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An historical review is given of American visceral leishmaniasis (AVL),

American cutaneous leishmaniasis (ACL) in Brazil is caused by a variety of dermotropic Leishmania species and the greatest diversity of these parasites is to be found in the Amazon Region.Transmission of the causal agents involves different species of phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) in close relationship with the mammalian reservoir hosts of the parasites, with the consequent formation of a number of different transmission cycles throughout the country. The data from ecological and epidemiological studies on the different species of the subgenera Viannia and Leishmania, together with those from experimental laboratory transmissions, have either suggested or definitely indicated certain species of sand flies as being responsible for the transmission of ACL. Relatively few, however, have been considered as outstandingly important vectors.According to the taxonomic criteria proposed by Young and Duncan (1994), three genera of sand flies are recognized in the New World: Lutzomyia França & Parrot, 1924; Brumptomyia França &Parrot, 1921 and Warileya Hertig, 1940. The genus Psychodopygus Mangabeira, 1941 has been accepted by some (Fraiha et al. 1971, Fraiha & Ward 1974, Forattini 1973, Lainson et al. 1973 and modifications of the taxonomy have been suggested (Galati 2003). In this review, however, we propose to follow that of Young & Duncan (1994). Vectorial competence of some neotropical sand fliesLutzomyia (Nyssomyia) intermedia (Lutz & Neiva, 1912) -L. intermedia, described from specimens collected in the Fazenda Ouro Fino, in the state of Minas Gerais (MG), where it was found to be abundant in houses, was one of the first species of sand fly to be described in the Neotropical Region.In the 1940's, important studies on the biology of L. intermedia s.l. were made by Barretto (1943) in the state of São Paulo (SP), together with observations on the behaviour of some other species of sand fly. It is a species found in both primary and secondary forests and particularly in areas where deforestation has gradually modified the ecological profile -clearly seen in those parts of the country that underwent past colonization. As long ago as 1943, Barretto suggested that L. intermedia s.l. had, in fact, developed a preference for secondary forest or low, bushy vegetation located in areas suffering from such human impact and according to Tolezano et al. (1980), the environmental changes that took place in SP at the beginning of the 20th century certainly modified the composition of the phlebotomine fauna. While this caused other species of silvatic sand fly to disappear, or survive at low frequency, L. intermedia s.l. adapted so well to the peridomestic habitat that it actually has become the predominate species of sand fly in a new epidemiological profile for ACL in this region. These authors further suggested that the small numbers of this sand fly now captured in the remaining forest indicates that transmission of ACL by L. intermedia is now taking place solely outside of that habitat.Like most s...

The immunopathogenic competences of Leishmania (V.) braziliensis and L. (L.) amazonensis were reviewed in the light of more recent features found in the clinical and immunopathological spectrum of American cutaneous leishmaniasis. It was shown a dichotomy in the interaction between these Leishmania species and human T-cell immune response; while L. (V.) braziliensis shows a clear tendency to lead infection from the localized cutaneous leishmaniasis (LCL), a moderate T-cell hypersensitivity form at the centre of the spectrum, toward to the mucocutaneous leishmaniasis (MCL) at the T-cell hypersensitivity pole and with a prominent Th1-type immune response, L. (L.) amazonensis shows an opposite tendency, leading infection to the anergic diffuse cutaneous leishmaniasis (ADCL) at the T-cell hyposensitivity pole and with a marked Th2-type immune response. Between the central LCL and the two polar MCL and ADCL, the infection can present an intermediary form known as borderline disseminated cutaneous leishmaniasis, characterized by an incomplete inhibition of T-cell hypersensitivity but with a evident supremacy of Th1 over Th2 immune response (Th1 > or = Th2). These are probably the main immunopathogenic competences of L. (V.) braziliensis and L. (L.) amazonensis regarding the immune response dichotomy that modulates human infection outcome by these Leishmania parasites.

As the first species of Leishmania encountered were the agents of human visceral and cutaneous leishmaniasis, it is understandable that studies on these parasites for a long time concentrated on those organisms commonly causing disease in man. Epidemiological studies over the past 20 years or so, however, have led to the inescapable conclusion that the genus Leishmania is comprised of numerous species of well adapted parasites, in a wide range of mammals, throughout most of those tropical and subtropical regions of the world where phlebotomine sandflies exist (Diptera: Psychodidae). Many of the leishmanias probably never gain entrance into man: due either to an incapacity to survive in his tissues, or (more likely) because the natural sandfly vectors do not feed on him. The leishmanias that do infect man are, nevertheless, among the greatest protozoological scourges of mankind, and a better understanding of their life-cycles may well help in future prevention or control of the diseases they cause. With few exceptions the leishmaniases are zoonoses, with a major source of infection in wild or domestic animals. In the Americas, the disease is essentially a rural one, and most commonly acquired by those penetrating forested or wooded regions. The following paper deals with the better known human leishmaniases of the New World, and some new ones, and discusses the major historical events in the laborious task of elucidating their ecology and epidemiology.

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Six species of Leishmania are at present known to cause cutaneous and/or mucocutaneous leishmaniasis in Brazil, and they are all to be found in the Amazon region of this country. The eco-epidemiology of each is discussed, with the observation that the Amazonian leishmaniases are all zoonoses, with their source in silvatic mammals and phlebotomine sandfly vectors. With man's destruction of the natural forest in southern Brazil, some sandfly species have survived by adapting to a peridomestic or domiciliary habitat in rural areas. Some domestic animals, such as dogs and equines are seemingly now involved in the epidemiology of the disease. No such process has yet been reported in the Amazon region, but may well take place with the continuing devastation of its forest.