Biology Reference
In-Depth Information
pattern. Early studies
49,50
documented the preferential penetration of the
cecal and colon wall during early migration. This migratory stage was
recognized in mice prior to its discovery in pigs, highlighting the
important role abnormal hosts can play in exploring fundamental aspects
of the Ascaris life-cycle and basic parasite biology. As early as 1920,
Ransom and Foster
48
detected Ascaris larvae in the portal vein on day 1
post-infection, the first researchers to document the role of a blood vessel
in larval migration.
The timing of Ascaris larval migration is similar in both mice and pigs
and extends over an approximately 10- to 14-day period. When infective
embryonated eggs are administered to a mouse by gastric intubation (see
Figure 5.1
), larvae hatch in the small intestine, migrate to the large
intestine and within 2 to 3 hours post-infection can be recovered from the
cecal and colonic tissues.
49
e
51
From there, larvae migrate to the liver as
early as 4 hours post-infection.
51
A few larvae can be detected in the
lungs very quickly but the vast majority does not appear until days 4 to 5
post-infection.
51
e
53
Larval numbers then peak in this organ between
FIGURE 5.1
In experiments involving the mouse as a model organism, embryonated
ova (1) are typically administered by means of gastric intubation into the stomach (2).
Larvae hatch in the small intestine (3) and migrate to the large intestine (4), where they
penetrate the cecal and colonic wall (5). From there, larvae migrate to the liver (6) and then
to the lungs (7).
