Detection of Leishmania RNA Virus 1 in Leishmania (Viannia) panamensis Isolates, Panama

We detected Leishmania RNA virus 1 (LRV1) in 11 isolates of Leishmania (Viannia) panamensis collected during 2014-2019 from patients from different geographic areas in Panama. The distribution suggested a spread of LRV1 in L. (V.) panamensis parasites. We found no association between LRV1 and an increase in clinical pathology.

Insights into the Genetic Diversity of Leishmania (Viannia) panamensis in Panama, Inferred via Multilocus Sequence Typing (MLST)

Leishmaniasis is a disease caused by parasites of the genus Leishmania and transmitted by sand fly vectors. Tegumentary leishmaniasis is the most prevalent clinical outcome in Latin America, afflicting people from 18 countries. In Panama, the annual incidence rate of leishmaniasis is as high as 3000 cases, representing a major public health problem. In endemic regions, L. panamensis is responsible for almost eighty percent of human cases that present different clinical outcomes. These differences in disease outcomes could be the result of the local interplay between L. panamensis variants and human hosts with different genetic backgrounds. The genetic diversity of L. panamensis in Panama has only been partially explored, and the variability reported for this species is based on few studies restricted to small populations and/or with poor resolutive markers at low taxonomic levels. Accordingly, in this study, we explored the genetic diversity of sixty-nine L. panamensis isolates from different endemic regions of Panama, using an MLST approach based on four housekeeping genes (Aconitase, ALAT, GPI and HSP70). Two to seven haplotypes per locus were identified, and regional differences in the genetic diversity of L. panamensis were observed. A genotype analysis evidenced the circulation of thirteen L. panamensis genotypes, a fact that might have important implications for the local control of the disease.

Specificity of Stenurus (Metastrongyloidea: Pseudaliidae) infections in odontocetes stranded along the north-west Spanish coast

Parasites extracted from the lungs and the pterygoid sinus complex of 6 species of odontocetes stranded along the north-west Spanish coast (Northeast Atlantic) between 2009 and 2019 were morphologically identified. The samples belonged to 14 specimens, including 3 harbour porpoises, Phocoena phocoena, 6 short-finned pilot whales, Globicephala macrorhynchus, 1 long-finned pilot whale, Globicephala melas, 1 Risso's dolphin, Grampus griseus, 1 striped dolphin, Stenella coeruleoalba and 2 bottlenose dolphins, Tursiops truncatus. All animals (14/14) were infected by nematodes of the genus Stenurus spp.; moreover, two of them presented a mixed lung nematode infection by Stenurus spp. and Halocercus spp., and another two a mixed infection by Stenurus spp. and the trematode Nasitrema spp. in the pterygoid sinuses. The morphological characterization of the Stenurus specimens revealed the existence of three different species: Stenurus minor, present in the pterygoid sinuses of harbour porpoises with a mean intensity of 43.0 ± 9.0; Stenurus globicephalae, in the pterygoid sinuses of pilot whales and the Risso's dolphin (370.3 ± 579.4); and Stenurus ovatus infecting bottlenose and striped dolphins’ lungs (47.7 ± 76.5). This is the first citation of S. minor and S. ovatus in odontoceti from the Galician coast. Nematodes of the genus Stenurus are frequent in odontocetes stranded along the north-west Spanish coast. A clear host-parasite association was observed between S. minor and the Phocoenidae family, between S. globicephalae and the subfamily Globicephalinae and between S. ovatus and subfamily Delphininae. Different trophic position and niche segregation may lead to different patterns of specificity.

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Stenurus is the most prevalent lungworm in odontoceti.

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First description of S. minor and S. ovatus in Galician waters.

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Short-finned whales are the most intensely infected odontocetes.

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Stenurus infection is favored by the greater length of the host.

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Stenurus spp show a clear pattern of specificity with their hosts.

Characterization of Leishmania spp. Causing Cutaneous Lesions with a Negative Parasitological Diagnosis in Panama

A total of 123 DNA samples from Panamanian patients with cutaneous leishmaniasis (CL) lesions were evaluated. These samples were previously confirmed with CL by a specific KDNA-Viannia PCR but had a negative parasitological diagnosis (Group A). Epidemiological variables, such as age, sex, geographic origin, evolution time, and the number and location of the lesions, were analyzed. No significant differences (p < 0.05) were found when these variables were evaluated against a control panel of 123 CL lesion samples from CL patients with positive parasitological diagnoses (Group B). Of the 123 samples (Group A), 67% (82/123) gave positive results when re-analyzed by PCR-hsp70. An analysis of 69 of these samples via PCR-hsp70-RFLP showed that 59.4% (41/69) of the found restriction patterns corresponded to Leishmania (Viannia) panamensis and 40.6% (28/69) to Leishmania (Viannia) guyanensis. Finally, the sequence and phylogenetic analysis of 32 of the samples confirmed the species in 21 (65.6%, 21/32) samples, originally characterized as L. (V.) panamensis. However, 11 samples (34.4%, 11/32), initially identified via RFLP-Hsp70 as L. (V.) guyanensis, matched the sequence of a genetic variant known as Leishmania sp.1. These results point out the species/genetic variants of Leishmania in the case of CL lesions with an apparently low parasite load.

Genomic diversity and genetic variation of Leishmania panamensis within its endemic range

Species belonging to the Leishmania (Viannia) subgenus are important causative agents of cutaneous and mucocutaneous leishmaniasis in Central and South America. These parasites possess several distinctive biological features that are influenced by their genetics, population structure, and genome instability. To date, several studies have revealed varying degrees of genetic diversity within Leishmania species. Particularly, in species of the L. (Viannia) subgenus, a generalized high intraspecific genetic diversity has been reported, although, conflicting conclusions have been drawn using different molecular techniques. Despite being the most common Leishmania species circulating in Panama and Colombia, few studies have analyzed clinical samples of Leishmania panamensis using whole-genome sequencing, and their restricted number of samples has limited the information they can provide to understand the population structure of L. panamensis. Here, we used next generation sequencing (NGS) to explore the genetic diversity of L. panamensis within its endemic range, analyzing data from 43 isolates of Colombian and Panamanian origin. Our results show the occurrence of three well-defined geographically correlated groups, and suggests the possible occurrence of additional phylogeographic groups. Furthermore, these results support the existence of a mixed mode of reproduction in L. panamensis, with varying frequencies of events of genetic recombination occurring primarily within subpopulations of closely related strains. This study offers important insights into the population genetics and reproduction mode of L. panamensis, paving the way to better understand their population structure and the emergence and maintenance of key eco-epidemiological traits.

First report of imported canine visceral leishmaniasis cases in Panama, Central America: Public health implications

According to the last leishmaniasis report from the Pan American Health Organization (2021) so far Panama is considered free of visceral leishmaniasis (VL). Although the presence of potential vectors and reservoirs involved in the VL transmission cycle have been described in some rural regions of the country, no cases have been reported in humans and domestic or wild animals. Dogs play an important role in the urban transmission of VL; therefore, it is important to detect possible cases of canine visceral leishmaniasis (CVL) in the country. In this sense,this study reports for the first time the Leishmania (Leishmania) infantum infection in imported dogs in Panama. Eleven dogs with clinical suspicion of CVL were evaluated by parasitological (bone marrow aspirate smear), serological (indirect immunofluorescence and/or reference immunochromatographic rapid test) and molecular tests (conventional PCR). The dogs included in this study were analyzed during the period from 2013 to 2020. All dogs presented clinical manifestations compatible with CVL. The samples were initially evaluated by smears and/or rapid serological tests by private practice veterinarians, and later confirmed by serological and/or molecular tests at the national reference laboratory for Leishmania diagnosis. The diagnosis was confirmed in 5/11 dogs by serological, parasitological and/or conventionals PCR targeting kDNA minicircle and Hsp70 gene. Leishmania (L.) infantum species was identified in 3/5 dogs by PCR-RFLP and by sequencing Hsp70-PCR products. This study evidenced the need to increase awareness of private practitioners as well as public health veterinarians on visceral leishmaniasis (VL), and to consider this parasitosis in the differential diagnosis of dogs with clinical and epidemiological characteristics compatible with the disease.

Surveillance and genotype characterization of zoonotic trypanosomatidae in Didelphis marsupialis in two endemic sites of rural Panama

Didelphis marsupialis has been reported as a competent reservoir for trypanosomatid parasites infections. The aim of this study was to measure Trypanosoma cruzi, T. rangeli, and Leishmania spp. infection rates and to characterize discrete typing units (DTUs) of T. cruzi in D. marsupialis from two Chagas disease endemic sites in Panama. Blood from 57 wild-caught D. marsupialis were examined from two rural communities, Las Pavas (N = 18) and Trinidad de las Minas (N = 39). Twenty-two (38.60%) opossums were positive for flagellates by general hemoculture. T. cruzi infection was confirmed by positive hemoculture and/or kDNA based PCR performed in 31/57 (54.39%) blood samples from opossums. T. rangeli infection was confirmed by hemoculture and/or TrF/R2-Primer PCR assay applied on 12/57 (21.05%) blood samples. Nine (15.79%) D. marsupialis harbored T. cruzi/T. rangeli coinfections. All opossums tested negative for Leishmania spp. by PCR assays based on kDNA and HSP70 gene amplification. There was a significant association between T. cruzi infection and site (Fisher exact test, p = 0.02), with a higher proportion of T. cruzi infected opossums in Las Pavas (77.78%, n = 14/18) compared to Trinidad de las Minas (43.59%, n = 17/39). A significant association was found between habitat type and T. cruzi infection in opossums across both communities, (X² = 6.91, p = 0.01, df = 1), with a higher proportion of T. cruzi infection in opossums captured in forest remnants (76%, 19/25) compared to peridomestic areas (37.5%, 12/32). T. rangeli detection, but not T. cruzi detection, may be improved by culture followed by PCR. TcI was the only DTU detected in 22 T. cruzi samples using conventional and real-time PCR. Eight T. rangeli positive samples were characterized as KP1(-)/lineage C. Trypanosome infection data from this common synanthropic mammal provides important information for improved surveillance and management of Chagas disease in endemic regions of Panama.

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Trypanosoma cruzi infection is common in Didelphis marsupialis from the studied sites.

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T. rangeli infection was confirmed in many opossums.

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All opossums tested negative for Leishmania infection.

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A higher proportion of T. cruzi infected opossums came from forest remnants.

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T. cruzi parasites were characterized as TcI and T. rangeli as KP1(-)/lineage C.

Genetic Diversity of Trypanosoma cruzi in Panama Inferred by Multi-locus Sequence Typing of Mitochondrial Genes

The objective of this study was to provide information on Trypanosoma cruzi genetic diversity among isolates obtained from different biological sources circulating in endemic areas of Panama. Initial discrete typing units (DTUs) assignment was performed evaluating three single locus molecular markers (mini-exon, heat shock protein 60 and glucose-6-phosphate isomerase genes). Further diversity within TcI lineages was explored using a multi-locus sequence typing approach with six maxicircle genes. Haplotype network analysis and evolutionary divergency estimations were conducted to investigate the genetic relatedness between Panamanian TcI isolates and isolates from different endemic regions in the Americas. Our molecular approach validated that TcI is the predominant DTU circulating in Panama across different hosts and vector species, but also confirmed the presence of TcIII and TcVI circulating in the country. The phylogenetic tree topography for most Panamanian TcI isolates displayed a high level of genetic homogeneity between them. The haplotype network analysis inferred a higher genetic diversity within Panamanian TcI isolates, displaying eight different haplotypes circulating in endemic regions of the country, and revealed geographical structuring among TcI from different endemic regions in the Americas. This study adds novelty on the genetic diversity of T. cruzi circulating in Panama and complements regional phylogeographic studies regarding intra-TcI variations.

Evaluation of cytochrome b sequence to identify Leishmania species and variants: the case of Panama

BACKGROUND

The genetic heterogeneity of Leishmania parasites is a major factor responsible for the wide variety of Leishmania-associated manifestations. Consequently, understanding the genetic make-up of Leishmania species using suitable molecular markers is an important component of realising local and regional scale disease risk. The cytochrome b (cytb) is frequently used to type New World Leishmania species. However, its potential to discriminate Leishmania species and variants requires further evaluation.

OBJECTIVES

To explore the capacity of cytb gene to identify New World Leishmania species and variants and to develop an approach able to type local Leishmania species and variants.

METHODS

We retrieved 360 partial and complete Leishmania cytb gene sequences publicly available in GenBank database to study all single nucleotide polymorphisms (SNPs) across the cytb gene that differentiate New World Leishmania species. This information was used to develop an approach based upon the polymorphisms found in a DNA segment of 948bp. We also compared the typing results found with this technique with the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) profiling obtained using HSP70 gene as target. One hundred Panamanian isolates were used to both typed Leishmania species and assess local genetic variability.

FINDINGS

We found complete agreement between our cytb approach and the PCR-RFLP profiling method based on HSP70 for Leishmania species identification. Ninety-two isolates were identified as L. panamensis, although other Viannia species were found circulating at a lower frequency. Three L. panamensis haplotypes were identified in Panamanian provinces. We also provide an initial report of L. guyanensis haplotypes circulating in Panama.

MAIN CONCLUSIONS

Cytb gene sequence encompasses key main SNPs that aid to identify Leishmania species. The cytb approach developed with this information was able to identify and assess genetic variability of local Leishmania species found in this study.

Repeat-Driven Generation of Antigenic Diversity in a Major Human Pathogen, Trypanosoma cruzi

Trypanosoma cruzi, a zoonotic kinetoplastid protozoan parasite, is the causative agent of American trypanosomiasis (Chagas disease). Having a very plastic, repetitive and complex genome, the parasite displays a highly diverse repertoire of surface molecules, with pivotal roles in cell invasion, immune evasion and pathogenesis. Before 2016, the complexity of the genomic regions containing these genes impaired the assembly of a genome at chromosomal level, making it impossible to study the structure and function of the several thousand repetitive genes encoding the surface molecules of the parasite. We here describe the genome assembly of the Sylvio X10/1 genome sequence, which since 2016 has been used as a reference genome sequence for T. cruzi clade I (TcI), produced using high coverage PacBio single-molecule sequencing. It was used to analyze deep Illumina sequence data from 34 T. cruzi TcI isolates and clones from different geographic locations, sample sources and clinical outcomes. Resolution of the surface molecule gene distribution showed the unusual duality in the organization of the parasite genome, a synteny of the core genomic region with related protozoa flanked by unique and highly plastic multigene family clusters encoding surface antigens. The presence of abundant interspersed retrotransposons in these multigene family clusters suggests that these elements are involved in a recombination mechanism for the generation of antigenic variation and evasion of the host immune response on these TcI strains. The comparative genomic analysis of the cohort of TcI strains revealed multiple cases of such recombination events involving surface molecule genes and has provided new insights into T. cruzi population structure.

Molecular Identification of Parasites Causing Cutaneous Leishmaniasis in Panama

Isolates from 475 cutaneous leishmaniasis (CL) patients from three endemic regions were studied by three typing techniques. The molecular analysis from lesion scrapings based on hsp70 PCR-RFLP showed that 78.1% (371/475) restriction patterns corresponded to Leishmania (Viannia) panamensis, 19% (90/475) to Leishmania (Viannia) guyanensis, and 3.0% (14/475) to Leishmania (Viannia) braziliensis. Promastigotes isolated by culture from lesions of 228 patients (48.0%, 228/475) were identified by multi-locus enzyme electrophoresis. Of them, 95.2% (217/228) were typified as L. (V.) panamensis, 1.3% (3/228) as L. (V.) guyanensis, 2.2% (5/228) as L. (V.) braziliensis, and 1.3% (3/228) as hybrids (L. [V.] braziliensis/L. [V.] panamensis). However, a partial sequencing analysis of the hsp70 gene from 77 selected samples showed 16.9% (13/77) typified as L. (V.) panamensis, 68.8% (53/77) as Leishmania (V.) sp., 1, 3.9% (3/77) as L. (V.) guyanensis, 1.3% (1/77) as L. (V.) braziliensis outlier, 2.6% (2/77) as Leishmania (Viannia) naiffi, 2.6% as (2/77) Leishmania (V.) sp., and 2 and 3.9% (3/77) hybrid isolates of L. (V.) braziliensis/L. (V.) guyanensis. These results confirm L. (V.) panamensis as the predominant species and cause of CL lesions in Panama and that L. (V.) guyanensis, L. (V.) braziliensis, and L. (V.) naiffi are circulating to a lower degree. Furthermore, the determination of parasite isolates belonging to atypical clusters and hybrid isolates suggests the circulation of genetic variants with important implications for the epidemiology and clinical follow-up of CL in Panama. No evidence of the existence of parasites of the Leishmania (Leishmania) mexicana complex in Panamanian territory was found in this study.

Landscape disturbance impacts on Attalea butyracea palm distribution in central Panama

BACKGROUND

Increased Attalea butyracea palm propagation, notable for its role as key habitat for the primary Chagas disease vector in Panama, has been linked to landscape disturbance in single-palm observations in this region. Close proximity of these palms to human dwellings is proposed to increase risk of Chagas disease transmission from sylvatic transmission cycles to domestic transmission involving human populations. This study examines the relationship between landscape disturbance and mature A. butyracea spatial distribution, density, and proximity to human populations and vector and reservoir species' movement corridors at a regional scale in a 300 km2 heterogeneous tropical landscape in central Panama.

METHODS

We remotely identified the locations of over 50,000 mature A. butyracea palms using high-resolution WorldView2 satellite imagery. A local Getis-Ord Gi* spatial analysis identified significant clusters of aggregated palms. Associations between palm and cluster abundance and a landscape disturbance gradient, derived from official Panama land cover data, were tested using Chi-square tests for Homogeneity and Z-test for proportions. Kruskall-Wallis non-parametric analysis of variance tests were run to assess whether palm cluster area varied by disturbance level, or whether disturbance was associated with proximity of palms and palm clusters to susceptible populations or vector movement corridors.

RESULTS

Our findings indicate a regional relationship between landscape disturbance and A. butyracea occurrence. We observe a significant increase in both individual and clustered A. butyracea in secondary forest, but a reduction of palms in agricultural settings. We do not detect evidence of any reduction in abundance of palms in residential settings. The majority of residential and commercial buildings in our study area are within vector flight distance of potential vector habitat in palm crowns.

CONCLUSIONS

We observe probable anthropogenic elimination of A. butyracea palms in agricultural, but not residential, settings. Even in heavily deforested regions, significant concentrations of mature palms remain in close proximity to human establishments.

Plasmodium falciparum Genetic Diversity in Panamá Based on glurp, msp-1 and msp-2 Genes: Implications for Malaria Elimination in Mesoamerica

Panamá, together with all the nations in Mesoamerica, has committed to eliminate malaria from the region by 2020. As these countries approach malaria elimination and local transmission decreases, an active molecular surveillance to identify genotypes circulating along the border areas is particularly needed to accurately infer infection origin, drug resistance and disease propagation patterns in the region. This study evaluated the genetic diversity and allele frequencies of msp-1, msp-2 and glurp genes using different molecular analyses (nested PCR, PCR-restriction fragment length polymorphism (RFLP) and sequencing) from 106 autochthonous and imported P. falciparum isolates collected from different endemic areas in Panamá between 2003 and 2019. We also explored if P. falciparum genotypes assessed with these molecular markers were associated with relevant malaria epidemiological parameters using a multiple correspondence analysis. A strong association of certain local haplotypes with their geographic distribution in endemic areas, but also with parasite load and presence of gametocytes, was evidenced. Few multiclonal infections and low genetic diversity among locally transmitted P. falciparum samples were detected, consequent with the low transmission intensity of this parasite in Panamá, a pattern likely to be extended across Mesoamerica. In addition, several imported cases were genetically dissimilar to local infections and representative of more diverse extra-continental lineages.

Mixed infections by different Trypanosoma cruzi discrete typing units among Chagas disease patients in an endemic community in Panama

Background

Trypanosoma cruzi, the hemoparasite that causes Chagas disease, is divided into six Discrete Typing Units or DTUs: TcI-TcVI plus Tcbat. This genetic diversity is based on ecobiological and clinical characteristics associated with particular populations of the parasite. The main objective of this study was the identification of DTUs in patients with chronic chagasic infections from a mountainous rural community in the eastern region of Panama.

Methods

A total of 106 patients were tested for Chagas disease with three serological tests (ELISA, rapid test, and Western blot). Molecular diagnosis and DTU typing were carried out by conventional PCRs and qPCR targeting different genomic markers, respectively. As a control sample for the typing, 28 patients suspected to be chagasic from the metropolitan area of Panama City were included.

Results

Results showed a positivity in the evaluated patients of 42.3% (33/78); high compared to other endemic regions in the country. In the control group, 20/28 (71.43%) patients presented positive serology. The typing of samples from rural patients showed that 78.78% (26/33) corresponded to TcI, while 9.09% (3/33) were mixed infections (TcI plus TcII/V/VI). Seventy-five percent (15/20) of the patients in the control group presented TcI, and in five samples it was not possible to typify the T. cruzi genotype involved.

Conclusions

These results confirm that TcI is the main DTU of T. cruzi present in chronic chagasic patients from Panama. However, the circulation of other genotypes (TcII/V/VI) in this country is described for the first time. The eco-epidemiological characteristics that condition the circulation of TcII/V/VI, as well as the immune and clinical impact of mixed infections in this remote mountainous region should be investigated, which will help local action programs in the surveillance, prevention, and management of Chagas disease.

In situ study of cellular immune response in human cutaneous lesions caused by Leishmania (Viannia) panamensis in Panama

AIMS

Leishmaniasis is considered a disease with multiple clinical/immunopathological characteristics, depending on the immunity of the host and the species of the parasite. In Panama, the most prevalent species that causes localized cutaneous leishmaniasis (LCL) is Leishmania (Viannia) panamensis, and its immune response is poorly studied. Therefore, we evaluated by immunohistochemistry, the in situ immune response during this infection.

METHODS AND RESULTS

Biopsies from Panamanian patients with LCL were collected and processed by histological techniques. Infection by L. (V.) panamensis was demonstrated by isolation in culture and molecular characterization by Hsp70-RFLP. The in situ immune response was assessed by immunohistochemistry. The immune response was characterized by predominance of T cells, mainly CD8 cells that showed positive correlation with IFN-γ and Granzyme B. CD4 cells presented positive correlation with both IFN-γ and IL-13, pointed by mixed cellular immune response. Regulatory response was characterized by FoxP3 cells, which showed positive correlation to IL-10 but not with TGF-β.

CONCLUSIONS

L. (V.) panamensis infection triggers a mixed cellular immune response, characterized by the presence of pro-inflammatory, anti-inflammatory and regulatory elements in the skin lesion of Panamanian patients. These data contribute to a better understanding of the immunopathogenesis of Leishmania Viannia infection in Panama.

Long-term transmission patterns and public health policies leading to malaria elimination in Panamá

Background

The present study provides a countrywide perspective of the malaria situation in Panamá over a long-term framework, with the purpose of identifying historical malaria resurgence events and their potential causes.

Methods

A descriptive-ecological study was conducted by analysing demographic and epidemiological annual malaria time series data in Panamá (1884–2019) using several data sources. Malaria intensity indicators were calculated during the study period. The effects of El Niño Southern Oscillation on malaria transmission were also analysed using a retrospective analysis of malaria cases between 1957 and 2019.

Results

Several factors were identified responsible for malaria resurgence in Panamá, mostly related with Malaria Control Programme weakening. During the past 20 years (2000–2019) malaria has progressively increased in prevalence within indigenous settlements, with a predominance of male cases and a high proportion (15% of total cases) in children less than 5 years old. During this period, a significant and increasing proportion of the Plasmodium falciparum cases were imported. Retrospective analysis (1957–2019) evidenced that ENSO had a significant impact on malaria transmission dynamics in Panamá.

Conclusions

Data analysis confirmed that although authorities have been successful in focalizing malaria transmission in the country, there are still neglected issues to be solved and important intercultural barriers that need to be addressed in order to achieve elimination of the disease by 2022. This information will be useful for targeting strategies by the National Malaria Elimination Programme.

Population genetics of two chromatic morphs of the Chagas disease vector Rhodnius pallescens Barber, 1932 in Panamá

Rhodnius pallescens is the principal vector of Chagas disease in Panama. Recently a dark chromatic morph has been discovered in the highlands of Veraguas Province. Limited genetic studies have been conducted with regards to the population structure and dispersal potential of Triatominae vectors, particularly in R. pallescens. Next generation sequencing methods such as RADseq and complete mitochondrial DNA (mtDNA) genome sequencing have great potential for examining vector biology across space and time. Here we utilize a RADseq method (3RAD), along with complete mtDNA sequencing, to examine the population structure of the two chromatic morpho types of R. pallescens in Panama. We sequenced 105 R. pallescens samples from five localities in Panama. We generated a 2216 SNP dataset and 6 complete mtDNA genomes. RADseq showed significant differentiation among the five localities (F_CT = 0.695; P = .004), but most of this was between localities with the dark vs. light chromatic morphs (Veraguas vs. Panama Oeste). The mtDNA genomes showed a 97-98% similarity between dark and light chromatic morphs across all genes and a 502 bp insert in light morphs. Thus, both the RADseq and mtDNA data showed highly differentiated clades with essentially no gene flow between the dark and light chromatic morphs from Veraguas and central Panama respectively. We discuss the growing evidence showing clear distinctions between these two morpho types with the possibility that these are separate species, an area of research that requires further investigation. Finally, we discuss the cost-effectiveness of 3RAD which is a third of the cost compared to other RADseq methods used recently in Chagas disease vector research.

Prevalence and subtype distribution of Blastocystis sp. infecting children from a rural community in Panama

Blastocystis sp. is a commonly reported intestinal parasite with a worldwide distribution. Phylogenetic analyses describe at least 17 subtypes for this parasite, and nine of them have been found in humans. However, the prevalence and some epidemiological characteristics of this parasitic infection in rural communities are not well known. The objective of this cross-sectional study was to evaluate the prevalence, subtypes, and epidemiological factors related to Blastocystis sp. Infection in children from of a small rural community in the central area of Panama. For this, 66 fecal samples from children (1 to 12 years old), were initially analyzed for the presence of parasites by a formalin-ethyl acetate/concentration method. Molecular detection and identification of Blastocystis sp. subtypes were carried out by amplification and sequencing of a partial fragment of the small-subunit ribosomal RNA gene. Using data from a questionnaire, analyses of epidemiological conditions potentially associated with Blastocystis sp. transmission were also conducted. Microscopic diagnostics showed that 33.3% (22/66) of the analyzed samples presented entero-parasites. Among them, Blastocystis sp. was the most prevalent, with 21.2% (14/66), followed by the E. histolytica/dispar/moshkovskii complex 4.5% (3/66), Giardia lamblia 1.5% (1/66) and Strongyloides stercoralis 1.5% (1/66). PCR-based analyses detected a prevalence of Blastocystis sp. infection of 74.2% (49/66) in apparently healthy children. Phylogenetic analysis revealed two different subtypes of this parasite: ST1 with 42.2% (28/66) infected, and ST3 with 31.8% (21/66) infected. In addition, recent diarrhea was significantly associated with Blastocystis sp. infection. None of the other risk factors evaluated was statistically associated with infection. These results highlight the need to further investigate clinical, epidemiological, and genetic characteristics of Blastocystis sp. infections in this community.

Leishmania spp. Infection Rate and Feeding Patterns of Sand Flies (Diptera: Psychodidae) from a Hyperendemic Cutaneous Leishmaniasis Community in Panamá

American cutaneous leishmaniasis (ACL) is a common and important vector-borne parasitic zoonosis in Panamá. Here, we study Leishmania spp. infection rates and blood-feeding patterns among common sand flies in Trinidad de Las Minas, a rural community with hyperendemic ACL transmission, and where a deltamethrin fogging trial was performed. Sand flies were collected from April 2010 to June 2011 with light traps installed inside and in the peridomicile of 24 houses. We restricted our analysis to the most abundant species at the study site: Lutzomyia trapidoi, Lutzomyia gomezi, Lutzomyia panamensis, Lutzomyia triramula, and Lutzomyia dysponeta. We detected Leishmania spp. infection in sand flies by polymerase chain reaction (PCR) amplification of the internal transcribed spacer region 1 (ITS-1) in pooled females (1-10 females per pool). Host species of engorged sand flies were identified using a cytochrome b PCR. From 455 sand fly pools analyzed, 255 pools were positive for Leishmania spp., with an estimated infection rate (confidence interval) of 0.096 [0.080-0.115] before the deltamethrin fogging which slightly, but not significantly (P > 0.05), increased to 0.116 [0.098-0.136] after the deltamethrin fogging. Blood meal analysis suggested that pigs, goats, and birds were the most common sand fly blood sources, followed by humans and domestic dogs. DNA sequencing from a subsample of ITS-1 positive pools suggests that Leishmania panamensis, Leishmania naiffi, and other Leishmania spp. were the parasite species infecting the most common vectors at the study site. Our data confirm an association between sand fly species, humans, domestic dogs, and pigs and Leishmania spp. parasites in rural Panamá.

Regional biogeography of microbiota composition in the Chagas disease vector Rhodnius pallescens

Background

Triatomine bugs are vectors of the protozoan parasite Trypanosoma cruzi, which causes Chagas disease. Rhodnius pallescens is a major vector of Chagas disease in Panama. Understanding the microbial ecology of disease vectors is important in the development of vector management strategies that target vector survival and fitness. In this study we examined the whole-body microbial composition of R. pallescens from three locations in Panama.

Methods

We collected 89 R. pallescens specimens using Noireau traps in Attalea butyracea palms. We then extracted total DNA from whole-bodies of specimens and amplified bacterial microbiota using 16S rRNA metabarcoding PCR. The 16S libraries were sequenced on an Illumina MiSeq and analyzed using QIIME2 software.

Results

We found Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes to be the most abundant bacterial phyla across all samples. Geographical location showed the largest difference in microbial composition with northern Veraguas Province having the most diversity and Panama Oeste Province localities being most similar to each other. Wolbachia was detected in high abundance (48–72%) at Panama Oeste area localities with a complete absence of detection in Veraguas Province. No significant differences in microbial composition were detected between triatomine age class, primary blood meal source, or T. cruzi infection status.

Conclusions

We found biogeographical regions differ in microbial composition among R. pallescens populations in Panama. While overall the microbiota has bacterial taxa consistent with previous studies in triatomine microbial ecology, locality differences are an important observation for future studies. Geographical heterogeneity in microbiomes of vectors is an important consideration for future developments that leverage microbiomes for disease control.

First Case of Diffuse Leishmaniasis Associated With Leishmania panamensis

Leishmania panamensis is the most common species of Leishmania in Panama, and it is known to cause cutaneous leishmaniasis, disseminated cutaneous leishmaniasis, and mucocutaneous leishmaniasis; however, it not associated with diffuse cutaneous disease. In this study, we report the first case of diffuse cutaneous leishmaniasis caused by L panamensis.

A darker chromatic variation of Rhodnius pallescens infected by specific genetic groups of Trypanosoma rangeli and Trypanosoma cruzi from Panama

BACKGROUND

Rhodnius pallescens, the only species of this genus reported in Panama, has a wide geographical distribution and is associated with most cases of Chagas disease and human infections with Trypanosoma rangeli in this country. Thus far, no phenotypic variants of this triatomine have been registered. Similarly, genotyping of the trypanosomes that infect this vector has only been partially evaluated.

RESULTS

A total of 347 specimens of R. pallescens were collected in Attalea butyracea palm trees located near a mountainous community of the district of Santa Fe, province of Veraguas. Bugs were slightly longer and had a darker coloration compared to that reported for this species. Infection rates for trypanosomes performed with three PCR analyses showed that 41.3% of the adult triatomines were positive for T. cruzi, 52.4% were positive for T. rangeli and 28.6% had mixed T. cruzi/T. rangeli infections. Based on cox2 analysis, TcI was the single T. cruzi discrete typing unit (DTU) detected, and a genetic variant of KP1(-)/lineage C was the only genetic group found for T. rangeli.

CONCLUSIONS

A darker chromatic variation of R. pallescens predominates in a mountainous region of Panama. These triatomines show high trypanosome infection rates, especially with T. rangeli. Regarding T. rangeli genetic diversity, complementary studies using other molecular markers are necessary to better define its phylogenetic position.

Trypanosoma cruzi Infection in Rhodnius pallescens (Heteroptera: Reduviidae) Infesting Coyol Palms in the Dry Arch of Panamá

Ecoepidemiological scenarios for Trypanosoma cruzi Chagas transmission are partially shaped by kissing bug vector ecology. The presence of Attalea butyracea Kunth, the 'royal palm', is a major risk factor for Chagas disease transmission in Panamá given their frequent infestations by Rhodnius pallescens Barber, a major neotropical T. cruzi vector. It was assumed that in Panamá this relationship was very close and unique, limiting the niche of R. pallescens to that of Att. butyracea. However, here we present observations about T. cruzi-infected R. pallescens infesting coyol palms, Acrocomia aculeata Jacquin, in Pedasí district, Los Santos Province, Panamá. Between May 2015 and August 2016, we sampled kissing bugs from 83 coyol palms using mice-baited traps placed at the crown of each palm during the dry and wet season. We collected 62 R. pallescens and one Eratyrus cuspidatus Stål kissing bugs. Using logistic regression, we found that the probability of kissing bug infestation in coyol palms increased during the rainy season, with infructescence number and palm height. We examined adult R. pallescens bugs (n = 30) and found T. cruzi in 67% of the samples. We were able to isolate and characterize T. cruzi from parasites present in the feces from R. pallescens, all parasites belonging to the TC I lineage. We found that green fronds number and house proximity increased T. cruzi infection probability in kissing bugs collected in coyol palms. These results highlight coyol palms as a potential risk factor for Chagas disease transmission in the dry arch of Panamá.

Histopathological characteristics of cutaneous lesions caused by Leishmania Viannia panamensis in Panama

Cutaneous leishmaniasis (CL) is an endemic disease in the Republic of Panama, caused by Leishmania (Viannia) parasites, whose most common clinical manifestation is the presence of ulcerated lesions on the skin. These lesions usually present a chronic inflammatory reaction, sometimes granulomatous, with the presence of lymphocytes, plasma cells and macrophages. This study describes the histopathological characteristics found in the skin lesions of patients with CL caused by Leishmania (V.) panamensis in Panama. We analyzed 49 skin biopsy samples from patients with clinical suspicion of CL, by molecular tests (PCR for subgenus Viannia and HSP-70) and by Hematoxylin-Eosin staining. Samples were characterized at the species level by PCR-HSP-70/RFLP. From the 49 samples studied, 46 (94%) were positive by PCR and were characterized as Leishmania (V.) panamensis. Of these, 48% were positive by Hematoxylin-Eosin staining with alterations being observed both, in the epidermis (85%) and in the dermis (100%) of skin biopsies. The inflammatory infiltrate was characterized according to histopathological patterns: lymphohistiocytic (50%), lymphoplasmacytic (61%) and granulomatous (46%) infiltration, being the combination of these patterns frequently found. The predominant histopathological characteristics observed in CL lesions caused by L. (V.) panamensis in Panama were: an intense inflammatory reaction in the dermis with a combination of lymphohistiocytic, lymphoplasmacytic and granulomatous presentation patterns and the presence of ulcers, acanthosis, exocytosis and spongiosis in the epidermis.

Blood Meal Source Characterization Using Illumina Sequencing in the Chagas Disease Vector Rhodnius pallescens (Hemiptera: Reduviidae) in Panamá

Accurate blood meal identification is critical to understand hematophagous vector-host relationships. This study describes a customizable Next-Generation Sequencing (NGS) approach to identify blood meals from Rhodnius pallescens (Hemiptera: Reduviidae) triatomines using multiple barcoded primers and existing software to pick operational taxonomic units and match sequences for blood meal identification. We precisely identified all positive control samples using this method and further examined 74 wild-caught R. pallescens samples. With this novel blood meal identification method, we detected 13 vertebrate species in the blood meals, as well as single and multiple blood meals in individual bugs. Our results demonstrate the reliability and descriptive uses of our method.

Synanthropic Mammals as Potential Hosts of Tick-Borne Pathogens in Panama

Synanthropic wild mammals can be important hosts for many vector-borne zoonotic pathogens. The aim of this study was determine the exposure of synanthropic mammals to two types of tick-borne pathogens in Panama, spotted fever group Rickettsia (SFGR) and Borrelia relapsing fever (RF) spirochetes. One hundred and thirty-one wild mammals were evaluated, including two gray foxes, two crab-eating foxes (from zoos), four coyotes, 62 opossum and 63 spiny rats captured close to rural towns. To evaluate exposure to SFGR, serum samples from the animals were tested by indirect immunofluorescence assay (IFA) using Rickettsia rickettsii and Candidatus Rickettsia amblyommii antigen. Immunoblotting was performed using Borrelia turicatae protein lysates and rGlpQ, to assess infection caused by RF spirochetes. One coyote (25%) and 27 (43%) opossums showed seroreactivity to SFGR. Of these opossums, 11 were seroreactive to C. R. amblyommii. Serological reactivity was not detected to B. turicatae in mammal samples. These findings may reflect a potential role of both mammals in the ecology of tick-borne pathogens in Panama.

Risk factors associated with Trypanosoma cruzi exposure in domestic dogs from a rural community in Panama

Chagas disease, caused by Trypanosoma cruzi infection, is a zoonosis of humans, wild and domestic mammals, including dogs. In Panama, the main T. cruzi vector is Rhodnius pallescens, a triatomine bug whose main natural habitat is the royal palm, Attalea butyracea. In this paper, we present results from three T. cruzi serological tests (immunochromatographic dipstick, indirect immunofluorescence and ELISA) performed in 51 dogs from 24 houses in Trinidad de Las Minas, western Panama. We found that nine dogs were seropositive (17.6% prevalence). Dogs were 1.6 times more likely to become T. cruzi seropositive with each year of age and 11.6 times if royal palms where present in the peridomiciliary area of the dog's household or its two nearest neighbours. Mouse-baited-adhesive traps were employed to evaluate 12 peridomestic royal palms. All palms were found infested with R. pallescens with an average of 25.50 triatomines captured per palm. Of 35 adult bugs analysed, 88.6% showed protozoa flagellates in their intestinal contents. In addition, dogs were five times more likely to be infected by the presence of an additional domestic animal species in the dog's peridomiciliary environment. Our results suggest that interventions focused on royal palms might reduce the exposure to T. cruzi infection.

Calmodulin Polymerase Chain Reaction-Restriction Fragment Length Polymorphism for Leishmania Identification and Typing

A precise identification of Leishmania species involved in human infections has epidemiological and clinical importance. Herein, we describe a preliminary validation of a restriction fragment length polymorphism assay, based on the calmodulin intergenic spacer region, as a tool for detecting and typing Leishmania species. After calmodulin amplification, the enzyme HaeIII yielded a clear distinction between reference strains of Leishmania mexicana, Leishmania amazonensis, Leishmania infantum, Leishmania lainsoni, and the rest of the Viannia reference species analyzed. The closely related Viannia species: Leishmania braziliensis, Leishmania panamensis, and Leishmania guyanensis, are separated in a subsequent digestion step with different restriction enzymes. We have developed a more accessible molecular protocol for Leishmania identification/typing based on the exploitation of part of the calmodulin gene. This methodology has the potential to become an additional tool for Leishmania species characterization and taxonomy.

Macroecological patterns of American Cutaneous Leishmaniasis transmission across the health areas of Panamá (1980-2012)

American Cutaneous Leishmaniasis (ACL) is a neglected vector-borne zoonosis that persists despite increasing socio-economic development and urbanization in Panamá. Here, we investigate the association between environmental changes and spatio-temporal ACL transmission in the Republic of Panamá (1980-2012). We employ a macroecological approach, where patterns of variation in ACL incidence at the spatially coarse-grained scale of health areas are studied considering factors linked to the ecology of ACL transmission. We specifically study impacts of climatic variability, measured by the different phases of El Niño Southern Oscillation (ENSO), within diverse ecosystems and sand fly (Diptera: Psychodidae) vector species, as well as heterogeneous local climatic patterns, deforestation, population growth rates, and changes in social marginalization. We found that over the study period, patterns of ACL incidence: (i) were asynchronous with clusters changing from east to west of the Panamá Canal, (ii) trends increased in the west, and decreased or remained nearly constant in the east, independent of human population growth, (iii) generally increased in years following El Niño, and (iv) decreased as forest cover increased. We found no significant association between changes in socio-economic indicators and ACL transmission. Regarding vector abundance and presence, we found that studies had been biased to locations east of the Panamá canal, and that, in general, the abundance of dominant vector species decreased during the cold phase of ENSO. Finally, our results indicate that a macroecological approach is useful to understand heterogeneities related to environmental change impacts on ACL transmission.

On palms, bugs, and Chagas disease in the Americas

Palms are ubiquitous across Neotropical landscapes, from pristine forests or savannahs to large cities. Although palms provide useful ecosystem services, they also offer suitable habitat for triatomines and for Trypanosoma cruzi mammalian hosts. Wild triatomines often invade houses by flying from nearby palms, potentially leading to new cases of human Chagas disease. Understanding and predicting triatomine-palm associations and palm infestation probabilities is important for enhancing Chagas disease prevention in areas where palm-associated vectors transmit T. cruzi. We present a comprehensive overview of palm infestation by triatomines in the Americas, combining a thorough reanalysis of our published and unpublished records with an in-depth review of the literature. We use site-occupancy modeling (SOM) to examine infestation in 3590 palms sampled with non-destructive methods, and standard statistics to describe and compare infestation in 2940 palms sampled by felling-and-dissection. Thirty-eight palm species (18 genera) have been reported to be infested by ∼39 triatomine species (10 genera) from the USA to Argentina. Overall infestation varied from 49.1-55.3% (SOM) to 62.6-66.1% (dissection), with important heterogeneities among sub-regions and particularly among palm species. Large palms with complex crowns (e.g., Attalea butyracea, Acrocomia aculeata) and some medium-crowned palms (e.g., Copernicia, Butia) are often infested; in slender, small-crowned palms (e.g., Euterpe) triatomines associate with vertebrate nests. Palm infestation tends to be higher in rural settings, but urban palms can also be infested. Most Rhodnius species are probably true palm specialists, whereas Psammolestes, Eratyrus, Cavernicola, Panstrongylus, Triatoma, Alberprosenia, and some Bolboderini seem to use palms opportunistically. Palms provide extensive habitat for enzootic T. cruzi cycles and a critical link between wild cycles and transmission to humans. Unless effective means to reduce contact between people and palm-living triatomines are devised, palms will contribute to maintaining long-term and widespread, albeit possibly low-intensity, transmission of human Chagas disease.

[Knowledge and risk factors related to Chagas' disease in two Panamanian communities where Rhodnius pallescens is the main vector]

INTRODUCTION

The implementation of surveillance, control and prevention measures for Chagas´ disease requires an integrated approach. The sustainability of programs depends on community participation supported on a basic understanding of the problem.

OBJECTIVE

To evaluate the knowledge of people interviewed which facilitates or limits the surveillance, prevention and control of Chagas' disease in two endemic Panamanian communities where Rhodnius pallescens is the main vector.

MATERIALS AND METHODS

A questionnaire assessed the knowledge and risk factors related to Chagas' disease in 201 people over 10 years of age from the endemic communities of Las Pavas and Lagartera Grande located on the western shore of Panama Canal. Additionally, with the help of the residents, the presence of triatomine bugs in 93 dwellings was evaluated during a year.

RESULTS

Of those interviewed, 69.2% (139/201) had poor or very poor knowledge about Chagas' disease. Nearly 93% (187/201) was exposed to moderate or high risk factors. Triatomine bugs were collected in 20.4% (19/93) of the evaluated homes; 80% (66/76) of them were R. pallescens. Significant association was found between the presence of triatomines inside the houses and precarious housing (p<0.01).

CONCLUSION

Despite having been exposed to health education-related programs, it is necessary to strengthen the basic knowledge about Chagas' disease in the two communities before establishing prevention and surveillance measures which involve active participation of its inhabitants.

Survey of wild mammal hosts of cutaneous leishmaniasis parasites in panamá and costa rica

The eco-epidemiology of American cutaneous leishmaniasis (ACL) is driven by animal reservoir species that are a source of infection for sand flies that serve as vectors infecting humans with Leishmania spp parasites. The emergence and re-emergence of this disease across Latin America calls for further studies to identify reservoir species associated with enzootic transmission. Here, we present results from a survey of 52 individuals from 13 wild mammal species at endemic sites in Costa Rica and Panama where ACL mammal hosts have not been previously studied. For Leishmania spp. diagnostics we employed a novel PCR technique using blood samples collected on filter paper. We only found Leishmania spp parasites in one host, the two-toed sloth, Choloepus hoffmanni. Our findings add further support to the role of two-toed sloths as an important ACL reservoir in Central America.

Domestic dog health worsens with socio-economic deprivation of their home communities

Dogs play an important role in infectious disease transmission as reservoir hosts of many zoonotic and wildlife pathogens. Nevertheless, unlike wildlife species involved in the life cycle of pathogens, whose health status might be a direct reflection of their fitness and competitive abilities, dog health condition could be sensitive to socio-economic factors impacting the well-being of their owners. Here, we compare several dog health indicators in three rural communities of Panama with different degrees of socio-economic deprivation. From a total of 78 individuals, we collected blood and fecal samples, and assessed their body condition. With the blood samples, we performed routine hematologic evaluation (complete blood counts) and measured cytokine levels (Interferon-γ and Interleukin-10) through enzyme-linked immunosorbent assays. With the fecal samples we diagnosed helminthiases. Dogs were also serologically tested for exposure to Trypanosoma cruzi and canine distemper virus, and molecular tests were done to assess T. cruzi infection status. We found significant differences between dog health measurements, pathogen prevalence, parasite richness, and economic status of the human communities where the dogs lived. We found dogs that were less healthy, more likely to be infected with zoonotic pathogens, and more likely to be seropositive to canine distemper virus in the communities with lower economic status. This study concludes that isolated communities of lower economic status in Panama may have less healthy dogs that could become major reservoirs in the transmission of diseases to humans and sympatric wildlife.

Enteric parasites and enteroaggregative Escherichia coli in children from Cañazas County, Veraguas Province, Panama

This study was designed to examine the height-for-age z-scores (HAZ), and the prevalence of intestinal inflammation, gastrointestinal infections with parasites, and enteroaggregative Escherichia coli (EAEC) in rural Panamanian children. Stool microscopy and polymerase chain reaction (PCR) testing for EAEC detected Giardia lamblia (32%, 32 of 100) and EAEC (13%, 11 of 87) in the study participants, respectively. Anthropometric analyses showed that those children who were > 12 months of age had lower HAZ scores (mean of -1.449) than the reference population. As a group, the children in the study 1 to 5 years of age did not show recovery from the previously mentioned decline in terms of their HAZ. The HAZ means of the children infected with G. lamblia, EAEC, and Ascaris lumbricoides were -1.49, -1.67, and -2.11, respectively. Furthermore, the study participants with A. lumbricoides and EAEC infections in the presence of lactoferrin showed another decrease of 0.19 and 0.13, respectively, in their HAZ means.

Genetic, cytogenetic and morphological trends in the evolution of the Rhodnius (Triatominae: Rhodniini) trans-Andean group

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.

The calmodulin intergenic spacer as molecular target for characterization of Leishmania species

Background

Human leishmaniasis is a neglected disease caused by parasites of the genus Leishmania. Clinical aspects of this disease can vary significantly, reflecting the wide range of parasites in the genus Leishmania. Knowing accurately the Leishmania species infecting humans is important for clinical case management and evaluation of epidemiological risk. Calmodulin is an essential gene in trypanosomatids that modulates the calcium metabolism in various cellular activities. Despite its strong conservation in trypanosomatids, it has been recently observed that its untranslated regions (UTR) diverge among species.

Methods

In this study we analyzed the sequences and the absolute dinucleotide frequency of the intergenic spacer of the calmodulin gene (containing both, 3′ and 5′UTR) in nine reference Leishmania species and ten clinical isolates obtained from patients with cutaneous leishmaniasis.

Results

We show that the short calmodulin intergenic spacers exhibit features that make them interesting for applications in molecular characterization and phylogenetic studies of Leishmania. Dendrograms based on sequence alignments and on the dinucleotide frequency indicate that this particular region of calmodulin gene might be useful for species typing between the Leishmania and Viannia subgenera.

Conclusions

Mutations and composition of the calmodulin intergenic spacer from Leishmania species might have taxonomic value as parameters to define if an isolate is identical to a certain species or belongs to one of the two current subgenera.

What explains variation in the impacts of exotic plant invasions on the nitrogen cycle? A meta-analysis

Exotic plant invasions can notably alter the nitrogen (N) cycle of ecosystems. However, there is large variation in the magnitude and direction of their impact that remains unexplained. We present a structured meta-analysis of 100 papers, covering 113 invasive plant species with 345 cases of invasion across the globe and reporting impacts on N cycle-related metrics. We aim to explain heterogeneity of impacts by considering methodological aspects, properties of the invaded site and phylogenetic and functional characteristics of the invaders and the natives. Overall, plant invasions increased N pools and accelerated fluxes, even when excluding N-fixing invaders. The impact on N pools depended mainly on functional differences and was greater when the invasive plants and the natives differed in N-fixation ability, plant height and plant/leaf habit. Furthermore, the impact on N fluxes was related mainly to climate, being greater under warm and moist conditions. Our findings show that more functionally distant invaders occurring in mild climates are causing the strongest alterations to the N cycle.

Leishmaniasis sand fly vector density reduction is less marked in destitute housing after insecticide thermal fogging

BACKGROUND

Insecticide 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.

METHODS

We 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.

RESULTS

We 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.

CONCLUSION

Our results suggest the potential of insecticide application to control SF density and leishmaniasis transmission could depend on housing quality beyond insecticide efficiency.

Clinical cutaneous leishmaniasis rates are associated with household Lutzomyia gomezi, Lu. Panamensis, and Lu. trapidoi abundance in Trinidad de Las Minas, western Panama

American cutaneous leishmaniasis (ACL) transmission patterns have been increasingly associated with domestic and peridomestic environments. Here, we present results from an epidemiological survey of 94 people from 24 households in Trinidad de Las Minas, western Panama. We studied the role of sand fly abundance, housing quality, peridomicile landscape matrix, and vegetation structure on shaping household clinical ACL rate patterns at Trinidad de Las Minas. We found that sand fly abundance was significantly associated with household clinical ACL rates, with a 6% rate increase for each additional Lutzomyia gomezi sand fly found inside a domicile.

Changes in phlebotomine sand fly species composition following insecticide thermal fogging in a rural setting of Western panamá

American Cutaneous Leishmaniasis, ACL, is a zoonotic disease with a large richness of co-occurring vector species in transmission foci. Here, we describe changes in patterns of phlebotomine sand fly (Diptera: Psychodidae: Phlebotominae) species composition at the village of Trinidad de Las Minas, Capira, Panamá, a hyperendemic focus of ACL transmission, subjected to a vector control intervention with insecticide thermal fogging (ITF). Our study setting consisted of 24 houses, 12 subjected to two rounds of ITF and 12 kept as control. During 15 months (April 2010- June 2011) we monitored sand fly species composition and abundance with modified HP light traps inside (domicile) and outside (peridomicile) the studied houses. From 5628 sand flies collected, we were able to identify 5617 of the samples into 24 species, a number of species close to 25±1.6, the estimate from the Chao2 Index. The most abundant species were Lutzomya trapidoi (20%), Lu. gomezi (20%) and Lu. triramula (20%). Cluster analyses showed that most of the 24 houses had high similarity in relative abundance patterns of the six most common species, with only few peripheral houses not following the main cluster pattern. We also found that species richness was decreased to 22 species in the fogged houses, of which only 19 were found in the domiciliary environment. Changes in species richness were especially notorious at the end of the wet season. Our results suggest that species richness can decrease following ITF in domiciliary environments, primarily affecting the less common species.

Host life history strategy, species diversity, and habitat influence Trypanosoma cruzi vector infection in Changing landscapes

BACKGROUND

Anthropogenic 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 r(max), 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 r(max) were positively associated with higher vector infection rate at a site.

CONCLUSIONS/SIGNIFICANCE

In 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.

Evaluation of PCR for cutaneous leishmaniasis diagnosis and species identification using filter paper samples in Panama, Central America

Cutaneous leishmaniasis (CL) is a major vectorborne disease in Panama. In this study, the diagnostic performance and usefulness of two DNA extraction procedures from skin scraping samples collected on FTA filter paper for subsequent PCR diagnosis of CL was evaluated. A positive CL laboratory diagnosis was based on a positive parasitological test (Giemsa-stained smears or in vitro culture) and/or positive PCR test performed from skin scrapings collected in TE buffer (PCR-TE). Of 100 patients with skin lesions suggestive of CL, 82 (82%) were confirmed as CL positive. The sensitivity was calculated for each of the PCR approaches from samples collected on filter paper. The highest sensitivity was achieved by PCR-FTA processed by Chelex 100 (PCR-Chelex) (0.94). PCR-FTA extracted using the FTA purification reagent presented a lower sensitivity (0.60). Good concordance between routine PCR-TE and PCR-Chelex was observed (percent agreement=0.88, κ index=0.65). In conclusion, use of FTA filter paper for skin scraping collection combined with PCR is a reliable and convenient method for CL diagnosis in Panama, with comparable performance to the routine PCR method and with improved sensitivity compared with those of conventional parasitological methods.

A new endemic focus of Chagas disease in the northern region of Veraguas Province, Western Half Panama, Central America

BACKGROUND

Chagas disease was originally reported in Panama in 1931. Currently, the best knowledge of this zoonosis is restricted to studies done in historically endemic regions. However, little is known about the distribution and epidemiology of Chagas disease in other rural areas of the country.

METHODS AND FINDINGS

A cross-sectional descriptive study was carried out between May 2005 - July 2008 in four rural communities of the Santa Fe District, Veraguas Province. The study included an entomologic search to collect triatomines, bloodmeal type identification and infection rate with trypanosomes in collected vectors using a dot- blot and PCR analysis, genotyping of circulating Trypanosoma cruzi (mini-exon gene PCR analysis) and the detection of chagasic antibodies among inhabitants. The vector Rhodnius pallescens was more frequently found in La Culaca and El Pantano communities (788 specimens), where it was a sporadic household visitor. These triatomines presented darker coloration and larger sizescompared with typical specimens collected in Central Panama. Triatoma dimidiata was more common in Sabaneta de El Macho (162 specimens). In one small sub-region (El Macho), 60% of the houses were colonized by this vector. Of the examined R. pallescens, 54.7.0% (88/161) had fed on Didelphis marsupialis, and 24.6% (34/138) of T. dimidiata specimens collected inside houses were positive for human blood. R. pallescens presented an infection index with T. cruzi of 17.7% (24/136), with T. rangeli of 12.5% (17/136) and 50.7% (69/136) were mixed infections. In 117 T. dimidiata domestic specimens the infection index with T. cruzi was 21.4%. Lineage I of T. cruzi was confirmed circulating in these vectors. A T. cruzi infection seroprevalence of 2.3% (24/1,056) was found in this population.

CONCLUSIONS

This is the first report of Chagas disease endemicity in Santa Fe District, and it should be considered a neglected public health problem in this area of Panama.

[Evaluation of the toxic activity of the pyrethroid insecticides deltamethrin and lambdacyhalothrin in two Panamanian field populations of Rhodnius pallescens (Hemíptera: Reduviidae)]

INTRODUCTION

Systematic evaluation of the susceptibility of disease vectors to insecticides permits the detection of the development of insecticide resistance over time. This is necessary to evaluate the effectiveness of control methods and to plan management strategies of the resistance.

OBJECTIVE

The baseline susceptibility was determined for I and V instar nymphs of Rhodnius pallescens to the active ingredients of the insecticides deltamethrin and lambdacyhalothrin.

MATERIALS AND METHODS

The bioassays were applied to two field populations of R. pallescens collected in Chilibre and Cerro Cama, Panamá. A standard protocol for topical application was adapted from that developed for Rhodnius prolixus. Bioassays were performed using topical applications on the dorsal abdominal surface, with volumes of 0.1µl and 0.5µl acetone solution of insecticide for nymphs of stage I and V respectively, using 5µl and 25µl Hamilton microsyringes with a repeating dispenser. Ten nymphs were used for each insecticide concentration. Results. With the topical application of lambdacyhalothrin on first-instar nymphs from Chilibre and Cerro Cama, the LD50 values expressed in ng/insect were 0.13 and 0.11 respectively. In fifth-instar nymphs the LD50 values were 1.71 and 3.48, respectively. For deltamethrin, the topical application on first-instar nymphs resulted in LD50 values of 0.02 and 0.02, and in fifth-instar nymphs the LD50 values were 2.11 and 1.55, respectively.

CONCLUSIONS

In I and V instar nymphs from the two R. pallescens populations, resistance factor values demonstrated no significant difference in the toxic effects of the two insecticides and indicated that the R. pallescens populations were susceptible them.

Human trypanosomiasis in the eastern region of the Panama Province: new endemic areas for Chagas disease

The epidemiology of Chagas disease was studied in five rural communities located in the eastern region of the Panama Province. Serological tests for Trypanosoma cruzi infection revealed a prevalence of 5.88% (12/204). Hemocultures coupled with polymerase chain reaction (PCR) analysis showed a Trypanosoma rangeli infection rate of 5.88% (12/204). An overall trypanosome infection index of 11.76% (24/204) was detected in this population. A total of 121 triatomine specimens were collected in domestic and peridomestic habitats. Rhodnius pallescens was confirmed as the predominant species. Molecular analysis showed that 17.8% (13/73) of the examined insects were positive for T. cruzi, 17.8% (13/73) for T. rangeli, and 35.6% (26/73) presented mixed infections. Among 73 R. pallescens evaluated, 16.4% (12/73) contained opossum blood meals. The epidemiological implications of these findings are discussed.