The effect ofBlastocrithidia triatomae(Trypanosomatidae) on the midgut of the reduviid bugTriatoma infestans

Abstract

The pathogenic flagellate Blastocrithidia triatomae disrupts the digestion of Triatoma infestans; the midgut ultrastructure of bugs infected with the flagellate and of uninfected bugs is compared. Third or fourth instar larvae were dissected either unfed or 1 week after feeding. In all uninfected bugs extracellular membrane layers (e.m.l.) covered the apical microvillar border of the epithelial cells. Some midgut regions of bugs infected with B. triatomae appeared normal but often adjacent cells showed pathological effects. In affected cells the e.m.l. and the microvilli and finally the cells themselves were reduced or destroyed. Correlated with these observations of pathogenicity the method of attachment of parasites changed. When the e.m.l. were present only rarely were flagella found, but on extracellular membrane-free cells B. triatomae attached by flagellar enlargement to the microvillar border or, if this was reduced, to the apical host cell membrane. No hemidesmosome-like plaques were found at the attachment site. Although some flagella were inserted into the apical region of the cells no intracellular flagellates were observed.

Condition-dependent virulence of slow bee paralysis virus in Bombus terrestris: are the impacts of honeybee viruses in wild pollinators underestimated?

“…It is possible that infection induces a costly response by the host immune system; in this scenario, the host is unable to maintain a defence against the virus when resources are withheld, resulting in increased virus virulence and reduced lifespan (Moret and Schmid-Hempel 2000). It is also possible that infection reduces the resources in the gut that are available to the bee, or inhibits uptake of resources, as may be the case for trypanosomal gut parasites (Gorbunov 1987, 1996; Jensen et al 1990). Such effects may be exacerbated by any damage caused by viral replication within its host, with the pathogen’s virulence likely to be determined by a combination of these factors.…”

Condition‐dependent expression of virulence in a trypanosome infecting bumblebees

“…Secondly, infection may inhibit the utilisation of gut contents by actually destroying intestinal cells (e.g., Jensen et al (1990)). Thirdly, C. bombi may induce the host immune system, and the energy required for this induction may be sufficient to reduce host lifespan when additional resources are withheld (Moret and Schmid-Hempel, unpublished data).…”

Effect of blood components, abdominal distension, and ecdysone therapy on the ultrastructural organization of posterior midgut epithelial cells and perimicrovillar membranes in Rhodnius prolixus

“…In those sham-operated insects, the midgut cells displayed exactly the same appearance as seen in control insects (not shown). To take into account that microvilli are already present in the posterior midgut cells which have not reached the lumem of the gut even before blood meal (Jensen et al 1990, Schaub et al 1992, the reduction in its development after nerve-cord severance led us to suggest that microvilli distribution is related to nerve integrity. In addition, full development of a network of PMM observed when the insects were fed on Ringer's solution containing ecdysone indicates the influence of ecdysone on the morphogenesis of the posterior midgut epithelium cells.…”