Malaria and Rome: A History of Malaria in Ancient Italy, Robert Sallares [reading a book TXT] 📗

coarse deposits suggests that Roman rivers and floodplains were very different to those existing today. They were characterized by shallow channels, actively migrating, depositing bars of gravel.

Some reaches of the contemporary streams are trying to re-establish this condition but only to a limited extent due to confinement by high cohesive sandy-silt banks.¹⁷⁷

The ancient fluvial regime had very important consequences for malaria. The laterally mobile Roman rivers in shallow channels would have been more liable than their modern counterparts in deeper channels to flood the surrounding countryside. As the flood waters retreated, leaving pools here and there, mosquito breeding sites would have been created.¹⁷⁸ Thus it is likely that the rivers of Latium and Tuscany in the Roman period had a greater propensity to create mosquito breeding sites than they do today. Tibullus was right to fear the rivers of Latium and Tuscany in summer.

The overall effect of all the landscape changes which have been described was to provide more breeding sites for mosquitoes in general in Roman times. In coastal areas, if the water was brackish, those species of Anopheles mosquito that are the most dangerous vectors of human malaria had an advantage over other species of Anopheles. Even in Lazio, suitable breeding sites for mosquitoes can be scarce. In 1928–9 the lake at Nemi was partially drained to uncover Caligula’s ships, inadvertently providing new breeding sites for mosquitoes. In 1929 a sudden epidemic of P. falciparum malaria infected over half the population of the town, which had no previous history of endemic malaria in its hilly location (320 metres above sea level). Prior to the drainage operations there were not enough mosquitoes around to sustain the transmission of malaria in Nemi, given that the chances against transmission by any individual mosquito are extremely high, since most mosquitoes do not ¹⁷⁷ Brown and Ellis (1995: 69).

¹⁷⁸ An example of periodic flooding at a specific site is the Roman mausoleum at Fosso della Crescenza along the Via Veientana in southern Etruria (S. Judson in Fentress et al.

(1983: 70–2) ). On the rivers of southern Etruria see also Rendeli (1993: 122–5).

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Ecology of malaria

live long enough to transmit the disease.¹⁷⁹ P. falciparum, the most dangerous species of human malaria, is a very ancient parasite which was probably present in Mediterranean countries on a localized basis from the Neolithic period onwards, as has already been argued. It can certainly continue to exist in very small foci without spreading. It was not a new disease in classical times. Nevertheless the conclusion reached here is that the frequency of all types of malaria increased very substantially in Roman times primarily because of human modifications of the landscape which unintentionally favoured the vector mosquitoes. The demographic effects of this expansion on human populations demand detailed examination now.

¹⁷⁹ Hackett and Missiroli (1931: 64–5) on Nemi.

5

The demography of malaria

5. 1 D      

  

Bonelli rightly observed that in order to understand the impact of malaria on Italy in the past it is not enough simply to consider its demographic effects in purely quantitative terms.¹ It also influenced the entire lifestyle of people, even if it did not kill them, by forcing them to live away from the fields in which they had to work. In other words, malaria altered settlement patterns.² Old Salpi in Apulia was the most dramatic example of this in antiquity (see Ch. 10 below), but malaria also influenced settlement patterns within the city of Rome itself, as will be seen later (Ch. 8 below).

Malaria influenced agricultural systems by preventing intensive farming practices (Ch. 9 below). Nevertheless consideration of the demographic effects of malaria in purely mathematical and statistical terms is essential to understand the scale of its impact. The most fundamental weakness of nearly all recent literature on the question of the effects of malaria in Italy in antiquity is the absence of any appreciation in quantitative terms of the demographic effects of malaria on human populations in Europe in the past. This lack of knowledge about the demographic effects of malaria on human populations has permitted many researchers from different branches of scholarship to minimize the importance of malaria.

A good starting-point is the recent debate between Scheidel and Shaw concerning the explanation of excess seasonal mortality in the city of Rome in antiquity, as revealed by funerary inscriptions.³

Scheidel opted for malaria, in synergistic interactions with other diseases, as the principal cause. Shaw attempted to minimize the role of malaria. It is instructive to consider the flaws in Shaw’s argument. Shaw relied on national statistics which show that malaria ¹ Bonelli (1966: 662).

² Pinto (1982: 30) saw malaria as a determinant of settlement patterns in Tuscany in the medieval period.

³ Scheidel (1996); Shaw (1996).

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Demography of malaria

accounted for 2.2% of all deaths in Italy in 1887–9. He concluded that malaria was less important in Italy than in Greece, where 5.6%

of all deaths were attributed to malaria as recently as 1921–32.⁴ The most detailed statistics can be extremely misleading if they are not handled very carefully indeed. In this particular case, there are two major reasons why these national statistics for cause of death are unlikely to give an accurate estimate of the contribution of malaria to mortality in the city of Rome or in the Roman Campagna in antiquity.

The first rather elementary reason is quite simply that these national statistics lumped together mortality data from localities with intense malaria with data from places where there was no malaria at all to yield meaningless averages which may be completely inappropriate if applied to any particular locality. It is always possible in demography to aggregate data from two or more different regions and calculate the average, but the crucial question is whether the average so obtained is meaningful. As del Panta said in an article on infant and child mortality in early modern Italy: No satisfactory explanations can be given for the evolution of child and infant mortality in Italy without considering territorial differences. In