Bats, Trypanosomes, and Triatomines in Ecuador: New Insights into the Diversity, Transmission, and Origins of Trypanosoma cruzi and Chagas Disease

The generalist parasite Trypanosoma cruzi has two phylogenetic lineages associated almost exclusively with bats—Trypanosoma cruzi Tcbat and the subspecies T. c. marinkellei. We present new information on the genetic variation, geographic distribution, host associations, and potential vectors of these lineages. We conducted field surveys of bats and triatomines in southern Ecuador, a country endemic for Chagas disease, and screened for trypanosomes by microscopy and PCR. We identified parasites at species and genotype levels through phylogenetic approaches based on 18S ribosomal RNA (18S rRNA) and cytochrome b (cytb) genes and conducted a comparison of nucleotide diversity of the cytb gene. We document for the first time T. cruzi Tcbat and T. c. marinkellei in Ecuador, expanding their distribution in South America to the western side of the Andes. In addition, we found the triatomines Cavernicola pilosa and Triatoma dispar sharing shelters with bats. The comparisons of nucleotide diversity revealed a higher diversity for T. c. marinkellei than any of the T. c. cruzi genotypes associated with Chagas disease. Findings from this study increased both the number of host species and known geographical ranges of both parasites and suggest potential vectors for these two trypanosomes associated with bats in rural areas of southern Ecuador. The higher nucleotide diversity of T. c. marinkellei supports a long evolutionary relationship between T. cruzi and bats, implying that bats are the original hosts of this important parasite

El juego como facilitador para lograr aprendizajes significativos

Tesis (Educadora de Párvulos, Licenciado en Educación)El juego es una de las actividades más importantes de todo niño, porque además de satisfacer las necesidades lúdicas de los párvulos, favorece su ubicación en el ambiente y su captación de la realidad que lo circunda. Así también, estamos conscientes de que existen muchas formas de aprender, unas más apropiadas que otras, pero sin lugar a dudas el juego debe constituir el principal instrumento de aprendizaje, ya que, por medio de esta los niños experimentan la vida y comparten con otros; por tanto el aprendizaje es más efectivo y duradero cuando parte del mundo y las experiencias de los niños. Sin embargo, a través de las prácticas realizadas a lo largo de nuestra formación universitaria, hemos podido percibir, que a pesar de ser el juego lo que caracteriza a la infancia, generalmente sólo se limita a los momentos de esparcimiento de los niños, excluyéndolo del quehacer pedagógico. Es por ello y considerando todo lo anteriormente planteado, que nace la necesidad de abordar el juego infantil, sus diferentes tipos y características; así como también indagar respecto a la concepción constructivista y su postura respecto al aprendizaje significativo, el cual se caracteriza por ser funcional, ya que se reconocen los conocimientos anteriores y se aplican al enfrentarse y establecer relaciones con conocimientos nuevos. Por tanto será significativo en la medida en que se le asignen significado a todas las experiencias previas que el individuo trae, para que así se produzca una interacción dinámica entre lo que se conoce y lo nuevo por conocer. De esta manera se incentiva que el niño construya su propia red de conocimiento sobre la base de sus propias experiencias y de la interacción con otros. Así se está aprendiendo con sentido de manera pertinente, entre la relación de lo nuevo con lo que ya sabe. Esto y más es lo que abordaremos a continuación, dejamos por tanto la invitación a seguir viendo nuestro seminario

Bats, Trypanosomes, and Triatomines in Ecuador: New Insights into the Diversity, Transmission, and Origins of <i>Trypanosoma cruzi</i> and Chagas Disease

<div><p>The generalist parasite <i>Trypanosoma cruzi</i> has two phylogenetic lineages associated almost exclusively with bats—<i>Trypanosoma cruzi</i> Tcbat and the subspecies <i>T</i>. <i>c</i>. <i>marinkellei</i>. We present new information on the genetic variation, geographic distribution, host associations, and potential vectors of these lineages. We conducted field surveys of bats and triatomines in southern Ecuador, a country endemic for Chagas disease, and screened for trypanosomes by microscopy and PCR. We identified parasites at species and genotype levels through phylogenetic approaches based on 18S ribosomal RNA (18S rRNA) and cytochrome b (cytb) genes and conducted a comparison of nucleotide diversity of the cytb gene. We document for the first time <i>T</i>. <i>cruzi</i> Tcbat and <i>T</i>. <i>c</i>. <i>marinkellei</i> in Ecuador, expanding their distribution in South America to the western side of the Andes. In addition, we found the triatomines <i>Cavernicola pilosa</i> and <i>Triatoma dispar</i> sharing shelters with bats. The comparisons of nucleotide diversity revealed a higher diversity for <i>T</i>. <i>c</i>. <i>marinkellei</i> than any of the <i>T</i>. <i>c</i>. <i>cruzi</i> genotypes associated with Chagas disease. Findings from this study increased both the number of host species and known geographical ranges of both parasites and suggest potential vectors for these two trypanosomes associated with bats in rural areas of southern Ecuador. The higher nucleotide diversity of <i>T</i>. <i>c</i>. <i>marinkellei</i> supports a long evolutionary relationship between <i>T</i>. <i>cruzi</i> and bats, implying that bats are the original hosts of this important parasite.</p></div

Constructions in Ecuador where <i>Cavernicola pilosa</i> and <i>Triatoma dispar</i> were found in association with bats.

<p><b>A.</b> House with cinderblock walls at Rancho Alegre, Zamora Chinchipe where <i>C</i>. <i>pilosa</i> (inset) was inhabiting a roost of <i>Myotis</i> sp. <b>B.</b> Adobe barn in Chinguilamaca, Loja where <i>T</i>. <i>dispar</i> (inset) was found associated with <i>Molossus molossus</i> and <i>Myotis</i> sp. Arrows indicate the entrances to the bat roosts where the insects were collected.</p

Mitochondrial diversity of <i>Trypanosoma cruzi</i>.

<p>Nucleotide diversity (π) of mitochondrial lineages of <i>Trypanosoma cruzi</i> calculated for the haplotypes of the cytb gene. The subspecies <i>T</i>. <i>c</i>. <i>marinkellei</i> shows larger nucleotide diversity than the other examined lineages. Whiskers in each bar indicate the standard error.</p

Network genealogy using partial 18S rRNA gene sequences

<p>from eight new trypanosomes characterised in this study (in bold) plus 70 other sequences from all DTUs (TcI-TcVI and Tcbat) of <i>T</i>. <i>cruzi</i> and 22 sequences from <i>T</i>. <i>c</i>. <i>marinkellei</i>. Network constructed with the NeighborNet algorithm excluding all conserved sites and with uncorrected p-distance. Numbers in nodes correspond to bootstrap support values using the same parameter optimized for network inferences.</p

Mitochondrial phylogeny of <i>Trypanosoma cruzi</i>.

<p>Maximum likelihood tree of a fragment of the cytb gene of <i>Trypanosoma cruzi</i> and <i>T</i>. <i>dionisii</i> as outgroup, representing 60 haplotypes from 362 sequences. The parentheses at the tip labels contain the number of identical sequences per each haplotype, and in the TcIII-TcVI group the DTU identity for each haplotype is indicated. Numbers on branches correspond to bootstrap support values. Stars indicate the haplotypes found in Ecuador.</p

Results of PCR screenings for <i>Trypanosoma cruzi</i> and <i>Trypanosoma rangeli</i>.

<p>Results of PCR screenings for <i>Trypanosoma cruzi</i> and <i>Trypanosoma rangeli</i>.</p