**2.6. Determination of the epidemiological risk of infection**

It is understood that reservoirs provide an ecological system in which the infectious agent survives indefinitely. This system includes hosts, any intermediate host, or vector and any environmental component that is necessary to maintain the agent indefinitely [33]. Depending on the duration that hosts are able to maintain the parasite, they may be classified into primary

Reservoirs may be domestic, wild, or synanthropic, and for some species of the parasite, humans are the main reservoir. That is, the case of VL caused by *L. donovani donovani* and CL caused by *L. tropica tropica*. In the New World, leishmaniases are zoonoses; however, there is evidence of anthroponotic transmission during outbreaks, previously identified in the

Generally, within a focus, there is a primary reservoir for each species of *Leishmani*a; however, other mammals in the same area can become infected, thereby becoming secondary or accidental hosts. Domestic, synanthropic, or wild (marsupial carnivores, rodents, Meshed, insectivores, and primates) reservoir species infected with *Leishmania* may or may not show obvious signs of infection. In general, reservoirs do not exhibit symptoms of the disease [2]. To be a source of transmission is not necessary to be a primary reservoir, and it is possible that different populations of mammals can maintain a continuous cycle of infection and become

In America, approximately 310 species of mammals have been incriminated as possible reservoirs. More than half of these species have been incriminated just for having been detected as infected, but the majority of species have been studied and considered as wild reservoirs, such as species in the order Didelphimorphia, *Didelphis marsupialis* and *Didelphis albiventris*, which are important hosts of all Leishmania species, especially *L. amazonensis amazonensis* and *L. braziliensis*. Meanwhile the most important hosts of *L. mexicana* are *Peromyscus yucatanicus* and *Ototylomys phyllotis* rodents. For *L. panamensis* and *L. guyanensis,* an important reservoir

The most important domestic reservoir is the dog; canine species are mainly a reservoir of *L. infantum,* but cases of infection by *L. braziliensis* and *L. panamensis* have also been observed [37, 38]. Donkeys and horses have also been incriminated as secondary reservoirs [2].

The study of reservoirs has been associated with decreased interest because of the difficulty in establishing incrimination. Briefly, to incriminate a host reservoir, the following criteria must be met: chronic maintenance of populations of parasites in each ecosystem, presentation of a parasitic load sufficient to ensure transmissibility, and identification of an appropriate population density (20% or more of studied wildlife) to provide opportunities for host-vector, host-environment, or host-host interactions depending on the type of transmission [32].

The activities used for identifying reservoir hosts include clinical, serological, and parasitological evaluations of domestic and wild mammals within a given locality. Performing these activities requires the participation of professionals specialized in the capture, identification, and sampling of domestic and wild mammals. For CL, it is very important to examine the snout, ears, genitals, appendages, and areas with less body hair (as *Lutzomyia* bites may occur

(maintaining the infection for a long time), secondary, or accidental.

Andean region of the country [6, 34].

40 The Epidemiology and Ecology of Leishmaniasis

the source of infection or "primary reservoir" [35].

has been identified to be *Choloepus hoffmanni* sloths [36].

Studying the eco‐epidemiology of infection risk involves the identification of different segments of the population who are at risk of becoming infected with *Leishmania*. Through this methodology, the spatial, temporal, and population risk may be evaluated. Spatial risk corresponds to the macrofocus, or geographically and ecologically defined area in which the transmission process occurs, as defined by Pavlovsky [42] and developed for use in the study leishmaniasis by Rioux et al. [43]. A macrofocus can be recognized through the identification of ecological indicators such as the presence of certain plants, altitude, or average rainfall [3, 4, 7, 30].

Geographic information systems and spatial analysis of vector-borne diseases are currently very useful tools for the depiction of regions with a high prevalence of vector-borne diseases, allowing for the identification of risk factors for infection in a given area. From the human occupation perspective, establishment of specific schematic (noso‐ecological) maps is the last phase in the determination of risk areas; in these maps, research groups may depict the boundaries and internal organization of the foci. These maps are a tool for the study of human ecology but may also provide a practical guide to the health authorities responsible for the implementation and maintenance of programs for the prevention and control of disease.

Maps should have a small scale of one-billionth or 1 in 500,000, and in these maps, large zones of risk may be identified, that is, the macrofoci. The maps can be used to set parameters for vector density, that is, the spatial or geographical distribution of a vector at an appropriate density, or determine the correlation between the bioclimatic or phytoclimatic zones, and living areas or vegetation types in the areas where the vector species inhabits. Within these small-scale maps, the transmission areas for each *Leishmania* species and areas in which each vector inhabits can be determined [44].

Temporal risk corresponds to the period of greatest risk and can be defined in different time scales: daily, seasonal, or one or more years. Generally, it corresponds to the periods during which there is a higher density of vectors and greater risk of parasitic infection.
