MICROBIOLOGIC CONSEQUENCES OF HUMAN CIVILIZATION
Another example how man’s action can influence the spreading of epidemics is given to us by the history of the Spanish conquest of the Americas. When we think of such an enterprise, we are usually convinced it was possible only thanks to the military superiority of the old world inhabitants compared with the Aztecs and the Incas. This theory is true if we consider the Spaniards, besides their guns, brought, unconsciously, those that are called bacteriological weapons according to the modern terminology.
The true protagonists of that conquest weren’t firearms, but viruses and bacteria. In 1520 the smallpox virus was the first to attack and besides killing a lot of Aztecs,it also killed Montezuma’s nephew just on the night the latter was preparing the final assault on the four hundred Spaniards led by Cortez and forced to defend themselves in an open and very vulnerable place.
What the virus did was highly strategical because the Atzecs were so dicouraged for the death of their leader that they gave up the attack, So Cortez could reorganize, find allies, attack and destroy Tenochtitlan, the capital city[1].
Following the Spaniards smallpox went on advancing into Guatemala and later into Perù, allowing Pizzarro to conquer Cuzco, the capital city. Besides the great number of dead people the virus caused among the Amerinds, the fact that the Spaniards were spared, was interpreted first by the Aztecs and later by the Incas as if gods sided with the Spaniards. How differently might the victory of few hundreds of men over thousands of people be explained?
After smallpox measles followed, then maybe a typhus epidemic and at last certainly a flu one. The demographic consequences were ruinous: from 25-30 million people how many they were in Mexico when Columbus got to Hispaniola in 1492, in 1568 the Amerinds had diminished at about 3 million till to touch the lowest rate of about1,6 million in 1620. The same happened to the Amerinds of Perù as well[2].
Before the arrival of the Spaniards local populations had known contagious diseases ( we can find traces of them in the Aztec codes ) but they had never been so serious as the epidemics of the old world. The vastness of the territory at the inhabitants’ disposal with their relative scarse density and the low number of domestic animals, as an animal reserve of bacteria and viruses, had stopped the birth of viruses at high virulence.
There are a lot of more recent examples how the meeting of a community with a new virus may have ruinous effects. For example an epidemic of measles caused the end of two Indian tribes in South America and Alaska.
Recently man has begun another kind of action which might have very serious consequences: the invasion of ecological niches[3], this word is used to refer to zones of the earth where the conditions of ecosystem are those of the primordial times. So man gets in touch with viruses till now inacessible and belonging to the reserves of animal world. The effects are evident if we think that this way viruses, like HIV, which are responsible for AIDS and for the one of Ebola, have made the trans-species jump from the animal reserve to man.
Viruses (and bacteria) that are present in the ” ecological niches” and have become, for genetic selection, endemic in animal populations (for example monkeys) which live in those areas, are quite unknown to man.
When the human being, always owing to deforestation or manipulation, for any purpose, of living or dead animals living there, gets in touch with these unknown viruses, the consequences are totally unpredictable and often dramatic.
The need of feeding masses of people bigger and bigger causes some artificial animal reserves to be set up with two specific features: the first is that viruses and bacteria, present in natural animal reserves, are unknown in artificial ones, the second is that in the latter a huge overcrowding results.
The greatest natural reserve of influenzal viruses is the one of wild-geese and generally of water fowls, where microorganisms don’t cause diseases.
But when influenzal viruses pass to susceptible hosts, like battery chickens, they are subjected to a kind of reabsorption of the single viral components which make them particularly virulent and even lethal.
At present there are hundreds of thousands maybe millions of chickens[4] waiting for being infected by viruses who, with only one point of mutation, can become lethal when they are transferred to man.
Similarly also swine play an essential role in transferring influenzal viruses from man to water fowls and vice versa, that is they act as intermediate hosts.
Again we can see a human action, like an intensive farming of chickens and swine, can form a remarkable reserve of (influenzal) viruses which, because of the reabsorption of their components, may become particularly virulent.
[1] Mc Neill WH, Patterns of Disease Emergence in History. In Emerging viruses. Op.cit.pag.29-30
[2] Mc Neill WH, Plagues and peoples. Op.cit.pag.180.
[3] Cameron T W M; Parasitism-The Ecological Niche. In Parasites and Parasitism. Pag.25-37.London: Methuen & Co.LTD: New York: John Wiley & Sons, INC.
[4] Mc Neill WH, Patterns of Disease Emergence in History. In Emerging viruses.Op.cit. Pag.40-3
Translated from “Il Virus Intelligente” by Enrica Narducci
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Ferdinando Gargiulo offers you a new perspective on why new viral epidemics, assaults, infanticides, suicide epidemics and even environmental catastrophes. Always engaged in his research decides to create a blog to offer his readers content of high value.