What are the infectious larvae in Ascaris suum and Trichuris muris?

Abstract

In the present study, larvae of Ascaris suum and Trichuris muris were investigated by light and electron microscopy after incubation in a hatching medium containing 89% phosphate-buffered saline (pH 7.4), 10% RPMI-1640 and 1% sodiumhypochlorite at 40 and 37 degrees C, respectively. The larvae were obtained from fertilised eggs of the worms during defined phases of development (A. suum, 36th-50th day of development; T. muris, once a week from week 16 to 20). Light and electron micrographs of the larvae gave evidence that the third larval stage of A. suum is probably the infectious stage. The first moult of the larvae had already taken place before the 36th day of incubation starting at day 1. After 36 days of incubation, only the second larval stage was found within eggs. Some of these larvae were coated by a separated sheath so that a second moult of the larvae is reasonable. On the other hand, no sheathed larvae of T. muris were found in the eggs incubated for 20 weeks in distilled water. No signs of moult were seen for 20 weeks neither on light nor on the electron micrographs. Therefore, in T. muris, the first larval stage is the infectious stage, which was proven by means of re-infections of mice 16, 18 or 20 weeks after incubation of the eggs.

New Insights into Morphological and Biological Features of Capillaria aerophila (Trichocephalida, Trichuridae)

“…At the moment, the biological cycle of C. aerophila is considered direct, with a facultative, not mandatory, intervention of terrestrial worms in the transmission, which fit with biological characteristics of Trichuroid parasitic nematodes (Soulsby 1982;Campbell and Little 1991;Bowman et al 2002;Taylor et al 2007). Therefore, C. aerophila is one of those worms whose biological cycle has not been definitively elucidated yet, as for instance recently indicated also for the closely related Trichuroid murine whipworm (Kirchgässner et al 2008). …”

Quantifying metabolic activity of Ascaris suum L3 using resazurin reduction

“…Within the A. suum L3, we observed a bright fluorescence signal which was unevenly distributed inside the larval body. A coherent bright signal was emitted from a region inside the larvae at the posterior end, which we, based on morphological descriptions of Kirchgäßner et al [ 21 ], allocate to the worms’ midgut. Larvae incubated without resazurin showed no autofluorescence at λ ex = 555 nm (Fig.…”