Interactions Between Trypanosoma cruzi the Chagas Disease Parasite and Naturally Infected Wild Mepraia Vectors of Chile.

Chagas disease, which ranks among the world's most neglected diseases, is a chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi. Mepraia species are the wild vectors of this parasite in Chile. Host-parasite interactions can occur at several levels, such as co-speciation and ecological host fitting, among others. Thus, we are exploring the interactions between T. cruzi circulating in naturally infected Mepraia species in all areas endemic of Chile. We evaluated T. cruzi infection rates of 27 different haplotypes of the wild Mepraia species and identified their parasite genotypes using minicircle PCR amplification and hybridization tests with genotype-specific DNA probes. Infection rates were lower in northern Chile where Mepraia gajardoi circulates (10-35%); in central Chile, Mepraia spinolai is most abundant, and infection rates varied in space and time (0-55%). T. cruzi discrete typing units (DTUs) TcI, TcII, TcV, and Tc VI were detected. Mixed infections with two or more DTUs are frequently found in highly infected insects. T. cruzi DTUs have distinct, but not exclusive, ecological and epidemiological associations with their hosts. T. cruzi infection rates of M. spinolai were higher than in M. gajardoi, but the presence of mixed infection with more than one T. cruzi DTU was the same. The same T. cruzi DTUs (TcI, TcII, TcV, and TcVI) were found circulating in both vector species, even though TcI was not equally distributed. These results suggest that T. cruzi DTUs are not associated with any of the two genetically related vector species nor with the geographic area. The T. cruzi vectors interactions are discussed in terms of old and recent events. By exploring T. cruzi DTUs present in Mepraia haplotypes and species from northern to central Chile, we open the analysis on these invertebrate host-parasite interactions.

Campos-Soto R ，Ortiz S ，Cordova I ，Bruneau N ，Botto-Mahan C ，Solari A ... -  《-》

Fluctuations in Trypanosoma cruzi discrete typing unit composition in two naturally infected triatomines: Mepraia gajardoi and M. spinolai after laboratory feeding.

Mepraia species are hematophagous insects and the most important wild vectors of Trypanosoma cruzi, the causative agent of Chagas disease in southeastern South America. Because the domestic Triatoma infestans is already controlled, the transmission of different T. cruzi discrete typing units (DTUs) by Mepraia species deserves attention. Our aim is to gather information on the diversity of T. cruzi DTUs circulating in natural insect populations. Two groups of naturally infected bugs 21 Mepraia gajardoi and 26 Mepraia spinolai were followed-up after two or more laboratory feedings by means of minicircle-PCR assays to evaluate the composition of four T. cruzi DTUs by hybridization tests. Fluctuations from positive T. cruzi detection to negative and the converse, as well as single to mixed infections with different T. cruzi DTUs and the opposite were frequent observations after laboratory feeding in both Mepraia species. Single and mixed infections with more than two T. cruzi DTUs were detected after the first feeding; however mainly mixed infections prevailed after the second feeding. Laboratory feeding on three or more occasions resulted in a decreasing trend of the parasite burden. In a comparison with 28 infected and fed M. gajardoi collected one year before from the same vector colony T. cruzi DTUs composition changed, indicating that temporal variations occur in T. cruzi. Natural populations of Mepraia species can transmit complex mixtures T. cruzi DTUs which fluctuate over time after feeding, with a tendency to eliminate the parasitism after prolonged feeding.

Egaña C ，Pinto R ，Vergara F ，Ortiz S ，Campos R ，Solari A ... -  《-》

Comparing vector competence of Mepraia gajardoi and Triatoma infestans by genotyping Trypanosoma cruzi discrete typing units present in naturally infected Octodon degus.

Chagas disease is a vector-borne disease caused by the parasite Trypanosoma cruzi, and transmitted by triatomine insects to several mammal species. In Chile, the wild triatomine species are the endemic Mepraia species, and the only domestic vector of Chagas disease is Triatoma infestans. The aim of this study was to determine the competence of M. gajardoi compared to T. infestans as a T. cruzi vector using the naturally infected rodent Octodon degus. M. gajardoi amplified T. cruzi present in all O. degus studied while T. infestans only in half of the infected rodents. Both triatomine species excrete metacyclic trypomastigotes and amplified the same three T. cruzi DTUs, however, M. gajardoi showed differences in their ability to amplify TcI. TcV and TcVI had the same probability to be amplified by both triatomine species. Both species amplified mixed infections, with TcI-TcVI as the most represented. This study reports the higher vector competence of M. gajardoi in comparison to T. infestans.

Sandoval-Rodríguez A ，Rojo G ，López A ，Ortiz S ，Saavedra M ，Botto-Mahan C ，Cattan PE ，Solari A ... -  《-》

Trypanosoma cruzi over the ocean: Insular zones of Chile with presence of infected vector Mepraia species.

Chagas disease is one of the main zoonosis mediated by vectors in America. The etiologic agent Trypanosoma cruzi infects different mammals and is transmitted principally by the subfamily Triatominae. Mepraia is a genus endemic to Chile, responsible for transmitting T. cruzi in the sylvatic cycle. Mepraia includes three species: M. gajardoi and M. parapatrica inhabit coastal areas, while M. spinolai inhabits coastal and interior valleys. Previous studies reported the occurrence of Mepraia in Pan de Azucar Island, currently classified as M. parapatrica, but T. cruzi has not been reported in these insects. It is suggested that this could be due to infrequent insect feeding on mammalian hosts. In order to detect T. cruzi in insects from coastal islands, specimens from Pan de Azucar and Santa Maria Islands were examined. A region of kDNA of T. cruzi was amplified by PCR and hybridization assays were performed for T. cruzi genotyping of insect feces. The presence of infected insect and mixed T. cruzi infections was demonstrated. This is the first report of infected Triatominae in coastal islands in Chile. We discuss T. cruzi detection in insular zones, and the presumptive reservoirs that may participate in maintaining its transmission cycle in this habitat. Mixed and unidentified infections suggest that there are complex and unknown reservoir interactions in these habitats.

Rives-Blanchard N ，Torres-Pérez F ，Ortiz S ，Solari A ，Campos-Soto R ... -  《-》

Potential impact of climate change on the geographical distribution of two wild vectors of Chagas disease in Chile: Mepraia spinolai and Mepraia gajardoi.

Garrido R ，Bacigalupo A ，Peña-Gómez F ，Bustamante RO ，Cattan PE ，Gorla DE ，Botto-Mahan C ... -  《Parasites & Vectors》