Genetic diversity in peridomiciliary populations of Triatoma mexicana (Hemiptera: Reduviidae: Triatominae) in central Mexico.

Triatoma mexicana is an important vector of Trypanosoma cruzi-the etiological agent of Chagas disease. This triatomine species occurs in central Mexico, but little is known about its genetic variability. Using Cyt-b gene as a genetic marker, in this study, we determined the population genetic structure of T. mexicana collected from the States of Hidalgo, Guanajuato, and Queretaro where populations are largely peridomiciliary. A Bayesian approach was performed for the design of phylogenies, median-joining networks, and clustering among populations of T. mexicana. Our results show that the Hidalgo population was the most distinct, with the highest genetic and haplotypic variation (Hd = 0.963, π = 0.06129, and ɵ = 0.05469). Moderate gene flow (Nm) was determined among populations of Hidalgo and Queretaro. Populations from the three states showed differentiation (FST) values ranging from 0.22 to 0.3, suggesting an important genetic differentiation. The phylogenetic analysis showed the presence of five well-defined groups, as well as the haplotype network, where 24 haplotypes were observed forming five haplogroups with high mutational steps among them: 68 (Hgo-W2), 26 (Qto), 59 (Hgo-M), 44 (Hgo-W1), and 46 (Gto). Genetic isolation was apparently inferred in the Guanajuato population; however, the Mantel test did not show correlation between genetic (FST) and geographic (km) distances (p = 0.05). The STRUCTURE analyses showed seven genetic clusters and it was observed that a single cluster predominates in each sampled location. However, genetic admixture was detected in four localities. Our results show evidence that there are multiple species within the collected sampling area.

Circulating miR-146a as a possible candidate biomarker in the indeterminate phase of Chagas disease.

BACKGROUND: Chagas disease is considered important and presents intense inflammatory and fibrotic processes induced by the perpetuation of the parasite in the affected tissues and organs. Therefore, it is necessary to inquire about the host defense and attack mechanisms to have a more detailed knowledge about Chagas disease. MicroRNAs are found in blood, tissues and extracellular vesicles. These small regulators of gene expression are involved in physiological and pathological processes in both mammals and parasites. Several microRNAs have deregulated expression in chagasic heart disease, although little is known about their extracellular expression. Our main objective was to evaluate the involvement of miR-21, miR-146a and miR-155 in several samples from mice infected with the TcI Ninoa strain from the acute and indeterminate phases. We also explored a potential functional association of the selected microRNAs using STRING software. This software identified 23 pathways associated with Trypanosoma cruzi infection. In addition, eleven genes were identified through bioinformatics analysis, and we found that SMAD family member 5 was downregulated in both phases. This gene serves as a mediator in the TGF-ß signaling pathway. Thus, forty female mice of the CD1 strain were distributed into 4 groups and the expression levels of miR-21, miR-146a and miR-155 were measured in samples of heart tissue, total plasma and plasma extracellular vesicles by quantitative real-time polymerase chain reaction. RESULTS: Overexpression of miR-21, miR-146a and miR-155 was observed in heart and plasma in both phases. Moreover, in extracellular vesicles miR-21 and miR-146a were also overexpressed in the acute phase, whereas in the indeterminate chronic phase we found only miR-146a up-regulated. CONCLUSIONS: The expression of inflammatory microRNAs miR-21, miR-146a and miR-155 were up-regulated in each of the samples from acutely and chronically infected mice. The relevant finding was that miR-146a was up-regulated in each sample in both phases; therefore, this miRNA could be a possible candidate biomarker in Chagas disease.

Seroprevalence and geographical distribution of sero-positive blood donors to Trypanosoma cruzi at the central blood bank of the National Medical Center "La Raza".

BACKGROUND: Trypanosoma cruzi is a protozoan parasite that causes Chagas disease endemic to Latin-America. It is estimated that 1.0 to 1.5% of Mexicans are infected with T. cruzi, which constitutes a potential risk of disease transmission via contaminated blood. New cases are being reported worldwide due to the migration of infected people from endemic areas. STUDY DESIGN AND METHODS: Serum samples were collected from donors at the Central Blood Bank of the National Medical Center "La Raza" from July 2008 to December 2015 and analyzed for T. cruzi antibodies using Enzyme-linked Immunosorbent Assays. Blood donors were classified serologically as either negative or positive for Chagas disease based on the Official Mexican Standard NOM-032-SSA2-2014. The geographical distribution of sero-positive donors for Chagas disease was then determined based on the donor's areas of residence. RESULTS: Of the 510, 047 donors, 595 tested positive for Chagas disease. We found a prevalence of 0.12%, was higher in males (0.13%) than females (0.08%) In both genders, there were more sero-positive donors aged 51-65 years as compared to other age groups. Overall there were more positive donors from the State of Mexico, northern area of Mexico City, and southern area of Hidalgo State, with rates of 67.4%, 20.6%, and 5.9%, respectively. CONCLUSIONS: The seroprevalence of Chagas disease in blood donors attending to La Raza BB is low. Chagas disease is more prevalent in the older age groups; most sero-positive donors are from areas considered non-endemic to Chagas disease.

Comparative study of the stridulatory groove in species of Triatoma (Hemiptera: Reduviidae) from Mexico.

The stridulation in the subfamily Triatominae has been identified as a means of communication between species, produced by the friction of the proboscis on the prosternal stridulatory groove. Despite its biological significance, this phenomenon remains understudied, with the signal's production seemingly contingent upon the morphology of the stridulatory groove. In this study, we examined the morphology of stridulatory grooves in females and males of five species and two subspecies of Mexican triatomines using morphometric and scanning electron microscopical analysis. Our findings reveal that all analyzed species exhibit triangular-shaped stridulatory grooves with parallel ridges covering the entire groove, bordered on each side, and covered with setae. Surprisingly, we observed noticeable differences in the number of ridges and inter-ridge distance between the species Triatoma lecticularia and Triatoma rubida (p < 0.001 and p < 0.009, respectively), indicating sexual dimorphism in this aspect, a phenomenon not previously reported in the morphology of this structure. Our findings shed light on the intricate morphology of the stridulatory groove in Mexican triatomines, suggesting potential implications for their behavior and intra-specific communication.

Specific humoral and cellular immunity induced by Trypanosoma cruzi DNA immunization in a canine model.

Chagas disease has a high incidence in Mexico and other Latin American countries. Because one of the most important known methods of prevention is vector control, which has been effective only in certain areas of South America, the development of a vaccine to protect people at risk has been proposed. In this study, we assessed the cellular and humoral immune response generated following immunization with pBCSP and pBCSSP4 plasmids containing the genes encoding a trans-sialidase protein (present in all three forms of T. cruzi) and an amastigote specific glycoprotein, respectively, in a canine model. Thirty-five beagle dogs were divided randomly into 5 groups (n=7) and were immunized twice intramuscularly with 500 µg of pBCSSP4, pBCSP, pBk-CMV (empty plasmid) or saline solution. Fifteen days after the last immunization the 4 groups were infected intraperitoneally with 500,000 metacyclic trypomastigotes. The fifth group was unimmunized/infected. The parasitaemia in the immunized/infected dogs was for a shorter period (14 vs. 29 days) and the parasite load was lower. The concentration of IgG1 (0.612±0.019 O.D.) and IgG2 (1.167±0.097 O.D.) subclasses was measured (absorbance) 15 days after the last immunization with both recombinant plasmids, the majority of which were IgG2. The treatment of parasites using the serum from dogs immunized with pBCSP and pBCSSP4 plasmids produced 54% (±11.8) and 68% (±21.4) complement-mediated lysis, respectively. At 12 h post immunization, an increase in cytokines was not observed; however, vaccination with pBCSSP4 significantly increased the levels of IFN-γ and IL-10 at 9 months post-infection. The recombinant plasmid immunization stimulated the spleen cell proliferation showing a positive stimulatory index above 2.0. In conclusion, immunization using both genes effectively induces a humoral and cellular immune response.

First record of Triatoma longipennis, Usinger, 1939 (Hemiptera: Reduviidae: Triatominae) in Tecozautla, Hidalgo.

BACKGROUND: We report the presence of Triatoma longipennis for the first time in two localities in Hidalgo, Mexico. METHODS: This study was conducted at Tecozautla municipality, Hidalgo. Collection was performed in April 2022. RESULTS: We collected eight triatomines from Guadalupe: two fourth-instar nymphs, three fifth-instar nymphs, one female, and two males. In San Miguel Caltepantla, a female was collected inside a dwelling. One sample tested positive for Trypanosoma cruzi. CONCLUSIONS: These findings suggest the need to investigate the dynamics of this species with respect to the inhabitants of the study area.

Inflammatory myopathies and beyond: The dual role of neutrophils in muscle damage and regeneration.

Skeletal muscle is one of the most abundant tissues of the human body and is responsible for the generation of movement. Muscle injuries can lead to severe disability. Skeletal muscle is characterized by an important regeneration capacity, which is possible due to the interaction between the myoblasts and immune cells. Neutrophils are fundamental as inducers of muscle damage and as promoters of the initial inflammatory response which eventually allows the muscle repair. The main functions of the neutrophils are phagocytosis, respiratory burst, degranulation, and the production of neutrophil extracellular traps (NETs). An overactivation of neutrophils after muscle injuries may lead to an expansion of the initial damage and can hamper the successful muscle repair. The importance of neutrophils as inducers of muscle damage extends beyond acute muscle injury and recently, neutrophils have become more relevant as part of the immunopathogenesis of chronic muscle diseases like idiopathic inflammatory myopathies (IIM). This heterogeneous group of systemic autoimmune diseases is characterized by the presence of muscle inflammation with a variable amount of extramuscular features. In IIM, neutrophils have been found to have a role as biomarkers of disease activity, and their expansion in peripheral blood is related to certain clinical features like interstitial lung disease (ILD) and cancer. On the other hand, low density granulocytes (LDG) are a distinctive subtype of neutrophils characterized by an enhanced production of NETs. These cells along with the NETs have also been related to disease activity and certain clinical features like ILD, vasculopathy, calcinosis, dermatosis, and cutaneous ulcers. The role of NETs in the immunopathogenesis of IIM is supported by an enhanced production and deficient degradation of NETs that have been observed in patients with dermatomyositis and anti-synthetase syndrome. Finally, new interest has arisen in the study of other phenotypes of LDG with a phenotype corresponding to myeloid-derived suppressor cells, which were also found to be expanded in patients with IIM and were related to disease activity. In this review, we discuss the role of neutrophils as both orchestrators of muscle repair and inducers of muscle damage, focusing on the immunopathogenesis of IIM.

Triatoma pallidipennis (Stål, 1872) (Hemiptera: Reduviidae) and its potential for infestation in Tecozautla, Hidalgo state, Mexico.

Triatoma pallidipennis is an exclusive and widely distributed species in Mexico and one of the three main vectors that transmit Chagas disease in the country. The state of Hidalgo is an endemic area for Chagas disease where the presence of several species of triatomines has been reported. The objective of our work was to describe the morphology, colonization process, and reproductive behavior of T. pallidipennis in Guadalupe, Tecozautla, two years after the first collection of a specimen in this region. A total of 28 specimens was collected at both domicile and peridomicile, showing a 17.8% infection rate. The main collection site was a woodshed, and despite the collection of adults in the dwelling, we did not find eggs, exuviae, or nymphs. One female monitored from collection day until death laid 566 eggs, with a hatching rate of 95%, showing an increase of oviposition when cohabited with a male. The results showed the capacity that T. pallidipennis has to infest areas (mainly human dwellings) when it settles down, which would imply a risk for the population that lives in the locality.

Plasmid DNA immunization with Trypanosoma cruzi genes induces cardiac and clinical protection against Chagas disease in the canine model.

The only existing preventive measure against American trypanosomosis, or Chagas disease, is the control of the transmitting insect, which has only been effective in a few South American regions. Currently, there is no vaccine available to prevent this disease. Here, we present the clinical and cardiac levels of protection induced by expression to Trypanosoma cruzi genes encoding the TcSP and TcSSP4 proteins in the canine model. Physical examination, diagnostic chagasic serology, and serial electrocardiograms were performed before and after immunization, as well as after experimental infection. We found that immunization with recombinant plasmids prevented hyperthermia in the acute phase of experimental infection and produced lymphadenomegaly as an immunological response against the parasite and additionally prevented heart rate elevation (tachycardia) in the acute and/or chronic stages of infection. Immunization with T. cruzi genes encoding the TcSP and TcSSP4 antigens diminished the quality and quantity of the electrocardiographic abnormalities, thereby avoiding progression to more severe developments such as right bundle branch block or ventricular premature complexes in a greater number of dogs.

Biological and genetic aspects of crosses between species of the genus Meccus (Hemiptera: Reduviidae Triatominae).

The degree of reproductive isolation between Meccus phyllosomus and the remaining five species of the genus Meccus, as well as between Meccus bassolsae and Meccus pallidipennis, Meccus longipennis and Meccus picturatus, was examined. Fertility and the segregation of morphological characteristics were examined in two generations of hybrids from crosses between these species. The percentage of couples with offspring (fertile) was high in the vast majority of sets of crosses, with the exception of that between ♀M. phyllosomus and ♂Meccus mazzottii. In sets of crosses involving M. bassolsae specimens, no first-generation (F1) individuals were morphologically similar to M. bassolsae, but instead shared the morphology of the other parental species. A similar phenomenon was observed in most sets of crosses involving M. phyllosomus. These results indicated that different degrees of reproductive isolation exist among the species of Meccus involved in this study. The biological evidence obtained in this study does not support the proposal that M. bassolsae is a full species. It could indicate that, on the contrary, it should be considered a subspecies of a single polytypic species. The biological evidence does support the proposal that M. phyllosomus is a full species.

Morphological and Chromatic Variation in Four Populations of Triatoma mexicana (Hemiptera: Reduviidae).

Triatoma mexicana is an endemic species of Mexico and is distributed in the states of Hidalgo, Queretaro, Guanajuato, and San Luis Potosi, being naturally infected with Trypanosoma cruzi, which increases its importance in the region. The species description was made in 1848, but there are only a few studies on its morphology, biology, and behavior. The present manuscript shows the presence of morphological and chromatic variations among populations of T. mexicana from the states of Hidalgo (Valle del Mezquital and Meztitlan), Guanajuato and Queretaro. The study employed 136 specimens collected in four locations. Scanning electron microscopy was used to study the morphological characteristics of the head, pronotum, and scutellum; also, we measured the width of the abdomen and the total length in the specimens of each population. The morphometric analysis considered 19 variables in the previous structures. Significant differences were found in the dimensions of the head and pronotum, but not in the scutellum; there is clear discrimination among the four proposed populations. The chromatic patterns observed in the connexivum go from yellow to brown and show some significant differences related to geographical origin. The set of evaluated characters showed a higher degree of difference in the population of Guanajuato, clearly separating from the rest of the populations, indicating the possibility of a divergence process. The characteristics observed in the remaining populations could be adaptive responses to their habitat.

Susceptibility dynamics between five Trypanosoma cruzi strains and three triatomine (Hemiptera: Reduviidae) species.

American trypanosomiasis is a zoonosis caused by the parasite Trypanosoma cruzi and is transmitted mainly by blood-sucking insects belonging to the subfamily Triatominae. The importance of this parasite lies in its wide geographical distribution, high morbidity, and the fact that there has not yet been an effective treatment or vaccine. Previous studies have detailed the interactions between different triatomine species and T. cruzi strains. However, the factors necessary to establish infection in triatomines have not yet been fully elucidated. Furthermore, it is postulated that the coexistence between the parasite and triatomines could modulate the susceptibility to infection in these insects. Accordingly, in this study, we evaluated the susceptibility to T. cruzi infection in the species Triatoma (Meccus) pallidipennis, Triatoma barberi, and Triatoma lecticularia, which were infected with Ninoa, H8, INC-5, Sontecomapan, and Hueypoxtla strains. The criteria used to establish susceptibility were the amount of blood ingested by the insects, percentage of infected triatomines, concentration of parasites in feces, and percentage of metacyclic trypomastigotes in feces. These parameters were analyzed by fresh examination and differential count with Giemsa-stained smears. Our main findings suggest the following order of susceptibility concerning infection with T. cruzi: T. lecticularia > T. barberi > T. (Meccus) pallidipennis. Furthermore, the study concludes that an increased susceptibility to infection of triatomines that share the same geographic region with different strains of T. cruzi is not always a fact.

New report of Eratyrus cuspidatus Stål, 1859 (Hemiptera: Reduviidae: Triatominae) in the State of Campeche, Mexico.

INTRODUCTION: Triatomine bugs are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. METHODS: Triatomine bugs were collected and identified following established protocols. In addition, infection with T. cruzi was detected by microscopic and molecular analysis. RESULTS: We captured an adult male specimen of the Eratyrus cuspidatus species that has not been reported in the state of Campeche. CONCLUSIONS: This finding provides new information on the distribution of E. cuspidatus in Mexico. However, more studies are needed to determine their epidemiological significance.

Distribution of triatomine (Hemiptera: Reduviidae) vectors of Chagas disease in the state of Hidalgo, Mexico.

Chagas disease represents a significant public health problem in Mexico. In the state of Hidalgo, studies on the presence of triatomines are scarce and restricted to a few locations. To determine the risk of transmission in the state of Hidalgo and stratify the vector potential, the distribution of Triatominae was surveyed from 2015 to 2016 in collaboration with primary health care services and local communities. A total of 570 specimens was collected in 278 houses in 25 municipalities. The species of Triatominae detected were T. dimidiata with 391 samples, T. mexicana with 159 samples, T. gerstaeckeri with 17 samples, and T. barberi with three samples. The samples were collected in domestic and peridomestic areas. The general index of natural infection was 9.8%. Indices of colonization and crowding were determined for species and municipality and results were variable.

Two Triatoma dimidiata clades (Chagas disease vector) associated with different habitats in southern Mexico and Central America.

Triatoma dimidiata is the only reported Chagas disease vector in Campeche, Mexico. The purpose of this study was to determine the genetic variability of vectors from Campeche coastal and rain forest areas and establish a phylogenetic relationship with other T. dimidiata populations by analyzing the internal transcribed spacer-2 (ITS-2) region. The sequence length of samples from Campeche ranged from 469 to 478 basepairs. The ITS-2 variability among the populations enabled us to classify them into two clades with an 18-22 nucleotide difference. The genetic distance (0.042) between them confirms this divergence. Phylogenetic analysis of gene genealogies confirmed these two clades. Furthermore, the population genetic analyses showed two groups with little genetic similarity or migration between them. One group was associated with the tropical forest area and the other group was associated with a mainly coastal distribution. This correlation was also observed when T. dimidiata from other regions of Mexico and Central America were analyzed.

First record of Triatoma longipennis, Usinger, 1939 (Hemiptera: Reduviidae: Triatominae) in Tecozautla, Hidalgo

ABSTRACT Background: We report the presence of Triatoma longipennis for the first time in two localities in Hidalgo, Mexico. Methods: This study was conducted at Tecozautla municipality, Hidalgo. Collection was performed in April 2022. Results: We collected eight triatomines from Guadalupe: two fourth-instar nymphs, three fifth-instar nymphs, one female, and two males. In San Miguel Caltepantla, a female was collected inside a dwelling. One sample tested positive for Trypanosoma cruzi. Conclusions: These findings suggest the need to investigate the dynamics of this species with respect to the inhabitants of the study area.

Imported and Autochthonous Cases of Myiasis Caused by Dermatobia hominis: Taxonomic Identification Using the Internal Transcribed Spacer Region.

Dermatobia hominis is a fly endemic to and widely distributed throughout the Americas; it is found from the southern regions of Mexico to Argentina. However, because of widespread travel, myiasis has become common in countries where neither the disease nor the species that cause this infection are endemic. Central Mexico, for instance, is not a region where myiasis is endemic. We, thus, describe three cases of D. hominis myiasis: two autochthonous cases from the southern part of Mexico and one imported from Costa Rica. In addition, morphological and genetic identification was performed on the maggots extracted from the patients.

External female genitalia of six species of the genus Meccus (Hemiptera: Reduviidae: Triatominae).

Triatomine classification is based on morphological characteristics. Studies have been conducted to improve their identification by observing many characteristics. However, there are problems of differentiating among highly interrelated species and new criteria are required. The purpose of this study was to determine the morphological differences in the external female genitalia of M. pallidipennis, M. longipennis, M. picturatus, M. bassolsae, M. mazzottii, and M. phyllosomus in order to distinguish among species using scanning electron microscopy. Observations were made of the dorsal, posterior, lateral, and ventral views of the female external genitalia for each species. In the six species we studied, relevant differences were observed in the dorsal view of the X segment, as well as the IX, VIII, and VII tergites. In the posterior and lateral view, the most visible differences were registered in the gonocoxite size of the segments VIII, IX, and X. Finally, in the ventral view of the VII sternite, differences among species were observed in the size of the inflection in the top and upper corner. Our results show that it was possible to differentiate among the triatominae species for each of the four views by using a scanning electron microscope to analyze morphological characteristics of the VII, VIII, IX, and X abdomen segments.

Morphological and morphometric analysis of scutella of six species and two subspecies of Triatoma (Hemiptera: Reduviidae) in Mexico.

Morphological characters can be used to distinguish the vast majority of triatomine species, but the existence of high levels of phenotypic plasticity and recently diverged species can lead to erroneous determinations. To approach this problem, we analyzed the male and female morphologies of the scutella of Triatoma barberi, T. dimidiata, T. lecticularia, T. mexicana, T. recurva, T. rubida, and two sub-species, T. protracta protracta and T. protracta nahuatlae. Scutellum samples were observed by scanning electron microscopy and subjected to morphological analysis and morphometric investigation using a canonical discriminant analysis. The results revealed differences primarily in central depression shape, posterior process, and vestiture. We observed clear dimension-based differences in scutellum morphometry in all the taxa under study, providing sound evidence for species and subspecies differentiation. On the other hand, there is no difference between sexes in T. lecticularia, T. protracta protracta, and T. protracta nahuatlae. Our methodology can be implemented to differentiate species of the genus Triatoma.