Comparative Parasitology 67(2) 2000 - Peru State College

Comp. Parasitol.
67(2), 2000 pp. 241-243
Effects of a High-Carbohydrate Diet on Growth of Echinostoma
caproni in ICR Mice
MARK R. DARAS, SUSAN SISBARRO, AND BERNARD FRIED'
Department of Biology, Lafayette College, Easton, Pennsylvania 18042, U.S.A. (e-mail: friedb@lafayette.edu)
ABSTRACT: The effects of a high-carbohydrate diet (HCD) on the host-parasite relationship of Echinostoma
caproni Richard, 1964, in ICR mice were studied. The experimental diet was a customized HCD containing
63% carbohydrates, 14% protein, 4% fat, and 19% cellulose. The control diet, a standard laboratory diet,
contained 31% carbohydrate, 20% protein, 7% fat, and 42% cellulose. Thirty-six mice were each infected with
35 metacercarial cysts; 18 mice were fed the HCD and the remaining mice received the control diet. Equal
numbers of experimental and control mice were necropsied at 2, 3, and 4 weeks postinfection (p.i.). Comparisons
of worm body area in uniformly fixed and stained worms were made at 2, 3, and 4 weeks p.i. There was no
significant difference in body area in worms from each group at 2 and 3 weeks p.i. At 4 weeks p.i. the body
area of worms from hosts on the HCD was significantly greater than that of worms from hosts on the control
diet. The findings suggest that the HCD contributes to growth enhancement of E. caproni in ICR mice.
KEY WORDS: trematodes, high-carbohydrate diet, Echinostoma caproni, ICR mice, growth.
Previous studies in our laboratory have examined
the effects of various experimental diets
of hosts on growth and development of Echinostoma
caproni Richard, 1964, in Institute for
Cancer Research (ICR) mice. Sudati et al. (1996,
1997) used this model to study the effects of
high-lipid and high-protein diets, respectively, in
ICR mice. Rosario and Fried (1999) examined
the effects of a protein-free host diet on growth
and development of E. caproni in ICR mice.
Although studies are available on the effects
of a high-carbohydrate host diet on gastrointestinal
trematodes, this topic has been studied extensively
in rats infected with hymenolipid cestodes
(e.g., Read; 1959; Read and Simmons,
1963). It is clear from the literature that hymenolipids
thrive best in rodent hosts maintained on
high-carbohydrate diets (see Von Brand, 1973,
for review). Because of the lack of information
on gastrointestinal trematodes maintained in rodent
hosts fed a high-carbohydrate diet (HCD),
we initiated this study to examine the effects of
such a diet on worm recovery, growth, and distribution
of E. caproni in ICR mice. Echinostoma
caproni now is a well-established model
for conducting such studies of intestinal trematode
infections in nutritionally altered hosts.
Gracyzk and Fried (1998) examined the recent
literature on human echinostomiasis and
noted that it is a common but forgotten foodborne
disease. Because echinostomiasis may oc-
Corresponding author.
241
cur in people from socioeconomic groups that
have relatively high-carbohydrate, low-protein
diets, studies on the effects of HCD on the model
echinostome, E. caproni, seemed appropriate.
Materials and Methods
Metacercarial cysts of Echinostoma caproni were
removed from the kidney/pericardial region of experimentally
infected Biomphalaria glabrata (Say, 1818)
snails and fed by stomach tube (35 cysts per mouse)
to 36, 6 to 8-week-old, female ICR mice (Manger and
Fried, 1993). The experimental mice were fed a customized
HCD in pellet form containing 63% cornstarch
as a source of carbohydrate, 14% protein, 4%
fat, and 19% cellulose (Dyets Inc., Bethlehem, Pennsylvania,
U.S.A.). The control mice were fed a standardized
rat-mouse-hamster (RMH) 3000 diet in pellet
form containing 31% carbohydrate, 20% protein, 7%
fat, and 42% cellulose (US Biochemicals Co., Cleveland,
Ohio, U.S.A.). Both diets contained essential vitamins
and minerals as described previously. The HCD
was about 1.3 times more calorific than the normal diet
(Rosario and Fried, 1999).
A total of 36 mice was used in the experiment; 18
mice were maintained on the HCD, and the remainder
on the RMH diet. On the day of infection, the mice
were weighed and maintained 6 per cage on either the
HCD or the RMH diet. Food and water were provided
ad libitum. Six mice on the HCD and 6 mice on the
RMH diet were each necropsied at 2, 3, and 4 weeks
post infection (p.i.). Mice were weighed on the day
they were fed cysts and at necropsy. At that time, the
small intestine was removed from the pyloric sphincter
to the ileocecal valve and divided into 5 equal sections
numbered 1-5, beginning with the pylorus. Worms
were removed from the small intestine, and their location
and number in each section were recorded.
Worms were rinsed in Locke's solution and fixed in
hot (85°C) alcohol-formalin-acetic acid. Twenty
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