Malaria in a metropolitan region of Southern Germany: past, present and future perspectives on a protozoan infection with the potential of re-appearance in Central Europe.

Abstract

Background: Malaria occurred endemically in Germany until the twentieth century. Climate change and globalization are known to promote the spreading of malaria. Erlangen is a city with just under 120,000 inhabitants located in the Nürnberg metropolitan region, Federal State of Bavaria, Southern Germany. Historical findings, current climate data, microbiological data (local and state level) and vector surveillance data are used to estimate the risk of re-emergence and autochthonous transmission of malaria in the area of Erlangen.

Methods: Historical data was obtained by searching literature. Climatic data were retrieved from the German Climate Data Centre. Data on reported (supra-)regional infections were obtained from the Robert-Koch Institute. Cases of malaria diagnosed at the Institute of Clinical Microbiology, Immunology and Hygiene (University Hospital Erlangen) complement this data. The citizen science project "Mückenatlas" (Mosquito Atlas), the German mosquito database (CULBASE) and the company Biogents AG provided mosquito surveillance data.

Results: Malaria was highly endemic in Erlangen in the nineteenth century, with 18% of hospitalized patients suffering from this disease in 1860, but disappeared during the first half of the twentieth century. After the end of World War II, autochthonous 'malaria tertiana' (tertian malaria) occurred in neighbouring Nürnberg, demonstrating the regional malaria potential. In recent decades, the average monthly temperature increased by 1.6 °C. In Erlangen and the surrounding area, three potential vectors of tertian malaria parasites are prevalent (Anopheles messeae, Anopheles maculipennis sensu stricto, and Anopheles plumbeus). In addition, Anopheles daciae, which has unknown potential of Plasmodium transmission, and Anopheles claviger sensu lato have been detected. In recent years, malaria diagnosed in Erlangen mainly resulted from travelling to Africa. Plasmodium vivax accounted for only a small proportion of these cases (2010-2023: n = 5, 17%).

Conclusion: Future autochthonous transmission of malaria parasites in Erlangen is possible, although re-establishment of a natural transmission cycle is currently unlikely. In order to avoid unexpected autochthonous malaria, surveillance and prevention measures should be considered. Patients with fever after visiting endemic areas need to be analysed for Plasmodium infection.