Ultrastructural study of the host-parasite relationship of trypanosomatids in the housefly

Development of Monoxenous Trypanosomatids and Phytomonads in Insects

In this review, we summarize the current data on development of monoxenous trypanosomatids and phytomonads in various insects. Of these, Diptera and Hemiptera are the main host groups, and, consequently, most available information concerns their parasites. Within the insect body, the midgut and hindgut are the predominant colonization sites; in addition, some trypanosomatids can invade the foregut, Malpighian tubules, hemolymph, and/or salivary glands. Differences in the intestinal structure and biology of the host determine the variety of parasites' developmental and transmission strategies. Meanwhile, similar mechanisms are used by unrelated trypanosomatids, reflecting the limited range of options to achieve the same goal.

Genetic Diversity and Phylogenetic Relationships of Coevolving Symbiont-Harboring Insect Trypanosomatids, and Their Neotropical Dispersal by Invader African Blowflies (Calliphoridae)

This study is about the inter- and intra-specific genetic diversity of trypanosomatids of the genus Angomonas, and their association with Calliphoridae (blowflies) in Neotropical and Afrotropical regions. Microscopic examination of 3,900 flies of various families, mostly Calliphoridae, revealed that 31% of them harbored trypanosomatids. Small subunit rRNA (SSU rRNA) barcoding showed that Angomonas predominated (46%) over the other common trypanosomatids of blowflies of genera Herpetomonas and Wallacemonas. Among Angomonas spp., A. deanei was much more common than the two-other species, A. desouzai and A. ambiguus. Phylogenetic analyses based on SSU rRNA, glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) and internal transcribed spacer rDNA (ITS rDNA) sequences revealed a marked genetic diversity within A. deanei, which comprised four infraspecific genotypes (Dea1–Dea4), and four corresponding symbiont genotypes (Kcr1–Kcr4). Host and symbiont phylogenies were highly congruent corroborating their co-divergence, consistent with host-symbiont interdependent metabolism and symbiont reduced genomes shaped by a long coevolutionary history. We compared the diversity of Angomonas/symbionts from three genera of blowflies, Lucilia, Chrysomya and Cochliomyia. A. deanei, A. desouzai, and A. ambiguus were found in the three genera of blowflies in South America. In Africa, A. deanei and A. ambiguus were identified in Chrysomya. The absence of A. desouzai in Africa and its presence in Neotropical Cochliomyia and Lucilia suggests parasite spillback of A. desouzai into Chrysomya, which was most likely introduced four decades ago from Africa into the Neotropic. The absence of correlation between parasite diversity and geographic and genetic distances, with identical genotypes of A. deanei found in the Neotropic and Afrotropic, is consistent with disjunct distribution due to the recent human-mediated transoceanic dispersal of Angomonas by Chrysomya. This study provides the most comprehensive data gathered so far on the genetic repertoires of a genus of trypanosomatids found in flies from a wide geographical range.

Molecular phylogenetic redefinition of Herpetomonas (Kinetoplastea, Trypanosomatidae), a genus of insect parasites associated with flies

In order to review the taxonomy of the genus Herpetomonas through phylogenetic and morphological analyses we barcoded 527 insect trypanosomatids by sequencing the V7V8 region of the small subunit ribosomal RNA (SSU rRNA) gene. Fifty two flagellates, 90% of them from Diptera, revealed to be related to known species of Herpetomonas. Sequences of entire glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) and SSU rRNA genes were employed for phylogenetic inferences including representatives of all genera of Trypanosomatidae. In the resulting phylogenetic trees, the selected flagellates clustered into a monophyletic assemblage that we are considering as the redefined genus Herpetomonas. Internal transcribed spacer 1 (ITS1) rDNA sequences and putative secondary structures of this region were compared for evaluation of inter- and intraspecific variability. The flagellates were classified in six already known species and five new species. In addition, two Leptomonas spp. were moved to Herpetomonas, now comprising 13 valid species, while four species were excluded from the genus. Light and electron microscopy revealed the extreme polymorphism of Herpetomonas, hindering genus and species identification by morphological characteristics. Our findings also showed that some species of Herpetomonas are generalist parasites of flies and appear to be as cosmopolitan as their hosts.

Temporal and spatial fate of GFP-expressing motile and nonmotile Aeromonas hydrophila in the house fly digestive tract

To gain insight into the transmissibility of bacteria by house flies, the temporal and spatial fate of green fluorescent protein (GFP)-expressing motile and nonmotile strains of Aeromonas hydrophila was examined within the alimentary canal. Liquid food consumed by house flies is first stored in the crop and then is regurgitated and/or passed into the midgut. Once within the midgut, food is contained inside a double-layered peritrophic matrix (PM), with the inner layer enveloping digested material and forming fecal pellets for excretion. Between 1 and 12 h after ingestion, and irrespective of motility, live GFP+ A. hydrophila adhered to the luminal surfaces of the crop and inner PM of bacteria-fed flies. However, some nonadherent, motile bacteria moved freely within the PM lumen in the anteromedial midgut, whereas fecal pellets (lysed bacteria) continued passing posteriorly. At 12-24 h, adhered bacteria of both strains were lysed in the distal midgut, compressed into fecal pellets, and excreted. Viable bacteria in the crop visually exceeded numbers within these fecal pellets. Culture recovery at the same time points showed a 1,000-fold increase of viable bacteria at 2 h, presumably in the crop, with a temporal decline thereafter. Further, viable bacteria were recovered from vomit specks and orally contaminated substrates up to 2 h after feeding but never from feces. These results suggest that A. hydrophila is a transient resident of the house fly alimentary canal and is only orally transmissible for a short time after ingestion. Thus, regurgitation may be more significant than fecal transmission in the spread of some house fly transmitted bacterial diseases.

Insect trypanosomatids: the need to know more

Of ten recognized trypanosomatid genera, only two - pathogenic Trypanosoma and Leishmania - have been actively investigated for any length of time while the plant flagellates - Phytomonas - have recently begun to attract attention due to their role as agricultural parasites. The remaining genera that comprise parasites associated with insects have been largely neglected except for two or three containing popular isolates. This publication reviews current knowledge of trypanosomatids from insects.