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

primis ego non omni te assuescere coelo | Exhorter: fuge, perpetuo quod flatur ab Austro, | Quod coeno, immundaeque grave est sudore paludis.

²⁶ Fraser et al. (1998).

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malaria, since syphilis is predominantly a sexually transmitted disease (although congenital transmission through the placenta also occurs) affecting mainly adults. In holoendemic regions people develop acquired immunity to malaria in infancy and childhood and consequently do not have severe malarial fevers during the years of sexual maturity when they are most likely to encounter syphilis. Whether or not syphilis existed in pre-Columbian Europe is a controversial question which need not be considered here.

A possible example of a ‘neutral’ interaction, according to the perceptions of contemporary observers, was that between malaria and smallpox in early modern Rome. Lapi wrote that if women with tertian fevers touched or suckled children with smallpox they were liable to develop the relatively mild discrete form of smallpox (rather than the more dangerous confluent form). He maintained that in such cases the two different diseases would run their courses separately without getting confused with each other. Although Lapi seemed to believe that the two diseases were not interacting with each other, it is possible that what happened is that malaria depressed the immune systems of the women to the extent that they could develop secondary infections of smallpox (presumably following earlier primary attacks in their own childhood which generally conferred immunity).²⁷ Since smallpox certainly arrived in Italy during the Antonine ‘plague’ in the second century , if it was not present earlier, this interaction was possible from then onwards.²⁸ The focus of the rest of this section will be on definite synergistic interactions between malaria and other pathogens which endanger humans.

The gastro-intestinal diseases were indeed major causes of infant and child mortality in historical populations. In ancient Rome Celsus observed that most of the victims of diarrhoea and dysentery were children up to the age of ten.²⁹ However, the first point that needs to be made is that in European history populations with endemic malaria had higher overall mortality than populations with no experience of malaria (detailed demographic analysis in Ch. 5. 4 below). This can readily be seen by comparing the population of Florence in the thirteenth to fifteenth centuries with ²⁷ Lapi (1749: 48); Fenner et al. (1988: 51–2) on secondary smallpox infections. Endemic smallpox was finally eliminated from Italy in 1947.

²⁸ Duncan-Jones (1996) discussed the Antonine ‘plague’.

²⁹ Celsus 2.8.30.

Demography of malaria

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nineteenth-century Grosseto. In Florence, which had no history of endemic malaria, gastro-intestinal diseases, operating principally from July to September inclusive, were indeed the leading cause of infant deaths (outside years of epidemics of bubonic plague), the sort of pattern noted by Shaw. In spite of the effects of gastro-intestinal diseases on children, Herlihy and Klapisch-Zuber reached the conclusion that the average duration of life in Florence in the period in question was as high as forty, if years of major plague epidemics are excluded from consideration.³⁰ In contrast, life expectancy at birth in Grosseto much more recently was only twenty. This comparison shows that children assaulted by gastro-intestinal diseases alone have better survival chances than when malaria is present as well. It is also important to note that infant mortality is virtually unrepresented in the funerary inscriptions from the city of Rome in the fourth century  used by Shaw. Since direct mortality from P. falciparum malaria principally falls on infants and children where it is endemic, the bulk of its effects in terms of seasonal mortality would not be expected to be visible in those inscriptions in any case.

How does malaria exacerbate the effects of gastro-intestinal infections? P. vivax and P. malariae undergo the process of schizogony in erythrocytes in the peripheral blood vessels of the human body, but P. falciparum merozoites export proteins to the surface of infected erythrocytes which make them adhere to the capillaries of internal organs. Fixation inside internal organs in this way enables the P. falciparum parasites to undergo schizogony under a lower oxygen tension, which favours this process in this particular species of malaria. The most severely affected internal organs are the brain (causing cerebral malaria), the kidneys and the heart and the liver, and (most importantly for the discussion at this point), the placenta in pregnant women (especially primigravidae), in whom any acquired immunity to P. falciparum malaria tends to break down in the second and third trimesters. Lancisi noted that women were particularly badly affected during the malaria epidemic in Rome in  1695.³¹ In tropical Africa pregnant women are bitten twice as frequently as non-pregnant women by the mosquito Anopheles ³⁰ Herlihy and Klapisch-Zuber (1985: 83–4, 276–9). They refrained from constructing life tables for the population of Florence for reasons which will be considered in Chapter 11

below.

³¹ Lancisi (1717: 210–11).

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gambiae, increasing their chances of being infected by malaria, perhaps because pregnant women produce a larger volume of exhaled breath on average.³² Since mosquitoes are generally believed to locate their prey by detecting chemicals emitted in human breath, European vectors of malaria may also have responded in a similar way to pregnant women in the past (although it is also possible that mosquitoes detect chemicals in human sweat). A new idea which is currently attracting attention among researchers in medicine is that placental malaria is caused by a specific population (or set of haploid clones) of P. falciparum with a special affinity for certain chemical receptors generally found only or predominantly in the placentae of pregnant women.³³ The presence of large numbers of plasmodia in the placenta frequently causes miscarriages in non-immune women, or fetal anaemia and intrauterine growth retard-ation in women with some degree of immunity, leading to low birthweight infants who are particularly susceptible to diseases in general and gastro-intestinal infections in particular. Desowitz, a specialist in tropical diseases, put it as follows:

The babies that are born to the malarious usually have a