A case of Plasmodium falciparum malaria presenting 13 years after leaving an endemic area

Plasmodium falciparum usually causes an acute malaria infection, with symptoms presenting from 8 to 11 days onwards following inoculation by an infected mosquito. However, evidence suggesting chronic carriage of blood-stage infection, which can lead to recrudescence of parasitaemia as immunity wanes, has been documented in migrants from malaria-endemic to non-endemic regions. We report the case of a pregnant patient who presented in late 2020 with symptomatic P. falciparum malaria, having lived continuously in areas non-endemic for malaria (Spain and the UK) for 13 years. The patient was originally from Equatorial Guinea but had not visited a malaria-endemic region since leaving Africa in 2007. Serological characterisation of peripheral antibodies circulating 4 months prior to, during and 2 months after the acute malaria episode suggests induction of IgG recognising placental malaria-specific antigens during the pregnancy. These antibodies waned in titre following successful treatment of the acute malaria episode. Immunological recognition of other blood-stage parasite antigens prior to the acute episode was seen, consistent with an ongoing chronic infection, presumably contracted during childhood before the individual left Equatorial Guinea 13 years earlier. This represents one of the longest-documented periods between exposure and eventual clinical presentation with P. falciparum malaria, and the longest described in a pregnant patient. Our findings have implications for eradication programmes and patient care, with the need to consider P. falciparum infection in patients who have migrated to malaria non-endemic settings, particularly those with altered physiological states such as pregnancy, despite absence of a recent travel history to an endemic region.