Malaria and Rome: A History of Malaria in Ancient Italy (17 page)

Another important environmental factor for the larvae of Anopheles mosquitoes is the degree of salinity or freshness of the water. In Italy in antiquity marshes that were frequently flooded with seawater, such as those around Ravenna, were healthy, while those which did not have any natural or man-made connection with the sea, such as the Pontine Marshes, were pestilential. Similarly in early modern England marshes that were closed off from the sea tended to become breeding grounds for the mosquito ⁸⁹ Bonelli (1966: 678–9); Judson and Kahane (1963); Ravelli and Howarth (1988) and (1989).

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species
A. atroparvus
, a vector of malaria.⁹⁰ Vitruvius described the situation in Italy as follows:

When ditches have been excavated to provide outlets for (marsh) water to the seashore, and the sea rises during storms, overflows into the marshes and mixes the marsh water with seawater, the reproduction of the typical fauna of marshes becomes impossible . . . The Gallic marshes around Altinum, Ravenna, Aquileia, and other towns in such situations, next to marshes, illustrate this point, because they are extraordinarily healthy.

However, stagnant marshes which do not have outlets either in the form of rivers or ditches, like the Pontine Marshes, putrefy as they stand and emit noxious and pestilential vapours in such places.⁹¹

Similarly Strabo noted that Ravenna, although situated within marshes and dissected by rivers, received plenty of seawater during the tides, which periodically cleansed the marshes and eliminated ‘bad air’, dusaer≤a in Greek. Other ancient authors also described Ravenna. Sidonius Apollinaris noted that seawater came right up to the city’s gates on one side, while on the other side the water in the channels was extremely dirty. The larvae of
Anopheles
mosquitoes prefer clear water.⁹² There was a shortage of good drinking ⁹⁰ Dobson (1997). Compare the account in Pausanias 7.2.11, ed. Rocha-Pereira (1989), of how the silting up of the channel next to the city of Myus in Ionia by the river Maiander created an inland marsh cut off from the sea. The marsh became a breeding site for hordes of mosquitoes, forcing the abandonment of the city. This had happened by the time of Strabo 14.1.10.636C. Atarneus also suffered the same fate.

⁹¹ Vitruvius 1.4.11–12:
Fossis enim ductis aquae exitus ad litus, et mare tempestatibus aucto in paludis redundantia motionibus concitata marisque mixtionibus non patitur bestiarum palustrium genera ibi nasci . . . exemplar autem huius rei Gallicae paludes possunt esse, quae circum Altinum, Ravennam, Aquileiam, aliaque quae in eiusmodi locis municipia sunt proxima paludibus, quod his rationibus habent incredibilem salubritatem. Quibus autem insidentes sunt paludes et non habent exitus profluentes neque flumina neque per fossas, uti Pomptinae, stando putescunt et umores graves et pestilentes in is locis emittunt
. The words of the jurist Iuventius Celsus in Digest 17.1.16 are also sometimes quoted as evidence that Ravenna was healthy in the second century :
cum Aurelius Quietus hospiti suo medico mandasse diceretur, ut in hortis eius quos Ravennae habebat, in quos omnibus annis secedere solebat, sphaeristerium et hypocausta et quaedam ipsius valetudini apta sua inpensa faceret
(since Aurelius Quietus is said to have instructed a doctor, a guest of his, to make (at Quietus’s own expense) a ball-court, a sweating-room, and whatever else would be conducive to his own health, in the doctor’s own gardens at Ravenna which he was accustomed to visit every year). See also Borca (1996) with abundant further bibliography on Ravenna.

⁹² Sidonius Apollinaris,
Ep
. 1.5.5–6 to Heronius; Jordanes,
de origine actibusque Getarum
29, 148–51, ed. Mommsen (1882),
Monumenta Germaniae Historica. Auctorum Antiquissimorum Tomi v.

Pars Prior
; Martial 3.56; Procopius,
BG
1.1.16–23 (discussed critically by Fabbri (1991: 9–10) ); Michelini (1995); Manzelli (1997). Mazzarino’s idea, discussed by Michelini, that Ravenna owed its healthiness to the construction of the port of Augustus there for the Adriatic fleet, is untenable because Vitruvius makes it clear that other towns in the region, such as Aquileia and Altinum, were equally healthy. Consequently a factor specific to Ravenna itself cannot explain the salubrity of the entire region.

80

Ecology of malaria

Rovigo

Adria

N

o

P

River

GRANDE

BONIFICA

FERRARESE

Ferrara

Comacchio

A d r i a t i c

Valli di

Comacchio

S e a

Ravenna

E M I L I A

Imola

PINETA

DI CLASSE

Faenza

Cervia

Forli

R O M A G N A

Cesena

Rimini

Map 3. Ravenna and Emilia-Romagna

Ecology of malaria

81

water at Ravenna because of these hydrological conditions. Strabo regarded as a marvel the fact that the air over the marshes of Ravenna was healthy.⁹³ This suggests that most marshes in other parts of Italy were not healthy.

The coastal regions of northeastern Italy and the Po delta became heavily infested with both
P. falciparum
and
P. vivax
malaria in the late medieval period, as extensive alluviation gradually isolated towns like Ravenna and its marshes from the sea, thereby changing their chemical composition and altering mosquito breeding sites. Ravenna today is about ten kilometres from the sea, and the waterlogged Roman strata in the town are up to ten metres below the current ground level. Already in late antiquity and the early Byzantine period the immediate vicinity of the town had begun to dry up.⁹⁴ At that time Ravenna had a flourishing medical school which produced a series of commentaries on and Latin translations of the works of the Greek medical writers. It is quite possible that human interference with the natural environment, such as the bonifications attempted by Theoderic at the end of the fifth century , played a role in the deterioration of the situation.

Doni described Ravenna as afflicted with severe malaria in the seventeenth century.⁹⁵In the eighteenth century Francesco Ginanni wrote a comprehensive study of the natural history of the marshy woodlands in the vicinity of Ravenna. He noted the abundance in the woods in summer of the two species of mosquito that had been named
Culex cinereus
and
Culex fuscus
by Linnaeus, and observed that they bit humans frequently. However, it is striking that his account of the mosquitoes of Ravenna is located far away in his large book from his description of the ‘bad air’ of the region; Ginanni completely failed to connect mosquitoes with malaria. Nevertheless he ⁹³ Strabo 5.1.7.213C: πsti m†n oˆn ka≥ toıto qaumastÏn t0n ƒnq3de, tÏ ƒn 1lei toŸß åvraß åblabe∏ß e”nai.

⁹⁴ Fabbri (1991: 19) described the developments in the early Byzantine period as follows: in sostanza è una situazione di progressivo inaridimento idrico quello che la città vive nell’alto Medievo: una situazione di sempre più precarie condizioni igienico-ambientali, specialmente favorevoli allo stabilirsi della malaria in forma endemica. Già in queste condizioni si possono ricercare le premesse di fenomeni di depopola-mento e di crisi economia e funzionale. Squatriti (1992) is an interesting account of attitudes to marshes in early medieval Ravenna, but without any serious study of malaria or the relevant ancient sources. The most recent synthesis of Italian demographic history advocates a completely different view, so far as malaria in early medieval Italy is concerned: ‘
la malaria . . . si diffuse in vaste aree della penisola per effetto del degrado ambientale che trasformó in stagni e paludi gran parte delle pianure costiere e molte vallate interne
’ (G. Pinto in del Panta
et al
. (1996: 18).

⁹⁵ Cavarra (1993) and Bio (1994) described the medical culture of Ravenna;
CIL
11.10 for Theoderic’s activities at Ravenna (
sterili palude siccata
); Doni (1667: 86, 89).

82

Ecology of malaria

did accurately describe the environmental conditions that favoured endemic malaria, observing that the marshes of Ravenna tended to dry out in summer each year but retained some moisture, permitting plant growth.⁹⁶ Ginanni described the seasonality of malaria around Ravenna in the eighteenth century as follows:

The period of considerable danger from bad air in these pine woods usually runs from the summer solstice until the autumn equinox. However, it sometimes varies from year to year, because if the season is very hot, bad air begins as early as May and continues until the middle of October; nevertheless it regularly terminates during the first heavy and repeated autumn rains, which fill the already nearly desiccated beds of adjacent marshes with fresh water.⁹⁷

Ginanni argued that the ‘air’ of the town of Ravenna itself was healthier than its reputation suggested, although he acknowledged that ‘bad air’ was endemic in the surrounding area. Attempts to defend the reputation of settlements afflicted by malaria are frequently found in Italian local history. Ginanni observed that the unhealthiness of the air did not prevent numerous people living on the rich agricultural land in the vicinity of the Po delta. He even attempted to quantify mortality risks and concluded that the local inhabitants were much less likely to die from an infection of malaria than visitors to the area.⁹⁸ The reasons for that are now known; not only would those who survived childhood infections have developed acquired immunity, but the population of the area also has a high frequency of genetic mutations such as thalassaemia that confer some resistance to malaria (see Ch. 5. 3 below). This is evidence for intense pressure exercised by malaria as an agent of natural selection in the past in this region.⁹⁹ In fact, the distribution ⁹⁶ Ginanni (1774), ch.on
Acque
(pp. 105–21), chapter on
Aere
(pp. 122–34), section on mosquitoes (pp. 431–2). Jordanes,
de origine actibusque Getarum
, 57, shows that the famous pine forest along the coast south of Ravenna, described by Boccaccio, Dante, Byron, and other writers, already existed in late antiquity, since Theoderic encamped ‘about three miles from the city in the place called Pineta’ (
tertio fere miliario ab urbe loco qui appellatur Pineta
).

⁹⁷ Ginanni (1774: 132):
l’aere aliquanto pericoloso di queste Pinete è per l’ordinario dal solstizio di Estate infino all’equinozio di Autunno. Ma varia talora col variar delle annate, perché se calda molto è la stagione, vi principia l’aria pericolosa anche nel Maggio, e continua a mezza Ottobre; regolarmente però ella cessa d’esserlo nelle prime pioggie copiose, e replicate d’Autunno, che riempono d’acque dolci i letti, già quasi prosciugati de’vicini paduli
.

⁹⁸ Ginanni (1774: 133–4 n. 3).

⁹⁹ Interpretation of the situation is complicated by the fact that the Po delta region was an area of Greek colonization. It can be difficult to disentangle evolution
in situ
from gene flow caused by human migrations (the same problem occurs in Sardinia, discussed in Ch. 4. 3

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83

of b-thalassaemia mutations in this region closely matches the distribution of mosquito breeding habitats.¹⁰⁰ Thus Ginanni was right to argue that the local people were less likely to die in the short term from individual malarial infections. However malaria had profound long-term effects on such populations, sharply reducing overall life expectancy and distorting the age-structure of the population. These long-term effects were already obvious to Doni in the seventeenth century and will be described in more detail later on (see Chs. 5 and 11 below). Ginanni’s observations on the resistance of the local population to malaria are in fact paralleled by the situation in human populations in parts of tropical Africa today where malaria is endemic. In such African populations one is unlikely to die directly from malaria once one survives past a certain age in childhood—the precise age varies from region to region in Africa and depends on the transmission rate of malaria, in other words the frequency of infections—by which time acquired immunity has developed, but malaria nevertheless has a deep influence on age-specific life expectancy. Under such circumstances it is quite easy for both the inhabitants of regions with intense malaria themselves and outside observers to jump to the conclusion that malaria is not a major problem. The only legitimate inference to be drawn from such a conclusion, as in Ginanni’s case, is that it demonstrates a lack of understanding of the immunology of malaria—not surprising in an eighteenth-century author. It does not constitute evidence for any mildness or avirulence of the disease. The studies that were done at the beginning of the twentieth century showed that
P. falciparum
was common in the coastal regions of northeastern Italy alongside P. vivax and
P. malariae
, although
P. vivax
lasted longer than
P. falciparum
once eradication measures commenced. A survey in 1849

below). Greeks were present in the cities of Atria and Spina from the sixth century 

onwards (intermingled with Etruscans, other local Italic peoples, and later on Celts as well), who might well have carried with them genetic mutations related to malaria from their homeland in Greece, another area of endemic malaria. Consequently thalassaemia, for example, may already have occurred in northeastern Italy in the fifth century  even though the area did not yet suffer from malaria.

¹⁰⁰ In the province of Ferrara allele frequencies for b-thalassaemia mutations decrease from the Adriatic coast westwards, while in the province of Rovigo there is no such decrease (Barrai
et al
. (1984) ). In Ferrara, south of the river Po, marshy areas were largely confined to the east of the province, while in Rovigo, north of the Po, there were marshy areas throughout the entire province.