Sand fly (Phlebotominae) activity and abundance in vertical strata in a tropical dry forest in the Yucatan Peninsula, Mexico.

BackgroundThe recent geographical expansion of phlebotomine vectors of Leishmania infantum in the Mediterranean subregion has been attributed to ongoing climate changes. At these latitudes, the activity of sand flies is typically seasonal; because seasonal phenomena are also sensitive to general variations in climate, current phenological data sets can provide a baseline for continuing investigations on sand fly population dynamics that may impact on future scenarios of leishmaniasis transmission. With this aim, in 2011–2013 a consortium of partners from eight Mediterranean countries carried out entomological investigations in sites where L. infantum transmission was recently reported.Methods/Principal FindingsA common protocol for sand fly collection included monthly captures by CDC light traps, complemented by sticky traps in most of the sites. Collections were replicated for more than one season in order to reduce the effects of local weather events. In each site, the trapping effort was left unchanged throughout the survey to legitimate inter-seasonal comparisons. Data from 99,000 collected specimens were analyzed, resulting in the description of seasonal dynamics of 56,000 sand flies belonging to L. infantum vector species throughout a wide geographical area, namely P. perniciosus (Portugal, Spain and Italy), P. ariasi (France), P. neglectus (Greece), P. tobbi (Cyprus and Turkey), P. balcanicus and P. kandelakii (Georgia). Time of sand fly appearance/disappearance in collections differed between sites, and seasonal densities showed variations in each site. Significant correlations were found between latitude/mean annual temperature of sites and i) the first month of sand fly appearance, that ranged from early April to the first half of June; ii) the type of density trend, varying from a single peak in July/August to multiple peaks increasing in magnitude from May through September. A 3-modal trend, recorded for P. tobbi in Cyprus, represents a novel finding for a L. infantum vector. Adults ended the activity starting from mid September through November, without significant correlation with latitude/mean annual temperature of sites. The period of potential exposure to L.infantum in the Mediterranean subregion, as inferred by adult densities calculated from 3 years, 37 sites and 6 competent vector species, was associated to a regular bell-shaped density curve having a wide peak center encompassing the July-September period, and falling between early May to late October for more than 99% of values. Apparently no risk for leishmaniasis transmission took place from December through March in the years considered. We found a common pattern of nocturnal females activity, whose density peaked between 11 pm and 2 am.ConclusionsDespite annual variations, multiple collections performed over consecutive years provided homogeneous patterns of the potential behavior of leishmaniasis vectors in selected sites, which we propose may represent sentinel areas for future monitoring. In the investigated years, higher potential risk for L. infantum transmission in the Mediterranean was identified in the June-October period (97% relative vector density), however such risk was not equally distributed throughout the region, since density waves of adults occurred earlier and were more frequent in southern territories.

This chapter presents an overview of the vegetation types of the Yucatan Peninsula. Mean annual precipitation, terrain and soil characteristics explain the large-scale distribution of forest types in the Yucatan Peninsula. Tropical (high) forest is found in areas with >800 mm of mean annual precipitation, while dry (low) tropical forest is distributed in areas with <800 mm of mean annual precipitation. Tropical forest has canopy heights of more than 30 m and mostly presents three well-defined vegetative strata. The distribution of tropical forest is mainly in the central, eastern and southern parts of the Yucatan Peninsula. Dry tropical forest has canopy heights up to 20 m, and is widely distributed in the Yucatan Peninsula in different successional stages. Other woody vegetation types include mangroves, petenes and pine savannas. Open vegetation types include coastal dunes, marsh, and savanna vegetation. Disturbed tropical and dry tropical forest of all successional stages covers more than 7.4 million ha at present, and requires detailed management plans to maintain future ecosystems benefits.

Outbreaks of cutaneous leishmaniasis are relatively common among soldiers involved in nocturnal activities in tropical forests. We investigated the population dynamics of sand flies in a military training camp located in a remnant of Atlantic rainforest in northeastern Brazil, where outbreaks of cutaneous leishmaniasis have sporadically been described. From July 2012 to July 2014, light traps were monthly placed in 10 collection sites, being nine sites located near the forest edge and one near a sheep and goat stable. Light traps operated from 5:00 pm to 6:00 am, during four consecutive nights. Leishmania infection in sand flies was assessed using a fast real-time PCR assay. Cases of cutaneous leishmaniasis among soldiers were also investigated. In total, 24,606 sand flies belonging to 25 species were identified. Males (n = 12,683) predominated over females (n = 11,923). Sand flies were present during all months, being more numerous in March (n = 1,691) and April 2013 (n = 3,324). Lutzomyia choti (72.9%) was the most abundant species, followed by Lutzomyia longispina (13.8%), Lutzomyia complexa (5.3%), representing together >90% of the sand flies collected. Forty cases of cutaneous leishmaniasis were recorded among soldiers from January 2012 to December 2014. Leishmania isolates were obtained from eight patients and were all characterized as Leishmania braziliensis. Soldiers and anyone overnighting in Atlantic rainforest remnants should adopt preventative measures such as the use of repellents on bare skin or clothes and insecticide-treated tents.

Need for Integrated Research for a Sustainable Future in Tropical Dry Forests

Discovering the forest in plain sight: a pop-up Symposium focusing on seasonally dry tropical forests.

Nocturnal activity of the sand fly Lutzomyia longipalpis (Lutz & Neiva) was studied from August 1991 to July 1992 in a small rural community in Colombia where American visceral leishmaniasis is endemic. During 2 or 3 nights each month, sand flies were collected with hand-held aspirators each hour between 1730 and 0630 hours, from a pigpen and a cattle corral located 30 m apart. Host-seeking activity of L. longipalpis adults was characterized by 2 general patterns: (1) adult sand fly activity increased shortly after sunset and continued until just after sunrise, and (2) peak sand fly activity was greatest early in the evening (1830-2330 hours) and then declined steadily toward morning. Female L. longipalpis activity generally increased after 2030 hours, whereas that of males remained constant or declined as the evening progressed. There were seasonal differences in sand fly abundance between the 2 sites: peak abundance in the cattle corral occurred during hot, dry periods, whereas maximum abundance in the pigpen occurred when relative humidity was higher. Influence of relative humidity on activity varied with season. Sand fly activity tended to decrease at temperatures below 24 degrees C and increase in the presence of moonlight.

Phenology and population dynamics of sand flies in a new focus of visceral leishmaniasis in Eastern Azarbaijan Province, North western of Iran

Habitat preference and seasonal dynamics of Phlebotomus orientalis in urban and semi-urban areas of kala-azar endemic district of Kafta Humera, northwest Ethiopia

BackgroundEntomological surveillance of sand fly vectors was carried out to support leishmaniasis prevention and control measures in areas affected by the São Francisco River Transposition Project.MethodsSand flies were collected monthly between May 2011 and December 2014 in seven municipalities: Missão Velha, Brejo Santo, Lavras da Mangabeira, Iguatu, Mauriti, Jaguaribe and Jaguaretama, in dwellings, peridomicile and forest areas for three consecutive days, for a period of 12 h each day (18:00 to 06:00 h). Differences in species composition between sites were tested with Shannon’s diversity index, the similarity between habitats was estimated by the Sørensen’s qualitative similarity index and, for the most abundant species in each municipality, a standardized index of species abundance was applied. The influence of climatic factors on sand fly population densities was analyzed using Spearman’s correlation coefficients.ResultsA total of 214,213 sand fly specimens belonging to 18 species were captured. The most abundant species in all municipalities was Lutzomyia longipalpis (Lutz & Neiva, 1912). The municipalities of Mauriti and Missão Velha stand out in terms of high species richness, with the latter exhibiting the greatest diversity. The number of sand flies in the Iguatu, Jaguaribe and Jaguaretama municipality was higher during the rainy months, whereas the populations declined in the drier months; the sand fly population density in other municipalities (Missão Velha, Brejo Santo, Lavras de Mangabeira and Mauriti) showed negative correlation with rainfall.ConclusionsThis study confirms the presence of several Leishmania spp. vectors in the seven municipalities affected by the São Francisco River Transposition Project, with Lu. longipalpis being the most abundant species at all study sites. Vector populations in these municipalities should be monitored, ultimately to assess the associations between environmental changes and sand fly population dynamics and leishmaniasis transmission risk.

Tropical rain forests as carbon sinks

Relationship between annual rainfall and tree mortality in a tropical dry forest: Results of a 19-year study at Mudumalai, southern India

BackgroundLeishmaniosis is associated with Phlebotomus sand fly vector density, but our knowledge of the environmental framework that regulates highly overdispersed vector abundance distributions is limited. We used a standardized sampling procedure in the bioclimatically diverse Murcia Region in Spain and multilevel regression models for count data to estimate P. perniciosus abundance in relation to environmental and anthropic factors.MethodsTwenty-five dog and sheep premises were sampled for sand flies using adhesive and light-attraction traps, from late May to early October 2015. Temperature, relative humidity and other animal- and premise-related data recorded on site and other environmental data were extracted from digital databases using a geographical information system. The relationship between sand fly abundance and explanatory variables was analysed using binomial regression models.ResultsThe total number of sand flies captured, mostly with light-attraction traps, was 3,644 specimens, including 80% P. perniciosus, the main L. infantum vector in Spain. Abundance varied between and within zones and was positively associated with increasing altitude from 0 to 900 m above sea level, except from 500 to 700 m where it was low. Populations peaked in July and especially during a 3-day heat wave when relative humidity and wind speed plummeted. Regression models indicated that climate and not land use or soil characteristics have the greatest impact on this species density on a large geographical scale. In contrast, micro-environmental factors such as animal building characteristics and husbandry practices affect sand fly population size on a smaller scale.ConclusionsA standardised sampling procedure and statistical analysis for highly overdispersed distributions allow reliable estimation of P. perniciosus abundance and identification of environmental drivers. While climatic variables have the greatest impact at macro-environmental scale, anthropic factors may be determinant at a micro-geographical scale. These finding may be used to elaborate predictive distribution maps useful for vector and pathogen control programs.

Because tropical dry forests have been disturbed by humans more than wetter tropical forests, there is an urgent need for conservation of the remaining tropical dry forests, and thus a large amount of research has also been directed toward their restoration. The development of cost-efficient silvicultural treatments will be critical to achieve sustained use of forest products from the remaining natural dry forests, as well as for restoration efforts. Tropical dry forests present special problems for silviculturists because prolonged dry seasons reduce growth rates and can cause significant tree mortality, especially for seedlings. Coppice systems are particularly important in the regeneration of these forests. Management of both timber and nontimber products is confined largely to managing their extraction, with relatively little application of silviculture. Although reduced-impact logging operations are increasingly applied in tropical forests, postharvest silvicultural treatments have not been integrated in the management of tropical forests, particularly in dry forests. Management in any form is often complex in areas where dry forests have been fragmented and harvested for subsistence products, such as firewood, and are affected by the damaging effects of livestock grazing and wildfire.

Guanica Forest, with seasonal rainfall averaging 860 mm annually, is among the driest of tropical or subtropical forests studied to date. It is composed of over 12,000 live tree stems per hectare, only 2.3 and 12 percent of which exceed 10 cm DBH or 5 m in height, respectively. Of all stems greater than 2.5 cm DBH, 57 percent are stump or root sprouts, attributable to forest cutting 50 years earlier. The dry winter months induce maximum deciduousness and are reflected in a 50 percent reduction in leaf area index, from approximately 4.3 to 2.1. Although less in magnitude, leaf fall was also observed in the moderately dry midsummer months. Relative to wetter forests, tree species richness and total community biomass is low. Approximately 50 percent of the total live-plant biomass of 89.9 t/ha occurs below ground, a higher proportion than for any other comparable forest measured thus far. IN RECENT YEARS, tropical forests have received unprecedented ecological attention. Interest in these ecosystems has been stimulated, in part, by the alarming rate at which they are being modified or completely destroyed. But interest in them is also attributable to their vast stores of carbon and the potential effects of their disruption on the world's carbon balance. Most studies in the tropics have focused on forests growing in humid climates even though they account for a relatively small portion of the forested tropical landscape. Of the total global extent of tropical forest, Brown and Lugo (1982) estimated that about 25 percent is tropical and subtropical wet and rain forest and 33 percent tropical or subtropical moist forest. The remaining 42 percent is tropical or subtropical dry forest (sensu Holdridge 1967). Unlike humid forest, tropical and subtropical dry forest has been very little studied, particularly with respect to taxonomic composition, stand structure, biomass, primary productivity, and rates of carbon turnover. It is, therefore, difficult at the present time to evaluate the significance of tropical and subtropical dry or seasonal forest relative to the global carbon cycle. Additionally, data regarding biomass and related characteristics (e.g., growth and primary productivity) would be useful in assessing the resource potential of dry forest and in furthering our understanding of forest function, especially with respect to climate and seasonality. In 1981 we initiated a comprehensive, long-term study of structure, primary productivity, and plant succession in a subtropical dry forest in southwestern Puerto Rico. This paper reports on the taxonomic composition (woody plants), structure, and biomass of the forest.

Caves are unique habitats that are inhabited by a diverse and singular biota. Among these inhabitants are sand flies, which are of great epidemiological interest in the Neotropical region because they are vectors of Leishmania The period of activity of these insects is usually crepuscular and nocturnal, but there are reports of diurnal activity of sand flies in caves. Thus, the aim of this study was to evaluate the periodicity of daily activity of sand flies in cave environments in the municipality of Pains, Minas Gerais. Sand flies were collected with light traps, which were operated for 5 consecutive days in the rainy season and in the dry season. Samples were collected every 12 h and separated between photophase and scotophase periods. In total, 1,777 sand flies of 23 species were collected. The most abundant species was Lutzomyia renei (Martins, Falcão, and Silva) (44%), followed by Lutzomyia longipalpis (Lutz and Neiva) (15%), Evandromyia edwardsi (Mangabeira) (11%), and Micropygomyia quinquefer (Costa Lima) (6%). The richness and abundance of total sand flies and the abundance of male and female sand flies in the aphotic zone of the caves did not differ between the photophase and scotophase, but differed between photoperiods at the entrance and at sites surrounding the caves. From our study of the daily activity of these insects in this ecotope, it will be possible to know which period of the day is of greatest risk of exposure of vertebrates who visit or live in these environments, including the human population.