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

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

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