Malaria and Rome: A History of Malaria in Ancient Italy (15 page)

Other literary sources from late antiquity show that marshy environments were still feared then. Palladius duly made the standard observations that marshy and pestilential land should be avoided.⁶⁰ He then added a more interesting comment:

In any event a marsh must be avoided, especially if it faces south or west and tends to dry up during the summer, because of the pestilence or hostile little animals which it generates.⁶¹

Palladius’ observation of the extreme peril posed by marshes which desiccate during the summer leads on to consideration of the exact requirements of
Anopheles
mosquitoes for breeding pur-

⁵⁸ McFalls (1984: 118); Zei
et al
. (1990); Dobson (1997: 340–2); Barbosa and Arjona (1935: 11–18); Torpin (1941); Diagne
et al
. (2000) showed that the period of increased susceptibility to malaria continues for about two months
after
birth.

⁵⁹ Sallares and Gomzi (2001); Sallares
et al
. (2002); North (1896: 24) observed that the vicinity of Orte is particularly vulnerable to Tiber floods.

⁶⁰ Palladius,
opus agriculturae
1.5.5, ed. Rodgers (1975):
situs vero terrarum neque planus, ut stagnet
; 1.5.6:
qui ager pestiferi more fugiendus est
.

⁶¹ Palladius 1.7.4:
palus tamen omni modo vitanda est, praecipue quae ab Austro est vel occidente et siccari consuevit aestate, propter pestilentiam vel animalia inimica quae generat
.

Ecology of malaria

69

poses. Their larvae generally require water that is clear, in contrast to the larvae of
Culex
mosquitoes (non-transmitters of human malaria) which are happy in dirty water, although
Anopheles
larvae were also found in puddles of dirty water at Grosseto in the nineteenth century.⁶² In addition, the water must be well oxygenated.

This explains the success of spreading oil on the surface of pools as a modern control measure.
Anopheles
larvae prefer pool and canal margins where there is plenty of vegetation, which provides cover from predators. Sambon noted that at Ostia in the summer of 1900

all the pools and canals had enormous numbers of frogs, several species of fish (especially the young of the grey mullet), and swarms of dragonfly larvae and water beetles.⁶³ Consequently large permanent lakes are not necessarily any better for mosquitoes for breeding purposes than very small pools, which are only filled with water seasonally. Strabo noted that the large inland lakes of Tuscany, such as Vico, Bolsena, Chiusi, and Bracciano, produced substantial quantities of fish for the city of Rome.⁶⁴ A series of lakes along the coasts of Tuscany and Latium, such as the
Prilius lacus
near Grosseto and the lakes near Circeii, were also extensively exploited for fishing in Roman times.⁶⁵ In addition, the Romans created numerous artificial fishponds (
piscinae
) attached to coastal villas.

Such fishponds have been found at many locations along the coast of Etruria, such as Cosa, Torre Valdaliga, Grottacce, Pyrgi, and also in Latium and Campania. Recent research into these artificial fishponds concludes that their water was usually brackish: The archaeological evidence is decisive in showing that the Romans preferred brackish conditions for their seaside
piscinae
. . . Arrangements for mixing salt water and fresh water to create a brackish environment were ⁶² Celli (1900: 79) mentions Grassi’s observations at Grosseto. Austen (1901) discussed the differences between
Anopheles
and
Culex
mosquitoes.

⁶³ Sambon (1901
a
: 199).

⁶⁴ Strabo, 5.2.9.226C. Quilici (1979: 104–6), noting the frequent presence of fish in offerings in archaic tombs in the Roman Forum, stressed that the River Tiber itself was an important source of fish in the early stages of Roman history, although it was wholly inadequate (and heavily polluted) by the time of the Roman Empire, cf. Nutton (2000
b
: 66) and LeGall (1953: 267–8, 318–19). Pratesi and Tassi (1977: 43) described the rich fauna of fish in the modern Lago di Bolsena. Dennis (1878: 30) interpreted the prodigy in Livy 27.23.3,
Volsiniis sanguine lacum manasse
(the lake at Volsinii flowed with blood), as a sign that the area around the Lago di Bolsena was becoming unhealthy in the late third century . Magri (1999: 173) noted that the settlement of Monte Bisenzo nearby was finally abandoned in 1816 because of mal’aria arising from the Lagaccione marsh.

⁶⁵ On the
Prilius lacus
see Cicero,
pro Milone
74, with Celuzza (1993: 92–3) for the identification of the site of Clodius’ villa; Pliny,
NH
3.5.51.

70

Ecology of malaria

common features in Roman fishponds and are well represented in the archaeological record from both the late Republic and early Empire.⁶⁶

The chemical composition of water is very important for the breeding of
Anopheles
mosquitoes. Since they certainly can breed in brackish water, so long as it is not too salty, the water of some of these fishponds could have been favourable for malaria. The fish were an unfavourable factor for mosquito larvae, but a great deal would have depended on how much vegetation was present in these artificial fishponds. In any event, it is certain, as will be seen, that the coasts of Etruria and Latium were severely affected by malaria in the Late Republic and Early Empire. Strabo (quoted in Ch. 6 below) described the area around Circeii, which was a centre of fish farming, as pestilential. Consequently neither the hydraulic works of the fishponds nor their fish seriously impeded mosquito larvae.

The vicinity of the large inland lakes mentioned by Strabo was certainly heavily infested with malaria in the early modern period.

Nevertheless,
Anopheles
larvae can flourish at least as well in the small depressions in the ground, only containing water for a few months each year, that frequently occur on the lower slopes of hills in Latium and Tuscany, and particularly in the undulating terrain of the Roman Campagna. All the literature on the early modern Roman Campagna lays stress on the importance of small seasonal pools and puddles for the generation of malaria. Tommasi-Crudeli, scaling up the results of a small field survey to provide an estimate for the whole Roman Campagna, suggested that there were quite literally
thousands
of breeding sites for mosquitoes in the Roman Campagna in the nineteenth century, before many of the modern drainage operations. This was also the origin (besides rivers and streams) of much of the malaria in the past in southern Italy, where it frequently occurred in the absence of marshes or large lakes.⁶⁷ Consequently the most dangerous wetlands were those which tended to dry up in the summer, as Palladius observed, since there were no predators to eat the mosquito larvae. The ⁶⁶ Higginbotham (1997: 16); Rustico (1999) has also discussed the Roman fishponds recently.

⁶⁷
e.g.
North (1896: 113–15) emphasized that pools which dried up in summer were very dangerous; Tommasi-Crudeli (1892: 34). Tommasi-Crudeli and North also discussed this phenomenon in the region around Mantua, showing that it was not confined to Lazio, cf.

Dobson (1997) on England.

Ecology of malaria

71

anonymous author of a late-eighteenth-century discourse on mal’aria noted that many of the localities in the Roman Campagna which were marshy in winter became completely dry in summer.

Similarly in the marshlands of early modern England mortality from
P. vivax
malaria increased after dry summers as the marshes dried out.⁶⁸ The pseudo-Aristotelian
Problems
noted that after a wet spring and dry summer the autumn is lethal to all age-groups, but especially to children, the main victims of
P. falciparum
malaria when it is endemic.⁶⁹

That even large lakes were subject to major fluctuations in central Italy in antiquity is shown by the example of the former Lago di Fucino, in the territory of the Marsi beyond the Monti Simbruini, which experienced great fluctuations in its water level according to Strabo. Julius Obsequens recorded that the Lago di Fucino overflowed its banks for five Roman miles in all directions in 137 .

Draining it was another of Julius Caesar’s unfulfilled dreams. The emperor Claudius attempted at great expense to drain it. However, Tacitus’ account, stating that the tunnel that was originally constructed did not even reach half-way down the lake, illuminates the difficulties faced by the Romans in effectively performing major drainage operations. Claudius’ works were neglected by Nero.

Later attempts in antiquity were made by Trajan and Hadrian, but the lake was not drained completely and permanently until the operations of Prince Torlonia commenced in  1862.⁷⁰ The plain ⁶⁸ Anon. (1793: 23); Dobson (1980: 378–80); see Ch. 5. 4 below.

⁶⁹ [Aristotle,]
Problems
1.19.861b: Di¤ t≤, ƒ¤n toı ceim0noß bore≤ou ka≥ toı πaroß not≤ou ka≥ ƒpÎmbrou tÏ qvroß l≤an aÛcmhrÏn gvnhtai, qanat0deß g≤netai tÏ metÎpwron p$sin, m3lista d† to∏ß paid≤oiß, ka≥ to∏ß £lloiß d† dusenter≤ai ka≥ tetarta∏oi crÎnioi g≤nontai ƒn aÛt‘ (Why is it that if the north wind prevails in winter, and the spring is damp and rainy, and the summer is very dry, then the autumn is deadly to all, particularly children, while others suffer from dysentery and prolonged quartan fevers?). This is a typical description of a year ending with an autumn epidemic of malaria. The pseudo-Aristotelian
Problems
also contains a lot of other material on the seasonality of disease patterns.

⁷⁰ Strabo 5.3.13.240C. Leveau (1993) discussed the ideology of Roman attempts to manage the Fucine Lake. Pratesi and Tassi (1977: 222–5) described the modern environment of the basin. Giraudi (1989) suggested that the lake’s water level was low during the period
c
.300

– 200, followed by the Roman drainage, which he unjustifiably assumed to have been a complete success. The words of Julius Obsequens for 136 ,
M Lacus Fucinus per milia passuum quinque quoquo versum inundavit
—(the Fucine lake overflowed its banks by five miles), show that Giraudi’s generalizations must be taken cautiously. For the problems which beset the Roman drainage schemes see Tacitus,
Annals
12.56–7; Pliny,
NH
36.24.124; Suetonius, Claudius 20–21; Dio Cassius 61.33.5. Thornton and Thornton (1985) discussed the drainage works. The inscription
CIL
9.3915 and
SHA Hadrian
22.12 record the efforts of Trajan and Hadrian.

72

Ecology of malaria

of the former Lago di Fucino might be too cold today for
P. falciparum
, situated as it is at an altitude of 669 metres (but not for P. vivax). However, the water of the lake exercised a moderating influence on temperature in the past. In antiquity the lake was once surrounded by a primeval forest, Angitia, mentioned by Virgil.⁷¹

Deforestation of the mountain slopes encircling the basin, coupled with the effects of the modern drainage operation in 1862, significantly altered the microclimate of the region. It is now colder than it used to be, with more severe winter frosts. These climatic changes have eliminated the olive trees which formerly grew around the lake. They also gradually helped to convert the Fucine basin into an area of anophelism without malaria by the end of the nineteenth century. However, in the immediate aftermath of the drainage operations which commenced in 1862 it was observed that the frequency of malaria actually increased, presumably because the drainage left exposed areas of damp soil which had previously been permanently flooded, creating new breeding sites for mosquitoes. The example of the Fucine Lake illustrates the complexity of the environmental variables that have to be taken into account to understand the distribution and frequency of malaria. The modern experience suggests that the partial drainage achieved temporarily by Claudius would have actually increased the frequency of malaria around the remainder of the lake, especially considering that the climate as a whole was in any case warmer for much of the period of the Roman Empire (see Ch. 4. 5

below). The theme of unintended side-effects of human activity will recur in the course of this chapter.⁷²

Mosquito larvae can grow very rapidly, in a few days. They may live in moist ground for three or four days. Once they have pupated, it does not matter if the water of the pool evaporates completely and the ground completely desiccates, since it suits the adult mosquitoes to emerge from completely dry soil or sand, for example sand from the banks of the river Tiber as shown by Celli’s and Grassi’s experiments.⁷³ Gradual desiccation of pools during ⁷¹ Virgil,
Aeneid
7.759–60.

⁷² North (1896: 117–18) noted the temporary increase in malaria during the modern drainage operations, although by the end of the nineteenth century the Fucine basin had become one of the areas of anophelism without malaria discussed by Hackett and Missiroli (1931). Hare (1884: ii. 190) and Letta (1972: 13 n. 12) also commented on the presence of malaria around the lake in the early modern period.

⁷³ Celli (1900: 78); Sambon (1901
a
: 199).