Insects, people and disease: Adolpho Lutz and tropical medicine

The parasites of snakes … that appear temporarily as cytozoa

are undoubtedly sporozoans closely related to Drepanidae,

which are generally included in a specific group of

haemosporidia. In any case, they are quite distinct from the

parasites of malaria, whereas in many aspects they resemble

coccidia, that is, gregarins (Monocystis) and even sarcosporidia.

The future will tell whether we are justified in organizing

haemosporidia in one specific group and separating the genera

Danilewskya and Karyolysus, based on our current, quite

incomplete knowledge. I will keep Drepanidium as the name of

the genus, since it is the oldest, and call the parasites in the

blood of snakes Drepanidium serpentium, since I believe that I

must consider the various forms I have observed as belonging

to one [same] species.

 

The distribution of human malaria in São Paulo

Lutz's research into human malaria focused at first on Barra de Santos and the swampy lowlands near that port. In 1893, he twice verified Plasmodium malariae in people who had come down with the disease there. In his 1895 report, he described three more cases: one from the port of Taboado, along the Paraná River; the other two, a mother and daughter who lived in Mogy-Guassú. There

is no mention of human malaria in the 1896 report,88 even though this report contains the most information on the topic of

haematozoans in animals. The following year, 89 Lutz diagnosed fourteen cases in the acute stage of the disease. He attributed this increase to meteorological influences and also to his new access to patients hospitalized at Santa Casa in the city of São Paulo. But all of these came from outside the city. “We are still waiting,” he wrote, “[to find a] case of malarial fever displaying plasmodia in the blood contracted in São Paulo, [and this] should prove that the existence of paludism in the capital is no more than an old myth.”

The victims he examined in 1897 had picked up malaria along the banks of the Mogy-Guassú River (three cases, two of which in Porto Ferreira) and in Guarujá (one), Paranaguá (one), Serra Azul (one), and Motuca, near the Guariba River (one). One of the cases came from Rio de Janeiro. The largest number (six) occurred in the Serra de Santos highlands. The next year, Lutz encountered another

eleven cases,90 distributed as follows: Porto Ferreira (one), Salto de Itú (one), Inhaim (two), and Serra de Santos (two, plus an unspecified number “with pigmented leukocytes”); at Santa Casa, he also examined an ailing individual from a farm near Araraquara, a “chronic case, probably Italian in origin,” plus four cases from unspecified areas of rural São Paulo.

The thirty malaria victims he had examined until then and the information provided by other physicians allowed Lutz to draw a preliminary sketch of the geography of malaria in the state of São Paulo and its surrounds. The foci were concentrated in three regions: first, along the coast (Barra de Santos, Guarujá, and, outside the state boundary, Rio de Janeiro and Paranaguá); second, in coastal highlands, mainly around Santos; and last, along the banks of rural São Paulo's big rivers: Mogy-Guassú, Tietê, Paraná, and Piracicaba. Cases elsewhere were rare and not of great import. The malaria occurring near rural rivers only appeared when these reached a certain size; on the Tietê, for example, the malarial stretch was near the Itu falls. “Thus it is that between the coastal highlands and the banks of the big rivers there is a nearly unaffected zone, wherein lies the capital.”

Most of the cases were not serious: “They usually start as the common type and manifest in this form again during relapses. Tertian fever is more unusual and generally only observed in long-lasting cases, apparently the result of a gradual modification of the

quotidian type.”91

Lutz's reports indicate that he had been putting into practice the experimental program then predominant in so-called exotic pathology, whose introduction Delaporte (1989) attributes to Manson. As the French historian has shown, Laveran's studies had left two questions pending. The first had to do with the nature and function of certain forms displaying long motile filaments, found in extravasated blood; some believed these were bodies undergoing disintegration while others thought they represented a new stage in the parasite's development. The second problem concerned the way malaria spread. Although it was possible to produce the disease by inoculating healthy individuals with a sick person's blood, it did not appear to be contagious. Several hypotheses were suggested. Some believed that parasites penetrated the organism when they ingested stagnant water or inhaled the dust carried from swamplands; others thought the parasites that lived in these swampy areas infected mosquitoes, which in turn infected humans.

In 1894, Manson linked the two questions when he applied the hypothesis of the cycle of Filaria to motile filaments. He conjectured that the forms that appeared only in extravasated blood were flagellated spores, which was the parasite's first stage of life outside the human. Just as occurred in the case of filariasis, a mosquito or other blood-sucking insect would remove haematozoa from a human's blood vessels and then transfer them to water when it died. The parasite would return to the human via water or by air. This hypothesis underlay the research program to which Ronald Ross devoted his inquiries between 1894 and 1898, while exercising his duties as an officer of the Indian Medical Service.

Map of São Paulo, highlighting the area between Moji-Guaçu and

Guarujá. Organized by the Geographical and Geological

Commission, Chief Engineer João Pedro Cardoso. São Paulo, Weiszflog brothers, 1908. São Paulo: Weiszflog irmãos, 1908.

The object of study is infinitesimal and problematic: the extreme

delicacy of the filaments makes observation more difficult, and it

is necessary to find an element whose form and location are not

known. Furthermore, nothing guarantees that this research is

being conducted on an appropriate species. Hence the

strategies Ross devised for overcoming these problems. On the

one hand, [this meant] working with sterile mosquitoes, that is,

from larvae kept in captivity, making it possible to avoid the

complications brought by the invasion of foreign bodies. On the

other, [this meant] paying close attention to the plurality of forms

in which the flagellated bodies could present themselves. This

implied familiarity with insect parasites and with the normal

histology or pathology of the mosquito. (Delaporte, op. cit., p.96-

7, 98)

In the summer of 1897, one decisive observation provided Ross with the position and characteristics of the parasite inside the insect body: he discovered pigmented cells in the stomach wall of mosquitoes fed on the blood of sick people four or five days earlier. Around the same time, MacCallum ascertained that these cells played a role in the parasite's biological reproduction: in studying the crow's haematozoon, he verified that it presented itself in two forms, one masculine (hyaline bodies), and the other feminine (granule-containing bodies). At Manson's suggestion, Ross began exploring bird malaria. To trace the development and final position of the pigmented cells within the mosquito, he performed delicate dissections, daily, and verified that up until the eighth day, the cells grew in size and then opened up and released the filiform bodies. In the end, he came across them in the insect's salivary gland (ibid., p.99-100).

Ronald Ross (1857-1932) (Olpp, 1932, S347).

During that same period, Lutz was opening the bodies of different animals and then comparing their haematozoa with the plasmodium, in an effort to understand how they parasitized their host's organisms. At the same time, in his reports he sought to provide detailed descriptions of the morphology and location of the protozoans found in the blood of birds and humans struck by paludism, emphasizing those aspects that scholars of the disease considered the most intriguing. In 1898, he summarized his conclusions in these terms:

The observed haematozoon almost always had the form of a

plasmodium; four or five times it was accompanied by

crescents, and once we found only semi-crescent shapes.

Where there were crescents, lengthy observation usually

revealed flagellated bodies. We never found segmented forms

and only once did the plasmodia present pigment clumped

together in the center, as if preparing for segmentation … The

plasmodia were always of the type described, with thin,

irregularly distributed pigment in Brownian movement; they

displayed not very accentuated amoeboid movements, reached

or exceeded the size of a red blood cell, and did not segment in

the blood of the peripheral circulation. They did not correspond

precisely to any of the described types but resembled benign

tertian and quartan forms.

It was only in 1897 that Adolpho Lutz quite unexpectedly turned to the issue of its transmission by mosquitoes, as a result of the enigma we are about to describe.

 

The discovery of forest malaria

The railroads were built in São Paulo in the second half of the 19 th century as a direct result of the growth of the coffee industry. Until then goods were moved across land by caravans of mules on journeys that lasted days. As foreign trade expanded, this system became outdated and it became clear that new transportation methods had to be found to get merchandise to the coast more quickly. The solution was a railroad linking the provincial capital and the main coffee production areas to the port of Santos across the Santos or Cubatão mountains, which formed a section of the Serra do Mar mountain range.

The first studies for the railroad date back to the late 1830s. A preliminary project was submitted to English engineer Robert Stephenson, but the proposal was considered premature and was eventually dropped. In 1859, another group of Brazilians, headed by entrepreneur Irineu Evangelista de Souza (1813-89), the Baron de Mauá, was granted a 90-year license by the Imperial Government to build and run a railroad linking Santos to the São Paulo plains and on to Jundiai. In 1860, the São Paulo Railway Company Limited was set up in London and hired two experienced English engineers: James Brunlees and Daniel Makinson Fox. Faced with the difficulty of crossing the steepest parts of the mountain range, Fox put forward the idea of using a funicular system. It comprised four slopes, each with an 8% gradient, which were interconnected by landings. At these landings, fixed power units ran the steel cables that moved the trains up and down the mountains. Brazil's first long-distance railroad, crossing some 140 kilometers, the São Paulo Railway was completed around 10 months before forecast and was officially opened for service on 16 February 1867.

The railroad was built by approximately 5,000 laborers, who were lodged in a campsite at the top of the mountain. When it was concluded, only a few of the workers were kept on to help its running and maintenance; the rest were laid off. The original camp spawned a village called Alto da Serra, now Paranapiacaba, which means “place with a view of the sea” in Tupi-Guarani.

With ever greater amounts of coffee being shipped to Santos and with the growth of inland towns, the railway had to be doubled and a new funicular built, called Serra Nova. Running parallel to the other line, the new line was built using an endless rope, a genial device of counterbalances that controlled the vehicle that was going down at the same time as another was going up in the opposite direction. This meant the trains could cross the mountains without interrupting their journey. The stretch over the mountains was split into five 2-km-long sections, each with a maximum gradient of 8%. Between one landing and the next, the wagons were pulled by a small locomotive called the locobreque. Construction of the second funicular started in

1895, and it was opened on 28 December 1901. 92

In 1897-98, an epidemic of malaria spread among the workers building the new railway in a forest-covered section of the mountains. This environment was very different from the wetland plains usually associated with the disease. “The cases were intermittent benign quotidian tertian malaria,” wrote Adolpho Lutz in his 1897 report. “They were very frequent but not very serious and easily cured by quinine, though relapses were extremely common. They occurred both in the highest part of the mountains and on the mountainsides in very steeply sloping areas destitute of swamps, and they were not observed where the line crossed the mangrove swamps.”

The São Paulo Railway, the state's first, built by Robert Sharpe and

Sons, of London, according to a plan by British engineers James

Brunlees and Daniel Mackinson Fox, hired by the Baron of Mauá.

Photograph by Militão Augusto de Azevedo, 1865 (Walker & Braz,

2001, p.61).

 

Foothills with the engineer's house on the right. Lutz found workers

with malaria in this region (BR. MN. Fundo Adolpho Lutz, caixa

Malária – 23, maço 9).

There were other outbreaks of malaria at worksites for other railroads. Mauá, near Rio de Janeiro, and Guarujá, near Santos, were examples that Lutz cited. In his 1898 report, he merely commented that the quantity of cases in the Santos mountain region could naturally be explained “by the concentration of workers in a normally quite deserted area.” He did not bring the subject up again in subsequent reports. Malaria still remained on the agenda after its mode of transmission was deciphered in 1898-99, but almost always with reference to its most predictable habitats, i.e., plains and swampy valleys.

In 1901, the director of the Bacteriological Institute analyzed 17 positive results, mostly from Rincão. Lutz and his assistant Carlos Meyer investigated more than 50 people with malaria, the former on trips to Conceição do Itanhaem and the latter on visits to Guatapará, Rincão, and Rebouças. They collected large quantities of samples and undertook “an extensive study using a more or less adapted version of Romanowsky's staining method, which yielded many

magnificent preparations.” 93

The inland journeys in São Paulo state continued into 1902, 94 where epidemics of malaria were discovered in Peruibe and soon afterwards in areas near Conceição de Itanhaem and Iguape. Many cases were studied in Batatais, on the banks of the Sapucai River, and in Ribeirão Preto, where the disease was endemic.

During this period, Lutz vaguely alludes just once to the “many observations” he had made about the “coincidence of the three species of mosquito of the genus Anopheles … to which reference

will be made in a special paper on this subject.”95

His study only came to light in 1903, and it was only then that Lutz revealed the complexity of the enigma he had encountered with the outbreak of malaria in the Santos mountains, to which he dedicated so many years solving. And even so, the order of events that led to the discovery of the malaria that spread through the forests is not entirely clear.

The circumstances surrounding the outbreak in question had been different from those generally encountered. Most of the railroad being built between São Paulo and Santos linked the plain slightly above sea level to a peak on the mountain range around 900 meters above sea level, which stood beside even higher peaks. Here, the railroad crossed uninhabited forestland. The sharply sloping hillside could only be crossed using the cable system described earlier. This required that not only the track bed be built but also five engine rooms and a number of tunnels and viaducts to cross the gorges and ravines which different streams ran down. Given the steepness of the slope, there were a great number of waterfalls and no still water, “in the normal sense of the word.”

The first line of the railroad, opened in 1867, was the shortest and also the steepest. Lutz had been informed by eye-witnesses that while it was being built, intermittent fever had spread among the workers, but that the problem had ceased when the works had finished. No further cases had been noted among travelers or the personnel that took the train daily, nor among the few families that lived along the railroad.

When the new line was opened, hundreds of workers received housing in the middle of the forest on ranches that were only interconnected by tracks through the forest. Many cases of intermittent fever once again broke out, initially among those who lived on the ranches in the lower, hotter area, but soon spreading up to the top of the mountain, “often affecting almost all the people on a ranch in just a few days.” Normally, those who were affected only had to take short periods off work because the disease was mild and quinine was widely used to combat it, but relapses were nonetheless frequent.

 

Plans for the Cubatão Mountain railway (BR. MN. Acervo Adolpho

Lutz, caixa 23, maço 9).

Panorama from the Cubatão Mountains (Santos), where Adolpho

Lutz discovered forest malaria – 1, 2, 3, 4, 5 (BR. MN. Acervo

Adolpho Lutz, caixa 23, maço 9).

Lutz examined blood from different workers and found that they did indeed have malaria. Intrigued by the characteristics of the epidemic, which had broken out in an environment so different from that traditionally associated with the disease, Lutz decided to spend a few nights in a house built alongside the old railroad that belonged to an engineer friend of his, whose wife had fallen ill there.

On the very first evening, which came after a terribly hot day, we

were sitting around a lamp when a number of biting insects

appeared. They included Simulium pertinax Kollar, some

relatively harmless Culicidae with which I was familiar, and a

species I had never before seen, which had spotted wings and

an odd perpendicular position when it sucked. Though it was

delicate and small, it was clear that this was a voracious blood-

sucker which landed directly on the people present and on a

dog that also lived there, without buzzing first. The bites of this

mosquito are less painful than those of some other species. In

light of all these factors, many people do not notice them, which

means that this species, which mostly comes out at dusk, is

easy to miss.

I instantly felt sure I had found the mosquito I was after, even

though at that time nobody knew the characteristics of the

malaria transmitter. Soon afterwards, when it was discovered

that they are most likely to be species from the genus

Anopheles, I realized with some satisfaction that the new

species was indeed an Anopheles.

The final comment suggests that Lutz's ‘revelation’ about transmission by anophelines of this as yet unknown form of human malaria was actually written prior to the publication of the ground-breaking work on this topic by Grassi, Bignami, and Bastianelli (1899).

With the suspect species identified, the next step was to find out where its larvae were hatched. He had no doubt that they were aquatic, like other mosquitoes, and it did not take long to discover that in those forests there were few pools of standing water. “The issue was then to find water deposits suitable for them to breed.” Lutz found them “soon afterwards,” his speed in so doing being thanks to his skill as a zoologist and to an important prior experience.

When in Hawaii (1889-92), Lutz had studied the Pandanaceae (Freycinetia arnottii), a plant that collected water in its leaves and served as a habitat for a small crustacean (Orchestia). He was already familiar with the work of Fritz Müller, the first naturalist to study the relationships between animals and water-storing plants: in 1879 and 1880, he had described a small crustacean Ostracoda from the family Cytheridae (Elpidium bromeliarum), whose life cycle took place inside a bromeliad from Brazil. He tried to explain how this exclusive inhabitant of plants moved from one to another, which led Müller to present the first relationship between animals that make

up part of the bromeliad fauna. 96

Camp on the plain where Lutz examined workers with malaria.

 

Currently the site of the Piassagüera station, now abandoned. It was

opened in 1902 as the first stop in the “new mountain” cog railway

line (BR. MN. Fundo Adolpho Lutz, caixa 23, maço 9).

Lutz may well have been familiar with the work of other authors who were starting to investigate this phenomenon (and if he was not, he certainly became familiar with them during his own research). In 1883, Friedenreich described a coleoptera (Pentameria bromeliarum) whose larvae inhabited the water in Brazilian bromeliads. The following year, another coleoptera (Onthostygnus fasciatus) in Mexico was described in plants of this genus (D. Sharp, 1884), while Schimper (1884, 1888) published important papers about the physiology of these plants. In the year in which Lutz started his investigation in the Santos mountain region, F. W. Kirby (1897) showed that bromeliads from Chile harbored butterflies from the family Sphingidae, genus Castnides.

Bromelia plumier. Source: botu07.bio.uu.nl/brom/images/

 

list/bromel/Bromelia%20plumier%2096GR00628%20a.jpg, retrieved

22 June 2005.

If small crustaceans and other animals could live there, “of course mosquito larvae could too,” as Lutz wrote in 1903. “As there were so many bromeliads in the forests, I set to work examining them with high hopes.”

He only found frog larvae in the bromeliads that grew on rocks. The large trees in the area bore a plentiful supply of bromeliads, but their lowest branches were at least ten meters above the ground, well out of the scientist's reach. It would have been pointless to cut down a tree because the water in the plants that lived on them would spill out. Finally, a short while later, Lutz managed to find some more accessible bromeliads and found many larvae of the new Anopheles and of other mosquito species in both of them.

In 1903, after five years’ study, it was clear that “practically all the mosquitoes typical of the forest spend their larval phase in the water in bromeliads.”

In the time that elapsed between his first observations based on “an immediate, almost intuitive conviction” (Gadelha, 1994, p.178) and the publication of his discovery, Lutz designed suitable techniques for collecting larvae and breeding them in a laboratory. He studied the Bromeliad species and their distribution not only in the Santos mountains but also in other areas with a similar ecology. He took interest in all groups of animals that inhabited the water in these plants: tiny crustaceans (Ostracodes, Copepods, Lynceids); the larvae of Tipulidae, culicids of Corethra, Chironimus, and similar nematocers; and the larvae of aquatic coleopteras and amphibians. He noted that hylids and terrestrial planarias liked living in

bromeliads that had both water and land characteristics.97 And above all, he studied the habits of the forest mosquitoes once they reached their winged stage, without restricting himself to the bromeliad species.

He got together a network of collectors for his program and, partly thanks to his growing interest in entomology, he soon reached

remote corners of Brazil and a number of foreign countries.98

“Waldmosquitos und Waldmalaria,” which means forest mosquitoes and forest malaria, was published in Centralblatt für Bakteriologie, Parasitenkunde und Infektions-krankheiten (v.33, no. 4, 1903, p.282-

92),99 dated 16 September 1902, by Lutz himself. The article was the subject of a number of criticisms, and in the U.K. there was a long comment in the Journal of Tropical Medicine (1903, v.6, p.111-23) entitled “Forest Mosquitoes and Forest Malaria.” The Bulletin of the Pasteur Institute gave Lutz's contribution less credit (1903, v.1, p.183); other comments were published in Archiv für Schiffs- und Tropenhygiene (v.7, p.339-40), Münchener medizinische Wochenschrift (v.50, no. 6, p.264), Hygienische Rundschau (v.13, no. 18, p.937-8), Rif. Med. (v.19, no. 15, p.418), and also in Allgemeine Zeitschrift [für Entomologie] (v.8, no. 18-19, p.377), the latter by Paul Gustav Eduard Speiser.

 

Frog of the Hyla claresignata species, which inhabits bromelias,

collected in Teresópolis on 9 November 1929 (BR. MN. Fundo

Bertha Lutz).

Disease-carrying mosquitoes had been studied by doctors prior to this, who had picked up the skills they needed to deal with the biology and the system of Culicidae in practice, at haste, and not always in the most suitable of ways. One of their biggest problems was a shortage of specific knowledge about this group of animals.

As in the most prolific and chaotic phase in the search for pathogenic microbes, in the 1880s and 1890s, the eagerness in the hunt for potential winged transmitters of diseases from 1890 through 1910 enhanced knowledge about Culicidae, but at the same time engendered considerable confusion about identifying and naming the same species. England took the lead in these studies after Ronald Ross's discovery. At the request of the then Prime Minister Joseph Chamberlain, the Royal Society set up a committee to study the control of malaria in the colonies (Howard, 1930). One of its members was Edwin Ray Lankester, director of the British Museum; he suggested a survey be made to identify the different mosquitoes that existed in the world. In response, the British consulates and other government bodies were set in motion to achieve this goal. At the same time, the Museum of Natural History put together a collection of Diptera to provide support for worldwide knowledge in this realm. Frederick Theobald, a zoologist with the South Eastern Agricultural College in Wye, Kent, was appointed by Lankester to be superintendent of the ambitious project.

Adolpho Lutz was one of the researchers in Brazil to be contacted; he received his first news of the project on 24 March 1899, from the British Consulate General. As we shall see in the following book of this volume of his Complete Works, Lutz was to play a crucial role in Theobald's studies. He had already begun his systematic study of Culicidae in 1897 so could send his first shipment to the British zoologist as early as June 1899: “As I was then very busy with my analogous studies … I wrote back sending all my Culicidae, which included more than forty species,” wrote Lutz in 1903. These included mosquitoes from the forest and other species that he

considered new.100 Theobald confirmed the Brazilian collaborator's suspicions, and in his honor gave the name Anopheles lutzii to the new Anopheles collected in the zones where its habitat, the bromeliad, flourished. Another species was called Anopheles albipes.

In a letter to Theobald dated 23 September 1900, Lutz commented on the classification he had made and described the Anopheles lutzii. He had found it “near Santos in forests of … and on the mountainside, with a few, exceptional specimens near São Paulo, probably carried far from the mountainous and forest-covered area by the overflowing river.” Lutz continued:

I have also obtained some specimens from Mr. Schmalz,

collected in Joinville (SC). Usually, the larva grows in

bromeliads, as I suspected long ago, since the imago is

encountered in forests and on steep mountainsides where there

is no other [collection] of water. The larvae and nymph are brick

red. The imago bites men and dogs hungrily at dusk, when the

weather is hot, and enters the dwellings and huts built in the

forests. It was responsible for a number of epidemics of

intermittent fever among laborers employed in the construction

of the railroads. It may also bite by day in the shade.101

When he named that mosquito, Theobald inadvertently gave it the same name that Oswaldo Cruz had given another species of Anopheles, also in tribute to Lutz. In a review prior to 1903, the British entomologist included A. lutzii in the genus Myzomyia, so it was then named Myzomyia lutzii. The species previously described by Oswaldo Cruz was first included in the genus Pyretophorus by Blanchard, and later in the genus Myzorhynchella, created by Theobald.

Since the turn of the century, Oswaldo Cruz and Emil Goeldi (1859-1917) had been involved in the collection and classification of Diptera in Brazil. The former started this work even before he became director of the Manguinhos Serum Therapy Institute and Director General of public health, while the latter, a Swiss zoologist, was the director of the Pará Museum of Natural History and Ethnography in Belém, who published Os Mosquitos no Pará in 1905 (Sanjad, 2003). Carlos Chagas and Arthur Neiva soon joined the project. They came to publish a number of papers describing new species during the first years of the 20 th century in Brazilian journals that did not have international circulation, which made the classification of the specimens more confusing. The work by Oswaldo Cruz, the first in medical entomology, was published in O Brazil-Medico in 1901, the same year as Theobalds first volume.

Drawing of Kerteszia cruzi (formerly Myzomyia lutzii), that transmits

 

forest malaria discovered by Adolpho Lutz (BR. MN. Fundo Adolpho

Lutz, caixa 23, maço 9).

In 1908 (p.53), another important paper about Culicidae was published, this time by American entomologists Frederick Knab and Harrison Gray Dyar. They took the forest malaria transmitter out of the genus Myzomyia and put it back among the species of the genus Anopheles, now as Anopheles cruzii. “It gives us great pleasure to dedicate this interesting species to Dr. Oswaldo Cruz, renowned hygienist and bacteriologist from Rio de Janeiro. The larvae were discovered by Mr. A.H. Jennings in Panamas canal zone, living in the water between the leaves of bromeliads, which seems to be their only habitat.” Unlike Theobald, Knab and Dyar did not recognize either Myzomyia or Myzorhynchella as separate genera of Anopheles. “Furthermore, we have noted the existence of Manghinhosia lutzi Peryassú, which will also need to be named anew should it be ascertained – as we assume it will – that the new

genus 102 Manguinhosia is in no way separable from Anopheles.”

It is now known that Anopheles cruzii is the primary vector of what is known as “bromeliad malaria,” which is found in epidemics along the coast of São Paulo state and endemically from São Paulo down to Rio Grande do Sul state. It transmits malaria to man and is the only

known natural vector of simian malaria in the Americas. 103

But this knowledge did not emerge in a linear progression from the work published by Lutz in 1903. As with Chagas disease, there was a period of interruption and for a long while forest malaria stayed on the sidelines, with its misunderstood theories.

Lutz was not the only author to study the relationship between the epiphytic bromeliads of American forests and their fauna. An exhaustive inventory of these studies was presented in 1913 by Clodomiro Picado Twight in Les broméliacées, considérées comme

milieu biologique 104 . The Costa Rican biologist divided them into three categories: studies whose subject was animals adapted to bromeliads, without taking into consideration environmental conditions; those that looked into only the biology and distribution of the plants; and finally, those that concerned themselves with their relationship to the fauna. Of this latter group, the work by Adolpho Lutz stands head and shoulders above the rest.

This author states, on the one hand, that the Culicidae larvae

are bred by the hundreds in epiphytic bromeliads in Brazil; he

considers that at least one-fifth of the known Culicidae have

bromeliads as their exclusive habitat; by the same token, he

states that their waste does not rot while they remain within

them, but putrefies the moment they are removed from the plant

and placed within a wide-mouth jar (Picado, 1913, p.220).

In tropical forests, especially in intertropical America, epiphytic bromeliads took the place of swamplands. They formed what were, to all intents and purposes, wetlands in the air, and were very different from the environment of standing groundwater. The water in bromeliads constituted a special biological environment. Picado (p.327-9) viewed them as a permanent yet fractioned wetland above the ground, with the water coming from the daily condensation of atmospheric water, and with a cellulosic mud that did not rot, due to the plants’ own activity. It was inhabited by varied fauna, ranging from batrachus to protista, which could be split into two large groups: those animals that only inhabited bromeliads and those that also inhabited other environments. The bromeliad fauna known before Picado's research summed around 100 species. In the list he presented afterwards, the number had reached about 250.

 

Bromelia of the Vriesea incurvata species, frequently found in the woodlands of the Rio Verde estuary, Juréia Ecological Reserve, São

Paulo. Photograph by Erich A. Fischer (Revista da Sociedade

Brasileira de Bromélias, v.3, n.2, 1996, p.24). Many specialists helped him determine these animals, including Knab, Coquillet, and D. Keilin, who helped with Diptera, and Dyar,

who helped with Lepidoptera larvae. 105

The many authors listed by Picado described batrachus (Ohaus, 1900; L. Stejneger, 1911; C. Werkle, 1910); planarias (P. M. de Beauchamp, 1912, 1913); oligochaetes (W. Michaelsen, 1912); Odonata larvae like those of the genera Megaloprepus and Mecistogaster (Barret, 1900) and others (Knab, 1907; Philip P. Calvert, 1909); Orthoptera of the family Blattidae (R. Shelford, 1912) and others (A. Borelli, 1911); Diptera tipulids (Ch. P. Alexander, 1912), Rhyphidae and Eristalinae (F. Knab, 1912 and 1913), Borboridae (Knab and Malloch, 1912); Coleoptera such as the larvae of Helodidae (Knab, 1913; Picado, 1913) and others (H. Scott, 1912); Hemiptera (W. L. Distant, 1912); and butterflies (Walsinghan, 1913) and similar animals. Knab (1913) had also just described a Culicidae, the Megarhinus iris, which had been bred by F. W. Urich in Trinidad (Picado, p.221). Adolpho Lutz was the author of the most comprehensive study yet into forest mosquitoes, and Picado attributed the description of the disease-transmitting species to nobody else. It was certainly the Brazilian zoologist's work that formed the basis for one of his conclusions, set out as follows:

Knowledge of bromeliad fauna explains the existence of certain

infectious diseases (malaria, filariasis, etc.,) in the regions of

America that have no wetlands. The bromeliads shelter the

intermediate hosts (Culicidae, copepods, etc.) of parasites,

whose life cycles end with man or with some wild animal,

whether simiae or not. This is how these diseases persist, in the

absence even of man or of swampland. (Picado, 1913, p.329)

Adolpho Lutz's discovery had been confirmed by other important peers, above all by those researchers at the Oswaldo Cruz Institute who had been asked for help by businessmen who were investing in railroad construction and hydroelectric power generation in Brazil's malaria zones. In 1906, Carlos Chagas wrote about an outbreak of malaria at some 700 meters above sea level in a place where it seemed impossible for the Culicidae to live: “The fact caused us some surprise, which then evaporated when we discovered the Myzomyia lutzi in the region. This was on one of the ridges of the Serra do Mar mountain range, where the Companhia Docas de

Santos set up an important electricity facility.”106 At the same time, in Trinidad, F.W. Ulrich, and later Lassale and De Verteuil, also highlighted the role of forest mosquitoes [Anopheles (k) bellator] in transmitting malaria (Gadelha, 1994).

In the same year that Lutz published his work, Galli-Valério (1903) encountered oocysts in the stomach of specimens from Paranaguá (PR); five years later, Stephens and Christopheres (1908) included Myzomyia lutzi among the proven malaria vectors, since they found what they called ookinetes in it, which are malaria parasites at the stage prior to the zygote, when they take the form of tiny wriggling worms.

Even though this species was considered “dangerous,” Arthur Neiva (1909, p.76) believed the evidence that it transmitted the disease was inconclusive. In his view, the poor conditions in which the species were found in Italy after being preserved in alcohol and then sent to Galli-Valério made it impossible to know whether the oocysts he had encountered were of human or bird origin, and so the finding only increased the “likelihood that this anopheles transmits malaria.” However, the ookinetes seen by Stephens and Christophers could easily be detected in “any anopheles that has fed on gametocytes under transmission conditions; it should not be concluded from this discovery that the ookinete can always become a sporozoite.”

Such provisos signaled the need for a more comprehensive research program, but the growing acceptance of Anopheles lutzi as the protagonist of a special type of malaria transmission came to a sudden halt in the early years of the 1910s, and it was only in the 1940s that forest malaria reemerged as a subject of study and was targeted for sanitation control.

The controversy with Knab and Dyar and its

upshot

Gadelha (1994) and authors he quotes (Downs and Pittendrigh, 1946, 1949; Rachou, 1946) attribute the prolonged ostracism to criticisms made in 1912 by Frederick Knab. Though these criticisms were contained in articles signed only by this zoologist from the U.S. Department of Agriculture's Bureau of Entomology, they were endorsed by entomologist Harrison Gray Dyar.

Born in Wurzburg, Bavaria, on 22 September 1865, Frederick Knab emigrated with his family to the United States when he was eight. His father, Oscar Knab, was a printer and painter, and one of his brothers had served as a painter in the Bavarian court. Frederick Knab himself showed some artistic talent and after spending a time studying in Germany, he dedicated himself to landscape painting. His interest in natural history and insect life inspired him to take part in an expedition to the Amazon from 1885 to 1889. Later (1903-04), he worked as an illustrator for entomologist Stephen Alfred Forbes. The collaboration then set up with Leland Ossian Howard and Harrison Gray Dyar led to The Mosquitoes of North and Central America and the West Indies, a four-volume work published by the Carnegie Institute in Washington between 1912 and 1917. Much of the lengthy study was based on investigations performed in tropical and subtropical countries by Knab and Dyar. The former was also the author of a number of the illustrations included in the work. Dyar, for his part, took charge of the taxonomy part, and thanks to his comfortable financial status, he himself financed a number of the collection trips.

Harrison Gray Dyar (1866-1929) (Howard, 1930).

In 1906, Knab joined the U.S. Department of Agriculture's Bureau of Entomology. After the death of Daniel William Coquillett (1856-1911), he took over the curatorship of the collection of Diptera at the U.S. National Museum.

The Lepidoptera section had been curated since 1894 by Dyar, who was also an assistant at the Bureau of Entomology (1904-16) and a captain in the Sanitation Department of the U.S. Army (1924-29). One of the leading taxonomists of his time, he wrote what came to

be called Dyar's Rule, 107 by which different stages of life of a Lepidoptera could be determined by its head measurement. He published a number of articles about the North American species and also studied mosquitoes, especially in their larval stage.

When Knab died on 2 November 1918 of an undiagnosed disease he had contracted on a trip to Brazil, Dyar started researching mosquitoes in their adult phase. His studies into the masculine genitalia of the Culicidae were very important in classifying the group. He also studied the families Simuliidae, Psychodidae, and Chaoboridae.

Not only did Dyar often publish papers in his country's leading entomology journals, but he also set up lnsecutor lnscitiae Menstruus, which brought out fourteen volumes between 1913 and 1927. He died on 21 January 1929, having engaged in heated controversies with some of the leading names in American entomology, including Coquillet, J. B. Smith, and Henry Skinner.

The clash with Lutz started with the publication of an article by Frederick Knab (1912a) in Journal of Economic Entomology, in which he analyzed the transmission of diseases by blood-sucking insects. The same theme was also the subject of a written communiqué at the same time at the Entomological Society of

Washington. 108 At this session, when Howard set Lutz's theory about forest malaria against Knab's argument, the latter declared together with Dyar that the Brazilian zoologist had wrongly interpreted the facts that had led him to formulate his theory.

In the article in the American Association of Economic Entomologists’ publication, Knab stated that the studies into the role of blood-sucking insects in disease transmission that had recently been started were overwhelmingly vague, chaotic, and supported by questionable data collected by investigators with little biological training. “Since the discovery that certain blood-sucking insects are secondary hosts for pathogenic parasites, practically every insect that sucks blood either habitually or occasionally has been viewed as a potential disease transmitter or suspected of being such.”

He went on to say that only insects that were closely associated to man and that regularly sucked blood repeatedly could host and transmit a parasite from human blood. It would not be enough to do this from time to time, like the forest-dwelling mosquitoes studied by Lutz. Other prerequisites were their relative longevity, and continuous feeding on blood and reproduction. Only thus would there be enough individuals for the life cycle of the parasites they hosted not to be interrupted, including the definitive host – man – who would then be struck by an endemic disease.

These criteria were equally applicable to mosquitoes and any other blood-sucking insect. As Tabanidae and Simuliidae did not meet these criteria, they could be disregarded as disease transmitters. Actually, few insects would meet the requirements set by Knab: the Aëdes calopus, synonymous for Stegomyia fasciata and an intermediate host of the yellow fever organism; the Culex quinquefasciatus, transmitter of filariasis and dengue fever; and the Triatoma (Conorhinus) megistus, recently identified by Carlos

Chagas as a transmitter of a dangerous trypanosomiasis in Brazil.109

The Anopheles was a genus that did not seem so well adapted to humans, but in Knab's view, this impression arose from a dearth of knowledge about the habits of its different species. The evidence available at the time suggested that malaria transmitters inhabited areas near where man lived, while those that did not feed regularly

on blood were harmless. 110

Adolpho Lutz's ideas about mosquitoes and forest malaria contradicted such theories. Yet in Knab's article published a decade after the discovery, he stated his conviction that the Brazilian had “got his facts wrong.” Most likely, the Anopheles he had identified had had nothing to do with the outbreak of malaria among the workers camped in the Santos mountains.

 

Triatoma megistus, the “red barber,” drawn by Castro Silva (Chagas,

1909, estampa 9).

It is well known that in the tropics most people, even when they

appear healthy enough, have latent malaria. When such an

individual undergoes physical stress, such as fatigue, exposure

to the elements, or physical exertion, the disease is manifested

… The men already carried latent malaria when they reached

the area, and the exertion and exposure associated with their

work caused the disease to break out.

In the rebuttal published in the Proceedings of the Entomological Society of Washington, Lutz (1913a) struck out against this argument. “If such an etiology of a typical epidemic was possible, which no knowledgeable person could admit, the people that lived here and that were interested in discovering the cause would not have waited until two lay people thought this up, and I would not give myself the trouble of seeking a satisfactory explanation for the enigma.” The Brazilian zoologist reminded his critic that the climate in the area in which his studies took place was not in the least tropical, nor was it in the areas where the people who had contracted the disease came from. The huge effort they had made to distinguish typhoid fever and other fevers from malaria so as to gainsay the incorrect concept of “São Paulo fevers” had shown that the disease caused by the plasmodium discovered by Laveran was highly localized, “even in tropical countries. Actually, it is not to be found in many places where Anophelines dwell, which themselves are far from being ubiquitous.”

Lutz further argued that his findings had been confirmed by a number of scholars, in particular Carlos Chagas, “which is extremely important, since he observed a number of malaria epidemics in different places and studied the Anophelidae present there.” There had been records of other epidemics of malaria in places without wetlands but with a profusion of epiphytic bromeliads.

Observations made in different forested areas of the Serra do Mar mountain range that had characteristics similar to those described in 1903 by Lutz had led to the generally accepted belief in Brazil that large engineering projects in such environments would inevitably be accompanied by outbreaks of malaria. However, no sign of the illness had been found in worksites in dry areas in Campos and in inland forests that had no bromeliad anophelines.

It cannot be denied that some of the workers hired for these works were individuals that had chronic malaria, but they did not have a healthy bearing, and as Knab supposed, they could easily be identified and discounted.

Going further with his argument against his rival's theoretical assumption, Lutz stated that two malaria transmitters in Brazil – Cellia albimana and, most importantly, Cellia argyrotarsis – were common in uninhabited areas, moving closer to human habitations only in swampy areas. “The fact that they neither want nor prefer human blood is demonstrated by the well-known fact that they prefer the horse to the horseman … The same applies to all other species of Anopheles.”

People who entered areas where large animals were rare naturally attracted mosquitoes, and if they stayed there long enough,

the epidemic [would] accompany the growth of the infection

among the mosquitoes, and they themselves [would] grow in

numbers thanks to the easy feeding. It is a well-established fact

that a species can become an excellent intermediate or

definitive host of a parasite new to a region because the host for

the following stage was only recently introduced.

It is in this paragraph that the crux of the matter lies. Knab held that malaria, yellow fever, and other “parasitic” diseases were transmitted only by blood-suckers that were already accustomed to human blood. Knowledge about the different species capable of performing this role grew considerably at the time, but the system Knab adhered to was conservative, almost static. Lutz had perceived the chance of humans being involved in existing or emerging cycles in the wild, and not only for malaria. In a later communiqué – the counter-rebuttal to Knab's second article – the Brazilian scientist stated:

Messrs Dyar and Knab believe that mosquitoes that have never

been in contact with man cannot transmit disease. One must

place men in totally uninhabited areas to test his thesis. Overall,

this is rather difficult, but it so happens that in Brazil roads and

railroads have been built under such conditions, and there is

almost always a malaria epidemic. Epidemics of Leishmaniasis

skin sores have also been noted in absolutely deserted areas,

correctly attributed to transmission by Phlebotomus. I have also

witnessed a small epidemic of yellow fever among people who

lived in a place where one might expect there to be forest

mosquitoes. All this shows that the theoretical considerations

have not been respected by the facts, and all that is needed is

for the transmitter, whatever its past may be, to belong to a

category in which the parasite can develop; then it must have

repeated access to human beings, some infected and others

without immunity. As the development process takes time, its life

cannot be very short. For this reason, it is a favorable condition

for it to be egg-laying (Lutz, 1913b).

In his response to Lutz's first rebuttal read by Dyar at a session of the Entomological Society of Washington, Knab (1913a) had offered his mea culpa for the dogmatic tone he adopted in his first paper, and for his arrogance in putting forward explanations at such a distance in geographic and temporal terms from the problem studied by the Brazilian zoologist. “Personally, Dr. Lutz's writings have inspired me greatly, and it was in no way my intention to discredit him.”

After rereading his paper and its rebuttal, he had reached the conclusion that they were in agreement on all the points except one:

I am not inclined … to admit that a species of Anopheles which

is only found in uninhabited forests, and which normally could

not have access to human blood, should all of a sudden become

the host for a parasite of human blood. Certainly this could

occur, and maybe it is just this that is in question, but in my view

it would be so unusual as to require extremely conclusive proof.

Knab and Dyar had three hypotheses to explain the outbreak observed by Lutz. First, that he had not identified the true transmitter. Second, that the disease had been transmitted by Anopheles lutzii from a latent case among the workers; after a period of incubation, first in the mosquito and then in man, it had spread among humans as a consequence of bites by infected A. lutzii. Third, that there was a form of malaria among the wild animals that inhabited the forest which was transmitted by A. lutzii; when humans had entered the area, they had been exposed to bites by mosquitoes that had previously been infected by wild animals, and had developed the disease originated from them.

As Knab and Dyar themselves considered their second and third hypotheses implausible, they were convinced that Lutz had made some mistake, as explained in the first hypothesis.

In a short investigation trip, Dr. Lutz found one single species of

Anopheles at the location and immediately concluded that it was

responsible for the outbreak of malaria … He supposed that no

other species of Anopheles could be present because it seemed

to him that there was no suitable breeding ground except for the

bromeliads.

In justifying his “incredulity,” Knab turned to his own collection experiences in regions whose characteristics he considered similar to those encountered by the Brazilian zoologist. He had found two anopheline species in small pools in a mountain riverbed, two of which (A. argyritarsis and A. eiseni) occurred in southern Brazil. In Cordoba, Mexico, he had collected larvae in a canyon which was ‘washed’ by flash floods after each heavy rainfall.

Knab believed that the relationship between the malaria parasites and certain Anopheles species depended upon a highly delicate physiological adjustment. Of those that fed on blood from the same source in a given location, some were efficient hosts for the parasites, while others simply digested them together with the blood. Generally, the most common Anopheles in a region was the one that served as host, but it was not always easy to estimate the relative abundance of different species in a place, since some were more easily spotted than others, some better at hiding in rooftops, for example, or camouflaging themselves with objects of the same color.

With his line of argument, he aimed to show that Adolpho Lutz had failed to notice other anopheline species in the water that existed in

the Santos mountains.111 The American entomologist believed there may be another source of error in his theory.

The question arises naturally: how completely and for how long

were the laborers confined to the forest habitat? Did they not

take holidays, either individually or in small groups, away from

that area or pay night visits to taverns and places of pleasure

situated nearby? What we know of the habits of Homo tends to

give us reason to suspect as much!

The Santos Mountains in the first half of the twentieth century.

Source:

www.portocidade.stcecilia.br/fotos/santos_primeira_metade_sec_xx/

anchieta_imigrantes/g/serradesantos.jpg, retrieved 22 June 2005.

The third hypothesis that may explain Lutz's discovery seemed to Knab and Dyar no more than an interesting possibility.

There are no known material organisms that inhabit wild animals

and that can be transferred to man, though it seems plausible

that there may exist monkey parasites that can be transmitted

by forest Anopheles and that man may be susceptible to this. If

such a relationship does exist, it could be demonstrated by

means of a suitable study, but I consider that we do not have the

right to invoke it as an explanation for the present case based

on no more than its possibility.

What was left, then, was Lutz's claim that a totally “wild” Anopheles species had become an efficient host for the parasite of human malaria. In Knab's view, this seemed “so unlikely that no other evidence except for a demonstration of the presence of the parasites in the mosquito's salivary glands would make [him] accept it.”