**1. Introduction**

Leishmaniases are zoonosis caused by heteroxenous flagellate protozoa of genus *Leishmania* (Ross, 1903), order Kinetoplastida and family Trypanosomatidae. The infection is transmitted by the bite of infected female sand flies, dipteran insects of family Psychodidae, and subfamily Phlebotominae, genus *Lutzomyia* (New World) and *Phlebotomus* (Old World) [1]. These diseases are major public health problems, affecting indiscriminately men, women, and children, and are the ninth leading cause of infectious diseases in the world, despite remaining within the framework of neglected diseases [2–4]. Leishmaniases manifest in different clinical forms, mainly due to the variety of parasites that affect the human population [5]. They are endemic in 98 countries, reaching America, Europe, Asia, Africa, and Australia, with about 350 million people living in risk areas [2, 6, 7].

American visceral leishmaniasis (AVL) has become one of the most important tropical diseases, due to its high incidence, high mortality rates in untreated individuals, and malnourished children, and it can also progress to death [3]. In Latin America, AVL has been recorded in 12 countries, with 90% of cases occurring in Brazil. The geographical expansion of AVL in Brazil has enabled its establishment in urban areas of medium and large cities [3]. Autochthonous human cases are recorded in most Brazilian states, except Acre, Amapá, Amazonas, Paraná, Rondônia, and Santa Catarina [3, 8].

The etiologic agent of AVL in the Americas is *Leishmania (Leishmania) infantum chagasi* (Cunha and Chagas, 1937), whose main vector is *Lutzomyia (Lutzomyia) longipalpis* (Lutz and Neiva, 1912), a species with strong evidence of vector competence, and closely linked to the expansion process of the disease, as revealed by its wide geographical distribution in the Americas [9]. In Brazil, it is currently considered the main vector of AVL in all regions; however, its presence was not yet detected in the states of Acre, Amazonas, Rondônia, and Santa Catarina. The ability of *L. (L.) longipalpis* to often feed on domestic and synanthropic animals, as well as its remarkable anthropophily favored its adaptation to changing environments, favoring the maintenance of the transmission cycle in the rural environment and, at the same time, the spread of the disease into urban areas [9–12].

A variant epidemiological situation is observed in the central region of Brazil, in Corumbá and Ladário (Mato Grosso do Sul State), and Jaciara (Mato Grosso State), where *L. (L.) longipalpis* is absent and *Lutzomyia (Lutzomyia) cruzi* (Mangabeira, 1938) has been incriminated as a vector because of its high abundance, anthropophily, and natural infection with *L. (L.) infantum chagasi* [13–15].

Leishmaniases produce major impacts on human health as a consequence of environmental change, mainly through the possible expansion of transmission areas. Continuous environmental change processes, such as deforestation, fires, agriculture, mining, construction of dams and hydroelectric power plants, migration, unplanned urbanization, and lack of urban infrastructure are examples of situations that have led to an increase in people at risk of infection, and fostered the emergence of outbreaks of leishmaniasis in a new ecoepidemiological pattern [10, 16].

Geographic information systems (GIS) have generated valuable contributions to the control and prediction of vector-borne diseases [17–19], and to evaluate the influence of environmental factors on the habitats of vectors and hosts, and the risk of transmission to humans [20]. Such studies aim to characterize and analyze the spatial and temporal dynamics of the diseases and consequently identify epidemiological patterns, generating information that can be valuable tools when planning control actions.

**1. Introduction**

92 The Epidemiology and Ecology of Leishmaniasis

350 million people living in risk areas [2, 6, 7].

the disease into urban areas [9–12].

*infantum chagasi* [13–15].

Amazonas, Paraná, Rondônia, and Santa Catarina [3, 8].

Leishmaniases are zoonosis caused by heteroxenous flagellate protozoa of genus *Leishmania* (Ross, 1903), order Kinetoplastida and family Trypanosomatidae. The infection is transmitted by the bite of infected female sand flies, dipteran insects of family Psychodidae, and subfamily Phlebotominae, genus *Lutzomyia* (New World) and *Phlebotomus* (Old World) [1]. These diseases are major public health problems, affecting indiscriminately men, women, and children, and are the ninth leading cause of infectious diseases in the world, despite remaining within the framework of neglected diseases [2–4]. Leishmaniases manifest in different clinical forms, mainly due to the variety of parasites that affect the human population [5]. They are endemic in 98 countries, reaching America, Europe, Asia, Africa, and Australia, with about

American visceral leishmaniasis (AVL) has become one of the most important tropical diseases, due to its high incidence, high mortality rates in untreated individuals, and malnourished children, and it can also progress to death [3]. In Latin America, AVL has been recorded in 12 countries, with 90% of cases occurring in Brazil. The geographical expansion of AVL in Brazil has enabled its establishment in urban areas of medium and large cities [3]. Autochthonous human cases are recorded in most Brazilian states, except Acre, Amapá,

The etiologic agent of AVL in the Americas is *Leishmania (Leishmania) infantum chagasi* (Cunha and Chagas, 1937), whose main vector is *Lutzomyia (Lutzomyia) longipalpis* (Lutz and Neiva, 1912), a species with strong evidence of vector competence, and closely linked to the expansion process of the disease, as revealed by its wide geographical distribution in the Americas [9]. In Brazil, it is currently considered the main vector of AVL in all regions; however, its presence was not yet detected in the states of Acre, Amazonas, Rondônia, and Santa Catarina. The ability of *L. (L.) longipalpis* to often feed on domestic and synanthropic animals, as well as its remarkable anthropophily favored its adaptation to changing environments, favoring the maintenance of the transmission cycle in the rural environment and, at the same time, the spread of

A variant epidemiological situation is observed in the central region of Brazil, in Corumbá and Ladário (Mato Grosso do Sul State), and Jaciara (Mato Grosso State), where *L. (L.) longipalpis* is absent and *Lutzomyia (Lutzomyia) cruzi* (Mangabeira, 1938) has been incriminated as a vector because of its high abundance, anthropophily, and natural infection with *L. (L.)* 

Leishmaniases produce major impacts on human health as a consequence of environmental change, mainly through the possible expansion of transmission areas. Continuous environmental change processes, such as deforestation, fires, agriculture, mining, construction of dams and hydroelectric power plants, migration, unplanned urbanization, and lack of urban infrastructure are examples of situations that have led to an increase in people at risk of infection, and fostered the emergence of outbreaks of leishmaniasis in a new ecoepidemiological pattern [10, 16].

The AVL shows a persistent scenario in Brazil, with most of the factors contributing for its endemicity residing in processes that are external to the health sector. This makes the strengthening of new strategies necessary. Thus, this study is aimed to analyze the spatial and temporal distribution of AVL in Tocantins State, through evaluation of epidemiological and environmental factors that are potentially related to its expansion: disease incidence, presence of the vector *L. (L.) longipalpis*, type of land use, and deforestation. In the current scenario, where environmental changes impact public health, it is essential to intensify research in diseases related to the environment, especially vector-borne diseases such as AVL.
