BackgroundAnthropogenic land use may influence transmission of multi-host vector-borne pathogens by changing diversity, relative abundance, and community composition of reservoir hosts. These reservoir hosts may have varying competence for vector-borne pathogens depending on species-specific characteristics, such as life history strategy. The objective of this study is to evaluate how anthropogenic land use change influences blood meal species composition and the effects of changing blood meal species composition on the parasite infection rate of the Chagas disease vector Rhodnius pallescens in Panama.Methodology/Principal Findings R. pallescens vectors (N = 643) were collected in different habitat types across a gradient of anthropogenic disturbance. Blood meal species in DNA extracted from these vectors was identified in 243 (40.3%) vectors by amplification and sequencing of a vertebrate-specific fragment of the 12SrRNA gene, and T. cruzi vector infection was determined by pcr. Vector infection rate was significantly greater in deforested habitats as compared to contiguous forests. Forty-two different species of blood meal were identified in R. pallescens, and species composition of blood meals varied across habitat types. Mammals (88.3%) dominated R. pallescens blood meals. Xenarthrans (sloths and tamanduas) were the most frequently identified species in blood meals across all habitat types. A regression tree analysis indicated that blood meal species diversity, host life history strategy (measured as rmax, the maximum intrinsic rate of population increase), and habitat type (forest fragments and peridomiciliary sites) were important determinants of vector infection with T. cruzi. The mean intrinsic rate of increase and the skewness and variability of rmax were positively associated with higher vector infection rate at a site.Conclusions/SignificanceIn this study, anthropogenic landscape disturbance increased vector infection with T. cruzi, potentially by changing host community structure to favor hosts that are short-lived with high reproductive rates. Study results apply to potential environmental management strategies for Chagas disease.

No abstract

Abstract. Anthropogenic disturbance is associated with increased vector-borne infectious disease transmission in wildlife, domestic animals, and humans. The objective of this study was to evaluate how disturbance of a tropical forest landscape impacts abundance of the triatomine bug Rhodnius pallescens , a vector of Chagas disease, in the region of the Panama Canal in Panama. Rhodnius pallescens was collected (n = 1,186) from its primary habitat, the palm Attalea butyracea , in five habitat types reflecting a gradient of anthropogenic disturbance. There was a high proportion of palms infested with R. pallescens across all habitat types (range = 77.1-91.4%). Results show that disturbed habitats are associated with increased vector abundance compared with relatively undisturbed habitats. Bugs collected in disturbed sites, although in higher abundance, tended to be in poor body condition compared with bugs captured in protected forest sites.

Abstract. American tegumentary leishmaniasis is an increasing public health problem in Panama. This study describes the clinical characteristics and the molecular epidemiology of leishmaniasis in Panama over a 5-year period (2004)(2005)(2006)(2007)(2008). Additionally, we applied a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) -based assay to identify Leishmania species in clinical isolates, skin scrapings, and sandflies specimens. Whereas 60.3% of cases were detected with conventional parasitologic techniques (smear or in vitro culture), the PCR detected 72% positive patients. Our clinical-epidemiologic data corroborate the high incidence of L. ( Viannia ) panamensis and provide evidence of peridomestic and/or domestic transmission. Mucosal involvement was observed in 4.2% of the patients. The overall natural infection rate with Leishmania in 103 pools of sandflies was 0.46%. Lutzomyia gomezi and Lutzomya panamensis were the prevalent species incriminated as vectors at the capture sites in central Panama. This study contributes to a better knowledge of the current epidemiology of tegumentary leishmaniasis in Panama.

An entomologic search was carried out to collect intradomicile triatomines in dwellings from rural communities in the western border of the Panama Canal, Panama. Sixty-nine triatomines were collected inside 20 houses of 67 houses investigated. Rhodnius pallescens was the only triatomine species found and included adults of both sexes and nymphs. A significantly high Trypanosoma cruzi (72.7%) and T. rangeli (40%) vector infection rate was detected. Blood meal analysis showed that 68% of R. pallescens had fed on humans. Human serologic analysis and hemoculture performed on inhabitants from triatomine-infested houses showed that 32.1% (18 of 56) of the samples were trypanosome infected. Thirteen samples (23.2%) had antibodies against T. cruzi. Six of these seropositive samples were from children less than 15 years old. Trypanosoma rangeli was isolated in five hemoculture samples, all from children less than 11 years old. The epidemiologic implications of these findings in terms of human infection are discussed.

The Rhodnius Pacific group is composed of three species: Rhodnius pallescens, R. colombiensis and R. ecuadoriensis, which are considered important vectors of trypanosomes (Trypanosoma cruzi and T. rangeli) infecting humans. This group is considered as a recent trans-Andean lineage derived from the widespread distributed sister taxa R. pictipes during the later uplift of northern Andes mountain range. The widest spread species R. pallescens may be a complex of two divergent lineages with different chromosomal attributes and a particular biogeographical distribution across Central America and Colombia with several southern populations in Colombia occupying the same sylvatic habitat as its sister species R. colombiensis. Although the taxonomy of Rhodnius Pacific group has been well studied, the unresolved phylogenetic and systematic issues are the target of this paper. Here we explore the molecular phylogeography of this species group analyzing two mitochondrial (ND4 and cyt b) and one nuclear (D2 region of ribosomal 28S gene) gene sequences. The molecular analyses suggest an early divergence of the species R. ecuadoriensis and R. colombiensis, followed by a recent expansion of R. pallescens lineages. The phylogenetic relationship between sympatric R. pallescens Colombian lineage and R. colombiensis was further explored using wing morphometry, DNA genome size measurements, and by analyzing chromosomal behavior of hybrids progeny obtained from experimental crosses. Our results suggest that the diversification of the two R. pallescens lineages was mainly influenced by biogeographical events such as (i) the emergence of the Panama Isthmus, while the origin and divergence of R. colombiensis was associated with (ii) the development of particular genetic and chromosomal features that act as isolation mechanisms from its sister species R. pallescens (Colombian lineage). These findings provide new insights into the evolution of the Rhodnius Pacific group and the underlying biological processes that occurred during its divergence.

BackgroundInsecticide thermal fogging (ITF) is a tool to control vector borne diseases. Insecticide application success for vector control has been associated with housing materials and architecture. Vector abundance is correlated with weather changes. Nevertheless, housing quality and weather impacts on vector abundance have been unaccounted for in most New World insecticide control trials for leishmaniasis vectors.MethodsWe conducted a 15 month insecticide control trial that included two deltamethrin [6 mg a.i.m-2] based ITF interventions in 12 of 24 monitored houses at Trinidad de Las Minas, a hyperendemic cutaneous leishmaniasis transmission village in western Panamá. During the study we followed sand fly (SF) abundance, keeping track of rainfall and quantified housing quality using an index based on architecture and construction materials.ResultsWe found a 50 to 80% reduction in SF density in the fogged houses when compared with control houses, while controlling for seasonal changes in SF abundance associated with rainfall. We found heterogeneities in the reductions, as abundance changed according to SF species: Lutzomyia gomezi, Lu. panamensis, Lu. dysponeta and Lu. triramula reduced in density between 40% and 90% after ITF. In contrast, Lu. trapidoi density increased 5% after ITF. Differences in the impact of ITF were associated with housing quality, the most destitute houses, i.e., those with features that ease insect entrance, had a disproportionally larger SF abundance, in some cases with increased domiciliary SF density following the ITF.ConclusionOur results suggest the potential of insecticide application to control SF density and leishmaniasis transmission could depend on housing quality beyond insecticide efficiency.

SUMMARYThe sylvatic triatomine Rhodnius pallescens is considered to be the most important and widespread vector of Trypanosoma cruzi and Trypanosoma rangeli in Panama. However, its behavior and biological characteristics have only been partially investigated. Thus, to achieve sustainable and efficient control over Chagas disease in Panama, a better understanding of the ecology and biology of R. pallescens is essential. In this study we evaluated R. pallescens host feeding sources using a dot-blot assay, and the trypanosome infection index by PCR analysis in a Chagas disease endemic area of central Panama. It was found that in peridomestic palm trees, 20.3% of the examined bugs had fed on opossums (Didelphis marsupialis). However, we observed an increased anthropophagy (25.4%) for those bugs collected inside houses. Considering the domestic and peridomestic habitats as a whole, the proportion of collected R. pallescens infected with trypanosomes was 87.4%. In the two habitats the predominant infection was with T. cruzi (80-90%). Between 47-51% of the analyzed triatomines were infected with T. rangeli. Mixed infections (40-51%) were also detected. These findings provide a better basis for the implementation of a rational control and surveillance program for Chagas disease in regions where R. pallescens is endemic.