in non-endemic areas.