Ten global "hotspots" for the neglected tropical diseases

Potential Effects of Climate Change on Ecological Interaction Outcomes Between Two Disease-Vector Mosquitoes: A Mesocosm Experimental Study

The objective of this study was to experimentally assess the effects of different climate change scenarios on the outcomes of interactions between Aedes aegypti (L.) and Culex quinquefasciatus (Say) (Diptera: Culicidae) larvae. The experimental design maintained a constant density of specimens while the proportion of the species in different experimental climate change scenarios varied. Our results indicate that survival of the two species was not affected, but larval development and pupation times decreased under elevated atmospheric CO(2) concentration and high air temperature. In climate change scenarios with both species together, the survival of Ae. aegypti increased and its larval development time decreased with increasing density of Cx. quinquefasciatus. This may be attributed to the effects of intraspecific competition being more significant than interspecific competition in Ae. aegypti. Our study also reveals that climatic changes may affect the patterns of interactions between Cx. quinquefasciatus and Ae. aegypti. Alterations in climatic conditions changed the response of context-dependent competition, indicating the importance of studies on how ecological interactions will be affected by projected future climatic change.

Ecological and sociodemographic determinants of house infestation by Triatoma infestans in indigenous communities of the Argentine Chaco

BACKGROUND

The Gran Chaco ecoregion, a hotspot for Chagas and other neglected tropical diseases, is home to >20 indigenous peoples. Our objective was to identify the main ecological and sociodemographic determinants of house infestation and abundance of Triatoma infestans in traditional Qom populations including a Creole minority in Pampa del Indio, northeastern Argentina.

METHODS

A cross-sectional survey determined house infestation by timed-manual searches with a dislodging aerosol in 386 inhabited houses and administered questionnaires on selected variables before full-coverage insecticide spraying and annual vector surveillance. We fitted generalized linear models to two global models of domestic infestation and bug abundance, and estimated coefficients via multimodel inference with model averaging.

PRINCIPAL FINDINGS

Most Qom households were larger and lived in small-sized, recently-built, precarious houses with fewer peridomestic structures, and fewer livestock and poultry than Creoles'. Qom households had lower educational level and unexpectedly high residential mobility. House infestation (31.9%) was much lower than expected from lack of recent insecticide spraying campaigns and was spatially aggregated. Nearly half of the infested houses examined had infected vectors. Qom households had higher prevalence of domestic infestation (29.2%) than Creoles' (10.0%), although there is large uncertainty around the adjusted OR. Factors with high relative importance for domestic infestation and/or bug abundance were refuge availability, distance to the nearest infested house, domestic insecticide use, indoor presence of poultry, residential overcrowding, and household educational level.

CONCLUSIONS AND SIGNIFICANCE

Our study highlights the importance of sociodemographic determinants of domestic infestation such as overcrowding, education and proximity to the nearest infested house, and corroborates the role of refuge availability, domestic use of insecticides and household size. These factors may be used for designing improved interventions for sustainable disease control and risk stratification. Housing instability, household mobility and migration patterns are key to understanding the process of house (re)infestation in the Gran Chaco.

Leishmania (L.) mexicana infected bats in Mexico: novel potential reservoirs

Leishmania (Leishmania) mexicana causes cutaneous leishmaniasis, an endemic zoonosis affecting a growing number of patients in the southeastern states of Mexico. Some foci are found in shade-grown cocoa and coffee plantations, or near perennial forests that provide rich breeding grounds for the sand fly vectors, but also harbor a variety of bat species that live off the abundant fruits provided by these shade-giving trees. The close proximity between sand flies and bats makes their interaction feasible, yet bats infected with Leishmania (L.) mexicana have not been reported. Here we analyzed 420 bats from six states of Mexico that had reported patients with leishmaniasis. Tissues of bats, including skin, heart, liver and/or spleen were screened by PCR for Leishmania (L.) mexicana DNA. We found that 41 bats (9.77%), belonging to 13 species, showed positive PCR results in various tissues. The infected tissues showed no evidence of macroscopic lesions. Of the infected bats, 12 species were frugivorous, insectivorous or nectarivorous, and only one species was sanguivorous (Desmodus rotundus), and most of them belonged to the family Phyllostomidae. The eco-region where most of the infected bats were caught is the Gulf Coastal Plain of Chiapas and Tabasco. Through experimental infections of two Tadarida brasiliensis bats in captivity, we show that this species can harbor viable, infective Leishmania (L.) mexicana parasites that are capable of infecting BALB/c mice. We conclude that various species of bats belonging to the family Phyllostomidae are possible reservoir hosts for Leishmania (L.) mexicana, if it can be shown that such bats are infective for the sand fly vector. Further studies are needed to determine how these bats become infected, how long the parasite remains viable inside these potential hosts and whether they are infective to sand flies to fully evaluate their impact on disease epidemiology.

Blue marble health: a call for papers

In this month's editorial, Peter J. Hotez, Co-Editor-in-Chief of PLOS Neglected Tropical Diseases and Larry Peiperl, Chief Editor of PLOS Medicine, call for papers on “Blue Marble Health”: research on health problems that affect poorer people irrespective of the overall economic strength of the countries in which they live. Please see later in the article for the Editors' Summary