Persistence of Imported Malaria Into the United Kingdom: An Epidemiological Review of Risk Factors and At-risk Groups

Imported malaria: A 20-year retrospective study from a tertiary public hospital in Brussels, Belgium

BACKGROUND

Malaria continues to cause a significant number of infections in non-endemic regions. In this paper, we describe the epidemiological trend and morbidity of imported malaria diagnosed in a tertiary hospital in Brussels.

METHODS

We conducted a retrospective study describing a cohort of malaria episodes (in- and outpatients) at Centre Hospitalier Universitaire Saint-Pierre from 1998 to 2017. Epidemiological and clinical data were collected by reviewing medical files.

RESULTS

A total of 1011 malaria episodes were analyzed. Median age at diagnosis was 35 years, and 66 % of patients were men (672/1011). Malaria cases significantly increased over the two decades (from 17 in 1998 to 79 in 2017). Plasmodium falciparum malaria was most often diagnosed (846/935, 89 %), primarily from Central (530/935, 57 %) and West Africa (324/935, 35 %). Many cases (383/764, 50 %) were diagnosed in patients "visiting friends and relatives". HIV-infected and other immunocompromised patients were significantly more likely to present with severe malaria (at least one severity criteria as defined by the WHO) compared to other patients (24/57, 42 % vs 138/732, 19 %, p < 0.01 and 15/21, 71 % vs 147/767, 19 %, p < 0.001). Severe malaria was diagnosed in 16.9 % and the mortality rate was low (5/1011, 0.5 %).

CONCLUSION

Imported malaria increased over the years with a large, albeit stable number of cases diagnosed in patients visiting friends and relatives. These findings, along with the high rate of severe malaria in HIV and immunocompromised patients, underscore an urgent need for strengthened malaria surveillance and targeted preventive interventions.

Length of stay in at-risk areas and time to malaria attack on return

BACKGROUND

Experimental infection with Plasmodium falciparum results in malaria attack within a few days of exposure. However, we have regularly observed malaria attack within a short time after return, regardless of the time spent in an endemic area. We therefore aimed to assess whether the time before return and malaria attack varies according to length of stay.

METHODS

We used anonymized data from the French National Reference Centre for Malaria between 2006 and 2016. We analyzed 11,823 cases aged at least 1 year and diagnosed with P. falciparum malaria 1 day to 1 year after returning to France, after a stay of 1 day to 1 year in an at-risk area.

RESULTS

Trips had a median duration of 31 days [IQR: 19-56]. Median time between return from the endemic area and onset of malaria symptoms was 5 days [IQR: 0-10], and the median between return and malaria diagnosis was 9 days [IQR: 5-14]. Times to symptom onset or diagnosis were longer for stays of fewer than 15 days vs 15 days or more (for symptoms: 7 vs 4 days for longer stays, for diagnosis: 11 vs 9 days). For stays longer than 15 days, no variation was observed according to length of stay.

CONCLUSIONS

Aside from at-risk stays of fewer than 15 days, the time between return and malaria attack is constant and rather short, even after long stays. The 2 weeks following return should be considered as a risk period whatever the length of stay in an at-risk area.

Epidemiology and clinical features of imported malaria: a 14-year retrospective single-centre descriptive study in Prague, Czech Republic

Background

Malaria represents one of the most important imported tropical infectious diseases in European travellers. The objective of the study was to identify changes in the epidemiological features of imported malaria and to analyse the clinical findings and outcomes of imported malaria.

Methods

This single-centre descriptive study retrospectively analysed the medical records of all imported malaria cases in travellers treated at the Department of Infectious Diseases of University Hospital Bulovka in Prague from 2006 to 2019.

Results

The study included 203 patients with a median age of 37 years (IQR 30–48) and a male to female ratio of 3.72:1. Plasmodium falciparum was the predominant species (149/203), and its proportion significantly increased from 35/60 cases (58.3%) in 2006–2011 to 69/80 (86.3%) in 2016–2019 (p < 0.001). In contrast, the incidence of Plasmodium vivax malaria decreased from 19/60 cases (31.7%) in 2006–2011 to 5/80 (6.3%) in 2016–2019 (p < 0.001). Malaria was imported from sub-Saharan Africa in 161/203 cases (79.3%). The proportion of travellers from Southeast and South Asia decreased from 16/60 (26.7%) and 6/60 (10.0%) in 2006–2011 to 2/80 (2.5%) and no cases (0.0%) in 2016–2019, respectively (p < 0.001 and p = 0.006). Tourism was the most common reason for travel (82/203), however, the proportion of non-tourists significantly increased over time from 29/60 (48.3%) in 2006–2011 to 55/80 (68.8%) in 2016–2019, p = 0.015. Severe malaria developed in 32/203 (15.8%) patients who were significantly older (p = 0.013) and whose treatment was delayed (p < 0.001). Two lethal outcomes were observed during the study period.

Conclusions

This study demonstrated a significant increase in P. falciparum malaria, which frequently resulted in severe disease, especially in older patients and those with delayed treatment initiation. The rising proportion of imported malaria in non-tourists, including business travellers and those visiting friends and relatives, is another characteristic finding analogous to the trends observed in Western European and North American centres. The described changes in the aetiology and epidemiology of imported malaria may serve to optimize pre-travel consultation practices and improve post-travel diagnostics and medical care.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04282-8.

The spreading of parasites by human migratory activities

The global spread of parasites is unquestionably linked with human activities. Migration in all its different forms played a major role in the introduction of parasites into new areas. In ancient times, mass migrations were the main causes for the spread of parasites while in the recent past and present, emigration, immigration, displacement, external and internal migration, and labor migration were the reasons for the dispersal of parasites. With the advent of seagoing ships, long-distance trading became another important mode of spreading parasites. This review summarizes the spread of parasites using notable examples. In addition, the different hypotheses explaining the arrival of Plasmodium vivax and soil-transmitted helminths in pre-Columbian America are also discussed.

Spatiotemporal Distribution of Malaria in Spain in a Global Change Context

Malaria is one of the most cited vector-borne infectious diseases by climate change expert panels. Malaria vectors often need water sheets or wetlands to complete the disease life cycle. The current context of population mobility and global change requires detailed monitoring and surveillance of malaria in all countries. This study analysed the spatiotemporal distribution of death and illness cases caused by autochthonous and imported malaria in Spain during the 20th and 21st centuries using multidisciplinary sources, Geographic Information System (GIS) and geovisualisation. The results obtained reveal that, in the 20th and 21st centuries, malaria has not had a homogeneous spatial distribution. Between 1916 and 1930, 77% of deaths from autochthonous malaria were concentrated in only 20% of Spanish provinces; in 1932, 88% of patients treated in anti-malarial dispensaries were concentrated in these same provinces. These last data reveal the huge potential that anti-malarial dispensaries could have as a tool to reconstruct historical epidemiology. Spanish autochthonous malaria has presented epidemic upsurge episodes, especially those of 1917–1922 and 1939–1944, influenced by armed conflict, population movement and damaged health and hygiene conditions. Although meteorological variables have not played a key role in these epidemic episodes, they contributed by providing suitable conditions for their intensification. After the eradication of autochthonous malaria in 1961, imported malaria cases began to be detected in 1973, reaching more than 700 cases per year at the end of the second decade of the 21st century. Therefore, consistent and detailed historical studies are necessary to better understand the drivers that have led to the decline and elimination of malaria in Europe and other temperate countries.

Exploring the combination characteristics of lumefantrine, an antimalarial drug and human serum albumin through spectroscopic and molecular docking studies

Binding of lumefantrine (LUM), an antimalarial drug to human serum albumin (HSA), the main carrier protein in human blood circulation was investigated using fluorescence quenching titration, UV-vis absorption and circular dichroism (CD) spectroscopy as well as molecular docking. LUM-induced quenching of the protein (HSA) fluorescence was characterized as static quenching, as revealed by the decrease in the value of the Stern-Volmer quenching constant, K_sv with increasing temperature, thus suggesting LUM-HSA complex formation. This was also confirmed from the UV-vis absorption spectral results. Values of the association constant, K_a for LUM-HSA interaction were found to be within the range, 7.27-5.01 × 10⁴ M^-1 at three different temperatures, i.e. 288 K, 298 K and 308 K, which indicated moderate binding affinity between LUM and HSA. The LUM-HSA complex was stabilized by hydrophobic interactions, H-bonds, as well as van der Waals forces, as predicted from the thermodynamic data (ΔS = +50.34 J mol^-1 K^-1 and ΔH = -12.3 kJ mol^-1) of the binding reaction. Far-UV and near-UV CD spectral results demonstrated smaller changes in both secondary and tertiary structures of HSA upon LUM binding, while three-dimensional fluorescence spectra suggested alterations in the microenvironment around protein fluorophores (Trp and Tyr). LUM binding to HSA offered stability to the protein against thermal stress. Competitive drug displacement results designated Sudlow's Site I, located in subdomain IIA of HSA as the preferred binding site of LUM on HSA, which was well supported by molecular docking analysis.Communicated by Ramaswamy H. Sarma.