Historical importance of wetlands in malaria transmission in southwest of Spain.

Limnetica, 28 (2): x-xx (2008) Limnetica, 28 (2): 283-300 (2009) c Asociaci´ on Ib´ erica de Limnolog´ a, Madrid. Spain. ISSN: 0213-8409 Historical importance of wetlands in malaria transmission in southwest of Spain Arturo Sousa1,∗,F ´ atima Andrade2, Alfredo F´ elix3, Vicente Jurado4, Alejandra Le´ on-Botubol1, Pablo Garc´ a-Murillo1, Leoncio Garc´ a-Barr´ on5and Julia Morales1 1Department of Plant Biology and Ecology, University of Seville, C/ Profesor Garc´ a Gonz´ alez, 2, 41012 Seville, Spain. [email protected]; [email protected]; [email protected] 2Consejer´ a de Medio Ambiente de la Junta de Andaluc´ a, 41003 Seville, Spain; fatima.andrade.e[email protected] 3Empresa de Gesti´ on Medio Ambiental S. A. (EGMASA), 41092 Seville, Spain; [email protected] 4Area of Ecology, University of Pablo Olavide, 41013 Seville, Spain; 5Department of Applied Physics II, University of Seville, Avda. Reina Mercedes s/n, 41012 Sevilla, Spain. [email protected] 2 ∗Corresponding author: [email protected] 2 Received: 9/1/09 Accepted: 23/9/09 ABSTRACT Historical importance of wetlands in malaria transmission in southwest of Spain Malaria is a parasitic disease that is currently affecting a good number of countries with approximately one million deaths per year. Traditionally, this pathology has been related to wetlands and other unhealthy water bodies. It disappeared from most of Western Europe after the Second World War; however, its eradication from Spain took place later. In fact, the WHO didn’t ofcially declare malaria in Spain eradicated until 1964, after a gradual controlled process of the illness, through the improvement of health and hygienic conditions in the country, and the ght against the vectors, the parasite, and its reservoirs. In 1913, the Spanish regions with the largest number of municipalities with autochthonous malaria were, precisely, those containing larger areas covered by unhealthy water bodies (except for Extremadura). Among them, Western Andalusia outstood as the main region with the largest area of unhealthy malaria focuses and with high mortality and morbidity rates. Within Western Andalusia, Huelva —and especially its coastal areas— has been, for centuries, one of the provinces with greater endemicity. After the Spanish Civil War a process of reforestation with fast-growing species took place in the Coastal Aeolian Sheet of the Province of Huelva, which led to an 88 % reduction of the surface covered by ponds in this territory. These lagoons had started a natural regression process by the end of the XIXth Century related to the post-Little Ice Age warming in Andalusia. The parallel evolution of malaria patients and the regression process experienced by these wetlands for the above mentioned reasons have had a determinant inuence in the eradication of the disease. All of this leads us to consider the relevant role of wetlands when studying the future risk of malaria reemergence in SW Spain. Key words: Wetlands, malaria, peat ponds, climate change, Do˜ nana, Huelva, SW Spain. RESUMEN La importancia hist´ orica de los humedales del suroeste de Espa˜ na en la transmisi´ on de la malaria La Malaria es una enfermedad parasitaria que, actualmente, afecta a numerosos pa´ ses con alrededor de un mill´ on de fallecidos al a˜ no. Tradicionalmente esta patolog´ a se ha asociado a humedales y otros cuerpos de agua insalubres. Desapareci´ ode la mayor parte de Europa Occidental despu´ es de la II Guerra Mundial, pero en Espa˜ na su erradicaci´ on fue m´ as tard´ a. De hecho hasta 1964, la O.M.S. no declar´ o erradicada ocialmente la malaria en Espa˜ na, tras un paulatino proceso de control de la enfermedad, mediante la mejora de las condiciones higi´ enico-sanitarias del pa´ s, y las lucha contra los vectores y el par´ asito, as´  como sus reservorios. En 1913 las regiones espa˜ nolas con un mayor n´ umero de municipios con paludismo aut´ octono eran, precisamente, las que ten´ an una mayor supercie de cuerpos de aguas insalubres (con la excepci´ on de Extremadura). Entre ellas Andaluc´ a Occidental destacaba como la principal regi´ on con la mayor supercie de focos pal´ udicos insalubres, y con una elevada tasa de 284 Sousa et al. mortalidad y morbilidad. Dentro de Andaluc´ a Occidental Huelva, y especialmente su litoral, ha sido secularmente una de las provincias con mayor endemicidad. Tras la Guerra Civil Espa˜ nola se inicia un proceso de reforestaci´ on en el Manto E´ olico Litoral onubense, con especies de crecimiento r´ apido, que condujo a la reducci´ on del 88 % de la supercie de las lagunas turbosas de este territorio. Estas lagunas hab´ an iniciado un proceso natural de regresi´ on a nales del S. XIX asociados a calentamiento posterior a la Peque˜ na Edad del Hielo en Andaluc´ a. La evoluci´ on paralela del n´ umero de enfermos de paludismo y el proceso de regresi´ on de estos humedales, por las causas anteriores, ha inuido de manera determinante en la erradicaci´ on de la enfermedad. Todo ello nos lleva a considerar el papel relevante de los humedales en el estudio del riesgo futuro de re-emergencia de la malaria en el SW de Espa˜ na. Palabras clave: Humedales, paludismo, lagunas turbosas, cambio clim´ atico, Do˜ nana, Huelva, SO de Espa˜ na. INTRODUCTION Traditionally, the presence of malaria and its prevalence have been related to the existence of wetlands. This is made evident in the etymology of the Spanish word for malaria, “Paludismo”, which derives from the Latin Palus = “swamp, pool” (Corominas, 1997). Nowadays, malaria is considered as the most important among all the parasitic diseases. It affects more than 100 countries, causes approximately one million deaths per year and 40 % of the world population lives in risky areas (White & Breman, 1994; Rotaeche et al., 2001). Malaria was eradicated from most of West Europe after the end of the Second World War (D´ az et al., 2005). Its eradication from Spain occurred later. Concretely at the beginning of the 1960s, as a general improvement of the levels of health and hygiene in Spanish society, specifically through the prevention of infections, the elimination of vectors, and its possible reservoirs, among other strategies. In fact, there are documents reporting deaths until 1959 and people suffering autochthonous malaria until 1961. This is why it was only in 1964 when the WHO declared malaria as officially eradicated in Spain (Pletsch, 1965; Bueno & Jim´ enez, 2008). Several expert panels have alerted to the risk of reemergence of malaria in temperate (and mountainous) areas, from which it had been already eradicated, as a result of Global Warming (Parry, 2000; McCarthy et al., 2001). Some researchers (Loevinsohn, 1994; Mouchet et al., 1998; Martens, 2000) have posed the possibility of relating the expansion of this pathology to climatic modications or changes, such as Global Warming. Other authors question these analyses, considering them inaccurate (Reiter, 2004), labelling them as “green alarmism” (Bate, 2004) or pointing out that they disregard the historical epidemiology of the disease. As a result of this debate, studies on the risk of malaria reemergence have been performed in several West European countries, such as Italy (Romi et al., 2001) and the United Kingdom (Kuhn et al, 2003; Chin & Welsby, 2004). Although these results are not so denitive as their equivalent performed in Africa (Nchinda, 1998), they do contemplate certain risks related to Global Warming. In many cases, aquatic media constitute a necessary reservoir for the breeding of Anopheles, vectors of the Plasmodium parasite producing the disease. In spite of the above, the studies considering the role that wetlands are playing in this issue —as from a multidisciplinary perspective— are scarcer. Furthermore, studies approaching the issue as from a limnological perspective are still less frequent. This is how Kuhn et al. (2003) relate the reduction of malaria in the United Kingdom at the end of the XIXth century to the reduction of wetlands (among other factors). In addition, Reiter (2000) demonstrated that, during the XVIIth century, the mortality rate in England was duplicated, and even tripled, in the parishes located in swampy areas, as compared with those located elsewhere. In view of this background, this study introduces the preliminary results of a multidisciplinary project aimed at a thorough analysis of the Malaria and wetlands in SW Spain 285 historical evolution of malaria in SW Spain and its possible connections with wetlands. Therefore, the objective of our work is to analyse some of the main data about the number of patients and deceased related to malaria in SW Spain and, more specically, regarding the Coastal Aeolian Sheet in the Province of Huelva (Do˜ nana and its surroundings). Besides, our aim is contributing to knowledge on one of the reasons for the historical desiccation of a good portion of the Spanish wetlands. Finally, we will attempt to contribute with some preliminary considerations referred to the recent climatic trends and to the risk of reemergence of malaria in Spain. In order to attain these goals and considering that data is obtained from very different sources, there was a need to apply diverse methods, although always as from a multidisciplinary perspective. DATA AND METHODS The study is being performed on the basis of two different lines: relative information to deceased and malaria patients and the evolution of the area of the wetlands. On one hand, the intent is to reconstruct the evolution of malaria in SW Spain (Western Andalusia). These trends need to be put into context, as far as it is possible, within the framework of the rest of Spain. For this purpose, the study of the illness is introduced both at a more general level (the whole Spanish territory) and at a more detailed one (Western Andalusia and, within the latter, the Coastal Aeolian Sheet in the Province of Huelva). On the other hand, the data related to wetlands and other water bodies involve an approach on a scale similar to the previous one. First, we will introduce the data related to focuses of swamped areas and malaria for the whole Spanish territory. Further on, a more thorough analysis will be made on the particular case of the wetlands in the Coastal Aeolian Sheet in the Province of Huelva. The area is located in SW Spain (at approximately 37◦10latitude N and 6◦45longitude W), specically within the boundaries of the Do˜ nana Natural Park, between the tourist centres of Matalasca˜ nas, Mazag´ on and El Roc´ o. The Table 1. Time period under study on historical data on malaria and wetlands. Per´ odo temporal estudiado de datos hist´ oricos de malaria y humedales. Spatial scale XXth C. XIXth C. XVIIIth C. Malaria Spain Yes Partial data — SW Spain Yes Partial data Partial data Wetlands Spain Partial data — — SW Spain Yes Yes — best-preserved formations of hygrophyte heaths of Erica ciliaris in the whole Do˜ nana (Andalusian) environment, as well as a large number of small lagoons, are located in this area. Today, only a few disperse patches of the original community can be found; they are associated to a series of peat ponds known as Rivatehilos. In Table 1, a synthesis is provided of both the temporal distribution of the sources of data and the spatial scale used in the analysis of the historical data about Malaria and of that related to the evolution of the wetlands. Data related to patients and deceased by Malaria The data referred to the XVIIIth Century were obtained from the questionnaire sent by the royal geographer Tom´ as L´ opez (compiled by Ruiz Gonz´ alez, 1999) to the parish priests in all the Spanish towns. More precisely, the questions numbered four and thirteen referred to the stagnant waters in each district and to the predominant diseases therein. On the other hand, the data related to the mid XIXth Century were mostly collected from the Madoz geographic-statistical- historical dictionary (1848). Both in the XVIIIth and the XIXth centuries, the historical documents, report these data as referred to “tertians” and “quartans” and not to malaria. This terminology can be extrapolated to other European countries and its relationship with the malarial fevers has been clearly evidenced by Reiter (2000), when he analysed the clinical descriptions in England during the XVIth and XVIIth centuries, and in the case of Spain, by Riera (1984), when he studied the epidemics in the XVIIIth Century. Concerning the south of 286 Sousa et al. Spain, Sousa et al. (2006a) have also performed a comprehensive review, of this very issue, for the Provinces of Granada, Huelva and Seville during the XVIIIth Century. According to D´ az et al. (2005), during the period in which Malaria was endemic in Spain, the parasite responsible for the benign tertian fevers was Plasmodium vivax,for the malign tertian was Plasmodium falciparum, and for the quartan fevers Plasmodium malariae. With regard to the XXth Century, we have used diverse documents from the forest les in the region (compiled by Sousa & Garc´ a-Murillo, 2001) written by Manuel Kith Tassara and Gaspar de la Lama responsible for the intensive reforestation performed on the coastal sandy areas in the east of the Province of Huelva. In order to quantify the evolution of malaria in Spain during the XXth Century, a very thorough review was made of the Documentary Archive of the “Instituto Nacional de Estad´ stica” (National Institute of Statistics; hereinafter INEbase). These les correspond with yearly reports started in 1858 in compliance with the organic regulation issued by the General Royal Commission on Statistics (INEbase, 1858). The first complete data about malaria for the whole Spanish territory (understood as within the current international boundaries) appeared in 1900. An additional difficulty was the fact that the name of the disease kept changing in the various yearly reports at the INEbase; during the first years, reference is made mostly to the symptoms rather than to the aetiology itself. Between the early 1900s and 1930, the disease is called “Intermittent fever and malarial cachexia”. From there on, it appears under the name of “Paludismo”(malaria). These data allowed us to rebuild the trends (in absolute numbers) of malaria patients and deceased due to malaria in Spain during the XXth Century. For the years 1949 and 1954- 1961, for which complete data are available from all the provinces, the trends were represented cartographically (using the annual mean number of patients at a provincial scale). In order to analyse the seasonal variations of the disease, the monthly mean number of cases was also represented for the periods in which complete data are available (1949 and 1954-1960). Considering that the main objective of the study is SW Spain, in the case of the Andalusian region, a more detailed analysis was performed of the local evolution, always depending on the data available at the INEbase. In order to study the eradication of malaria in Western and Eastern Andalusia in a differentiated manner, we have used the provincial data for deceased (1916-1930) and malaria patients (1949 and 1954-1961) in absolute numbers. Evolution of the extension of the Wetlands In this section, reference will be made, rst, to the area occupied by malaria focuses all over Spain and, secondly, to the evolution of the areas covered by malarial wetlands in the Coastal Aeolian Sheet of the Province of Huelva. A review was made of the data available on wetlands and other water bodies (“colecciones l´ quidas” in original Spanish) suspicious of being focuses of malaria transmission. In this regard, very interesting information was found concerning the whole Spanish territory, at a regional scale, for the early XXth Century. This information was collected from the advanced summary of statistical data on malaria in Spain published by the Rural Health Inspection (General Department of Agriculture) for the years 1913 and 1916 (INEbase, 1915; INEbase, 1917). In these inventories, the surface covered by malaria “focuses” in hectares was collected, understood as the swamped land requiring sanitation in order to prevent it from becoming contagious focuses and to develop some sort of exploitation. These areas exclude —as it is textually pointed out in the aforementioned inventory— “the focuses involving rice plantations, hemp rafts, banks of channelled rivers and brooks, and road and railway ditches”. Even so, this inventory of water bodies might contain some articially swamped areas. Another innate limitation in these data is that, apparently, they exclude swamped areas that are not considered as unhealthy, thus limiting the accounting of wetlands that, potentially, are not a culture medium for the vector transmitting malaria. These inventories also contain data on the number of municipalities with cases of malaria Malaria and wetlands in SW Spain 287 Table 2. Sources of data used for the reconstruction of the area covered by peat ponds. Fuentes de datos empleadas en la reconstrucci´ on del ´ area ocupada por las lagunas turbosas. Period Fieldwork Aerial photography Satellite imagery Forestry archives Historical documents Historical maps Microtopographic analysis 1987 XXXX—— — 1956 —X—XX— — 19th (∼ ∼ ∼1869) ————XX X vs. their total number in each region, understood as the municipalities in which malaria is permanent (and not imported from other municipalities). Furthermore, they collect data on a number of malaria patients, number of deceased, morbidity, mortality, current pricing of the sites with malaria, approximate cost of works for their sanitation, lost work days due to malaria, current consumption of quinine, etc. In the particular case of the Coastal Aeolian Sheet in the Province of Huelva, in order to study the evolution of the surface covered by peat ponds, their situation in 1987, in 1956 and in the late XIXth Century was mapped. For this purpose, data from diverse sources were used, depending on the date, as summarised in Table 2. More precisely, we have used flights dated in 1956 (1:33 000) and in 1987 (1:20 000), (although we have also consulted flights dated in 1998 and in 2000), along with LANSAT-TM (1986), SPOT (1989) and LANSAT-TM (1990) satellite images. The analysed historical data obtained from documentary archives and sources (more than 20) are essentially from centuries XVI through XX, along with 49 writings and forest reports on scrubland in the region under study (1932-1978). Besides, studies were made on over 70 historical maps especially related to the XVIIIth, XIXth and early XXth centuries. The situation in 1987, and then in 1956, of the peat ponds to which the heathlands of Erica ciliaris are associated was mapped by means of eldwork and through the photointerpretation of aerial photographs and satellite images. The situation at the end of the 19th Century was mapped through the interpretation of the historical documentation in the light of the situation in 1956. However, by themselves, these data do not give way to a standard mapping. Therefore, the historical situation was represented in conventional mapping with the help of micro relief analyses. The original contour lines at a 1:10 000 scale (from more than 250 topographic elevations) were interpolated manually, following a method developed in earlier publications (Sousa & Garc´ a- Murillo, 2003). This method enables contour lines to be obtained approximately every 2 metres, from which a hypsometric map is constructed, revealing the original situation of the former large lagoons, thereby corroborating the historical sources. RESULTS Issues related to the historical distribution of malaria in Spain Although the origin of the disease is much older, the rst known European malaria pandemics date back to the XVIth Century (1557-1558) according to S´ aenz & Marset (2000). At the end of the XVIIIth Century, malaria was markedly epidemic in Spain (Rico-Avell´ o, 1950; Sousa et al., 2006a). During the XIXth century, it was still sig- nicantly virulent, although tending to be more severe in certain endemic regions that were primarily related to different types of inland aquatic ecosystems. During the XXth century, the drying up of wetlands, the improvement in hygienicsocial conditions, and the creation in 1924 of the Central Anti-Malaria Commission produced a slow reduction of the disease. According to the data in the INEbase (INEbase, 1955), an important rise in the number of malaria cases took place in Spain right after the Civil War; the greatest mortality took place during the years 1941, 1942 and 1943, when the number of deaths was tripled. In the case of the Ebro 288 Sousa et al. Delta, although the rise coincided with an increase in the area covered by rice plantations, this does not seem to be the cause for the new epidemic outbreak according to Fabregat (2007). Data obtained from INEbase source reveal that, as from the 1950 decade, there were many diseases whose morbidity was reduced, although the most pronounced decrease took place in malarial fevers. In the mid ’50s, Seville, Huelva and C´ adiz —in this order— were the three provinces in Spain with the largest number of malaria cases, highly distant from the rest, thus turning Western Andalusia into an important focus of endemic malaria. In 1959, the last individual decease due to autochthonous malaria occurred in Spain, while the last registered infected individuals in the provinces of C´ aceres, Huelva, Salamanca and Toledo (INEbase, 1961; INEbase, 1964). This pathology evidences a markedly rural distribution, which might be related to the proximity of wetlands and other swamped areas acting as reservoirs for the vector transmitting the disease. 2514 cases were reported in 1955, among which only 20 (0.79 %) belonged to provincial capitals, 160 (6.36 %) to municipalities with more than 20 000 inhabitants and, contrarily, 2334 (92.84 %) to municipalities with 20 000 or less inhabitants. The data in the INEbase do not always contain the complete number of malaria patients or deceased in the provincial, regional or national environments. Consequently, there was a need to find out whether the data on malaria patients or deceased can be used indistinctly, so as to reach a conclusion on the distribution of the main focuses of the disease. In order to solve this issue, an analysis was made of the correlation between absolute number of malaria patients and number of deceased at a regional level throughout Spain in 1913. This year was selected for the following three reasons: at that time, eradication work had not been started by the Central Anti-Malaria Commission, it was a year with a high number of deceased (almost 2000 deaths) and, finally, because this is a year for which data are available on the surface covered by malarial swamped areas throughout Spain. The analysis of provincial patients versus deceased in Spain in 1913, R2=0.9091, conrmed the expected correlation of both variables and, therefore, any of them could be used as a tool for exploring the evolution of the disease. A different although supplementary issue is the distribution of the number of malaria patients due to malaria in the whole Spanish territory. For this purpose, knowing how the disease was distributed during the last few years and before its denite eradication became especially interesting. As the pathology starts to be under control, the focuses with the greatest endemicity could be identied more clearly. As these focuses became known, an attempt could be made to establish if there was a relationship with the surface and the number of swamped areas. Figure 1 shows the provincial distribution of patients due to malaria in Spain during the 1949-1961 period. Although the number of cases decreased sig- nicantly as from 1949, when these years were analysed separately, in general terms, the pattern of provincial distribution of malaria patients in Spain remained constant. SW Spain continued to be the main focus of malaria. To be noted are the low course of the Guadalquivir (Seville, C´ adiz and the coastal sandy areas of Huelva), along with Extremadura (especially C´ aceres) and Ciudad Real. Also the Spanish Mediterranean coastal areas (especially Murcia) were included among them. They all correspond with provinces that have had or still have important swamped areas. Malaria focuses and wetlands in Spain The INEbase contains detailed data on diseases for which reporting was mandatory, such as malaria. The same source does also provide interesting data related to the presence and the distribution of the malaria focuses (INEbase, 1915; INEbase, 1917). The information provided is highly relevant because, on one hand, a quantification of the Spanish wetlands is made available, far before than that performed by Pardo (1948), in a comprehensive and systematic manner. On the other hand, it allows to relate the distribution of wetlands with that of malaria, especially because it refers to dates prior to the start of the anti-malaria campaigns all over Spain. Obviously, these data are not complete because they refer, exclusively, to areas with malaria and unhealthy due to the presence of water bo- Malaria and wetlands in SW Spain 289 5-20 infected per year < 5 infected per year 21-100 infected per year 101-400 infected per year 401-725 infected per year Figure 1. Mean number of malaria patients per province in Spain during the 1949-1961 period. Media provincial anual de enfermos por malaria en Espa˜ na durante el per´ odo 1949-1961. dies. Even so, they constitute a novel source of indirect limnological information by providing a rst historical image of the distribution of a certain group of wetlands in Spain in the early XXth Century. Figure 2 shows the regional distribution of malarial focuses, understood as potentially unhealthy water bodies but excluding many water accumulations of an anthropic character, some of which can act as important habitat for anophelines. For instance, rice elds, road and railway ditches, and hemp rafts; non-channelled brook and river banks are neither included. In 1913, the total malarial surface in the Spanish territory that was more or less swamped for diverse reasons reached 341 070 ha, a gure that was reduced to 313 200 ha by 1916. As can be seen in gure 2, Western Andalusia outstands as the region with the greatest surface of malarial focuses (above 200 000 ha) followed by La Mancha and Levante. However, the malaria focuses in the latter region evidenced a strong reduction during the next two years, as can be seen in gure 2. The same source includes other social and health-related data (the price of malarial land in pesetas, the cost of sanitation works, the yearly consumption of quinine, an assessment of the labour days lost due to malaria, etc.). Figure 3 shows the regional percentages of municipalities with autochthonous malaria in 1913 and 1916. These data do neither allow us to establish a statistically signicant correlation between the regional percentages of malarial municipalities and the surface of malarial focuses. However, when gures 2 and 3 are compared, it can be seen that, as a general rule, the regions where malaria is spread to a higher percentage of municipalities evidence a larger surface involving malarial areas or focuses. Denitely, Extremadura is an exception in this trend with 86.7 % of its municipalities suffering malaria. Except for this case, the regions with the largest surfaces covered with unhealthy water bodies (Western Andalusia, La Mancha and Levante) are the ones involving a greater density of malarial municipalities (between 40 and 60 % of the whole regions). Another interesting issue is the seasonal distribution of the disease. Monthly malaria patients data are available for all the Spanish territory corresponding to 1949 and the 1954-1960 periods. An individual analysis for the various years re- 290 Sousa et al. Figure 2. Regional distribution of malaria focuses in Spain in 1913 and 1916. Distribuci´ on regional de focos pal´ udicos en Espa˜ na en 1913 y 1916. veals a very homogeneous behaviour, regardless if referred to years with a high rate of patients, such as 1949 (33,919 cases), or to those with a scarce rate, such as 1960 (31 cases). Although the disease is present throughout the year, the number of cases increases during the warmest months and decreases during the coldest ones. This is a relevant issue because of the tentative relationship that could exist between the disease and climatic variables such as mean or minimal temperature and rainfall. In gure 4 we have summarised the mean seasonal distribution of malaria in Spain during 1949 and the 1954-1960 period. In gure 4 it can visualise how —at least during the second half of the XXth Century— the number of malaria patients is especially associated to the summertime. The pattern of maximum and minimum temperature is fundamental for the vector and parasite activity cycles as gathered by (D´ az et al., 2005). In a specic case of the eastern coastal area of Huelva, Anopheles atroparvus show a distribution that continues from June until the end of September, although the more numerous populations are located in June and August (L´ opez, 1989). According to Sallares (2006) environmental changes altering mosquito breeding sites in coastal wetlands had a substantial inuence on the history of malaria in many parts of Europe during the Holocene. The case of wetlands in the surroundings of Do˜ nana and malaria In the late XVIIIth Century, malaria (tertian and quartan fevers) was the most frequent pathology in most of Andalusia. No relationship could be Figure 3. Distribution, in percentage terms, of Spanish municipalities with autochthonous malaria with regard to the total number of municipalities in each region. Distribuci´ on en Espa˜ na, en porcentaje, de municipios con paludismo aut´ octono respecto del total de municipios de cada regi´ on. Malaria and wetlands in SW Spain 291 Figure 4. Monthly distribution of malaria patients due to malaria in Spain during the 1949-1960 period. Distribuci´ on mensual del n´ umero de enfermos por malaria en Espa˜ na durante el per´ odo 1949-1960. established for this period between malaria and the distribution of wetlands, considering that, in the late XVIIIth Century (1786-1792), a great epidemic of tertian fevers ravaged the whole Spanish territory (Segura, 1990). According to Rico-Avell´ o (1950), this one was the most severe malaria epidemic in Spain, surpassing the outbreaks occurred after the First World War and after the Spanish Civil War. In the XIXth Century, the data published by Madoz (1848) and Heraso (1890) do already highlight that the malarial fevers had acquired greater endemicity, due to the fact that they had started to be limited and concentrated in the most swampable areas. Thus, in connection with the Coastal Aeolian Sheet in the Province of Huelva, Heraso (1890) points out: “... additionally, a good number of infected lagoons and puddles are scattered on it, which ll up the environment with unhealthy malarial vapours” (translate to English). However, malaria continues to be a frequent disease all over Spain. Specifically, the municipalities of the eastern coastal area of the Province of Huelva, in which lagoons and marshlands are present or closer (Almonte, Moguer and Palos), are the ones where the presence of malaria appears more clearly. A comparative summary of the situation in these municipalities, within the environment of the Coastal Aeolian Sheet in the Province of Huelva, during the XVIIIth and XIXth centuries, is shown in Table 3. During the XXth Century, more-or-less complete statistics were already available, allowing the quantifying of the patient numbers and deceased due to malaria all over Spain. The evolution of the disease in the south of Spain conrms the greater signicance of the focuses located in Western Andalusia, as opposed to those in Eastern Andalusia. These results are consistent with the estimated size of the areas involving potentially unhealthy marshy or swamped locations in both regions in 1913 y 1916 (Fig. 2). As it can be seen in gure 5, from the points of view of both deceased and patients, Western Andalusia was a much more affected region than Eastern Andalusia throughout the XXth Century. This trend remains unchanged in the Coastal Aeolian Sheet of the Province of Huelva until the Table 3. Presence of tertian and quartan fevers in the municipalities of the Coastal Aeolian Sheet of the Province of Huelva during the XVIIIth and XIXth centuries. Presencia de ebres tercianas y cuartanas en los municipios del Manto E´ olico Litoral onubense durante los siglos XVIII y XIX. Municipality Most frequent diseases according to Tom´ as L´ opez (1785-1790) Most frequent diseases according to Madoz (1848) Almonte Tertian diseases Tertian diseases and some pneumonias produced by the vapours of the swamps and the warmth of the sand Bonares Tertian diseases Tertian diseases caused by humidity (winter) and by inammatory fevers (summer) Hinojos Tertian diseases or periodical fevers Tertian diseases and pneumonias Huelva Tertian diseases or periodical fevers — Lucena del Puerto Fevers — Moguer Typical seasonal diseases Intermittent diseases that started to disappear when the lagoon close to the city was desiccated Palos de la Frontera Seasonal diseases Intermittent fevers 298 Sousa et al. en registros instrumentales. In: Climate Change in Andaluc´ a: trends and environmental consequences. A. Sousa, L. Garc´ a-Barr´ on & V. Jurado (eds.): 81-95. Consejer´ a de Medio Ambiente. GARC´ IA-MURILLO, P. 2006. Reconstruction of the Abalario Landscape. 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