Spatiotemporal Distribution of Malaria in Spain in a Global Change Context

Abstract

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.

Drivers of autochthonous and imported malaria in Spain and their relationship with meteorological variables

“…This epidemic episode presents a relative decrease in 1918–1919 due to the increase in total mortality caused by the wrongly called “Spanish Influenza” pandemic (Chowell et al 2014 ). In 1918, the total number of deaths caused by this virus was estimated to be at least 147,114 people (Trilla et al 2008 ), although other authors report it as causing 230,036 deaths and highlight the coincidence of the mortality peaks of the 1918 influenza pandemic with an outbreak of malaria (Sousa et al 2020 ).…”

“…The main drivers of this outbreak are linked to population displacements, hunger, the scarcity of antimalarial drugs, and the proliferation of anopheles due to the abandonment of antimalarial campaigns (Rico-Avelló 1950 ; Rodríguez-Ocaña et al 2003 ; Barona and Perdiguero-Gil 2008 ; Sousa et al 2014 ). More recent studies have analyzed, separately, the spatial evolution of this epidemic peak in the different Spanish regions, with the authors concluding that the movements of both citizens and troops after the war conflict, along with the overcrowding and/or detention of population sectors in forced labor camps, contributed to intensifying this outbreak (Sousa et al 2020 ). From 1947, Spain recovered to the pre-Spanish Civil War levels of 1935.…”

“…These data were obtained from the Spanish epidemiological surveillance systems (SSIbase 2020 ), the Bulletins of the Carlos III Institute ( 2020 ), the Spanish Network of Epidemiological Surveillance ( 2020 ), and the Basic Surveillance System of the Valencian Community ( 2020 ). Herrador et al ( 2019 ) and Sousa et al ( 2020 ) have provided a good synthesis of these data sources, their online localization and their limitations.…”

“…To map the provincial distribution of autochthonous malaria and the regional distribution of imported malaria, we used Geographical Information System (GIS) data. Different studies have used GIS tools to analyze the morbidity and/or mortality of malaria at the regional, national or global scale, as well as the main drivers of the disease (Hay et al 2002 ; Omumbo et al 2002 ; Sipe and Dale 2003 ; Guerra et al 2006 ; Sousa et al 2014 , 2019 , 2020 ; Gwitira et al 2019 ; Battle et al 2019 ; Weiss et al 2019 ). In our case, we used these tools—from the data of the years available in SSIBase—to generate the mapping of the total number of people who died of autochthonous malaria in Spain (year 1949) and the total number of people infected with imported malaria (2010–2018).…”

“…The different types of malaria can be categorized according to the origin of the vectors of the genus Anopheles , which transmit the protozoa of the genus Plasmodium that cause malaria. From a quantitative perspective, the most frequent types of malaria are indigenous, or autochthonous malaria, and imported malaria (Sousa et al 2020 ). In the case of autochthonous malaria, the disease is acquired from the bite of an infected mosquito in a country where malaria is present, while imported malaria refers to malaria in patients who acquire the disease in endemic countries and who are diagnosed or start to show symptoms in countries where the disease has been eradicated (Díaz et al 2005 ; López-Vélez and Molina 2005 ).…”