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

To try to solve the problem, it is necessary now to examine in more detail the ecology of malaria in Italy, both in recent times and in antiquity.

⁴⁵ Lancisi (1717: 123) expressed the opinion that the unhealthy air of the Pontine region led to the decline of the Volsci. In contrast to the Volsci from the hills, the Latins were etymo-logically ‘the people of the plain’ (Quilici (1979: 30) ).

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The ecology of malaria in Italy

4. 1 M   

Before its eradication malaria was transmitted in Europe principally by mosquitoes belonging to a (complex of ) species that was originally called Anopheles claviger by Battista Grassi and later renamed Anopheles maculipennis. Roubaud and Wesenberg-Lund then noticed that malaria did not occur in many places where these mosquitoes were found, the puzzling phenomenon of anophelism without malaria. Anophelism without malaria was observed in Italy for example in such places as Colle Salvetti, Livorno, Massarosa, Naples, Pisa, Val di Chiana, and Viaréggio. In all these localities malaria appeared to have disappeared spontaneously by the end of the nineteenth century, even though there were still plenty of Anopheles mosquitoes around.¹ The resolution of the paradox of anophelism without malaria in Italy began when Falleroni, studying the mosquitoes of the Pontine Marshes, discovered that in places where malaria occurred the A. maculipennis mosquitoes always laid eggs which had one of two distinctive patterns, while in places where there was no malaria the mosquitoes produced eggs with other, different, patterns. It was then realized that what had been named A. maculipennis, a single species, was in fact a complex of different species with different habits. At that time the patterns on the eggs constituted the only morphological trait that could be used for differentiating these species.² Nine separate biological species are now recognized in the A. maculipennis complex in Europe (see Table 2). All the nine species may be identified in the fourth instar larval and adult female forms by chromosomal banding patterns, isoenzyme profiles, and DNA sequence analysis. Seven of the nine can be distinguished by specific patterns on the upper surface of their eggs and the form of the egg floats. A. martinius and A. sacharovi can be distinguished from the other seven species, but ¹ Hackett and Missiroli (1931); Hackett (1937); Fantini (1994); Gilles and Warrell (1993: 115–16).

² Falleroni (1926); Missiroli (1938: 9–10).

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Table 2. Palaearctic mosquito species in the Anopheles maculipennis complex Species

Author

A. atroparvus

Van Thiel (1927)

A. beklemishevi

Stegnii and Kabanova (1976)

A. labranchiae

Falleroni (1926)

A. maculipennis s.s.

Meigen (1818)

A. martinius

Shingarev (1926)

A. melanoon

Hackett (1934)

A. messeae

Falleroni (1926)

A. sacharovi

Favre (1903)

A. subalpinus

Hackett and Lewis (1935)

Source: White (1978) and Ramsdale and Snow (2000). The A. maculipennis complex belongs to the subgenus Anopheles of the genus Anopheles, while tropical species that transmit malaria belong to the subgenus Cellia. Several other species in the A. maculipennis complex only occur in North America. Besides the mosquitoes of the A. maculipennis complex, the mosquitoes of the Anopheles claviger complex had a secondary role as malaria vectors in Europe (Zamburlini (1998); Schaffner et al.

(2000) ). Five other important mosquito species or complexes of species are mentioned in this book: Anopheles gambiae (the principal vector of malaria in tropical Africa), Anopheles pharoensis (vector of malaria in Egypt), Anopheles plumbeus (possible vector of malaria in England), Aedes aegypti (the vector of yellow fever), and Aedes albopictus (the original vector of dengue fever).

not from each other, by slight differences in adult morphology.

Three of these species were very important vectors of malaria in the past. A. labranchiae occurred in North Africa, Corsica, Sardinia, Sicily, central and southern Italy, parts of the Murcia and Alicante provinces of Spain, and Croatia. A. sacharovi occurred in mainland Italy, Sardinia, Greece, and the eastern Mediterranean, while A.

atroparvus was widespread in Spain and northern Europe, reaching its southern limit in Italy in Campania. A. atroparvus takes the place of A. labranchiae in northern Italy, while the two species coexist in central Italy. A fourth important vector-species, A. superpictus, occurs sporadically in southern Italy and Sicily. However, it does not belong to the A. maculipennis complex and its main geographical distribution lies in the Balkans and Near East. The study of chromosome translocations has shown that A. labranchiae, A.

sacharovi, and A. atroparvus are closely related to each other, within the A. maculipennis complex. All three can breed in brackish water in marshes near the coast, but also in fresh water in inland streams and (in modern times) in rice-fields.³

³ Ramsdale and Snow (2000) provide maps showing the current distribution of the Euro-

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3. Anopheles labranchiae, the most important mosquito vector of malaria in western Mediterranean countries in the past. According to Falleroni (1926: 565), who first identified it as a separate species, ‘it can be said that the winged insect does not live outdoors; it takes shelter and nourishes itself in houses, cowsheds, and pigsties’ ( l’insetto alato si può dire non viva all’aperto; si ricovera e si nutrisce nelle abitazioni, nelle stalle, nei porcili ). © The Natural History Museum, London.

The existence of regions in which there were lots of mosquitoes but no malaria, such as the northeastern coast of Italy around Ravenna (see Ch. 4. 2 below), is probably one reason why the ancient Greeks and Romans apparently failed to notice the connection between the periodic intermittent fevers of malaria and mosquito bites, as far as can be seen from extant literature. In Europe the theory that mosquito bites caused malaria was first proposed in print by Giovanni Maria Lancisi in his famous work de pean species of Anopheles mosquitoes. In some cases these are different from their known historical distributions as a result of modern eradication campaigns.