Urban distribution of Phlebotominae in a cutaneous leishmaniasis focus, Argentina

Abstract

Urbanization and vector domestication are currently proposed as factors that contributed to the recent increase of American cutaneous leishmaniasis (ACL). Is likely also urban transmission? Oran is the main city in the Argentinean hyper-endemic area of ACL, and human cases in urban residences are usually reported. In order to assess the spatial distribution of risk, phlebotomine traps were located in different environments of Oran. A total of 7,787 sand flies were captured: Lutzomyia neivai (98.1%), Lutzomyia migonei (1.2%), Lutzomyia cortelezzii (0.7%), and one Lutzomyia shannoni. During the season of transmission (April-May) a single sand fly was obtained in one out of five urban sites, while a trap in a peri-urban pigsty captured up to 2,985 Lu. neivai/night. Captures performed in the other season of vector activity (September-October) revealed that small-scale changes in the pigsty environment resulted in noticeable changes in the abundance of Lu. neivai. In addition, in a new neighbourhood, on the fringe of the city, 1,073 Lu. neivai/site were captured in the forested edge but one in the yard of the houses. Therefore, in this urban ACL focus the human-vector effective contact risk is still associated with peri-urban vegetation and ecotone modifications despite the urban residence of the cases.

Urban Transmission of American Cutaneous Leishmaniasis in Argentina: Spatial Analysis Study

“…The results of this spatial analysis study performed in San Ramón de la Nueva Orán, the city with the highest prevalence of cases of ACL in Argentina, 6 provides further evidence for the potential occurrence of urban transmission of this infection. In general, use of a patient's home residence as a marker of the place of infection acquisition is not accurate because contact between patient and vector can occur outside the home.…”

“…has been recently reported in urban and periurban zones in the San Ramón de la Nueva Orán. 6 Ecotones, areas of transition between two or more ecosystems that have common characteristics to both ecosystems, are in this case represented by secondary vegetation edges adjacent to urban and rural areas, and appear to be places with the highest potential risk of transmission. 37 Moreover, these places are located near neighborhoods with clusters of pediatric cases with high ORs.…”

“…neivai metapopulation source-sink pattern, which is characterized by a stable population (source), a location in a favorable habitat for the species (e.g., secondary vegetation patches), and other populations in non-favorable habitats (urban zones). 6 The above mentioned vector population would have high mortality rates and would thereby support a relative stability in population levels because of recolonization from the source population. 38 The possibility that human populations can serve as a reservoir of ACL is not ruled out in this setting.…”

“…This hypothesis is based on the absence of high incidence of urban cases with epidemic cycles. 6,20 Orán is surrounded by large areas dedicated to agricultural activity (with residual secondary vegetation), which serve as potential foci for rodent plagues, previously reported in other countries as potential reservoirs of Leishmania spp. 13,15,16 Different environmental disturbances caused by humans can be associated with increases in ACL incidence.…”

“…punctigeniculata . [5][6][7][8] Lutzomyia neivai is the unique species of phlebotomus sand fly in the region for which infection with Leishmania sp. has been proved.…”