Comparative observations were made on cercariae of Echinoparyphium sp. from Physa gyrina in Charlie's pond, Stokes County, North Carolina and cercariae of Echinostoma trivolvis from Helisoma trivolvis in Northampton County, Pennsylvania. The cercaria of Echinoparyphium sp. has 43 collar spines, lacks penetration and paraesophageal glands, and has a conical tail without fin folds. The cercaria of E. trivolvis has 37 collar spines, penetration and paraesophageal glands, a finger-like process at the tip of the tail and fin folds. The length of the cercarial body and tail of E. trivolvis was significantly greater than that of Echinoparyphium sp. Cercariae of both species encysted in Biomphalaria glabrata snails in single and concurrent infections. In concurrent infections with a single cercaria of each species, 2 encysted metacercariae were adjacent to each other in the saccular kidney of the snail at 24 hr postinfection. The diameter of encysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp. Echinoparyphium sp. metacercariae excysted at 39 C in an alkaline trypsin-bile salts medium used previously to excyst E. trivolvis. The length of excysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp.

Thin-layer chromatography (TLC) and histochemistry studies were done on the neutral lipid content of the digestive gland gonad (DGG) complex of Helisoma trivolvis infected with four species of larval trematodes. Two of the species, Ribeiroia sp. and Zygocotyle lunata, contained rediae, and the two others, Spirorchis sp. and an armatae xiphidiocercaria, contained sporocysts. The DGG infected by each species had its own distinct neutral lipid profile as determined by TLC. All profiles differed from that of the uninfected DGG. Densitometric TLC studies showed some quantitative differences in free sterols in infected versus uninfected DGGs. Visual observations of the chromatograms showed that all four species caused a marked elevation in the triacylglycerol fraction in the DGG as compared with the uninfected controls. Oil Red O (ORO) histochemistry studies showed that levels of neutral lipids were increased in the DGGs of infected versus uninfected samples. These histochemistry studies showed a variable distribution of neutral fat, ranging from its absence in the cercariae of Z. lunata and the armatae xiphidiocercaria to ORO-positive droplets in the excretory system of Ribeiroia sp. Rediae and sporocysts contained ORO-positive material in the body wall and in the space between cercariae.

High-performance thin-layer chromatography (HPTLC) was used to determine neutral lipids and phospholipids in the intestinal trematode Echinostoma caproni from experimentally infected ICR mice fed a high-fat diet (hen's egg yolk) as compared with worms from mice fed a standard laboratory diet. Worms were removed from the hosts at 2, 3, and 4 weeks postinfection (p.i.). Analysis by TLC-densitometry showed significantly greater amounts of triacylglycerols and free sterols at 2, 3, and 4 weeks p.i. in worms from mice on the high-fat diet as compared with worms from mice on the standard laboratory diet. Significantly greater amounts of phosphatidylcholine and phosphatidylethanolamine were found in worms from mice on the high-fat diet as compared with worms from those on the standard diet at 2 weeks p.i. but not at 3 and 4 weeks p.i. The results of this study suggest that the host diet influences the lipid content of E. caproni adults.

The RAG-2-deficient mouse, a strain of genetically altered mice lacking B- and T-lymphocytes, was used as a host for Echinostoma caproni. In all, 12 male RAG mice were exposed to 25 cysts each, and 12 served as uninfected controls. Mice were necropsied at 2 and 3 weeks postinfection (p.i.). The mean number+/-SE (9.7+/-2.4) of worms recovered from infected mice at 2 weeks p.i. was not significantly different from that recovered at 3 weeks p.i. (6.5+/-2.2). The intestinal circumference of infected RAG mice was significantly greater than that of the controls at 2 and 3 weeks p.i. A significant goblet cell hyperplasia occurred at 2 weeks p.i., but the response was not effective in eliminating worms from the RAG mice. The effect of a high cyst burden was examined by exposure of 8 RAG and 8 ICR mice to 100 cysts each. The body length and area and the oral sucker area of worms grown in RAG mice were significantly greater than those of worms grown in ICR mice. Worm recovery at up to 3 months p.i. was examined in RAG mice exposed to 25 cysts and necropsied every 2 weeks p.i. The mean worm recovery recorded at 2 weeks p.i. was significantly greater than that noted at 12 weeks p.i., at which time worm rejection from the RAG mouse host first occurred. The RAG mouse is a useful host for studies on E. caproni in a murine host that lacks B- and T-lymphocytes.