The causation and importance of nervous lesions in American trypanosomiasis

Bull. Org. mond. Sant '1970, 42, 739-743 Bull. Wid Hithi Org.J The Causation and Importance of Nervous Lesions in American Trypanosomiasis F. KOBERLE l The final cause of nerve-cell destruction during infections with Trypanosoma cruzi has not yet been definitively established. It seems that a cytotoxic or cytolytic substance con- tained within the leishmania forms is probably liberated after their disintegration and acts, mainly at a short distance and in high concentrations, on the ganglion cells in the vicinity of the ruptured pseudocysts. Recent studies with the electron microscope favour this hypothesis. The destruction of nerve cells in the central or perpipheral nervous systems or in both is responsible for the so-called " late manifestations" of Chagas' disease, which therefore represent " neuropathies " or Chagas' syndromes, i.e., sequelae of the acute phase of the T. cruci infection. Nervous cell lesions in the acute phase of Chagas' disease were described by Vianna (1911). He observed in human cases where parasites had metas- tasized into the central nervous system " a strong reaction which leads not rarely to a destruction of nerve cells " in the vicinity of ruptured pseudocysts. Moenckeberg (1924) mentioned severe degenerative lesions of the ganglion cells of the heart during the acute disease in dogs. However, these lesions have been forgotten or overlooked in Chagasic cases since these first observations. When such lesions were recorded, in cases of megaoesophagus for example (Amorim & Correia Neto, 1931 ; Etzel, 1934; Vasconcelos & Botelho, 1937; etc.), they were attributed to other infectious diseases or to avita- minosis B1. When the present author stressed the ganglion cell destruction during the acute phase of Chagas' disease, and its importance for the so-called " late manifestations" of the Chagasic patient (Koberle, 1956), the problem again became current. CAUSE OF NERVOUS LESIONS IN AMERICAN TRYPANOSOMIASIS From systematic investigations in human cases of Chagas' disease and of experimentally or naturally infected animals, it was concluded that, in the acute "Head, Department of Pathology, Faculty of Medi- cine, University of Sao Paulo, Ribeirao Preto, Brazil. phase, destruction of ganglion cells occurs in the vicinity of ruptured pseudocysts. As these lesions appeared after the disintegration of the leishmania forms, the presence of a neurotoxic or neurolytic substance liberated by the disintegration of the leishmania forms was postulated. Only ganglion cells in the immediate vicinity of the ruptured pseudocysts show severe alterations, indicating that this hypothetical neurotoxic substance acts at a very short distance or in high concentration. In experi- ments carried out in dogs with intracerebral inocula- tion of a suspension of macerated culture forms of Trypanosoma cruzi, local lysis of the nervous tissue in the brain was obtained. Heating the suspension above a temperature of 100°C for 5 minutes abolished its neurolytic activity (Koberle, 1956). The experi- ment was repeated by Eichbaum (1959) who, however, obtained only a slight local reaction or none. Negative results were also observed by Oliveira & Meyer (1959), who inoculated trypanosomes into a nerve cell culture of chicken embryo brain, but this negative result is not conclusive because chickens are not susceptible to T. cruzi infection. J6rg (1964) also was unable to demonstrate neurotoxic activity by injecting a suspension of culture forms of T. cruzi intravenously into rats, rabbits and dogs. The same experiment had been performed earlier by Muniz & Azevedo (1947) and necessarily failed because the toxic substance, as already emphasized, acts only at a short distance or in high concentration. Russian investigators (Klyueva & Roskin, 1946; Klyueva, 2513 739- F. KOBERLE 1947) have demonstrated an endotoxin with a cancer- olytic action, but Hauschka & Goodwin (1948) could not verify its existence. Coudert (1958) suggested that enzymatic activity of this cancerolytic substance could interfere with the metabolism of ribonucleic acid. In fact, the exact action of the toxic substance is still unknown. It is noteworthy that Chagas (1928) postulated the existence of a toxin, and Torres (1941) suggested a "noxin ", to explain certain lesions in the acute phase of the disease. Based on histological investiga- tions, Alvarenga (1960) believed in the presence of a cytotoxin, because the occurrence of many leish- mania forms in a circumscribed area and their sub- sequent disintegration may produce degeneration and necrosis of any type of cell. MacClure & Poche (1960) studying experimental acute Chagas' myo- carditis in white mice by means of electron-micros- copy, found lesions of the heart muscle cells which they interpreted as degenerative lesions produced by a toxin of the disintegrated leishmania forms. As the destruction of nerve cells in the acute phase of Chagas' disease is today generally accepted as having been proved, but the existence of a toxin has not yet been demonstrated, other attempts have been made to explain the mechanism of ganglion-cell destruction. One of these tries to explain the lesion through the intense inflammatory reaction around the ruptured pseudocysts (Dominguez & Suarez, 1962; Andrade, 1968). Nerve cells, especially the peripheral nerve cells, are very resistant to inflamma- tions of any type. Perhaps one of the best examples of such resistance is in chronic ulcerative colitis in which the inflammatory infiltration is extremely intensive throughout the wall of the large intestine, but the ganglion cells of the plexuses are perfectly preserved. As already stressed, the degenerative lesions of the nerve cells appear immediately after the rupture of the pseudocysts, before the inflam- matory reaction appears. It is a very precocious reaction; therefore, the subsequent inflammation cannot be the cause of this nerve-cell lesion. Another hypothesis is that of the direct destruc- tion of the nerve cells through the parasitism of the nerve cell (Okumura, 1966). Investigations have been performed on more than 100 000 ganglion cells from mice, rats and dogs in the acute phase of experimental Chagas' disease and only 20 parasitized ganglion cells have been found. In chronic human cases no parasitized nerve cells were found among 350 000 ganglion cells (Koberle & Alcantara, 1960); therefore, it seems very unlikely that this mechanism could be responsible for the destruction of nerve cells. Immunoallergic mechanisms have also been suggested as the cause of nerve-cell lesions (Muniz, 1967). It has been demonstrated that by the seventh day of acute infection the destruction of ganglion cells in the vicinity of the ruptured pseudocyst can be observed. Since antibodies in sufficient quantity have not yet been produced by the organism at this early stage of the infection, the immunoallergic mechanism for nerve-cell lesions must also be dis- carded. Tafuri (1968), in performing detailed electron- microscopic studies on heart ganglia of white mice experimentally infected with T. cruzi, was able to demonstrate the presence of leishmania forms in the Schwann cells, and lytic lesions of these cells and the adjacent ganglion cells after the disintegra- tion of these leishmanias. This mechanism, well illustrated by ultrastructural studies, is in accordance with the features disclosed by the light microscope and suggests a destruction of nerve cells through the agency of a toxic substance existing within the leishmanias and liberated after their disintegration. Recently, Seneca (1969) reported on a " chagas- toxin", a lipopolysaccharide, producing in mice degenerative lesions of the liver, heart and kidneys but not of the central nervous system. As this sub- stance was innoculated by intraperitoneal injections, and not locally into the nervous system, the results are not convincing. There is, without doubt, a destruction of nerve cells after the rupture of the parasitized host cell and the disintegration of the leishmanias. It is obvious that this destruction occurs principally during the acute phase of the disease, when the parasitism is very intense and the specific defence of the organism is not yet mobilized Counting all the ganglion cells of the rat heart, Alcantara (1959) verified a destruc- tion of more than 80% of the ganglion cells in the acute phase of a T. cruzi infection. As it is believed that the nervous lesions are of decisive importance for the future behaviour of the organism, Koberle (1957) was of the opinion that " the destiny of the Chagasic patient is determined in the acute phase of his disease ". IMPORTANCE OF THE NERVOUS LESIONS IN AMERICAN TRYPANOSOMIASIS Chagas' disease was considered until 1956 as an infectious disease which begins with an acute febrile 740 CAUSATION AND IMPORTANCE OF NERVOUS LESIONS IN CHAGAS' DISEASE and septicaemic phase, followed by a chronic afebrile and apparently asymptomatic phase. In this chronic phase, repeated metastasis of parasites into the heart muscle, with inflammatory reactions after the rupture of pseudocysts, leads to a chronic Chagasic myocarditis, which frequently causes the death of the patient by heart failure. Since 1956, two different pathological processes have been distinguished in American trypanosomiasis (Koberle, 1957). (1) Chagas' disease itself, characterized by an acute septicaemic phase, in which, besides the well- known inflammatory reactions, severe lesions of the nervous system appear. After the development of the specific defence of the macro-organism, this acute phase turns into a chronic one, with the extremely rare presence of parasites in the circulating blood and tissues. (2) Chagas' syndromes, or so-called " late mani- festations ", these are the results of more or less marked destruction of ganglion cells (which occurred in the acute phase) in the central and or peripheral nervous systems or in both. A subject of disagreement during many decades in Brazil was the endemic megaoesophagus and its etiology in Central Brazil. Only a few physicians in the hinterland believed in an infectious etiology and fewer still considered the possibility of a link with Chagas' disease. However, Chagas (1916) reported a dysphagia which appeared during the acute phase of Chagas' disease or during the recovery period and he thought that this dysphagia might be the begin- ning of mal de engasgo (megaoesophagus), so frequent in those areas where Chagas' disease is endemic. It has been demonstrated that megaoesophagus is really caused by T. cruzi infection through destruc- tion of the intrinsic ganglion cells during the acute disease (Koberle, 1955). In further investigations, it has now been shown that other dilatations of hollow muscular organs (megacolon, megaduodenum, mega- cystis, bronchoectasia, etc.) have the same feature in common, i.e., a marked diminution of the number of ganglion cells of the instrinsic plexuses, caused by acute T. cruzi infection. The chronic Chagasic heart also shows a similar denervation. Numerous clinical investigations have revealed through the mecholyl test the denervation of Chagasic organs with and without morphological manifestations. Based on quantitative studies of 200 hearts, 200 oeso- phagi, 100 colons and 50 bronchi of chronic Chagasic patients, with and without morphological manifesta- tions in these organs, the limits of denervation tolerance for the heart, large intestine, bronchi and oesophagus have been established (Koberle, 1962): (1) heart, 25%; (2) colon, 55%; (3) bronchus, 75%; (4) oesophagus, 95%. Comparative studies of cases of megaoesophagus from Europe revealed the same intensity of denerva- tion in the entire organ as found in Chagasic mega- oesophagus. There exist more than 30 theories about the pathogenesis of megaoesophagus, but today the great majority of investigators have accepted denervation as being responsible for the syndrome. Generally, many years pass before the functional disorder leads to impressive hypertrophy and dilatation. This fact explains the latent interval between the acute phase-in which the ganglion cells are destroyed-and the final stage of megadolicho- esophagus. It is believed that the essential destruc- tion of the nervous system, which decides the future of the patient, occurs in the acute phase. Besides the already mentioned experimental results, there is also chemical evidence that nerve-cell destruction occurs in the acute phase in man. One illustration is the case of a child aged 9 months who, after a severe acute infection, could no longer swallow, or defecate except after an enema. Heller's cardiomyotomia was performed twice. After the last surgical interven- tion, the child died, and the autopsy revealed a megaoesophagus and a megacolon which had developed during 10 months. Counting ganglion cells in three levels of the oesophagus disclosed that in the upper third, there was 1 nerve cell (normally 700), in the middle third there were 3 ganglion cells (normally more than 1000) and in the lower third there were 2 ganglion cells (normally more than 1500). This corresponds to a denervation of 99.9%. In the colon also a denervation of more than 90% was found. It is obvious that this enormous denerva- tion was not caused in the 9 months after the acute phase, but during the acute phase, because the symptoms were present immediately after the acute phase. Thus the impressive degree of denervation explains the extremely short interval between destruc- tion of ganglion cells and development of morpho- logical manifestations. In the chronic Chagasic heart, a more or less marked chronic myocarditis can nearly always be found, and this is the reason why, even today, many investigators still believe that the chronic cardio- pathy, with its peculiar morphological features and singular symptomatology, is caused by this chronic inflammatory process. However, Oliveira (1968) 741 742 F. KOBERLE was able to reproduce electrocardiographic changes, the morphological alterations and even the " chronic myocarditis " of Chagas ' cardiopathy by inoculating large doses doses of catecholamines, thereby proving the neurogenic origin of Chagas' heart disease. The present author believes that the denervation of the heart is the essential, but not the unique, factor responsible for the chronic Chagasic cardiopathy. Time, overload, stress and a chronic myocarditis also influence the evolution of the heart disease. Chagas (1913) described more than 200 cases (mainly children) with central nervous system manifestations, which he considered to be sequelae of acute Chagas' disease. The present author believes that Chagas was correct and that a basic morphological feature of these sequelae is fewer gan- glion cells in certain areas of the central nervous system. This reduction in the number ganglion cells in the central nervous system was demonstrated in the spinal cord by Schwartzburd & Koberle (1959) and in the cerebellum by Brandao & Zulian (1966). In spite of some contrary opinions, the present author is convinced that the importance of Chagas' disease lies in the destruction of nerve cells in the acute phase of the infection. This point of view is a fundamental one, because it provides a completely different orientation to the treatment of this wide- spread disease. Chagas' disease is not a problem of curative medicine but a challenge for preventive medicine. RE1SUMEt PATHOGENIE ET IMPORTANCE DES LESIONS NERVEUSES DANS LA TRYPANOSOMIASE AMERICAINE La cause exacte de la destruction des cellules nerveuses au cours des infections 'a Trypanosoma cruzi n'a pas encore ete 6tablie avec certitude. I1 semble qu'une substance cytotoxique ou cytolytique pr6sente dans la forme leishmanienne soit lib6r6e apres d6sagregation du parasite et agisse, surtout 'a faible distance et a concentra- tion 6lev6e, sur les cellules ganglionnaires au voisinage des pseudokystes d6sagr6g6s. Des etudes recentes au microscope electronique sem- blent appuyer cette hypothese. C'est a la destruction de cellules du systeme nerveux central et/ou periph6rique que sont imputables les * manifestations tardives * de la maladie de Chagas, qui correspondent par cons6quent a des e neuropathies > ou syndromes de Chagas, c'est-a-dire A des sequelles de la phase aigue de l'infection a T. cruzi. REFERENCES Alvarenga, R. J. (1960) Lesoes de tecido adiposo na fase aguda da doenca de Chagas experimental, em camun- dongos, Inaugural dissertation in the Faculty of Medi- cine, University of Minas Gerais, Brazil AlacAntara, F. G. (1959) Z. Tropenmed. Parasit., 10, 296-305 Amorim, M. F. & Correia Neto, A. (1932) An. Fac. Med. S. Paulo, 8, 110-127 Andrade, Z. (1968) Anatomia patologica da doenca de Chagas - curso sobre a doenca de Chagas na Facul- dade de Medicina de Minas Gerais. In: Romeu Can- gado, J., ed., Doenca de Chagas, Belo Horizonte Brandao, H. S. J. & Zulian, R. (1966) Rev. Inst. Med. trop. S. Paulo, 8, 281-286 Chagas, C. (1913) Nouv. Iconogr. Salpet., 26, 1-8 Chagas, C. (1916) Mem. Inst. Osw. Cruz, 8, 37-60 Chagas, C. (1928) Rev. esp. Med. Cirug. Guerra, 11, 15-18 Coudert, J. (1958) J. mid. Lyon, 5, 217 Dominguez, A. & Suarez, J. A. (1963) Z. Tropenmed. Parasit., 14, 81-85 Eichbaum, F. (1961) Pesquisas s6bre a presenCa de subs- tdncias toxicas em culturas de Trypanosoma cruzi. In: Anais do Congresso Internacional sobre a Doetifa de Chagas, 1959, Rio de Janeiro, vol. 2, pp. 479-491 Etzel, E. (1934) An. Fac. Med. S. Paulo, 10, 383-395 Hauschka, T. S. & Goodwin, M. B. (1948) Science, 107, 600-607 JMrg, M. E. (1964) Bol. chil. Parasit., 19, 84-87 Kluyeva, N. G. (1947) Amer. Rev. soviet Med., 4,408-414 Kluyeva, N. G. & Roskin, G. (1946) Amer. Rev. soviet Med., 4, 127-129 Koberle, F. (1955) Rev. paul. Med., 47, 643-661 Koberle, F. (1956) Zbl. allg. Path. path. Anat., 95, 468- 475 Koberle, F. (1957) Rev. goiana Med., 3, 155-180 Koberle, F. (1962) Wien. klin. Wschr., 74, 144-151 CAUSATION AND IMPORTANCE OF NERVOUS LESIONS IN CHAGAS' DISEASE 743 K3berle, F. & Alcantara, F. G. (1960) Hospital (Rio de J.), 57, 1057-1062 MacClure, E. & Poche, R. (1960 Virchows Arch. path. Anat., 333, 405-420 Moenckenberg, J. G. (1924) Die Erkrankungun des Myokards und des spezifischen Muskelsystems. In: Handbuch der Speziellen pathologischen Anatomie und Histologie, Berlin, Springer, vol. 2, pp. 426-486 Muniz, J. (1967) Hospital (Rio de J.), 72, 29-54 Muniz, J. & Azevedo, A. P. (1947) Hospital (Rio de J.), 32, 165-188 Okumura, M. (1966) ContribuiVdo para o estudo das lesc8es dos neur6nios do plexo mienterico do colo na molestia de Chagas experimental no camundongo branco (Mus musculus L.), Inaugural dissertation in the Faculty of Medicine of Sao Paulo, Brazil Oliveira M., M. & Meyer, H. (1959) Hospital (Rio de J.), 55, 899-903 Oliveira, J. S. M. (1968) A patogenia do aneurisma da ponta na cardiopatia chagdsica, Inaugural dissertation in the Faculty of Medicine of Ribeirio Preto. Brazil Schwartzburd, H. & Koberle, F. (1959) Z. Tropeiiled. Parasit., 10, 309-314 Seneca, H. (1969) Trans. roy. Soc. trop. Med. Hig.. 63, 535-539 Tafuri, W. L. (1968) Rev. Ass. med. Minas Gerais. 19. 3-39 Torres, C. B. M. (1941) Mem. Inst. Osw. Cru:., 36, 391-404 Vasconcelos, E. & Botelho, G. (1937) Cirugia do newgae- sofago, Sio Paulo Vianna, G. (1911) Mem. Inst. Osw. Cruz, 3, 276-293