Experimental studies on vitamin A metabolism in infestation with clonorchis sinensis
Department of Parasitology, College of Medicine, Yonsei University, Seoul, Korea
(Director: Professor Chin-Thack Soh)
Since the Chinese liver fluke, clonorchis sinensis, was first described by
Mcconnel(1875). it has been established that the adult fluke lives in the biliary
passages of many mammalian hosts, including human body.
Concerning pathogenicity, a multitude of symptoms has been described in patients
with clonorchiasis. Based on reports by Inouye (1903), Mayer (1916), Oldt (1927),
Becrovitz (1931), Otto (1937), of decreasing frequency: fatigue, weakness, weight
loss, abdominal pains, indigestion, ascites, increased or decreased appetitie,
nausea and vomiting, diarrhea, constipation, jaundice, paresthesia, edema, night
blindness, dizziness, pyrosis, gaseousness, importence, headaches, paplitations,
and hot-cold sensations.
It is commonly asumed that severe illnesses are due to haavier worm loads, and
that in light infestations the symptoms are usually negligible, though it might be
deeply related with the duration of the infestation. However, the nutritional
disturbances, including weak vision or night blindness aree not uncommon among the
people with clonorchis infestation in endemic areas, and it is recognized that the
disease is due to the functional and pathological changes of the liver itself.
though such signs could be closely related with vitamin A deficiency,there have
been no reliable experimental reports covering vitamin A metabolism in liver fluke
infestation. The purpose of this study is to add new information to this field.
Materials and Methods
Male rabbits 1.5-2.0 kg in weight were used as the experimental animal. From
February thru April they were fed mainly with hay, and from May thru September with
fresh grass leaves and remnants of bean curd. Both control and infested groups were
observed for a seven month period.
The metacercariae of clonorchis sinensis from fresh water fish were cfollected by
the digestion medthod:
Control (B group)………………………………Not infested, healthy.
Mild infestation (C group)………………… 100 metacercariae were given.
Moderate infestation (D group)…………… 300 metacercariae were given.
Heavy infestation (E group)…………………600 metacercariae were given.
Extra……………………2,000 metacercariae were fed for short term observation.
The plasma level of vitamin A was determined by the Dann & Evelyn's Cyorgy
modified method with the blood which was drawn at 6:00 a.m. each day. At the same
time, examinations of body weight, liver function tests(thymol turbidity test,
prothrombin test, total protein calculation) and hemoglobin and red cell
determinations were made. Along with this experiment, patho-histological
examinations of the liver and of the eye of rabbits which were sacrificed or which
died of malnutrition were carried on.
Three groups of 30 rabbits were infested with the metacercariae of clonorchis:
100,300, 600 for each. Biologicaland histochemical studies have been carried on
over a seven month period.
1. Plasmal level of vitamin A and β-carotene: Although the B group (control) had
been maintained above 50 γ% for seven months, the infested groups showed a
tendency to decrease from the time of two to four weeks after the infestation and
continued below the normal line until seven months, except during August (the 6th
month), when diet was ample in vitamin A. The order of decreasing frequency were
the control, light, moderate, and heavy infestation groups. β-carotene was 0-9% of
normal range, both in the control and in the infested animals.
2. Absorption of vitamin A from intestine: 2,0000 I.U. of vitamin A was given
orally to each group six months after infestation, and observations were made for
eight hours. The rate of absorption was accelerated according to the grade of worm
burden, especially in heavy infestation. The peak of the curve appeared 4-5 hours
3. Body weight: Generally, the weight showed an increasing curve until seven
months after the infestation, though the degree was different according tot he worm
burden; in order were the B, C, D, and E groups.
4. Liver function tests: There were practically no significant differences
between infested and unifested groups. Only the globulin showed a slight increase
several weeks after the infestation; there was no reversal of A/G ratio.
5. Histopathology of liver: One week after the infestation, peribiliary
inflammation appeared and developed into thickening of the bile duct wall,
enlargement of bile ducts, proliferation of the biliary epithelium and somethimes
desquamation and new formation of bile capillaries with crypt formation in the bile
ducts. Infestations of several months duration, the periportal tissue developed
fibrosis in varying degrees in many portions of the parenchyma. In some areas the
hepatic cells were destroyed, and cirrhosis and fatty metamorphosis were sometimes
observed. The degree of change almost paralleled the degree and duration of
6. Histopathology of eye: No histologic changes were detectable for about two
months, except in the group with the extra heavy infestaion by 2,000 metacercariae.
In general, pathological manifestations were observed five months after infestaion.
Some of the rabbits showed a slight focal desquamation of the limbal bulbar
conjunctive and epidermidalization, slight rete peg formation and keratinization of
the corneal epithelium. In most cases, there was moderate large and small round
cell infiltration beneath the epithelium and the rods and cones layer showed
vacuolation and disinteegration with rarefication of the outer nuclear layer.
The reason for the low level of vitamin A plasma value in clonorchiasis
infestations is still dubious for final conclusion, so long as the ability of
vitamin A absorption and liver function have been within normal range. But the
following factors would give an appropriate answer for the puzzle.
a. The chronic inflammatory condition of the liver will consume more vitamin A.
b. Desquamation of the bile duct wall and damage to liver cells will cause
outflow of vitamin A from the Cytoplasm.
c. Indirectly, vitamin A shall serve as one of the nutritional sources for the
1. The plasma level of vitamin A in infested groups continued at a lower level
than in the uninfested group.
2. The ability to absorb vitamin A was accelerated according tot he loads of
3. The body weight in the infested group stayed at a lower level for seven months
4. No significant disturbances of liver function were observed.
5. The liver showed inflammatory changes within one week after infestation, and
this converted gradually to the cirrhotic stage.
6. During the several months after the infestation, there appeared epithelial
changes in the cornea and degenerative signs in the retinal rods and cones layer.