Ascaris suum: A Revision of Its Early Migratory Path and Implications for Human Ascariasis

Abstract

During the course of carrying out studies on the role of intestinal immunity in blocking the migration of larval Ascaris suum in the pig, it was discovered that the prevailing understanding of larval penetration sites was at variance with our observations. Therefore, a detailed investigation of the migration of A. suum 1.2 larvae through the intestine was initiated. The results demonstrate that the 1.2 larvae invade almost exclusively the wall of the pig cecum and colon and not the small intestine as is generally believed. The larvae were recovered from the mucosa of the cecum and colon as early as 3 hr postinoculation (PI) with infective eggs and were recovered from the liver by 6 hr PI. The maximal recovery of larvae (total larvae and larval/g of mucosa) from the intestinal mucosa occurred between 6 and 12 hr PI; by 24 hr PI, virtually all of the larvae had disappeared from the mucosa. These observations correct a common misunderstanding of this aspect of the life cycle of A. suum in the pig, and they raise 2 issues related to the biology and pathogenesis of Ascaris in humans. What is the actual migratory and development behavior of Ascaris lumbricoides and A. suum in humans and the potential risk for liver lesions? Most authors, in describing the life cycle of A. lumbricoides, either ignore or discount a possible obligatory liver stage of development, and, consequently, the potential for lesion formation similar to that which occurs in pigs infected with A. suum. This issue takes on added importance with the growing evidence that A. suum is an important zoonoses.

The effect of a diet with fructan-rich chicory roots on intestinal helminths and microbiota with special focus on Bifidobacteria and Campylobacter in piglets around weaning

“…As suggested for the large intestinal parasites O. dentatum and T. suis (Petkevičius et al, 2004;Thomsen et al, 2005), A. suum may have been negatively affected by changes in the physico-chemical conditions (e.g. higher production of short-chain fatty acids (SCFA) and lower pH) in the caecum and proximal colon, as these sites are where the newly hatched larvae invade the mucosa before migrating through the liver and lungs and returning to the small intestine (Murrell et al, 1997). These changes of living conditions are likely to occur as the caecum and proximal colon are also the main sites for bacterial degradation of carbohydrates, yielding substances such as SCFA and lactic acids (Jensen and Jørgensen, 1994).…”

Inactivation of Single-Celled Ascaris suum Eggs by Low-Pressure UV Radiation

“…Our method of determining viability by embryonation in 28 days is consistent with existing regulations for determination of Ascaris egg viability in biosolids (41). To understand the difference between the use of incubation and the use of infectivity for determining viability, it is useful to review the Ascaris life cycle, which has been described by various authors (9,17,27,34). Briefly, when Ascaris eggs are excreted in the feces of a host, each of them contains a single cell, which requires 6 to 12 weeks of aerobic incubation in the environment (or less time in the laboratory under ideal conditions) to divide and grow into an infective, third-stage larva (12).…”

Changes in trehalase activity and trehalose level during Ascaris suum (Nematoda) embryogenesis

“…The L 2 larvae penetrate the alimentary system of the host, most frequently per os, and there they hatch. Before they reach the mature form in the intestine, they migrate through liver, heart and lunges tissues of the host and get through three further moultes processes (Murrel et al, 1997). The embryo of the nematode develops using in the internal environment owing to the substrates and their precursors accumulated in the egg during oogenesis .…”