**Geographical and Environmental Variables of Leishmaniasis Transmission**

Roqueline A.G.M.F. Aversi-Ferreira, Jucimária Dantas Galvão, Sylla Figueredo da Silva, Giovanna Felipe Cavalcante, Ediana Vasconcelos da Silva, Naina Bhatia-Dey and Tales Alexandre Aversi-Ferreira

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/57546

**1. Introduction**

Leishmaniasis, an infectious disease is not contagious. It belongs to the group of tropical neglected diseases [1, 2] that are ignored as priority in terms of eradication. It is estimated to be the ninth largest cause of disease among infected individuals [3, 4] ; it can cause intense epidemics that are primarily associated with the nutritional and the migratory factors [5, 6].

Most likely leishmaniasis originated in East Africa, however, it has been reported in ancient Egypt and in Christian Nubian approximately 4,000 B.C. In fact, it appears that Egyptians got the disease in the trade, as Egyptian Nile Valley is not a niche to sand flies [7]. Currently it has been reported in more than 80 countries, primarily in the developing countries in 4 continents, reaching indices around 500,000 new cases/year, with relatively higher incidence in India, Bangladesh, Nepal, Sudan and Brazil; approximately 200 million people have been estimated to get the exposure to the risk of its transmission [8].

Protozoan *Leishmania*, a unicellular flagellate, is the root cause of the disease; the parasite is transmitted to humans via female sand flies and manifests into two main forms: visceral [LV], and tegumentary [LT], the later divides into cutaneous [LC] and mucocutaneous [LMC] sub forms [7] (figure 1). Leishmaniasis has different clinical forms depending on the parasite, immune responses of the infected individuals and additional still unknown factors. Indeed,

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studies on leishmaniasis could be focused on both unknown and known factors to eradicate this disease.

The LV, also known as Kala-azar (Indian name), black fever or DumDum fever, is the most severe form of leishmaniasis (figure 1) caused by *Leishmania donovani* and *Leishmania infan‐ tum* (*Leishmania infantum chagasis*, a subspecies typical of Brazil), both protozoans belonging to the same family, *Trypanossomatidae*. These species have different geographical distribution: *Leishmania infantum* is typical of South America, Europe and Northern Africa, while *Leishmania donovani* is commonly found in Eastern Africa.

LV is a chronic and systemic disease characterized by anemia, mucosal ulcers, fever, hepato‐ megaly and splenomegaly, lymphadenopathy, pancytopenia, weight loss, weakness and, eventually death due to lack of treatment [9].

The most common form of leishmaniasis in the world is LC, it can progress to other forms and is caused by about 20 different species of *Leishmania*; it is known with various different names, such as Aleppo boil, Chiclero ulcer, Bauru's ulcer, Bay sore, Biskra button, Lahore sore, Oriental sore, Pian bois, Uta and leishmaniasis tropica.

LMC produces destructive and disfiguring lesions in the body, especially in the face (figure 1), they are primarily caused by *Leishmania braziliensis* and rarely by *Leishmania aethiopica*.

Regardless of the type of leishmaniasis this disease is transmitted through the bite of the female sand flies and the geographical distribution of this disease is directly associated with the habitat of its vector. Phlebotomine sand flies primarily inhabit hot and wet tropical regions with regular pluvial index [10], however, sometimes they also inhabit the dry and hot places; therefore, the environmental and geographical niches of this vector that are associated with its natural vertebrate hosts are determinants of the disease transmission.

The association of the vector with natural reservoir became a propitious factor towards keeping an endemic status for leishmaniasis. In fact, there are many natural reservoirs such as canine, avian (chicken), bovine, equine, caprine, ovine, swine and feline [11-14] ; all of them inhabit the same regions as Phlebotomine.

**Figure 1.** Clinical features of *cutaneous leishmaniasis* (left), and *mucocutaneous leishmaniasis* (right).

In addition, an important factor associated with leishmaniasis occurrence is the canine leishmaniasis (figure 2), a zoonosis that indirectly indicates the prevalence of this disease in humans at a specific site.

studies on leishmaniasis could be focused on both unknown and known factors to eradicate

The LV, also known as Kala-azar (Indian name), black fever or DumDum fever, is the most severe form of leishmaniasis (figure 1) caused by *Leishmania donovani* and *Leishmania infan‐ tum* (*Leishmania infantum chagasis*, a subspecies typical of Brazil), both protozoans belonging to the same family, *Trypanossomatidae*. These species have different geographical distribution: *Leishmania infantum* is typical of South America, Europe and Northern Africa, while *Leishmania*

LV is a chronic and systemic disease characterized by anemia, mucosal ulcers, fever, hepato‐ megaly and splenomegaly, lymphadenopathy, pancytopenia, weight loss, weakness and,

The most common form of leishmaniasis in the world is LC, it can progress to other forms and is caused by about 20 different species of *Leishmania*; it is known with various different names, such as Aleppo boil, Chiclero ulcer, Bauru's ulcer, Bay sore, Biskra button, Lahore sore,

LMC produces destructive and disfiguring lesions in the body, especially in the face (figure 1), they are primarily caused by *Leishmania braziliensis* and rarely by *Leishmania aethiopica*.

Regardless of the type of leishmaniasis this disease is transmitted through the bite of the female sand flies and the geographical distribution of this disease is directly associated with the habitat of its vector. Phlebotomine sand flies primarily inhabit hot and wet tropical regions with regular pluvial index [10], however, sometimes they also inhabit the dry and hot places; therefore, the environmental and geographical niches of this vector that are associated with

The association of the vector with natural reservoir became a propitious factor towards keeping an endemic status for leishmaniasis. In fact, there are many natural reservoirs such as canine, avian (chicken), bovine, equine, caprine, ovine, swine and feline [11-14] ; all of them inhabit

its natural vertebrate hosts are determinants of the disease transmission.

**Figure 1.** Clinical features of *cutaneous leishmaniasis* (left), and *mucocutaneous leishmaniasis* (right).

this disease.

*donovani* is commonly found in Eastern Africa.

106 Leishmaniasis - Trends in Epidemiology, Diagnosis and Treatment

eventually death due to lack of treatment [9].

the same regions as Phlebotomine.

Oriental sore, Pian bois, Uta and leishmaniasis tropica.

Indeed, leishmaniasis is associated with the tropical and the equatorial zones, poor sanitary conditions and surveillance in the areas where the parasites and the vectors are close to the reservoir and the humans, therefore, the most important point to understand the cause of epidemic and the transmission of the disease is the knowledge on the geographical and the environmental variables. Nevertheless, both these variables will be considered here into two categories: the worldwide and the regional.

In the geographic terms, the worldwide variables represent the geographic area where the vector has its niches and where the climate is favorable to its development. However, there are places and the environmental factors that are relatively propitious to the transmission of leishmaniasis than other factors such as higher population of the sand flies; these are consid‐ ered.as the regional variables that would be accountable for the frequency of the disease.

In the environmental terms, the worldwide variables indicate the global climate and the associated landscape; however, the anthropomorphic factors and the climate peculiarities in a specific region represent the regional variables.

This chapter will present the worldwide and the regional aspects of geographical and envi‐ ronmental variables associated with leishmaniasis transmission.

**Figure 2.** A photographic representation of a dog displaying clinical symptoms of canine leishmaniasis.
