Trypanosoma cruzi: A review of biological and methodological factors in Mexican strains.

Trypanosoma cruzi, responsible for Chagas disease, is a serious public health problem in Latin America with eight million people infected in the world. Clinical manifestations observed in humans due to T. cruzi infection are largely associated with the wide biological and genetic heterogeneity of the parasite. This review presents an overview of the parasitological aspects of various strains of T. cruzi isolated mainly in Mexico, as well as an analysis of the methodological processes used to determine their virulence that could be influencing their biological characterization. We emphasize the importance of using uniform protocols to study T. cruzi virulence, taking into account factors related to: strain (i.e. developmental stage, lineage, biological origin, genetic variability), animal model used (i.e. role of hormones, host immune response, age) and methodology (i.e. inoculum size, inoculation route, and laboratory conditions used during strain maintenance). These uniform protocols will then allow proposing elements for understanding clinical evolution and management of the disease, for providing adequate treatment, and for developing tools for future vaccines against Chagas disease.

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.

What makes an effective Chagas disease vector? Factors underlying Trypanosoma cruzi-triatomine interactions.

The Chagas disease is caused by the parasite Trypanosoma cruzi, which infect blood-feeding triatomine bugs to finally reach mammal hosts. Chagas disease is endemic in Latin America, and is ranked among the 13 neglected tropical diseases worldwide. Currently, an estimate of 7 million people is infected by T. cruzi, leading to about 22 000 deaths per year throughout the Americas. As occurs with other vectors, a major question towards control programs is what makes a susceptible bug. In this review, we focus on findings linked to insect gut structure and microbiota, immunity, genetics, blood sources, abiotic factors (with special reference to ambient temperature and altitude) to understand the interactions occurring between T. cruzi and triatomine bugs, under a co-evolutionary scenario. These factors lead to varying fitness benefits and costs for bugs, explaining why infection in the insect takes place and how it varies in time and space. Our analysis highlights that major factors are gut components and microbiota, blood sources and temperature. Although their close interaction has never been clarified, knowledge reviewed here may help to boost the success of triatomine control programs, reducing the use of insecticides.

Seroprevalence of Triatoma virus (Dicistroviridae: Cripaviridae) antibodies in Chagas disease patients.

BACKGROUND: Chagas disease is caused by Trypanosoma cruzi, and humans acquire the parasite by exposure to contaminated feces from hematophagous insect vectors known as triatomines. Triatoma virus (TrV) is the sole viral pathogen of triatomines, and is transmitted among insects through the fecal-oral route and, as it happens with T. cruzi, the infected insects release the virus when defecating during or after blood uptake. METHODS: In this work, we analysed the occurrence of anti-TrV antibodies in human sera from Chagas disease endemic and non-endemic countries, and developed a mathematical model to estimate the transmission probability of TrV from insects to man, which ranged between 0.00053 and 0.0015. RESULTS: Our results confirm that people with Chagas disease living in Bolivia, Argentina and Mexico have been exposed to TrV, and that TrV is unable to replicate in human hosts. CONCLUSIONS: We presented the first experimental evidence of antibodies against TrV structural proteins in human sera.

Differences on biological attributes of three populations of Meccus pallidipennis Stål (Hemiptera: Reduviidae).

BACKGROUND & OBJECTIVES: Meccus pallidipennis is one of the most epidemiologically important vectors of Trypanosoma cruzi to reservoir hosts in nine states of Mexico. Triatomines occurring in distinct locations normally adapt to local conditions. The aim of this study was to examine the biological attributes of three populations of M. pallidipennis from areas with different environmental characteristics as a factor influencing the triatomine capacity for T. cruzi transmission. METHODS: The values of biological parameters related to the life cycle, the number of blood meals to molt to next instar, fecundity and percentage of females after a biological cycle of three populations of M. pallidipennis were evaluated. A cohort of each of the three studied populations from different geographical areas of Mexico was maintained under similar laboratory conditions and then compared with each other. RESULTS: The life cycle was less than six months in all the studied cohorts, with differences among them. The number of blood meals to molt was lower for the cohort from Izϊcar de Matamoros. Laid eggs per day per female was lower for the cohort from Luvianos. In contrast, no important differences were recorded on the percentage of mortality, egg eclosion rate or percentages of obtained females. INTERPRETATION & CONCLUSION: It was found that an important level of heterogeneity exist between the three studied populations of M. pallidipennis, apparently influenced by the remarkable differences on environmental conditions on the localities where the founders were initially collected, that emphasizes the necessity of studies on local populations of triatomines.

Genome size determination in chagas disease transmitting bugs (hemiptera-triatominae) by flow cytometry.

Because information about genome size in triatomines is scarce and contradictory, we performed DNA quantification by flow cytometry in 13 species belonging to five genera (Dipetalogaster, Eratyrus, Panstrongylus, Rhodnius, and Triatoma) to infer overall tendencies and phylogenetic associations. The results show that the haploid DNA content of the subfamily Triatominae varies nearly 4-fold, from<0.7 pg in Rhodnius species (0.6x10(9) bp) to 2.7 pg in Triatoma delpontei (2.6x10(9) bp). Considering that triatomines present similar chromosome numbers, we suggest that genome size differences are the result of variation in the quantity of repetitive DNA sequences localized in hetero and euchromatin. Changes in heterochromatin are particularly important when considering populations or closely related species; in more distant taxa, euchromatic changes also play a role. Our analyses indicate that flow cytometry is a useful tool for population, taxonomic, and evolutionary studies in this subfamily.

[Importance of three triatoma vectors of Trypanosoma cruzi in Mexico]. / Tres especies de triatominos y su importancia como vectores de Trypanosoma cruzi en México.

Observations made in the field and in the laboratory on three vectors of Trypanosoma cruzi: Triatoma barberi, T. pallidipennis and T. dimidiata are here presented. Results are compared in relation with their ecotopes, vectorial capacity, biological characteristic, entomological indexes and capture places. In relation with their ecotopos T. barberi has preference for the interior of the human home, in walls, directly in contact with beds; T. pallidipennis, when it is inside the houses, prefers floors and among clothes, although their main ecotope is wild; T. dimidiata has localization in floors, specially under the beds, in the angle between wall and floor; T. barberi and T. dimidiata are attracted by the light. The cycles of life were of 523, 171 and 510 days, respectively for Triatoma barberi, T. pallidipennis and T. dimidiata. The vectorial capacity was determined according to the time taken in defecating during or after its sucking blood: T. barberi defecates during its feeding, while T. pallidipennis and T. dimidiata make it from 10 to 20 and of 20 to 30 minutes after starting the process, respectively. The indexes of natural infection were of 56.6 for T. barberi, 29 for T. pallidipennis and 15.6 for T. dimidiata, The metacyclogenics indexes that indicate percentages of metacyclics trypomastigotes in later intestine of vectors was in T. barberi 76.6, T. pallidipennis 15 and T. dimidiata 26, with what it can be concluded that the first species is the best transmitter of T. cruzi in Mexico.

Tres especies de triatominos y su importancia como vectores de Trypanosoma cruzi en México. / [Importance of three triatoma vectors of Trypanosoma cruzi in Mexico]

Observations made in the field and in the laboratory on three vectors of Trypanosoma cruzi: Triatoma barberi, T. pallidipennis and T. dimidiata are here presented. Results are compared in relation with their ecotopes, vectorial capacity, biological characteristic, entomological indexes and capture places. In relation with their ecotopos T. barberi has preference for the interior of the human home, in walls, directly in contact with beds; T. pallidipennis, when it is inside the houses, prefers floors and among clothes, although their main ecotope is wild; T. dimidiata has localization in floors, specially under the beds, in the angle between wall and floor; T. barberi and T. dimidiata are attracted by the light. The cycles of life were of 523, 171 and 510 days, respectively for Triatoma barberi, T. pallidipennis and T. dimidiata. The vectorial capacity was determined according to the time taken in defecating during or after its sucking blood: T. barberi defecates during its feeding, while T. pallidipennis and T. dimidiata make it from 10 to 20 and of 20 to 30 minutes after starting the process, respectively. The indexes of natural infection were of 56.6 for T. barberi, 29 for T. pallidipennis and 15.6 for T. dimidiata, The metacyclogenics indexes that indicate percentages of metacyclics trypomastigotes in later intestine of vectors was in T. barberi 76.6, T. pallidipennis 15 and T. dimidiata 26, with what it can be concluded that the first species is the best transmitter of T. cruzi in Mexico.

Enteroparasitosis en poblaciones indígenas y mestizas dela Sierra de Nayarit, México / Enteroparasitoses in indigenous and mestizo individuals from the Nayarit mountain range, Mexico

Comparamos las prevalencias de enteropa-rasitosis a partir de 420 individuos, 306 de ellos eran indígenas y 114 eran mestizos, sin dife-renciación de género, y de todos los rangos de edad, de la Sierra de Nayarit. Se hicieron seis viajes al campo a la región durante un año para recoger muestras de materia fecal, algunos individuos proporcionaron solamente una muestra y otros cinco muestras. Las muestras de materia fecal fueron diluidas en una solución de formalina al 10 por ciento en una relación 1:10, para su conservación durante su transporte a la Ciudad de México, donde se procesaron por análisis coproparasitoscópico directo teñido con solución de lugol. Nosotros encontramos 59,8 por ciento de entamoeba histolytica, 22,2 por ciento de Giardia lamblia, 22,2 por ciento de Enterobius vermicularis, 15,4 por ciento de Hymenolepis nana, 2 casos de taeniosis (0,7 por ciento), 21 casos de ascariosis (6,9 por ciento), 2 casos de estrongyloidosis (0,7 por ciento) y 7 casos de trichuriosis (2,3 por ciento) entre la población huichol. En la población mestiza, encontramos 43,9 por ciento de entamoebosis, 14,0 por ciento de giardiosis 9,6 por ciento de hymenolepiosis, 5 casos de ascariosis, 2 de taeniosis, 1 de strongyloidosis y 1 de enterobiosis. Los resultados se analizaron por la prueba del Chi-cuadrada y revelaron diferencias estadísticas significativas entre las dos poblaciones estudiadas

Dermatitis verminosa reptante / Dermatitis cutaneous larva migrans

Se comunica un brote epidémico de Larva migrans cutánea, posterior a lluvias intensas al paso del huracán Celia, en siete estudiantes y un profesor de la Facultad de Ciencias. El diagnóstico se estableció clínicamente; se realizaron frotes sanguíneos para cuantificación de eosinófilos. Fueron tratados con albendazol a dosis convencionales y tiabendazol tópico