Epidemiological analysis of 133 malaria cases in Shanxian County, Shandong Province, China

Objective: To conduct an analysis of the epidemiological changes in malaria that have occurred in Shanxian county from 2002 to 2016. Methods: A retrospective study was conducted and data were collected from web-based reporting system to explore the epidemiological characteristics in Shanxian county from 2002 to 2016. All individual case information was obtained from village malaria servicers organized by the local Shandong Institute of Parasitic Diseases. Results: A total of 133 cases were identified as malaria in Shanxian county during this period, including 124 indigenous cases(93.2%) and 9 imported cases(6.8%). The 124 indigenous malaria cases were infected with Plasmodium vivax(P. vivax), whereas 7 of the 9 confirmed imported cases were infected with Plasmodium falciparum(P. falciparum), 1 was infected with Plasmodium ovale(P. ovale) and 1 patient was infected with P. falciparum mixed with P. vivax. The total number of malaria cases included 86 males(64.7%) and 47 females(35.3%). Age of the patients ranged from 1 to 83 years, although most(64.7%) infections occurred in the 21-to 60-year-old age group. Remarkably, 117 of the total malaria cases(98.0%) were reported from 2006-2011. The epidemic season was from June to October, with the peak occurring yearly from July to September. The most common occupation of the infected patients was farmer. In total, 58.1% of the cases occurred in 3 townships, namely, Fugang, Huanggang and Caozhuang. Conclusions: In Shanxian county, the local malaria incidence experienced an emerge-peak-control-eliminate status. However, due to the numbers of migrant labourers returning from Africa, imported cases were continuous and presented an increasing annual trend, which became a non-negligible and a significant impediment for malaria elimination. Therefore, the need to eliminate instances of malaria reintroduction to receptive malaria-free areas should drive strategies to align with the epidemiological changes.