Epidemiological investigation of one case of imported falciparum malaria in Guangzhou City

Objective To investigate the epidemiological characteristics of one imported falciparum malaria case in Guangzhou City, in order to clarify its risk of transmission. Methods One volunteer blood donor who was diagnosed as falciparum malaria 14 d after whole blood donation in Guangzhou Blood Center on 9 April 2016, and one blood recipient who received red blood cell transfusion from this blood donor were enrolled in this study. Epidemiological data of those two subjects were collected and epidemiological investigations were conducted on them. On 27 April 2016, one whole blood sample with 5 mL was collected from blood donor. And on 27 April 2016 and 12 May 2016, two whole blood samples with 5 mL each time were collected from the blood recipient respectively. Three whole blood samples were detected for Plasmodium etiological test by blood smear microscopy. And nested PCR method was used to test Plasmodium nucleic acid of three whole blood samples. According to DNA sequencing results of the nested PCR amplification products, the gene of Plasmodium was genotyped and phylogenetic tree was constructed. Results ① The blood donor in this study had a history of migrant workers in the endemic areas of malaria. After returning to China, he had similar clinical manifestations of malaria, such as chills and fever. According to the blood smear microscopy results of his whole blood sample, he was diagnosed as falciparum malaria. ② The blood recipient in this study did not show typical symptoms of malaria. And blood smear microscopy results of his two whole blood samples showed that no Plasmodium was found. ③ The nested PCR results of whole blood samples from the blood donor and recipient in this study were all Plasmodium falciparum positive. The sequence of homology comparison results of Plasmodium 18S rRNA gene in the three blood samples from the blood donor and recipient in this study showed that the similarity of three gene sequences was 100%, which conformed to the results of clinical blood smear microscopy. ④ The constructed results of phylogenetic tree showed that Plasmodium 18S rRNA genotypings of three whole blood samples all were Plasmodium falciparum genotypes and the gene sequences were on the same root, further confirmed that the blood recipient infected Plasmodium falciparum via blood transfusion from the blood donor. Conclusions In this study, the blood donor was infected with Plasmodium falciparum imported from Africa. The recipient was also infected with Plasmodium falciparum via blood transfusion from this blood donor, but no typical malaria symptoms were found. Key words: Malaria, falciparum; Polymerase chain reaction; Blood transfusion; Blood safety; Epidemiologic studies