GIOVAN COSIMO BONOMO (1663-1696): Discoverer of the etiology of scabies

International Journal of Dermatology 1998;37(8):625-630

Marcia Ramos-e-Silva, MD, PhD
Associate Professor of Dermatology
From the School of Medicine, HUCFF-UFRJ
Universidade Federal do Rio de Janeiro, Brazil

Presented at the Symposium of the History of Dermatology Society
March 20 1997, San Francisco, California, USA.

The history of the discovery of the agent of scabies and of the disease itself is fascinating and controversial.1 Articles with completely different interpretations on this subject, reporting conflicting stories and raising questions are found in the literature.

The drawings made by Bonomo in 16872 prove that he did actually observe and study the agent of scabies back in the seventeenth century,1 (Figure 1) but who was first to describe the parasitic etiology of scabies? Was it Francesco Redi, Giovan Cosimo Bonomo, Diacinto Cestoni or even someone before them? Were Bonomo and Cestoni the same person? Was Giovan Cosimo Bonomo a pseudonym for Diacinto Cestoni? Did they study the mite together or separately almost during the same period?

Figure 1: Bonomo's drawings 2

These questions and many others about the discoverers of this mite are still disagreed about and some will never be settled because the existing documentation is either incomplete or lost.

Although its agent was not recognized and its cause was attributed to a humoral nature, scabies was probably already known by Aristotle (384-322 BC), who was the first to use the term 'akari' to designate a wood-dwelling mite. Scabies was mentioned by many writers in different times3 and a description of the condition was found in an Arabian manuscript written by a physician called Abu el Hasan Ahmed el Tabari, of Tabaristan, who lived around 970.4 In the twelfth century, Saint Hildegard (1098-1179), Abbess of the Rupertsberg Convent, near Bingen, wrote a book named 'Physika' which includes the first actual reference to the Acarus scabiei, and Avenzoar (1091-1162), a Moorish physician practicing in Spain, described what would seem to be the mite but did not relate it to the itch.5,6

Scabies was known in Europe by various names. It was gale for the French, itch for the English, and Krätze for the German. In those days, it was widespread, specially among poor people with bad hygiene, exactly as it is today, but even some important and wealthy persons also had the disease.6,7 This was the case of Napoleon I, who seems to have suffered from the itch during almost his whole life.7 One of the oldest academic societies in the world, the Crusca Academy, founded in Florence in 1582, defined 'pellicello', a term used for Sarcoptes or Acarus scabiei, in the second edition of its dictionary, published in 1623, as 'a tiny mite generating in the scab-ridden skin, the biting of which produces acute itching'.8
Although the mite was known long before Bonomo described it, as is widely documented, it was not considered the cause of the disease; which was believed to be of humoral nature. Galen (129-200) attributed it to 'melancholic juices'; Avicenna (980-1037) to 'corrupt blood'; and Velamonte to 'pungent ferment'. Those who recognized its contagiousness explained it as the effect of the humors and ferments evaporating from the body.6 During this period there was no doubt about the doctrine of spontaneous generation. It was accepted, since the time of Aristotle, that lice originated from meat, fleas from filth, and moths from wool, and that the presence of the acarus on the skin of scabies patients was considered a proof of the corruption of the flesh and blood caused by internal ailment.3,6

The seventeenth century was characterized by two opposing intellectual forces. On one side, a culture that was the inspiration for a series of bold innovators in the fields of science, literature, and art, and which gave us a totally new vision of the world. It was the time of Galileo, Campanella, Bruno, Caravaggio, Bernini and many others. On the other side, there was a culture which revolved around the Church and assumed a severely intransigent and antagonist position with the first.6

During the second half of the seventeenth century, empiricism, a method created by the English philosopher Francis Bacon (1561-1626), was used for various studies, specially in Italy where science was particularly active. This method introduced experimentation as the fundamental basis for science.

Using the empirical method, Francesco Redi (1626-1698) antagonized the spontaneous generation theory by demonstrating that flies only appear on putrid flesh if other flies had previously deposited their eggs. Redi was the chief physician of Grand Duke Cosimo III and leader of one of the schools of thought of that time. He and Giovan Cosimo Bonomo, a young naval physician, were regular visitors of Diacinto Cestoni's pharmacy, in Livorno, a meeting place for men of letters and science.6

Brumpt, in his book published in 1936, states that the etiology of scabies seems to have been discovered by Redi in 1687 and that its pathogenic role was evident after the studies of Renucci, in 1834.9

Nevertheless, it is most likely that the real discoverer of the parasitic nature of scabies was Dr. Giovan Cosimo Bonomo with the collaboration of the apothecary and naturalist Diacinto Cestoni; both of them Francesco Redi's disciples.3

From 1685 to 1687, and probably at the Spa of the city of Livorno, Italy, they studied the morphology and physiology of Sarcoptes scabies, explained the contagious nature of scabies by the passage of the mite from person to person, suggested medications, and finally drew the mite and its eggs as observed under the microscope.

Lane,1 in 1928, stated that it is generally accepted that the letter written by Bonomo to Francesco Redi2 is the first accurate description of the mite and has very accurate drawings of its appearance. The original and so important letter (Figures 2 and 3), written on July 18, 1687, is in Arezzo, Italy,3 and a document of such great significance has to be mentioned every time scabies' history is referred.1

Figure 2: First page of Bonomo's letter 3

Figure 3: Last page of Bonomo's letter with his signature 3

The discovery of Sarcoptes scabiei was announced in a small book, written by Francesco Redi, entitled "Observations about the 'pellicelli' of the human body, made by Gio. Cosimo Bonomo and written by him with other observations in a letter to Francesco Redi, Florence, 1687".2 (Figure 4) In this book Redi explains the researches of Bonomo, who appears as the sole author, and Cestoni, who figures as a collaborator.3

Figure 4: Cover of Redi's book 2

In the English medical literature, the first notice of this investigation appears in an article written by Mead and published in 1703.10 This paper has great historical interest and is an abstract of part of Bonomo's letter to Redi2 translated into English. The most important subsequent paper, still before the general acceptance of the acarus origin for scabies, was that of Wichmann,11 from Hannover, Germany, in 1786. In the booklet called 'Etiology of the itch', he compared his own drawings to the ones copied by Mead from illustrations in Bonomo's letter.1

In the letter to Francesco Redi,2 written in 1687, as translated by Mead,10 in 1703, Bonomo says: "having frequently observed that the poor women, when their children are troubled with the itch, do with the point of a pin pull out of the scabby skin little bladders of water, and crack them like fleas upon their nails; and that the scabby slaves in the Bagno at Livorno do often practice this mutual kindness upon one another; it came into my mind to examine what these bladders might really be.

"I quickly found an itchy person, and asking him where he felt the greatest and most acute itching, he pointed to a great many little pustules not yet scabbed over, of which picking out one with a very fine needle, and squeezing from it a thin water, I took out a very small white globule scarcely discernible: observing this with a microscope, I found it to be a very minute living creature, in shape resembling a tortoise of whitish color, a little dark upon the back, with some thin and long hairs, of nimble motion, with six feet, a sharp head, with two little horns at the end of the snout."

In this part of his letter Bonomo made an accurate description of the six legged larva with its rapid movements and not of an adult which has eight legs.

"Not satisfied with the first discovery, I repeated the search in several itchy persons, of different age, complexion and sex, and at different seasons of the year, and in all found the same animals; and that in most of the watery pustules, for now and then in some few, I could not see any.
"And though by reason of their minuteness, and color the same with the skin, it is hard to discern these creatures upon the surface of the body, nevertheless I have sometimes seen them upon the joints of the fingers in the little furrows of the cuticula, where with their sharp head they first begin to enter, and by this gnawing and working in with their body, they cause a most troublesome itching, till they are got quite under the cuticula, and then it is easy to see how they make ways from place to place by their biting and eating, one single one happening sometimes to make several pustules, of which I have often found two or three together, and for the most part very near to one another.

"With great earnestness I examined whether or not these animalcules laid eggs, and after many inquiries, at last by good fortune while I was drawing the figure of one of them by a microscope, from the hinder part I saw drop a very small and scarcely visible white egg, almost transparent and oblong, like to the seed of a pineapple.

"I oftentimes found these eggs afterwards, from which no doubt these creatures are generated, as all others are, that is from a male and female, though I have not yet been able by any difference of figure to distinguish the sex of these animals."

From what Bonomo wrote in these two last paragraphs he actually saw a female laying an egg and stated that reproduction was carried out by the mating of a male and a female, although he could not see their sexual differences. He was much ahead of his time because spontaneous generation was the prevailing theory.

"From this discovery it may be no difficult matter to give a more rational account of the itch, than authors have hitherto delivered us. It being very probable that this contagious disease owes its origin neither to the melancholy humor of Galen, nor the corrosive acid of Sylvius, nor the particular ferment of van Helmont, nor the irritating salts in the serum or lympha of the moderns, but is no other than the continual biting of these animalcules in the skin, by means of which some portion of the serum oozing out through the small apertures of the cutis, little watery bladders are made, within which the insects continuing to gnaw, the infected are forced to scratch, and by scratching increase the mischief, and thus renew the troublesome work, breaking not only the little pustules, but the skin too, and some little blood vessels, and to making scabs, crusty sores, and such like filthy symptoms."

At this point Bonomo disagreed with the humoral and spontaneous generation theory accepted at that time and stated that the passage and biting of the skin by the acarus was the cause of the pruritus. Above all, he described with great accuracy the etiopathogenic mechanism of lesions formation in scabies.

"From hence we come to understand how the itch proves to be a distemper so very catching, since these creatures by simple contact can easily pass from one body to another, their motion being, wonderfully swift, and they as well crawling upon the surface of the body as under the cuticula, being very apt to stick to every thing that touches them, and a very few of them, being once lodged, they multiply a pace by the eggs which they lay.

"Neither is it any wonder if this infection be propagated by the means of sheets, towels, handkerchiefs, gloves, etc., used by itchy persons, it being easy enough for some of these creepers to be lodged in such things as those, and indeed I have observed that they will live out the body 2 or 3 days."

In his letter Bonomo stated that Sarcoptes scabiei could be transmitted by direct contact, and that it sticked to almost everything, so transmission also occur through clothes and other fomites. In his experiments he also observed that the mite could live out of the body for some days.
"Nor in the last place shall we be at a loss to know the reason of the cure of this malady by lixivial washes, baths and ointments made up with salt, sulphurs, vitriols, mercury's, simple, precipitate or sublimate, and such sort of corrosive and penetrating medicines. These being infallibly powerful to kill the vermin lodged in the cavities of the skin, which scratching will never do, partly by reason of their hardness, and partly because they are too minute as scarcely to be found by the nails.

"Neither do inward medicines perform any real service in this case, it being always necessary after a tedious use of these to have recourse to those external already mentioned. And if in practice we oftentimes experience that this disease, when we think it is quite cured by unction, does nevertheless in a short time return again, this is not strange, since though the ointment may have killed all the living creature, yet it may not probably have destroyed all their eggs, laid as it were in the nests of the skin, from which the may afterwards breed again and renew the distemper. And upon this account, it is very advisable after the cure is once performed, still to continue the ointing for a day or two more; which is the easier to do, because these liniments may be made agreeable enough, and of a good smell, as particularly is that compounded of the ointment of orange flowers or roses, and a small quantity of red precipitate."2

To finish his so complete and exciting observations Bonomo suggested that the cure of the itch could be accomplished by the use of local therapy, as sulphur, which is used until now. He stated that internal drugs were not effective and local treatment had to go on for two or three more days after the cure of the itch. This time would be necessary to prevent relapses because of the presence of eggs that, after hatching, could then start a new biological cycle of the parasite.

Immediately after the letter of Bonomo and publication of Redi's book,2 the Pope's chief physician, Giovanni Maria Lancisi (1654-1720) began a dispute with Bonomo. Lancisi thought scabies had a humoral origin that preceded the proliferation of the acarus, and, although he recognized the presence of the parasite, he discarded it as the single cause of the disease. In the course of this dispute, because of Lancisi's position as the Pope's chief physician, the fact that he invoked the Scriptures, and the fate of previous scientists as Galileo; Bonomo was persuaded not to continue the debate. His discovery was then completely forgotten.6 As Ernest Besnier and Adrian Doyon said later and very pertinently, it was a time when the medical brain was not yet prepared to accept this discovery.12

It is easy to attribute the paternity of the discovery of the parasitic origin of the itch to Bonomo and not to Redi. The first affirmed and afterwards sustained it in a polemic with Lancisi, while Redi showed some hesitation in accepting such a subverting idea, besides the fact that Redi himself admitted he was publishing the results of Bonomo's investigation.3

It is difficult to establish with precision and certainty how much is owed to Bonomo and Cestoni.3 Usually their names are referred to as two distinct persons who worked together, but there are some authors, as Raspail and Devergie, that claim they are the same person. Raspail stated that Cestoni, a pharmacist of Livorno, Italy, wrote a letter to the celebrated Italian naturalist, Francesco Redi, in 1687, under the pseudonym of Giovan Cosimo Bonomo because he feared persecution, since his ideas related to scabies were opposed to the spontaneous generation theories.5 In January 15, 1710, thus twenty three years after Bonomo had written his experiences to Redi, Cestoni wrote a letter to Antonio Vallisnieri, repudiating the original one and claiming the entire credit for the discovery of acarus, which appeared just under Bonomo's name, for himself.13

Most of the authors on the subject believe that Bonomo and Cestoni were different persons; among them are Fürstenberg and Hebra, whose careful researches into the historical and other aspects of this matter gave much weight to their views and established Bonomo's existence.5,6 Very little is known about him, specially before and after he lived in the city of Livorno in Italy. Most information was obtained from letters written by him or to him. His father was a French pharmacist named Stefan, who died in Livorno in 1684, where his mother was still living in 1690. It is known that he was a regular visitor of Cestoni's pharmacy and received the Livorno citizenship in 1690, as a public and solemn recognition. He studied scabies and its agent with Cestoni probably at the Livorno spa, built in 1602 by Ferdinand I. In 1691 he was designated as the physician of Anna Maria, daughter of the Grand Duke Cosimo III, wife of Giovanni Guglielmo, representative in Germany. He went to Neuburg and later to Düsseldorf. Unfortunately, after this period which is thought to have been the most happy part of his life, very little was heard of him again.3 Bonomo probably died in 1696 in Florence at the early age of 33.14

It is believed that Cestoni, probably knowing the destiny of his former collaborator and that Redi had already died, claimed the credit because nobody would question him. 3,13 In his original letter2 Bonomo said that Diacinto Cestoni had assured him that he had many times seen old women extracting something on the point of a needle that had been introduced under the skin of children affected with scabies.5 Faucci3 states that probably the naturalistic study of the acarus is due to Cestoni, a very clever researcher, while Bonomo, a very keen naval physician, is responsible for the observations regarding to the external cure of scabies. The result of his investigations led him to use the resolute expressions contained in his autographed letter, revealing how absolute his conviction was about the cause of the disease. There was no doubt that Diacinto Cestoni was an example of honesty, as recognized by all. Having to reconcile his true honesty with his conduct on the authorship vindication, Faucci suggests what he called a 'retrospective illusion': the long period after the researches and the distant memories in Cestoni's mind slowly changed, transforming his part of the discoveries into the essential part of the work in common, and making Bonomo's cooperation insignificant and negligible; therefore he convinced himself to claim all the credit for the discovery, besides the fact that it was always quoted solely under Bonomo's name.3

It was only in 1834, almost two centuries later, that Renucci, a young student, re-established the fact that the acarus was the cause of scabies.15 After this, a period of intense investigations on scabies began, and Ferdinand Hebra (1816-80), by particular self-experiments, was the one that did the most to settle once and for all the problem of scabies. He published his views on diagnosis, etiology, and treatment of this disease in 1844 and made an eulogy of Bonomo's and Cestoni's work.16

Hebra also stated that Giovanni Cinelli Calvoli, in 1689, claimed to have seen the acarus ten years before Cestoni. Calvoli declared that a certain Protasio Felice Salvetti, whom he had employed to make drawings, had revealed his researches to Bonomo and Cestoni. Despite his claims to priority in the discovery of the itch mite, Calvoli, it is said, did not regard it as the cause of scabies. It is also claimed that, before Bonomo and Cestoni, Scaliger, in 1557, Joubertus, in 1577, Fallopius, in 1584, Rondelet, in 1592, Vidius, in 1586, and Schenck, in 1600, knew and wrote about acarus. Some of these authors however confused it with lice, which was not an uncommon error at that time or even later.5

Favarielle, in a thesis on scabies, written in Paris in 1805, still affirmed it was produced by a syphilitic or a scorbutic infection of the humors and by a degeneration of the transpiration.5

It was Cumston, in 1924, who credited Bonomo for the discovery and first description of Sarcoptes scabiei,5 and, finally in 1927, Razzauti came across Bonomo's signed letter which had been preserved in the Library of Fraternità di S. Maria of Arezzo.14 Its publication that year proved that, in fact, the discovery of the acarian origin of scabies preceded Renucci's paper and its official scientific recognition by 150 years.3

It is contrary to historical proof to ascribe to others than Bonomo and Cestoni the discovery of the parasitic origin of the itch. Francesco Redi, however, although not acting directly in the discovery, must be honored for being Bonomo and Cestoni's Master, in the widest sense of the word. With his admirable example he showed them the way to be followed, always stimulated their work, guided it with his wise advice and gave them during and after their investigation all the needed help, so that it might be accomplished and therefore known and spread.3

Giovan Cosimo Bonomo, in collaboration with Diacinto Cestoni, discovered the etiologic agent, stated that it reproduced through the union of a male and a female, affirmed it laid eggs (Bonomo actually saw the mite laying an egg), suggested its transmission by clothes and fomites, and speculated about the reasons some local treatments were effective and some systemic were not. That was in 1687,2 three hundred and 10 years ago; and their study, even though not immediately recognized, marked the first notice of the parasitic theory of infectious diseases; demonstrating for the first time that a microscopic organism could be the cause of a disease. It may even be said without doubt that Bonomo's and Cestoni's discovery initiated a new era in Medicine.6

Acknowledgement: The author wishes to thank Dr. Torello Lotti, Montecatini, Italy; Dr. Carlos Lacaz, São Paulo, Brazil; Dr. Stephen Greenberg and the staff of the National Library of Medicine, Washington, DC., United States; for their help in obtaining some of the ancient documents used in this paper.

1. Lane JE. Bonomo's letter to Redi - an important document in the history of scabies. Arch Dermatol Syphilogr 1928;18:1-25.
2. Redi F. Osservazioni intorno a pellicelli del corpo umano fatte dal Dottor Gio: Cosimo Bonomo e da lui com altre osservazioni scritte in una lettera all'illustriss. Sig. Francesco Redi. Florence:Piero Matini, 1687.
3. Faucci U. Contributto alla storia della scabbia. Siena:Bernardino, 1932.
4. Rihad M. Der arabische Arzt At-Tabari; Übersetzung einzelner Abschnitte aus seinen "Hippokratischen Behandlungen". Arch Geschichte Medizin 1927;19:123-68.
5. Beeson BB. Acarus scabiei. Study of its history. Arch Dermatol Syphilogr 1927;16:294-307.
6. Montesu MA, Cottoni F. G.C. Bonomo and D. Cestoni. Discoverers of the parasitic origin of scabies. Am J Dermatopathol 1991;13:425-7.
7. Coutinho E. Tratado de clínica das doenças infectuosas, parasitárias e peçonhentas. Rio de Janeiro:Guanabara Koogan, 1957:675-80.
8. Vocabolario dell'Accademia della Crusca. 4ed. Florence:Accademia della Crusca, 1729:38. Apud Montesu MA, Cottoni F. G.C. Bonomo and D. Cestoni. Discoverers of the parasitic origin of scabies. Am J Dermatopathol 1991;13:425-7. and Apud: Faucci U. Contributto alla storia della scabbia. Siena:Bernardino, 1932.
9. Brumpt E. Précis de Parasitologie. Paris:Masson, 1936:1107-18.
10. Mead R. Translation of part of Bonomo's letter to Redi, 1687. Philosophical Trans 1703;23:1296-9.
11. Wichmann JE. Aetiologie der Krätze. Hannover, 1786.
12. Besnier E, Doyon A. Apud Beeson BB. Acarus scabiei. Study of its history. Arch Dermatol Syphilogr 1927;16:294-307.
13. Dechambre A. ed. Dictionnaire encyclopédique des Sciences Mèdicales. Paris:Masson. 1873:596-7.
14. Razzauti A. Francesco Redi e la scoperta della patogenesi della scabbia. Riv Sci Med Nat 1927;18:167-95.
15. Renucci JD. Thèse inaugurale sur la decouverte de l'insecte qui produit la contagion de la gale, du prurigo et du phlyzacia. Paris:1835. Apud Beeson BB. Acarus scabiei. Study of its history. Arch Dermatol Syphilogr 1927;16:294-307.
16. Hebra F. On the diseases of the skin, including the exanthemata. London:New Sydenham Society, 1868:175-8. Apud Montesu MA, Cottoni F. G.C. Bonomo and D. Cestoni. Discoverers of the parasitic origin of scabies. Am J Dermatopathol 1991;13:425-427.