Nevertheless the chronology of the introduction of malaria to Sardinia is as controversial as the chronology of its spread in mainland Italy, and even more difficult to resolve, given the lack of evidence. Brown advocated a late-spread theory. He suggested that P.
falciparum malaria was not significant on the island during the time of the nuraghic culture in the Bronze Age and Early Iron Age, even though he accepted that the malaria vector species A. labranchiae has probably been present there for several million years. Brown argued that malaria first became a major problem in the fifth century owing to deforestation, a new agricultural system in the plains, and imports of slaves infected with malaria during the period of Carthaginian domination of the island. However, there is no positive evidence for this interpretation of the origin of malaria on Sardinia.¹¹⁷ It is generally assumed that the nuraghi were designed for defensive purposes. Since the highest densities of nuraghic settlement were in lowland regions with intense malaria until it was eradicated after the Second World War, Brown ¹¹⁵ Coluzzi and Sabatini (1995); Ramsdale and Snow (2000).
¹¹⁶ On the unhealthiness of Sardinia see Cicero, Epist. ad familiares 7.24.1; Livy 23.34.11; Pausanias 10.17.11; Pomponius Mela, de situ orbis 2.123, ed. Parroni (1967): ceterum fertilis et soli quam caeli melioris, atque ut fecunda ita paene pestilens (otherwise Sardinia is fertile, with better soil than air, it is almost as pestilential as it is fertile); Silius Italicus, Punica 12.371.
¹¹⁷ Brown’s (1984) hypothesis that the distribution and frequency of glucose-6-phosphate dehydrogenase deficiency (see also Ch. 5. 3 below) in Sardinia can be explained principally in terms of gene flow during the Carthaginian and Roman periods is rejected by Sanna et al.
(1997: 300, 313–14), who assign the principal role to the selective pressure of malaria.
The absence of the sickle-cell trait (haemoglobin S) from Sardinia counts heavily against Brown’s gene-flow hypothesis. [Aristotle,] peri thaumasion akousmaton, 100.838b recorded the Carthaginian devastation of Sardinia.
Ecology of malaria
91
assumed that they must have been built before the spread of malaria. He dismissed the idea that the nuraghi might have been a defence against malaria as well. However, it has been frequently been observed that mosquitoes, being weak fliers, are reluctant to fly up to the higher storeys of multi-storey dwellings. At Ostia in the summer of 1900 Sambon observed that ‘in human habitations they usually occupy the kitchens and rooms on the ground floor’.¹¹⁸ The idea that the upper stories of buildings were safer with regard to malaria was in fact widespread both in Italy and elsewhere in pre-modern Europe. North made the following observations on the Roman Campagna in the last century:
It is not uncommon to find houses in the Campagna constructed with all the living rooms on the top floor; and it is a matter of universal opinion that the upper storey of a house is safer and healthier, as far as malaria is concerned, than the lower, and practical expression is given to this belief by the method of construction adopted.¹¹⁹
Similar beliefs were held by the inhabitants of the Pontine Marshes: Any one who visits the Pontine Marshes may see in the open air, at different intervals, platforms erected upon poles four or five metres high on which, in summer, people sleep during the night . . . In fact, what we see done in the Pontine Marshes, by the people who sleep in the open air during the fever season, is repeated, in exactly the same form, in many malarious regions of Greece, and in the jungles of the East Indies.¹²⁰
In Holland, Pringle . . . noted that the wealthy in ‘dry’ houses and apart-ments raised above the ground were least liable to the disease of the marshes and in England ‘persons have maintained themselves in good health during sickly seasons, by inhabiting the upper stories of their house.¹²¹
Herodotus confirms that the idea of the greater safety of the upper storey of a house goes back to antiquity. He states that the inhabitants of some parts of Egypt slept in towers to avoid mosquito bites: The inhabitants have devised various means for protecting themselves from the abundant mosquitoes. Those who live upstream of the marshes ¹¹⁸ Sambon (1901 a: 199).
¹¹⁹ North (1896: 104).
¹²⁰ Tommasi-Crudeli (1892: 136). Celli (1900: 84) observed that the raised sleeping platforms in the Pontine Marshes did not necessarily totally prevent infection, since mosquitoes would make the effort to fly up to them if they were extremely hungry, but they would have reduced the transmission rate.
¹²¹ Dobson (1997: 355).
92
Ecology of malaria
have towers in which they sleep, since the mosquitoes are prevented by the winds from flying up to the towers.¹²²
Consequently it is possible that protection from mosquitoes was one of the purposes of the nuraghi, although there cannot be any proof in view of the complete absence of documentary sources from prehistoric Sardinia.¹²³ The earliest human skeletal remains from Sardinia which are affected by porotic hyperostosis date to the Late Neolithic period, c.4000–3200 .¹²⁴ It is possible, but not certain, that this condition was produced by P. falciparum malaria in the skeletons in question. Nevertheless it is very likely that the frequency of malaria on Sardinia did increase substantially in the second half of the first millennium , just as it did on the mainland of Italy.
The first report of a Roman army being destroyed by disease on Sardinia dates to 234 , just four years after the Romans had gained control of the island.¹²⁵ Strabo noted that Sardinia was unhealthy in summer, especially the fertile lowlands from which the Romans wished to export grain to Rome. Since Sardinia, like Sicily, was an important source of grain to feed the population of the city of Rome, there is no doubt that ships returning would have transported both the mosquitoes themselves and people infected with malaria to the city of Rome. Commenting on the difficulty of pacifying the island, he states it was not profitable to maintain army camps continuously in pestilential areas. This was because of the high mortality rate among the Roman soldiers from P. falciparum malaria. This passage shows that the Romans included mortality from diseases in their accounting of the profitability of military enterprises.
The island is unhealthy in summer, especially the fertile regions . . .
generals sent there sometimes resist [sc. raids by the indigenous tribes dwelling in the mountains], but sometimes they give up the task, since it is ¹²² Herodotus 2.95.1: prÏß d† toŸß k*nwpaß åfqÎnouß ƒÎntaß t3de sf≤ ƒsti memhcanhmv-na. toŸß m†n t¤ £nw t0n ‰lvwn ojkvontaß oÈ p»rgoi ∑felvousi, ƒß toŸß ånaba≤nonteß koim0ntai: oÈ g¤r k*nwpeß ËpÏ t0n ånvmwn oÛk oÍo≤ tv ejsi Ëyoı pvtesqai. People who actually lived in the marshes of Egypt used mosquito nets instead, according to Herodotus.
¹²³ For the use of the upper floors of houses for living purposes see Barker and Rasmussen (1998: 156). Tognotti (1996: 73–91) discussed the statistics for mortality from malaria in Sardinia in the nineteenth century; Tognotti (1997).
¹²⁴ Sanna et al. (1997: 296–7).
¹²⁵ Zonaras 8.18.P.I.401a–b, ed. Pinderus (1844), corpus scriptorum historiae Byzantinae xxx: ƒß d† t¶n Sard° tÏn åstunÏmon Po»plion Korn&lion πpemyan . . . Ø g3r Korn&lioß ka≥ t0n stratiwt0n pollo≥ ËpÏ nÎsou ƒfq3rhsan (they sent the praetor Publius Cornelius to Sardinia . . . Cornelius and many of his soldiers were killed by disease.).
Ecology of malaria
93
not profitable to maintain a military camp continuously in unhealthy areas.¹²⁶
Not surprisingly, the enemies of Gaius Gracchus were delighted when he was sent as quaestor to Sardinia. They doubtless hoped that he would not return. The Roman army with which Gaius Gracchus was serving did indeed suffer severely in the winter. This was probably the result of the synergistic interactions (discussed in detail in Ch. 5. 2 below) of P. falciparum malaria with the respiratory diseases of winter.¹²⁷ But Gracchus himself did return. A passage in Tacitus also shows that the Roman Senate was well aware
that people sent to Sardinia were likely to succumb to the bad air of the island:
The Senate decreed that four thousand freedmen of suitable age, who had been corrupted by this superstition, should be sent to the island of Sardinia to curb bandits there, and if they died owing to bad air, the loss would be of no consequence.¹²⁸
For the poet Martial Sardinia was a synonym for death.¹²⁹
4.4 M , ,
After this digression on Sardinia, we must return to the environmental factors which influence the distribution of mosquitoes.
Besides the distribution and chemical composition of bodies of water, man-made structures undoubtedly also made a significant contribution to the spread of malaria in Italy in antiquity. In the nineteenth century it was noticed that malaria tended to spread along the new railway lines that were being constructed in Italy.
¹²⁶ Strabo 5.2.7.225C: noser¤ g¤r Ó n[soß toı qvrouß, ka≥ m3lista ƒn to∏ß eÛkarpoısi cwr≤oiß . . . oÈ d† pempÎmenoi strathgo≥ t¤ m†n åntvcousi, prÏß 4 d’ åpaud0sin, ƒpeid¤n m¶
lusitel[ trvfein sunec0ß ƒn to∏ß nosero∏ß stratÎpedon.
¹²⁷ Plutarch, Tiberius and Gaius Gracchus 22.4 and 23.2, ed. Ziegler (1971): jscuroı d† ka≥
nos*douß ‹ma ceim0noß ƒn SardÎni genomvnou (there was a severe and unhealthy winter on Sardinia). Cicero, epist. ad Quintum 2.3.7 was aware that on Sardinia (in contrast to Latium) there was some risk of transmission of malaria even in winter. Livy 41.6.6 describes the crip-pling of another Roman army on Sardinia by pestilence in 178 . Logan (1953: 176–92) discussed the epidemiology of malaria in Sardinia. Strabo’s evidence that Roman commanders were concerned about the mortality from malaria on Sardinia shows that the theme of Curtin (1989) was already being consciously considered (if only in qualitative terms) two thousand years before the period upon which Curtin chose to focus.
¹²⁸ Tacitus, Annals 2.85.3: factumque patrum consultum ut quattuor milia libertini generis ea supersti-tione infecta quis idonea aetas in insulam Sardiniam veherentur, coercendis illic latrociniis et, si ob gravitatem caeli interissent, vile damnum.
¹²⁹ Martial 4.60.
94
Ecology of malaria
15. Reconstruction of a typical traditional peasant hut in the Pontine region, on display in the Parco Nazionale del Circeo. Spraying of the interior walls of dwellings with DDT broke the malaria transmission cycle in Italy by irritating the mosquitoes and driving them outside, where it was too cold for P. falciparum sporogony in the mosquito and frequently too cold for the mosquito itself, according to the explanation given by Mario Coluzzi. The mosquitoes became irritated after about five minutes and flew away before they had absorbed enough DDT to actually kill them (which would have taken about forty-five minutes). Since the irritant effect drove away the mosquitoes before they had absorbed enough DDT
to actually kill them, natural selection did not operate on mosquito populations in Italy and they did not develop resistance to DDT. However, the same strategy is less effective in Africa today because both the mosquitoes and the malaria parasites are happy outdoors in the tropical heat.
For example, being sent to work on the forty-four kilometre stretch of railway line between Taranto and Torremare was a death sentence, according to Bonelli. The Fiumicino–Ponte Galera and Rome–Chiarone routes in Lazio ranked among the most lethal railway lines in Italy. It was realized that the construction of embankments and cuttings for railway lines often interfered with natural drainage patterns and altered the level of the water table. In addition, the pits which were excavated to provide earth for Ecology of malaria
95
embankments often subsequently became filled with water and provided excellent breeding sites for mosquitoes.¹³⁰
In antiquity Strabo explicitly commented on Roman road building in Latium and noted the cuttings through hills and embankments across valleys which Roman engineers designed for their roads. Similarly Pliny noted the roads cut through mountains.¹³¹
Modern experience in Italy in the nineteenth century with railways suggests that Roman (and also earlier Etruscan) road building would have played a significant role in creating favourable new breeding habitats for Anopheles mosquitoes. Similarly ‘road building was linked intimately with the proliferation of malaria’ in Bengal in India during the British rule in the nineteenth century .¹³² The ancient accounts of his life state that Gaius Gracchus organized a considerable volume of road construction in Italy, after his return from Sardinia. Modern historians have failed to realize the irony of his work. By having roads built, Gracchus unwittingly assisted the spread of malaria in those very same depopulated parts of Italy which he desired to rejuvenate.¹³³
The nuraghi of Sardinia served to introduce the question of the design and construction of housing, another very important topic.
As Varro put it:
The situation of villas, the size of the buildings, and the directions in which colonnades, doors, and windows face, are matters of very great interest.¹³⁴
Unfortunately, as has often been observed by modern scholars, the atrium of Roman houses contained a pool of rainwater in the impluvium, a possible habitat for mosquito larvae (so long as there were no fish in it). It is not clear if the presence of the impluvium was important in practice in relation to malaria. Eugenia Tognotti, in her book on malaria in Sardinia, noted that A. labranchiae likes houses which are dark inside, providing cover, with small windows, ¹³⁰ Bonelli (1966: 667 n. 11), quoting the Inchiesta Iacini; Tognotti (1992: 25); Celli (1900: 147).
¹³¹ Strabo 5.3.8.235C: πstrwsan d† ka≥ t¤ß kat¤ t¶n c*ran ØdoŸß, prÎsqenteß ƒkkop3ß te lÎfwn ka≥ ƒgc*seiß koil3dwn (they constructed roads throughout the land, with cuttings through hills and embankments across valleys); Pliny, NH 36.24.125: vias per montes excisas (roads cut through mountains).
¹³² Klein (1972: 140–1).
¹³³ Plutarch, Tiberius and Gaius Gracchus 28, ed. Ziegler (1971); Potter (1979: 79–83, 101–9) on the Roman road network in south Etruria.
¹³⁴ Varro, RR 1.4.4: quod permagni interest, ubi sint positae villae, quantae sint, quo spectent porticibus, ostiis ac fenestris.
96
Ecology of malaria
a description which fits a lot of traditional housing in Mediterranean countries.¹³⁵ Sambon described the habits of what was then called A. maculipennis at Ostia at the end of the nineteenth century: The adult insects were found in great numbers in the houses and stables of the district. In stables they seemed to rest by preference on the old dusty cobwebs which heavily curtained the ceilings. In the houses they chose the darkest corners, often resting under beds, tables, and chairs, or on dark-coloured clothing, but more frequently on the ceilings, especially when these were begrimed with the smoke of winter fires and well out of the way of danger. In the bedrooms of an inn at Ostia, which had a blue stripe all round their whitewashed ceilings, the Anopheles seemed to settle by choice on the dark stripe for protection. It is almost ridiculous how these insects escape detection by those who are not in the habit of looking for them.¹³⁶
A. labranchiae is a non-diapausing species of mosquito. It remains active indoors and continues to bite humans nearly all the year round, although malaria parasites cannot develop inside it in the winter when it is too cold. Consequently it was very vulnerable to the modern malaria-control strategy of spraying the interior walls of dwellings with the insecticide DDT. In contrast the other main vector of malaria in Mediterranean countries, A. sacharovi, hibernates outdoors in the winter cold and does not become active until May each year. The northern European malaria vector A. atroparvus tolerates cold temperatures well but does not hibernate completely, unlike A. sacharovi. Consequently it sometimes bites humans in houses in winter.¹³⁷
Since mosquitoes dislike flying upwards, theoretically the upper storeys of multi-storey buildings in the city of Rome should h
ave been healthier than the ground-floor levels. In the seventeenth century Doni emphasized the importance of building design and town planning.¹³⁸ There was a view in early modern literature that tall buildings with narrow streets provided protection against ‘bad air’. This point of view had antecedents in antiquity, since Tacitus reports that after the great fire in Rome in 64 some people did not like Nero’s plan to rebuild the city with lower buildings and wider streets, since they thought that the old layout was healthier:¹³⁹
¹³⁵ Jones (1908: 534) on impluvia; Tognotti (1996: 98).
¹³⁶ Sambon (1901 a: 199).
¹³⁷ Coluzzi (1999); Shute (1951).
¹³⁸ Doni (1667: 18–23).
¹³⁹ Grandazzi (1997: 182) on the history of the old layout of the city, attributed in antiquity to the haste with which it was rebuilt after the sack by the Gauls in 390 .
Ecology of malaria
97
However, there were some people who believed that the old layout was more conducive to health because the narrowness of the streets and the height of buildings kept out the heat of the sun; but now the lack of shade in the broad open spaces meant that the summer heat was more intense.¹⁴⁰
However, people who lived in the upper storeys still had to go out periodically. The evidence of the ancient medical authors (discussed in detail in Ch. 8 below) indicates that malaria was common in the city of Rome both before and after the new town-planning regulations introduced by Nero, in spite of the frequency of multi-storey buildings. The hills of Rome, although healthy for those (the elite) who lived on top of them, probably had an adverse effect on those who lived below them. North made the significant observation that ‘experience shows that the benefit obtained [sc.
from living above ground-floor level] is not always as great as might be expected, and this is especially the case when the building is sheltered in any way by neighbouring hills’.¹⁴¹ He collected interesting information on housing and malaria in the Roman Campagna and followed Tommasi-Crudeli and earlier writers such as Knight in concluding that the custom of building houses around the four sides of a square or rectangle, with virtually all the windows opening internally on to the quadrangle, was intended to keep ‘bad air’ out.¹⁴² Modern experience shows that well-designed housing can help to keep mosquitoes out, although such measures may have little effect if people are in the habit of sleeping outside (at ground level) in hot weather, as frequently happens in the countryside in hot countries, to protect their crops.¹⁴³ Consequently the anecdote recounted by Varro in relation to the Pompeian forces on Corcyra during the civil war does have some plausibility, although it also ¹⁴⁰ Tacitus, Annals 15.43: Erant tamen qui crederent veterem illam formam salubritati magis con-duxisse, quoniam angustiae itinerum et altitudo tectorum non perinde solis vapore perrumperentur: at nunc patulam latitudinem et nulla umbra defensam graviore aestu ardescere.
Malaria and Rome: A History of Malaria in Ancient Italy Page 14
