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

that the necessary precautions had not previously been taken on Corcyra (modern Corfu):

Did not our Varro here, when the army and fleet were on Corcyra and all the houses were full of the sick and dead, make his comrades and servants healthy again by constructing new windows to let in the north wind and excluding the pestilential winds, by changing [the positions of ] doors, and by other measures of this kind?¹⁴⁴

Since it is quite common for blood feeds by female mosquitoes to be interrupted and then finished on another person, it is possible for one mosquito to infect several people in a single household.¹⁴⁵

Certain houses which are particularly badly exposed to mosquitoes may become foci of malarial infection within a community. Households with children are most likely to end up playing this role, since gametocytes (the blood stage of the parasite’s life cycle which can reinfect mosquitoes) are mainly found in children in areas where malaria is endemic. The acquired immunity of those adults who survive infection in childhood reduces gametocyte production to insignificant levels in such areas. The dangerous species of mosquito either show a definite preference for human blood (so A.

sacharovi), or at least are as willing to bite humans as they are to bite other animals (so A. labranchiae). These two species enter houses or other man-made structures without hesitation. In contrast, other species of Anopheles mosquito in Italy which are not significant vectors of malaria prefer to bite other animals, generally cattle, and show little interest in entering houses. Hackett and his co-workers demonstrated this in their comparison of Val di Chiana in Tuscany, an area of anophelism without malaria in the early twentieth century, with Fiumicino, which had some of the most intense malaria in the world.¹⁴⁶

It is very important to bear in mind the possibility that the geographical distribution of mosquito species may change over time, following local environmental change. This is doubtless what happened at Ravenna, for example. Consequently regions with anophelism without malaria within the last hundred years were not necessarily like that in earlier periods of history. The southern end ¹⁴⁴ Varro, RR 1.4.6: Non hic Varro noster, cum Corcyrae esset exercitus ac classis et omnes domus reple-tae essent aegrotis ac funeribus, immisso fenestris novis aquilone et obstructis pestilentibus ianuaque permuta-ta ceteraque eius generis diligentia suos comites ac familiam incolumes reduxit?

¹⁴⁵ Conway and McBride (1991).

¹⁴⁶ Missiroli et al. (1933); Hackett (1937: 38–41, 75–6, 209–12).

Ecology of malaria

16. The

southern end

of the Val di

Chiana and

Lago Trasimeno, viewed

from the

Fortezza

Medicea

above

Cortona.

99

100

Ecology of malaria

of the Val di Chiana (243–60 metres above sea level), particularly in the vicinity of Chiusi, was certainly unhealthy in the medieval and Renaissance periods, as Dante, Boccaccio, and other writers observed. Unfortunately there is no explicit evidence available for the health status of the area in antiquity. Dante bracketed the Val di Chiana with the Maremma and Sardinia as notoriously unhealthy regions: As the pain would be, if the diseases of the hospitals of the Val di Chiana, between July and September, and of the Maremma and Sardinia were all together in one ditch.¹⁴⁷

From the sixteenth century onwards repeated efforts were made to drain the flooded valley, especially by constructing a large canal, the Canal Maestro, to remove water to the Arno river. Leonardo da Vinci was the most famous of the numerous engineers who took an interest in the region’s problems. However, these efforts were vitiated for a long time by political rivalry between Rome and Florence as well as by the low gradient of the plain (the same problem as in the Pontine Marshes). Alexander’s detailed study of the Val di Chiana reached the conclusion that piecemeal drainage works were doomed to failure; only a grand plan dealing with the entire territory simultaneously would work, and this was not finally achieved until the late eighteenth and early nineteenth centuries by Vittorio Fossombroni. The drainage of the Val di Chiana did not eliminate Anopheles mosquitoes, but in some way facilitated a change in the balance between different species so that zoophilic species became prevalent. Similarly Pisa, whose territory suffered from intense malaria during the Renaissance period, had become an area of anophelism without malaria by the end of the nineteenth century, while the coastal region north of Pisa around Viareggio, which eventually became another area of anophelism without malaria, had been described as ‘marshy and pestilential’ ( paludosa e pestifera) in the seventeenth century.¹⁴⁸

¹⁴⁷ Dante Alighieri, La Commedìa. Inferno. Canto .46–9, ed. Lanza (1996): Qual dolor fora, se delli spedali | di Valdichiana tra ‘l luglio e ‘l settembre | e di Maremma e di Sardinia i mali | fossero in una fossa tutta insembre.

¹⁴⁸ Alexander (1984); Luchi (1981: 417–20), on the archaeology of the Val di Chiana in the territory of Chiusi, noted that Livy 5.36.3 indicates that at least part of it was exploited extensively instead of intensively ( latius possideant quam colant); Dennis (1878: 294); Pinto (1982: 10, 17–18, 30).

Ecology of malaria

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4. 5 C  

Roads and housing are good examples of factors which were very important at the local level. However, not all factors were so localized in their effects, above all climatic change. Huntington suggested in 1910 that the introduction of malaria to Italy occurred in the late third century  as a result of increasing aridity (and hence, drier summers) which created more favourable environmental conditions for Anopheles mosquitoes. Although that idea was interesting in principle, far less was known in 1910 about climatic change in the past and its causes and consequences than is known today. The question requires a fresh examination. It has already been noted that the earth’s average temperature is now approaching levels that were last attained in the Neolithic period, before 3000 , probably as a result of anthropogenic global warming in the last few years. In between, the climate was generally cool-er, but there were still periodic fluctuations of temperature