Acta Parasitologica, Vol.45, No. 2, 2000, 123-124 Machnicka Barbara -
Fasciolosis (Ed. J. P. Dalton), CABI Publishing - CAB International 1999, Wallingford, Oxon
OX10 8DE, U.K.
W. Stefanski Institute of Parasitology Polish Academy of Sciences, Twarda 51/55, 00-818
The book "Fasciolosis" contains 15 chapters covering the large spectrum
of problems connected
with the life-cycles, development, intermediate and final hosts as well
as pathology and control of
Fasciola hepatica, a common parasite of livestock and humans in
temperate climatic zones.
Fasciolosis is still the disease of the great economical importance.
According to some estimates
every year about 600 mln of domestic animals became infected worldwide;
only in the USA alone
the economical losses are determined at over $ 2 bln. Moreover, during
the last decade the human
fasciolosis was stated as an emerging food-born zoonosis in some parts of
the world. Reports
estimate that as many as 2.4 to 17 mln people are infected. It is worth
mentioning that the number of reported clinical cases and of infected
people identified during epidemiological surveys have
been increasing since 1980.
Economic effects of fasciolosis in livestock can range from sudden death
as a result of massive
infection to subclinical infections which produce marked economic
effects. Ovine fasciolosis can
result in significant blood losses with all associated consequences. In
sheep and cattle, the
reduction of weight gain and other adverse effects depend on the parasite
burden. Infection has
also deleterious effect on milk quantity and quality; it causes lower
fertility rates in cattle and
The first two chapters deal with the life cycle of the parasite and
development in the intermediate
host as well as the control of snail transmission by drainage programme
or fencing of wet areas,
chemical and biological control.
The description of the parasite anatomy, its tegument, parenchyma,
musculature, nervous and
reproductive systems are given at a light and electron microscopy levels.
The development and
function of each organ system is described in detail. This chapter is
very important for
understanding the cellular and tissue organisation, physiology and
self-defence of the parasite.
This chapter shows the progress accomplished recently in our
understanding of the fine structure
of all the major organ systems of the liver fluke.
The chapter on the epidemiology and control describes the main
conditions, which determine the
occurrence of fasciolosis such as climatic and environmental conditions.
All these factors have
their influence on the development of F. hepatica eggs and
intermediate host, parasite development
in the snail, and metacercarial survival.
Particular attention is paid to the problems connected with resistance to
F. hepatica and F.
gigantica. Infection with F. hepatica may result in a different
degree of acquired resistance which
varies depending on the host species. Horses and adult pigs show a marked
degree of innate
resistance. Level of acquired resistance in sheep shows individual
variations; some "primitive"
races demonstrate well expressed innate resistance.
The protective immunity is mainly expressed at the gut mucosa level, but
it must be taken into
account that acquired resistance in cattle may be a consequence of
fibrosis of liver parenchyma and
fibrosis and calcification of the bile ducts.
A wealth of fascinating new knowledge is gathered on the ways of parasite
evading the persistent
attacks from the host immune system. It is achieved in many cases by the
antibody-cleaving enzymes and anti-inflammatory agents. Several
mechanisms allow to repulse
offensives of immune effector cells and their toxic products. Liver
immunosuppressive factors which probably facilitate the parasite passage
through the liver
The chapter on the control of fasciolosis is important from practical
viewpoint. The control options
depend on the local husbandry and climatic conditions together with
socio-economic factors. The
treatment as the principal method employed to control fasciolosis, should
reduce the intensity of
infection in a flock or herd and is beneficial for lowering the parasite
burden on the pasture.
Because of the presence of wild reservoir hosts, usually it is not
possible, however, to achieve a
total eradication of fasciolosis in a certain area.
The expected prevalence of fasciolosis may be forecasted for bigger
territories and developed
further to computerised system in order to design the better ways of
fasciolosis control and
optimise strategic preventive measures for the control of disease over
the following year, among
them the frequency of drug application.
The chapter on the fluke metabolism represents the background knowledge
for the new
chemotherapeutics development. Metabolic pathways are increasingly
becoming targets for
anthelmintic drugs and, therefore, attention has to be especially focused
on differences in
metabolism between the host and the parasite.
Research developments on the neuromusculature of trematodes offer the
further prospect of
identifying pharmacologically important receptors and ion channels and of
potential targets for chemotherapeutic exploitation. Recent information
neuromuscular receptors in helminth parasites have a unique physiology
which often considerably
differs from those in vertebrates.
The vaccine development will provide producers with an alternative,
environmentally friendly, cost effective and sustainable strategy for the
control of fasciolosis. F. hepatica infection can
induce host immune responses which are effective in killing of the
parasite and conferring the
protection against fasciolosis. In contrast to cattle, sheep do not
acquire resistance to a secondary
F. hepatica infection following primary exposure. The ability of
the merino sheep to acquire
resistance to F. gigantica indirectly suggests that F.
F. gigantica differ in some
fundamental biochemical trail.
The chapter covering current development of research on vaccines
knowledge beginning from the use of irradiation-attenuated metacercariae,
some substances being
excretions/secretions of the fluke such as: fatty acid binding proteins,
cathepsin L, hemoglobin, paramyosin, Kunitz-type serine proteinase, and
finally naked DNA
encoding protective antigens. Each of the above substances was tested
experimentally as a vaccine
and showed diversified activity from the damage of tegument of developing
flukes to the reduction
of adult worms' fecundity. These experiments demonstrated significant
differences among animal
species in the induction of protection against liver flukes.
The genetic organisation and variability of F. hepatica are the
main problems of molecular studies
presented in the book. Another direction of research deals with the
ability of appropriate gene
expression systems of the liver fluke to produce substances which could
serve as vaccines. The
main problem to be solved is the mechanism by which flukes can
co-ordinate the complex changes
in gene expression that need to occur during their development.
The separate chapter is devoted to the epidemiology, immunology and
molecular biology of
Fasciola gigantica, a causative agent of similar illnesses in zones
with a tropical climate. Although
not fully comprehensive, it is very useful for comparative purposes.
"Fasciolosis" edited by J. P. Dalton, is written by a group of 34
authors, deserving full credits for
producing this work of excellent quality. The book is well presented and
readable with a good
balance between review chapters and general background reference-type
material. Inspite being
rather research-oriented, it remains, at the same time, an excellent
reference book which can be
recommended for undergraduate and postgraduate students in medical,
veterinary and life sciences
as well as for those conducting investigations in the field of
fasciolosis. KEY WORDS: Fasciolosis
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