HELMINTHOLOGIA, 40, 2:65-75, 2003
Taxonomy
and biology of proteocephalidean cestodes:current state and perspectives
T.
SCHOLZ, A. de
CHAMBRIER*
Institute of Parasitology, Academy of Sciences of the
Czech Republic, Branišovská 31, 370 05 Èeské Budìjovice, Czech Republic,
E-mail: tscholz@paru.cas.cz; *Département des Invertébrés, Muséum
d’histoire naturelle,PO Box 6434, CH-1211 Geneva 6, Switzerland
Summary
The order
Proteocephalidea includes almost 400 species of tapeworm parasites (Cestoda) of
fish, amphibians, and rep-tiles, with one species recently found in a mammal (the
black-eared opossum in Mexico). Members of the order ty-pically possess four
muscular suckers on the scolex, which may also have an apical organ (glandular
or glandulo-mus-cular), a functional or vestigial apical sucker, or a
rostellum-like organ armed with hooklets, thus resembling that of
cyclophyllidean cestodes. Presumably, a narrow host specificity of species
parasitic in siluriform fish in the Neo-tropical region, would make the
proteocephalideans a suitable model for studies of parasite-host co-evolution.
However, the systematics of the order and the phylogenetic relationships of
individual genera and subfamilies are insufficiently known. The validity of the
Monticelliidae, one of the only two existing proteocephalidean families, has
even been questioned. Molecular data (sequences of 18S and 28S rRNA genes) also
support the invalidity of the Mon-ticelliidae. Sequencing has provided valuable
information but has still failed to resolve phylogenetic relationships of the
Proteocephalidea, especially the numerous genera and species parasitic in
Neotropical catfish. It is now obvious from molecular data that the most
abundant genera, such as Proteocephalus
and Ophiotaenia, are artificial
assembla-ges of unrelated taxa, but much more information is neces-sary for a
better understanding of interrelationships within individual proteocephalidean
subfamilies as well as rela-tionships of proteocephalideans to tetraphyllidean
and other cestodes. The information about the life-cycles of proteocephalideans
is also scarce, with the most data relat-ed to the development of the species of
Proteocephalus and Ophiotaenia
from freshwater fish and reptiles in the Holarctic region. In the Neotropics,
fish and possibly other lower vertebrates probably serve as the second
intermediate or paratenic hosts but no detailed data based on experimental
infections or field observations are yet available.
HELMINTHOLOGIA, 40, 2:79-85, 2003
The
nitrergic nervous system in flatworms
M.
K. S. GUSTAFSSON, T. V. GAIVORONSKAJA1, N. B. TERENINA1,
O.O. TOLSTENKOV1
Department of Biology, Åbo Akademi University,
Artillerigatan 6, FIN-20520 Åbo, Finland; 1Institute of
Parasitology, Russian Academy of Sciences, Lenin Avenue 33, 117071 Moscow,
Russia, E-mail: magustaf@abo.fi
Summary
In order
to bring the knowledge about the nitrergic nervous system in flatworms one step
further, the pattern of cGMP immunostaining (IS), after stimulation with a
nitric oxide donor, and in the presence of an inhibitor of phosphodies-terase,
was studied in activated plerocercoid larvae of Diphyllobothrium dendriticum and in adult Fasciola hepa-tica. In D.
dendriticum, cGMP-IS was detected in multi-polar nerve cells and in nerve
fibres close to muscle fibres and in many terminals beneath the tegument. In F.
hepa-tica, cGMP-IS was detected in nerve fibres around the oral sucker, in
the main nerve cords and around the intestinal ducts. The pattern of cGMP-IS was
compared to that of the NADPH-diaphorase staining, the 5-HT-IS, and the
GYIR-Famide-IS. The cGMP-IS, the NADPH-d staining and the 5-HT-IS occur in
separate sets of nerves. However, in F.
hepatica, coexistence was observed between the cGMP-IS and the GYIRFamide-IS.
HELMINTHOLOGIA, 40, 2:87-91, 2003
Phylogeny
of anisakid nematodes: a review
S.
D'AMELIO
Department of Sciences of Public Health, Parasitology
Section, University of Rome "La Sapienza", P. le Aldo Moro 5,00185
Rome, Italy, E-mail: sdamelio@uniroma1.it
Summary
The
systematics and classification of anisakid nematodes and the relationships among
genera and species have been the subject of many speculations. DNA nucleotide
sequen-ces have been used for the inference of the phylogenetic relationships
among anisakid taxa. These studies have pro-vided a new insight into the
evolution of this parasitic group. Here, three examples of such studies are
given: 1) at population level (the Phocascaris phocae/cystophorae pro-blem); 2) at species level (taxonomic
rank and evolution of Contracaecum
osculatum baicalensis); 3) at genus level (the phylogenetic relationships
among species of Contra-caecum and Phocascaris).
HELMINTHOLOGIA, 40, 2:93-95, 2003
Is
postcyclic transmission under estimated as an epizootiological factor for
acanthocephalans?
B.
Nickol
School of Biological Sciences, University of
Nebraska-Lincoln, Lincoln, Nebraska 68588, USA, E-mail: bnickol@unlnotes01.unl.edu
Summary
Postcyclic
transmission is taken to mean the transfer of adult worms from one definitive
host to another. Such transmission of enteric worms is known to be possible for
acanthocephalans of ten species. There have been many claims for the
significance of postcyclic transmission, but to be of life history importance,
the transferred worms must survive long enough to mature or sexually mature
worms must transfer. Unlike paratenic transmission, which results from transfer
of cystacanths located extraintestinally in the prey host, the intestinal
location of worms to be transferred postcyclically gives no apparent clue to its
occurrence in nature. Studies that demonstrate laboratory transfer and survival
to maturity and successful transfer of gravid acanthocephalans are beginning to
accumulate, however. The apparent ease with which enteric worms are transferred
in the laboratory suggests that postcyclic transmission is important in nature.
Such transmission of enteric worms through predation or cannibalism could
distribute acanthocephalans to groups of animals that otherwise would be
inaccessible.
HELMINTHOLOGIA, 40, 2:97-102, 2003
The
future of anthelmintics in sustainable parasite control programs for livestock
P.
J. Waller
c/-
SWEPAR, National Veterinary Institute, Uppsala SE-751 89, Sweden, E-mail: Peter.Waller@sva.se
Summary
The
development of resistance to all the currently available anthelmintic classes by
the important nematode parasites of grazing livestock presents a major challenge
to the continuation of efficient livestock productivity. The situation is most
serious in the small ruminant (sheep and goat) industries, particularly in the
hot and humid regions of the world, but is escalating at such a rate that all
countries with significant sheep and goat numbers must consider that tackling
this problem is an urgent priority. Although anthelmintic resistance in cattle
parasites appears to be of minor concern, there is clear evidence that this is
now increasing. This review presents an overview of the principles developed by
experts, on ways to manage the conflicting objectives of efficient worm control
and at the sa-me time delay the selection for anthelmintic resistance.
HELMINTHOLOGIA, 40, 2:103-108, 2003
Trichinella
prevalence in the domestic and sylvatic cycle and its importance as foodborne
pathogen
K.
Nöckler
Federal Institute for Risk Assessment, Diedersdorfer Weg
1, 12277 Berlin, Germany, E-mail: k.noeckler@bfr.bund.de
Summary
Human
trichinellosis poses a threat for human health world wide. The paper refers to
the current situation in Europe where four autochthonous Trichinella species namely T.
spiralis, T. britovi, T.
nativa and T. pseudospiralis were discovered up to now. Every year human
trichinellosis cases occur in many European countries due to the consumption of
raw or improperly treated pork, wild boar or horse meat which could pass the
food chain because of a failure in meat inspection. In this context
epidemiological aspects of Trichinella
in the domestic and sylvatic cycle are explained and natural and artificial
factors for the maintenance as well as risk factors to acquire trichinellosis
are presented. Conclusions refer to the current needs for improv-ing consumer
protection according to the “White Paper on Food Safety” of the European
Commission which gives emphasis on a modern risk analysis consisting of risk
assessment, risk communication and risk management measures.
HELMINTHOLOGIA, 40, 2:109-115, 2003
Aspects
of human helminthiasis in sub-Saharan Africa
D.
W. T. CROMPTON
WHO Collaborating Centre for Soil-Transmitted
Helminthiases, Institute of Biomedical and Life Sciences, University of Glasgow,
Glasgow, G12 8QQ, Scotland, E-mail: dwtc@tyndrum.demon.co.uk
Summary
The
people of sub-Saharan Africa are the world’s most heavily afflicted population
in terms of the burden of disease involving helminth infections. Despite
numerous control programmes, helminth infections persist and, in some case, may
be increasing. The current situation is reviewed and new initiatives based on
deworming measures are discussed. Attention is drawn both to progress and to the
challenges that must be overcome if morbidity due to helminthiasis is to be
controlled and reduced in sub-Saharan Africa.
HELMINTHOLOGIA, 40, 2:117-121, 2003
Development
of molecular tools to explore genetic diversity in Echinococcus
multilocularis
J.
M. Bart, I. Breyer1, B. Gottstein1, T. Romig2,
R. Piarroux
Santé Environnement Rural, Université de Franche-Comté,
Besancon, France; 1Institute
of Parasitology, University of Berne, Berne, Switzerland, E-mail. bruno.gottstein@ipa.unibe.ch; 2Section
Infectiology, University of Ulm, Ulm, Germany, E-mail: romig@uni-hohenheim.de
Summary
In order
to identify risk factors for the occurrence of alveolar echinococcosis on both
regional and local levels in Europe, studies have to be performed to describe
factors influencing the infection pressure to the human population, with special
emphasis on the changing epidemiological situation in transmitting animals.
However, risk of infection may not only be determined by the abundance of, and
contact with, parasitic eggs, but also by genetically fixed differences in
pathogenicity between parasite strains. Therefore, typing of isolates collected
from different areas in foxes, as well as in humans presenting with various
lesions, should lead to a better understanding of the putative role of the
genetic diversity of Echinococcus
multilocularis. In addition, if such differences would correlate with the
region of origin, a valuable tool would be available to trace sources of
infection. Unfortunately, to date, with the genetic markers currently used, very
limited variation have been detected within the world-wide population of E.
mul-tilocularis. Consequently, the differences, in terms of pre-valence,
pathogenicity or susceptibility to chemotherapy, observed in humans in the three
main foci (Europe, Asia and North America) could not be correlated with the
putative genetic typing of the parasite. Development of highly sensitive
molecular tools which can detect genetic variations in small populations, would
be useful for tracking the spatial and temporal dynamics of the infection of
humans. With regard to results obtained with other pathogens, such as Leishmania, Candida, Schistosoma,
microsatellite analysis and single nucleotide polymorphisms (SNPs) asses-sed by
single-stranded conformational polymorphism or Constant Denaturant Capillary
Electrophoresis (CDCE) may prove their relevance and their power of
discrimi-nation and finally allow for a distinction between closely-related genotypes.