Expression of Proteins, Glycoproteins, and Transcripts in the Guts of Fasting, Fed, and Trypanosoma cruzi-Infected Triatomines: A Systematic Review

Chagas disease is caused by the hemoflagellate protozoan Trypanosoma cruzi. The main transmission mechanism for the parasite in endemic areas is contact with the feces of an infected triatomine bug. Part of the life cycle of T. cruzi occurs in the digestive tract of triatomines, where vector and parasite engage in a close interaction at a proteomic-molecular level. This interaction triggers replication and differentiation processes in the parasite that can affect its infectivity for the vertebrate host. With the aim of compiling and analyzing information from indexed publications on transcripts, proteins, and glycoproteins in the guts of fasting, fed, and T. cruzi-infected triatomines in the period 2000-2022, a systematic review was conducted following the PRISMA guidelines. Fifty-five original research articles retrieved from PubMed and ScienceDirect were selected; forty-four papers reported 1-26,946 transcripts, and twenty-one studies described 1-2603 peptides/proteins.

What Do You Need to Know before Studying Chagas Disease? A Beginner's Guide

Chagas disease is one of the most important tropical infections in the world and mainly affects poor people. The causative agent is the hemoflagellate protozoan Trypanosoma cruzi, which circulates among insect vectors and mammals throughout the Americas. A large body of research on Chagas disease has shown the complexity of this zoonosis, and controlling it remains a challenge for public health systems. Although knowledge of Chagas disease has advanced greatly, there are still many gaps, and it is necessary to continue generating basic and applied research to create more effective control strategies. The aim of this review is to provide up-to-date information on the components of Chagas disease and highlight current trends in research. We hope that this review will be a starting point for beginners and facilitate the search for more specific information.

Immunopathological Mechanisms Underlying Cardiac Damage in Chagas Disease

In Chagas disease, the mechanisms involved in cardiac damage are an active field of study. The factors underlying the evolution of lesions following infection by Trypanosoma cruzi and, in some cases, the persistence of its antigens and the host response, with the ensuing development of clinically observable cardiac damage, are analyzed in this review.

Semblanza del Dr. Francisco Biagi Filizola

Es para nosotras un honor compartirles esta breve semblanza de quien fue quizás nuestro más grande mentor y formador en este maravilloso mundo de la Microbiología y Parasitología. Y es evidente que, para todos nosotros, el Dr. Francisco Biagi Filizola es un ícono mexicano de la investigación y docencia, exitoso en muchos aspectos y orgullo de nuestra máxima casa de estudios, la Universidad Nacional Autónoma de México.

Enfermedad de Chagas: biología y transmisión de Trypanosoma cruzi

En 1909, Carlos Justiniano Chagas describió por primera vez las manifestaciones clínicas de la enfermedad de Chagas. El parásito hemoflagelado Trypanosoma cruzi (agente) se caracteriza por la presencia de un flagelo, y en su citoplasma presenta organelos como el citostoma, los glicosomas, los reservosomas y un núcleo. El ciclo de vida de T. cruzi se inicia cuando el vector defeca sobre la piel del hospedero sus heces contienen tripomastigotes metacíclicos, que infectan las células del vertebrado. Los vectores de esta enfermedad pertenecen a la Subfamilia Triatominae, insectos hematófagos, nocturnos y con la capacidad de localizar a sus hospederos mediante la detección del calor. T. cruzi tiene efectos en la biología del insecto triatomino, en su comportamiento, en el funcionamiento del intestino, su sistema inmunológico y la microbiota asociada. En el hospedero mamífero, el parásito activa la respuesta inmune innata, y las citocinas tienen un papel clave para controlar la infección o bien evolucionar a la cronicidad. T. cruzi presenta una amplia diversidad genética, y bajo condiciones de laboratorio se han demostrado sus diferentes grados de virulencia y tropismo hacia los órganos blanco; sin embargo, no existe una asociación clara entre las cepas y el comportamiento clínico de la enfermedad. Esta revisión aborda la historia del descubrimiento de la enfermedad de Chagas y discute aspectos recientes sobre la biología de T. cruzi para comprender la dinámica de su transmisión.

High chromosomal mobility of rDNA clusters in holocentric chromosomes of Triatominae, vectors of Chagas disease (Hemiptera-Reduviidae)

The subfamily Triatominae (Hemiptera-Reduviidae) includes more than 150 blood-sucking species, potential vectors of the protozoan Trypanosoma cruzi, causative agent of Chagas disease. A distinctive cytogenetic characteristic of this group is the presence of extremely stable chromosome numbers. Unexpectedly, the analyses of the chromosomal location of ribosomal gene clusters and other repetitive sequences place Triatominae as a significantly diverse hemipteran subfamily. Here, we advance the understanding of Triatominae chromosomal evolution through the analysis of the 45S rDNA cluster chromosomal location in 92 Triatominae species. We found the 45S rDNA clusters in one to four loci per haploid genome with different chromosomal patterns: On one or two autosomes, on one, two or three sex chromosomes, on the X chromosome plus one to three autosomes. The movement of 45S rDNA clusters is discussed in an evolutionary context. Our results illustrate that rDNA mobility has been relatively common in the past and in recent evolutionary history of the group. The high frequency of rDNA patterns involving autosomes and sex chromosomes among closely related species could affect genetic recombination and the viability of hybrid populations, which suggests that the mobility of rDNA clusters could be a driver of species diversification.

Bacteria cultured from the gut of Meccus pallidipennis (Hemiptera: Reduviidae), a triatomine species endemic to Mexico

The study of intestinal microbiota in vector insects like triatomines is paramount in parasitology because many parasitic species inhabit the vector's gut. Although knowledge on the gut microbiota in various vectors of the parasitic flagellate Trypanosoma cruzi has grown, research efforts have focused on South American triatomines. This study reports the isolation of bacterial microbiota in the anterior and posterior gut of Meccus pallidipennis (a triatomine species endemic to Mexico) by culture, as well as its identification by phenotypic and biochemical tests and its quantification by counting colony-forming units. The study was performed on fifth-instar nymph and adult specimens of M. pallidipennis, either laboratory-bred or collected in the field and either infected or not with T. cruzi. Overall, 17 bacterial species were identified, with the genera Bacillus and Staphylococcus being the most prevalent regardless of the origin of the insects. No differences were observed in the number of bacterial species in the gut of laboratory-bred and field-collected insects, neither with respect to life stage or infection status. In general, the Shannon-Weaver diversity index was higher in non-infected insects than in infected ones. Further studies using non-culture methods are required to determine whether bacterial species diversity is modified by laboratory breeding.

Higher temperatures reduce the number of Trypanosoma cruzi parasites in the vector Triatoma pallidipennis

Background

Relatively little is known about how pathogens transmitted by vector insects are affected by changing temperatures analogous to those occurring in the present global warming scenario. One expectation is that, like their ectothermic vectors, an increase in temperature could reduce their fitness. Here, we have investigated the effect of high temperatures on the abundance of Trypanosoma cruzi parasites during infection in the vector Triatoma pallidipennis.

Methods

We exposed T. pallidipennis nymphs to two strains (Morelos and Chilpancingo) of T. cruzi. Once infected, the fifth-instar bugs were distributed among three different temperature groups, i.e. 20, 30, and 34 °C, and the resulting parasites were counted when the bugs reached adulthood.

Results

The number of parasites increased linearly with time at 20 °C and, to a lesser extent, at 30 °C, especially in the Chilpancingo compared to the Morelos strain. Conversely, at 34 °C, the number of parasites of both strains decreased significantly compared to the other two temperatures.

Conclusions

These results suggest negative effects on the abundance of T. cruzi in T. pallidipennis at high temperatures. This is the first evidence of the effect of high temperatures on a pathogenic agent transmitted by an insect vector in the context of global warming. Further tests should be done to determine whether this pattern occurs with other triatomine species and T. cruzi strains.

Graphical abstract

Response to Infection by Trypanosoma cruzi in a Murine Model

Cardiopathy is a common, irreversible manifestation of the chronic phase of Chagas disease; however, there is controversy as to how the causes for progression from the acute to the chronic phase are defined. In this work, the presence of the parasite is correlated with the occurrence of cell infiltration and fibrosis in cardiac tissues, as well as IgG detection and disease progression in a murine model. Fifty CD1 mice were infected intraperitoneally with Trypanosoma cruzi, while 30 control were administered with saline solution. Parasitemia levels were determined, and IgG titers were quantified by ELISA. At different times, randomly selected mice were euthanized, and the heart was recovered. Cardiac tissue slides were stained with HE and Masson trichrome stain. A significant increase in parasitemia levels was observed after 15 days post-infection (dpi), with a maximum of 4.1 × 10⁶ parasites on 33 dpi, ending on 43 dpi; amastigote nests were observed on 15–62 dpi. Histological analysis revealed lymphocytic infiltration and fibrotic lesions from 8 dpi until the end of the study, on 100 dpi. The presence of plasma cells in the myocardium observed on 40–60 dpi, accompanied by seropositivity to ELISA on 40–100 dpi, was regarded as the hallmark of the transition phase. Meanwhile, the chronic phase, characterized by the absence of amastigotes, presence of cell infiltration, fibrotic lesions, and seropositivity, started on 62 dpi. A strong correlation between parasitemia and the presence of amastigote nests was found (r² = 0.930), while correlation between the presence of fibrosis and of amastigote nests was weak (r² = 0.306), and that between fibrosis and lymphocyte infiltration on 100 dpi was strong (r² = 0.899). The murine model is suitable to study Chagas disease, since it can reproduce the chronic and acute phases of the human disease. The acute phase was determined to occur on 1–60 dpi, while the chronic phase starts on 62 dpi, and fibrotic damage is a consequence of the continuous inflammatory infiltration; on the other hand, fibrosis was determined to start on the acute phase, being more apparent in the chronic phase, when Chagas disease-related cardiopathy is induced.

Coinfection by Trypanosoma cruzi and a fungal pathogen increases survival of Chagasic bugs: advice against a fungal control strategy

Triatomine bugs carry the parasitic protozoa Trypanosoma cruzi, the causal agent of Chagas disease. It is known that both the parasite and entomopathogenic fungi can decrease bug survival, but the combined effect of both pathogens is not known, which is relevant for biological control purposes. Herein, the survival of the triatomine Meccus pallidipennis (Stal, 1872) was compared when it was coinfected with the fungus Metarhizium anisopliae (Metschnikoff) and T. cruzi, and when both pathogens acted separately. The immune response of the insect was also studied, using phenoloxidase activity in the bug gut and hemolymph, to understand our survival results. Contrary to expectations, triatomine survival was higher in multiple than in single challenges, even though the immune response was lower in cases of multiple infection. We postulate that T. cruzi exerts a protective effect and/or that the insect reduced the resources allocated to defend itself against both pathogens. Based on the present results, the use of M. anisopliae as a control agent should be re-considered.

[Training of general practitioners, a Mexican medical school curriculum evaluation]

BACKGROUND

Educational curricula require constant improvement to respond to the needs of students, institutions and society.

OBJECTIVE

To evaluate the Plan de Estudios 2010 of the Facultad de Medicina de la Universidad Nacional Autónoma de México.

METHODS

Documentary and qualitative study of three phases. First, revision of trends of general medicine in special databases and comparison of curricula between universities. Second, focus groups with clinical teachers and basic sciences to investigate experiences and opinions in relation to trends in general medicine. Third, a "Generalists Committee" was convened to whom the results were presented (phase one and two) and the recommendations were adapted to adapt the results to the general practitioner's context. The participants were informed about the research objective and their participation was voluntary, the anonymity of theirs comments was protected.

RESULTS

The trend towards specialization in clinical practice defines the future of general medicine, and the administrative uses have an impact on the practices of the general practitioner and on the patient's medical relationship.

CONCLUSION

Various aspects mainly educational and assistance hindered the quality of the practice of general medicine.

Activity of the prophenoloxidase system and survival of triatomines infected with different Trypanosoma cruzi strains under different temperatures: understanding Chagas disease in the face of climate change

BACKGROUND

Little is known about how human disease vectors will modify their life history patterns and survival capacity as a result of climate change. One case is that of Chagas disease, which has triatomine bugs and Trypanosoma cruzi as vectors and parasite, respectively. This work aimed to determine: (i) the activity of the prophenoloxidase system (prophenoloxidase and phenoloxidase activity, two indicators of immune ability) in three intestine regions (anterior midgut, posterior midgutand rectum) of the triatomine bug Meccus pallidipennis under three temperature conditions (20 °C, 30 °C and 34 °C) against two T. cruzi strains [ITRI/MX/14/CHIL (Chilpancingo) and ITRI/MX/12/MOR (Morelos)], and (ii) whether vector survival varies under these three temperatures after infection by these T. cruzi strains.

RESULTS

Our results indicate that prophenoloxidase activity was lower at higher temperatures, that the level of prophenoloxidase activity elicited by each strain was different (higher in Chilpancingo than in Morelos strains), and that prophenoloxidase activity was more intense in the anterior midgut than in the posterior midgut or rectum. Survival rates were lower in insects maintained at higher temperatures and infected by Chilpancingo strains.

CONCLUSIONS

These results indicate that climate change could lead to lower prophenoloxidase activity and survival rates in triatomines when infected with different T. cruzi strains, which could reduce the vector capacity of M. pallidipennis.

In vitro activity of steroidal dendrimers on Trypanosoma cruzi epimastigote form with PAMAM dendrons modified by "click" chemistry

The increasing use of dendrimers shows promise for the treatment of inflammatory diseases, Chagas disease and other conditions such as cancer. In this study, the activity of 1st and 2nd generation dendrimers over T. cruzi in the epimastigote stage was tested. Dendrimers were derived from α-ethynylestradiol (EE) modified with PAMAM-type dendrons through a triazole ring. The activity of each compound was evaluated in five doses (from 1.3 to 20 µmol/mL) by flow cytometry, including benznidazole (Bz) as positive control. The findings show that an equivalent concentration of 14.8 µmol/mL of 2nd generation (G) dendrimer is 8 times more effective than Bz at 24 h, and it maintains its superiority at 48 h with an IC₅₀ = 1.25 ± 0.19 µmol/mL. A TUNEL assay showed that dendrimers induce cell death in T. cruzi epimastigotes mostly via apoptosis, unlike Bz, which induces death via necrosis in more than 50% of cells.

Effects on Meccus pallidipennis (Hemiptera: Reduviidae) Eggs Exposed to Entomopathogenic Fungi: Exploring Alternatives to Control Chagas Disease

Meccus pallidipennis Stål is a vector for Chagas disease. The extensive use of pyrethroid insecticides to control triatomines in Mexico has resulted in the development of resistant populations. As an alternative control approach, the effects on M. pallidipennis eggs of two entomopathogenic fungi, Isaria fumosorosea Wize (Hypocreales: Cordycipitaceae) EH-511/3 and Metarhizium anisopliae (Metschn.) Sorokin (Hypocreales: Clavicipitaceae) EH-473/4, were examined. Egg mortality was estimated 1 mo after egg infection, based on hyphal growth and unsuccessful hatching as proxies for infection and death. Sporulation and conidial production rates were also recorded. Mortality rates caused by I. fumosorosea and Me. anisopliae were 92% ± 3.1 and 88% ± 3.7, respectively. Sporulation rate and conidial production were greater in I. fumosorosea than in Me. anisopliae. Transmission electron microscopy revealed hyphal penetration by both fungal species and damage to embryonic epidermal and cuticular cells. Our results demonstrated that I. fumosorosea and Me. anisopliae are promising candidates for controlling M. pallidipennis eggs and offer alternatives to control the transmission of Chagas disease under natural conditions.

Identification of O-Glcnacylated Proteins in Trypanosoma cruzi

Originally an anthropozoonosis in the Americas, Chagas disease has spread from its previous borders through migration. It is caused by the protozoan Trypanosoma cruzi. Differences in disease severity have been attributed to a natural pleomorphism in T. cruzi. Several post-translational modifications (PTMs) have been studied in T. cruzi, but to date no work has focused on O-GlcNAcylation, a highly conserved monosaccharide-PTM of serine and threonine residues mainly found in nucleus, cytoplasm, and mitochondrion proteins. O-GlcNAcylation is thought to regulate protein function analogously to protein phosphorylation; indeed, crosstalk between both PTMs allows the cell to regulate its functions in response to nutrient levels and stress. Herein, we demonstrate O-GlcNAcylation in T. cruzi epimastigotes by three methods: by using specific antibodies against the modification in lysates and whole parasites, by click chemistry labeling, and by proteomics. In total, 1,271 putative O-GlcNAcylated proteins and six modification sequences were identified by mass spectrometry (data available via ProteomeXchange, ID PXD010285). Most of these proteins have structural and metabolic functions that are essential for parasite survival and evolution. Furthermore, O-GlcNAcylation pattern variations were observed by antibody detection under glucose deprivation and heat stress conditions, supporting their possible role in the adaptive response. Given the numerous biological processes in which O-GlcNAcylated proteins participate, its identification in T. cruzi proteins opens a new research field in the biology of Trypanosomatids, improve our understanding of infection processes and may allow us to identify new therapeutic targets.

Bacterial symbionts in human blood-feeding arthropods: Patterns, general mechanisms and effects of global ecological changes

Due to their high impact on public health, human blood-feeding arthropods are one of the most relevant animal groups. Bacterial symbionts have been long known to play a role in the metabolism, and reproduction of these arthropod vectors. Nowadays, we have a more complete picture of their functions, acknowledging the wide influence of bacterial symbionts on processes ranging from the immune response of the arthropod host to the possible establishment of pathogens and parasites. One or two primary symbiont species have been found to co-evolve along with their host in each taxon (being ticks an exception), leading to various kinds of symbiosis, mostly mutualistic in nature. Moreover, several secondary symbiont species are shared by all arthropod groups. With respect to gut microbiota, several bacterial symbionts genera are hosted in common, indicating that these bacterial groups are prone to invade several hematophagous arthropod species feeding on humans. The main mechanisms underlying bacterium-arthropod symbiosis are discussed, highlighting that even primary symbionts elicit an immune response from the host. Bacterial groups in the gut microbiota play a key role in immune homeostasis, and in some cases symbiont bacteria could be competing directly or indirectly with pathogens and parasites. Finally, the effects climate change, great human migrations, and the increasingly frequent interactions of wild and domestic animal species are analyzed, along with their implications on microbiota alteration and their possible impacts on public health and the control of pathogens and parasites harbored in arthropod vectors of human parasites and pathogens.

Effects of Trypanosoma cruzi on the phenoloxidase and prophenoloxidase activity in the vector Meccus pallidipennis (Hemiptera: Reduviidae)

Background

Triatomine insects are vectors of Trypanosoma cruzi, the causal agent of Chagas disease. The insect-parasite interaction has been studied in relation to the transmission and prevalence of this disease. For most triatomines, however, several crucial aspects of the insect immune response are still unknown. For example, only for Rhodnius prolixus and Triatoma infestans has the activity of phenoloxidase (PO) and its zymogen prophenoloxidase (proPO) been reported in relation to the hemolymph and anterior midgut (AM). The aim of this study was to gain insight into the immune response to T. cruzi infection of an important triatomine in Mexico, Meccus pallidipennis.

Methods

Parasites were quantified in the rectal contents of infected M. pallidipennis groups. We examined some key factors in disease transmission, including the systemic (hemolymph) and local (gut) immune response.

Results

Parasites were present in the rectal contents at 4 days post-infection (pi) and reached their maximum density on day 7 pi. At 7 and 9 days pi mainly metacyclic trypomastigotes occurred. Compared to the control, the infected insects exhibited diminished PO activity in the hemolymph on days 9, 16 and 20 pi, and in the AM only on day 9. Additionally, infected insects displayed lower proPO activity in the hemolymph on day 1, but greater activity in the AM on day 28.

Conclusions

The parasite strain originating from M. pallidipennis rapidly colonized the rectum of nymphs of this triatomine and developed high numbers of metacyclic trypomastigotes. Neither the changes of concentrations of PO and proPO in the hemolymph nor in the AM correlated with the changes in the population of T. cruzi.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3016-0) contains supplementary material, which is available to authorized users.

Th-17 cytokines are associated with severity of Trypanosoma cruzi chronic infection in pediatric patients from endemic areas of Mexico

In Chagas disease the clinical, acute and chronic manifestations are the result of the interaction between the parasite and the host factors. The balance between inflammatory and anti-inflammatory immune responses is essential for the increase or resolution of the manifestations in individuals infected with T. cruzi. To identify if children with chronic Chagas disease and heart injury is related with non-regulated Th1, Th2 and Th17 responses. We included 31 children with T. cruzi confirmed chronic infection from endemic areas of Mexico. Subsequently, they were separated according to their ECHO and ECG results into three groups according to the severity of cardiac involvement. Circulating Th1, Th2 and Th17 cytokine profiles were performed by Luminex assays and the results were analyzed by bivariate and multivariable analysis. Patients were classified in asymptomatic chronic (group 1, N=12); individuals with IRBBB in ECG and incipient lesions in ECHO (Group 2, N=8) and Patients with severe chronic symptomatic disease (Group 3, N=11). The analysis of immune mediators revealed that patients with severe cardiac manifestations had significant higher levels (p <0.05) of Th17 related cytokines including IL-17 and IL-6 as well as IFN-γ and IL-2. Also patients with severe cardiomyopathy exhibit increased levels of IL-13 (p <0.05) after multivariate analysis. High levels of Th17 related cytokines including IL-17, IFN-γ, IL-6 and IL-2 and pro-fibrotic factors such as IL-13 could be associated to the severity of cardiac involvement in children with chronic T. cruzi infection. These cytokines could be useful as indicators for the early identification of cardiac damage associated to the T. cruzi infection.

Chagas Disease in Mexico: Report of 14 Cases of Chagasic Cardiomyopathy in Children

Chagas disease is a parasitic infection mainly found in Latin America; it is transmitted by a triatomine, also known as assassin bug or kissing bug. In humans, the parasite causes mostly cardiac disorders. Two-thirds of the Mexican territory are regarded as risk areas for vector transmission of Trypanosoma cruzi, the causal agent. The parasite can be found as a blood-borne trypomastigote or as an intracellular amastigote. The progression and severity of lesions could be due to frequent reinfections or to infection by highly virulent strains. A total of 3,327 individuals younger than 18 years old, living in risk areas for this disease in the rural setting of the States of Queretaro, San Luis Potosi, and Veracruz, underwent a seroepidemiological study. Among them, 37 subjects were seropositive for T. cruzi, and were studied to look for signs of cardiac pathology, which has only been reported in adults. A clinical record was prepared for all included individuals, and electrocardiography (ECG) and echocardiography (ECHO) studies were performed; 25 cases showed lesions compatible with the onset of Chagas cardiomyopathy. The other 12 patients showed either normal ECG and ECHO data or showed abnormal parameters that were not regarded as significant. Lesions found in the onset of Chagas cardiomyopathy in children are herein reported, along with 14 cases of cardiac pathology compatible with Chagas disease. Our results indicate that patients younger than 18 years can show a cardiac pathology similar to that observed in adults.

Relationships between altitude, triatomine (Triatoma dimidiata) immune response and virulence of Trypanosoma cruzi, the causal agent of Chagas' disease

Little is known about how the virulence of a human pathogen varies in the environment it shares with its vector. This study focused on whether the virulence of Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae), the causal agent of Chagas' disease, is related to altitude. Accordingly, Triatoma dimidiata (Hemiptera: Reduviidae) specimens were collected at three different altitudes (300, 700 and 1400 m a.s.l.) in Chiapas, Mexico. The parasite was then isolated to infect uninfected T. dimidiata from the same altitudes, as well as female CD-1 mice. The response variables were phenoloxidase (PO) activity, a key insect immune response, parasitaemia in mice, and amastigote numbers in the heart, oesophagus, gastrocnemius and brain of the rodents. The highest levels of PO activity, parasitaemia and amastigotes were found for Tryp. cruzi isolates sourced from 700 m a.s.l., particularly in the mouse brain. A polymerase chain reaction-based analysis indicated that all Tryp. cruzi isolates belonged to a Tryp. cruzi I lineage. Thus, Tryp. cruzi from 700 m a.s.l. may be more dangerous than sources at other altitudes. At this altitude, T. dimidiata is more common, apparently because the conditions are more beneficial to its development. Control strategies should focus activity at altitudes around 700 m a.s.l., at least in relation to the region of the present study sites.

Transmission Capacity of Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) by Three Subspecies of Meccus phyllosomus (Heteroptera: Reduviidae) and Their Hybrids

Three behaviors of epidemiological importance: the time lapse for the onset of feeding, actual feeding, and defecation time for Meccus phyllosomus pallidipennis (Stål), Meccus phyllosomus longipennis (Usinger), Meccus phyllosomus picturatus (Usinger), and their laboratory hybrids were evaluated in this study. The mean time lapse for the beginning of feeding was between 0.5 and 8.3 min considering all instars in each cohort, with highly significant differences only among fifth-instar nymphs, females, and males of M. p. pallidipennis and M. p. longipennis relative to the hybrid cohorts. Four hybrid (LoPa [M. p. longipennis and M. p. pallidipennis] and LoPi [M. p. longipennis and M. p. picturatus] and their reciprocal experimental crosses) cohorts had similar mean feeding times to one of the parental subspecies, but longer than the other one. The remaining hybrid cohort (PaPi [M. p. pallidipennis and M. p. picturatus]) had longer feeding times than both of its parental subspecies. The specimens of the LoPa and LoPi hybrid cohorts defecated faster than the respective instars of the three parental cohorts. With exception of first- and fifth-instar nymphs, PaPi cohorts defecated faster than the remaining seven cohorts. More than 60% of defecation events occurred during feeding in the six hybrid cohorts. Our results indicate that hybrid cohorts have more potential to acquire infection and transmit Trypanosoma cruzi Chagas than their parental cohorts.

Survival and immune response of the Chagas vector Meccus pallidipennis (Hemiptera: Reduviidae) against two entomopathogenic fungi, Metarhizium anisopliae and Isaria fumosorosea

BACKGROUND

Chagas disease is a key health problem in Latin America and is caused and transmitted by Trypanosoma cruzi and triatomine bugs, respectively. Control of triatomines has largely relied on the use pyrethroids, which has proved to be ineffective in the long term. Alternatively, the use of entomopathogenic fungi has been implemented to control triatomine bugs. These fungi are highly efficient as they induce a reduction in immune response on insects. Meccus pallidipennis is the main triatomine vector of Chagas disease in Mexico. In this work we investigated the effects of two entomopathogenic fungi, Metarhizium anisopliae and Isaria fumosorosea, on M. pallidipennis nymphs in terms of insect survival and immune response.

METHODS

We had an infected and a control group for each fungal species and assessed: a) insect survival during 30 days; and, b) phenoloxidase (PO) and prophenoloxidase (proPO; two key traits in insect immune response) at 24, 48, 96 and 144 h. For survival we used Kaplan-Meier survival analysis while for immune response we used factorial, repeated-measures ANOVA for each fungal species.

RESULTS

Animals treated with M. anisopliae died sooner than animals treated with I. fumosorosea. Infected animals showed lower PO and proPO values than sham individuals, with a clear decrease in these parameters at 24 h with no further changes after this time.

CONCLUSIONS

Our study widens the possibility of entomopathogenic fungi being used for triatomine control. The negative effect on PO and proPO seems mediated by a down-regulation of the triatomine immune response.

Immune defence mechanisms of triatomines against bacteria, viruses, fungi and parasites

Triatomines are vectors that transmit the protozoan haemoflagellate Trypanosoma cruzi, the causative agent of Chagas disease. The aim of the current review is to provide a synthesis of the immune mechanisms of triatomines against bacteria, viruses, fungi and parasites to provide clues for areas of further research including biological control. Regarding bacteria, the triatomine immune response includes antimicrobial peptides (AMPs) such as defensins, lysozymes, attacins and cecropins, whose sites of synthesis are principally the fat body and haemocytes. These peptides are used against pathogenic bacteria (especially during ecdysis and feeding), and also attack symbiotic bacteria. In relation to viruses, Triatoma virus is the only one known to attack and kill triatomines. Although the immune response to this virus is unknown, we hypothesize that haemocytes, phenoloxidase (PO) and nitric oxide (NO) could be activated. Different fungal species have been described in a few triatomines and some immune components against these pathogens are PO and proPO. In relation to parasites, triatomines respond with AMPs, including PO, NO and lectin. In the case of T. cruzi this may be effective, but Trypanosoma rangeli seems to evade and suppress PO response. Although it is clear that three parasite-killing processes are used by triatomines - phagocytosis, nodule formation and encapsulation - the precise immune mechanisms of triatomines against invading agents, including trypanosomes, are as yet unknown. The signalling processes used in triatomine immune response are IMD, Toll and Jak-STAT. Based on the information compiled, we propose some lines of research that include strategic approaches of biological control.

[Identification of immunodominant components of an isolate of Trypanosoma cruzi by immunoblot and its standardization for diagnostic purposes]

INTRODUCTION

Conventional serology was used for the detection of Trypanosoma cruzi infection, with diverse sensitivity and specificity results. Due to the number of samples with doubtful results, it is necessary to develop additional confirmation tests such as the immunoblot.

OBJECTIVE

The aim of this study was identify major immunogenic proteins of T. cruzi isolate and establish criteria for immunoblot positivity with diagnostic purposes.

METHODS

Immunoblot initial standardization was performed, determining optimal concentrations of antigen, serum, and second antibody. Thirty-five positive and thirty negative sera were assayed to evaluate different criteria of positivity and determine which provides greater sensitivity and specificity.

RESULTS

Immunoblot of T. cruzi positive sera shared a rich pattern of components with molecular weights between 10-250 kDa. Twelve components had a recognition rate higher than 50%, of which the polypeptides of 27, 32, 34, and 38 kDa were close to 100%. Of the positivity criteria evaluated, the recognition of the components of 27 and 32 kDa provided sensitivity and specificity of 100%.

DISCUSSION

The Immunoblot is suitable for confirmation of infection by T. cruzi, so it is strongly recommended for confirmation and discrimination of discordant cases.

Revisión de 13 especies de la familia Triatominae (Hemiptera: Reduviidae) vectores de la enfermedad de Chagas, en México

Los transmisores de Trypanosoma cruzi, flagelado causante de la enfermedad, se dividen en intradomiciliados, peridomiciliados y silvestres. Entre los intradomiciliados se encuentran, Triatoma barberi y Triatoma dimidiata, que son los que representan un mayor riesgo para la Salud Pública, en México. Aunque Triatoma dimidiata se encuentra principalmente dentro de la vivienda, en Yucatán tiene un comportamiento peridomiciliar, dentro de este grupo se encuentran la mayoría de los transmisores de la enfermedad de Chagas Meccus longipennis, M. mazzottii, M. pallidipennis, M. phyllosomus, M. picturatus, Triatoma gerstaeckeri, T. mexicana, T. rubida, Dipetalogaster máxima, Panstrongylus rufotuberculatus y Rhodnius prolixus. Los transmisores peridomiciliados son de menor riesgo en la dinámica de transmisión comparados con los intradomiciliados. Para el control de los transmisores intradomiciliados, se deben emplear programas de educación para la salud, mejoramiento de vivienda e insecticidas; mientras que para los vectores visitantes o peridomiciliados, son necesarios programas de educación para la salud, uso de mosquiteros, pabellones y cementación de las bardas de piedra.

A revision of thirteen species of Triatominae (Hemiptera: Reduviidae) vectors of Chagas disease in Mexico

Vectors of Trypanosoma cruzi, parasite responsible for Chagas disease, are divided in intradomestic, peridomestic and sylvatic. The intradomestic are Triatoma barberi and Triatoma dimidiata, two species that represent the highest health risk among the Mexican population. Triatoma dimidiata is a species found mainly inside human habitats, but in Yucatan, it corresponds to the peridomicile vectors. Also in the peridomicile most of Chagas disease vectors are found: Meccus bassolsae, M. longipennis, M. mazzottii, M pallidipennis, M. phyllosomus, M picturata, Triatoma gerstaeckeri, T mexicana, T rubida, Dipetalogaster máxima (the last two are in the process of becoming adapted to the domicile), Panstrongylus rufotuberculatus which occasionally enters the domicile in its adult stage, and Rhodnius prolixus, which is practically controlled in the country. Peridomestic vectors are of lower risk in the transmission dynamics, as compared to the intradomestic ones. For the control of the intradomestic vectors, health education programs, improvements of housing, and the use of pesticides are essential To control the peridomestic vectors, health education programs are required, as well as the use of mosquito nets on doors and windows and around beds, aside from cementing the stone wall fences.

[Evaluation of the function and ventricular synchrony in patients with latency stage of Chagas' disease]

OBJECTIVE

To compare the left ventricular function and the ventricular synchrony in patients with Chagas disease in latency stage respect to a control group.

METHODS

We analyze a prospective, comparative, transversal and non randomized study of the left ventricular function (LVF) and the ventricular contraction synchronicity (VCS) in 36 subjects with positive serology for Chagas disease (18 males and 18 females), with mean of 15 +/- 5-years-old. The findings were compared with respect to 23 control volunteers (11 males and 12 females) with mean of 28 +/- 5-years-old. LVF and VCS were evaluated using equilibrium radionuclide angiography images (ERNA). The comparison of both Chagas and control populations was carried out by t Student test for independent samples, considering a statistically significant value of p < 0.05.

RESULTS

The parameters of the ventricular function and the ventricular synchronicity in subjects with positive serology for Chagas disease were not statistically different with respect to the parameters of the control group. However, although they have a homogeneous contraction, the mean time of contraction for the right and the left ventricle is statistically smaller with respect to the control group.

CONCLUSIONS

In clinically incipient stages of Chagas disease we do not found abnormalities in the ventricular function and the ventricular synchronicity. It's necessary to consider the follow up of the studied populations using indices for the identification of abnormalities of the autonomic nervous system.

Insecticide and community interventions to control Triatoma dimidiata in localities of the State of Veracruz, Mexico

Three different interventions to control Triatoma dimidiata in the State of Veracruz were implemented: X-1 = whole dwelling spraying, X-2 = middle wall spraying, X-3 = household cleaning. Cyfluthrin was sprayed 3 times with 8 month intervals. After each spraying, insects were collected and sent to the laboratory to be recorded and to determine genus and species of the adult triatomine bugs, and nymphs were counted. Trypanosoma cruzi presence was determined. With X-1, the infestation, colonization, and natural infection indexes were reduced to 0% in the 3 localities, with respect to t0. With X-2, the infestation index was reduced to 10% at t3 in 3 localities; the colonization index was reduced to 0% in only 1 locality at t3, and the natural infection index was reduced to 0% at t3. With X-3 the 3 indexes were not effectively reduced but they decreased with respect to the baseline study. Insecticide application to the whole dwelling is a more efficient intervention than its application to only the lower half of the walls and to the cleaning of houses.

[Fascioliasis in children. A study of 10 cases]

These are the observation found in ten children with fascioliasis diagnosis at the Servicio de Parasitología, of the Instituto Nacional de Pediatría, from 1979 to 1990; six children in scholar age; one prescholar and three teenagers; only one was female. Four of them lined at the State of Mexico; three at Morelos; one at Puebla, another one at Oaxaca and the other one at Mexico City. In nine of the watercress eaten was confirmed. The most important clinic manifestations were: fever, weight lose, paleness, hepatomegaly, hiporexia, right hypochondrium pain and diarrhoea. Diagnosis was established by: counterimmunoelectrophoresis, indirect haemagglutination and there were found eggs by simple sedimentation, Ritchie's method and microscopic study of duodenal sample. Leukocytes counts were between 11,000 and 34,000/mm3. Eosinophils were to 77% with 24,430 totals. Only in three of them haemoglobin was found under 9 g/dL. All of them had hypergammaglobulinemia. In nine patients the alkaline phosphatase was found in higher levels; only in three of them, transaminase, oxalacetic and glutamic piruvic were found in higher levels. The most effective drug in the treatment was dehidroemetine.