HELMINTHOLOGIA, 38, 4: 243-250, 2001
Workshop on bird schistosomes and cercarial dermatitis held at Dolní Věstonice
(Czech Republic) September 10-14, 2001
The Workshop was organized by Department of Parasito- including both specific as well as nonspecific definitive
logy, Faculty of Science, Charles University, Prague; De- hosts is required.
partment of Tropical Medicine, Faculty Hospital Bulovka, The investigation on bird schistosomes is supported by the
Charles University, Prague; Department of Microbiology, Grant Agencies of the Czech Ministry of Health (o. NJ-
Faculty of Medicine in Pilsen, Charles University; Czech 6718-3) and Chares University (38/2000/1LF).
Society for Parasitology. The organizers express thanks for
financial supports provided by Olympus CS Ltd., Dione
Ltd., Bio-Rad Ltd., Dynex Technologies Ltd. and Dispolab Life cycle of trematodes D. loossi
Ltd.
D. A. AZIMOV, E. A. SHAKARBAEV
Bird schistosomes overview
Institute of Zoology, Uzbek Academy of Science, A. Niya-
L. KOLÁŘOVÁ zov Street 1, Tashkent, 700095, Uzbekistan,
E-mail: uzzool@uzsci.net
Department of Tropical Medicine, 3rdClinic of Infectious
and Tropical Diseases, Charles University, Faculty Hospi- Trematodes Dendritobilharzia loossi are parasites locali-
tal Bulovka, Studničkova 7, 128 00 Prague 2, Czech Re- zed in blood vessels of pelicans and ducks and are distri-
public; E-mail: lkolar@lf1.cuni.cz buted in various reservoirs of the basin of the rivers Syr
Darya and Amu Darya.
As parasites living within either circulatory or nasal tissue Intermediate hosts of D. loossi Anisus spirorbis is registe-
of their vertebrate hosts, schistosomes evoke severe health red. Infection of molluscs by the cercariae of Dendritobil-
problems. The worms have developed mechanisms not on- harzia in natural conditions reached 1.5 %. At the tempera-
ly to survive in the hosts, but have evolved to become sig- ture of 26-32°C cercariae started emerging from the mol-
nificant pathogens of birds and mammals throughout the luscs in 26 days.
world. The initial phase of schistosome infection, cercarial During the examination of the infected birds, schistoso-
dermatitis, is caused by schistosome larval stages (cerca- mula were found in blood vessels of lungs in 72 hours and
riae). From the human point of view, the skin disease re- in 5-10 days in liver and kidneys. Differentiation of male
sults from the penetration of the skin by cercariae belong- and female trematodes was recorded from 12 th day post in-
ing to different animal and human genera, the life cycle of fection. In 15 days the trematodes reached sexual maturity.
which takes place in freshwater or marine snails. The most Thus, the life cycle of this trematode for the first time was
important causative agents of the emerging disease are cer- revealed, which takes place by the scheme: definitive host
cariae of bird schistosomes, namely of genus Trichobilhar- (maritae) - an egg - miracidum - the intermediate host (pa-
zia. Whereas in birds, the infection leads to fluke matura- rental and daughter sporocyst) - cercarium - definitive host.
tion, the fate of parasites in a nonspecific human host is
still unclear. However, it seems that even the destruction of
parasites occurs at various intervals post cercarial infec- On Schistosoma research in Iceland
tion, the worms may also partially develop and migrate
within the nonspecific host and thus cause various clinical K. SKIRNISSON, L. KOLÁŘOVÁ1
symptoms and signs. The character of possible human
health complications seems to correlate with the parasite Institute for Experimental Pathology, Keldur, University of
development in specific hosts; in the case of visceral schi- Iceland, Reykjavík, Iceland; 1Department of Tropical Me-
stosomes migrating and living mainly in the circulatory dicine, 3rd Clinic of Infectious and Tropical Diseases, Pra-
systém, and in the case of nasal schistosomes developing gue, Czech Republic; E-mail: karlsk@hi.is
in the central nervous system during the prepatent period,
pulmonary and neurologic symptoms, respectively, might During late summer in 1995 to 1997, repeated outbreaks of
be considered. Therefore, the investigation on life cycles maculopapular skin eruptions were noted on legs of chil-
243
dren after wading in the pond of the Family Park in Reyk- the summer of 1999. In 1998 the figures were much lower,
javík, Iceland. Investigation, starting in autumn 1997, re- just 25 %. Around 200 lakes and costal areas have been re-
vealed that the causative agent was a previously undescri- ported as sites of SI.
bed schistosome cercaria of the genus Trichobilharzia (Ko- It is likely that the number of unrecorded cases is large, be-
lářová et al., 1999). Since 1997, the infection prevalence of cause single cases do not always come to the authorities’
Lymnaea peregra, the only snail occurring in the pond, has knowledge.
been 7.9, 0.4, 0, 1.5 and 2.3 %, respectively. Also the cer- It is obvious that the weather conditions affect the occur-
caria has been found in L. peregra from two other Icelan- rence of SI. The main reason is the more frequent water
dic ponds. However, the final host of the species is still un- contact at higher water temperatures and the conditions fa-
known. In 1999, another Trichobilharzia sp. cercariae was vouring the population of intermediate hosts and therefore
found in L. peregra in Iceland. Two adult Trichobilharzia increased shedding of cercaria.
species have already been found in two Icelandic whooper Cercarial dermatitis seems to be uniformly distributed in
swans Cygnus cygnus. Furthermore, a representative of Or- Sweden, but there is a need to demonstrate the presence of
nithobilharzia has been found in Larus fuscus (Eydal et al., cercaria, as there is uncertainty in the interpretation of skin
1998). symptoms.
Bird schistosomes in Lymnaea stagnalis Epidemiological studies related to
(L.) and Planorbarius corneus (L.) from cercarial dermatitis in lakes of the
selected lakes in Poland Savoy District (France)
E. ŻBIKOWSKA
J.-P. DUBOIS, A. BUET, I. CUSIN, A. DELORAINE1,
Department of Invertebrate Zoology, Institute of General S. GERDIL, L. HEDREVILLE1, G. MAURIN
and Molecular Biology, Nicholas Copernicus University,
Toruń, Poland; E-mail: ezbikow@biol.uni.torun.pl INRA, BP 511 F 74203 Thonon-les-Bains, France;
1
CAREPS, BP 217, F 38043 Grenoble Cedex 9, France; E-
Snails were investigated in 10 Poland lakes during 1998- mail: Dubois@thonon.inra.fr
2001 (from May to September). Bird schistosomes were
found in snails from 4 lakes only; Trichobilharzia ocellata
Epidemiological studies have been achieved, based on in-
in L. stagnalis and Bilharziella polonica in P. corneus.
quiries.
Thermal preferences, duration of life of parasitised snails
Questionnaires were given to swimmers, beach lifeguards,
and the number of released cercariae by them in laboratory
pharmacists and doctors. Environmental data, such as cli-
conditions were examined.
matic conditions and distribution of the gastropods were
Parasitised snails selected lower temperatures than non-pa-
also recorded. Swimmers who had agreed to give contact
rasitised ones. Long existence of snails and the total num-
information were called back within the week to evaluate
ber of released cercariae were inversely proportional to
the percentage of infected people.
temperature.
These studies revealed that:
- even under bad climatic situation, more than 15 % of
swimmers had lesions
Swimmers’ itch in Sweden - dermatitis cases increased with the time of contact in
the water and occurred more often in the morning
C. THORS, E. LINDER - the frequency of dermatitis fluctuated reaching highest
levels in August
Swedish Institute for Infectious Disease Control (SMI) and - stable warm temperature favoured cercarial emission
Microbiology and Tumorbiology Center (MTC) Karolin- from snails
ska Institutet, S171 82 Solna, Sweden; - everybody could be infected, but existing allergy
E-mail: cecilia.thors@smi.ki.se caused strong reactions.
These studies gave generally limited information. Reasons
In August and September of 1999 we made an inquiry to were the lack of pertinent data and the low number of res-
the Environment and Health Administrations in Sweden pondents limited a statistical approach. Of those that retur-
about the occurrence of swimmers’ itch (SI). 254 out of ned questionnaire, pharmacists proved to yield the best re-
287 municipalities answered. Half of the municipalities levant information. Repeated inquiries could provide infor-
(125/248), having lakes, had problems due to SI, the majo- mation regarding annual changes in severity of cercarial
rity for several years. 66 out of 125 (53 %) reported SI in dermatitis.
244
Contribution to the study of the (Pampiglione et al., 1992). Furcocercariae, morphological-
ly related to Cercaria nassa, were found in Nassa reticula-
cercarial dermatitis in the Rhône-Alpes tus. These furcocercariae may be the cause of human der-
area (France) matitis in this locality.
P. SILAN, J. P. DUBOIS1, C. HALPENNY
Cercarial dermatitis in Austria: the
CNRS (UMR 5000), Station Méditerranéenne de l’Envi- recent situation and future aspects
ronnement Littoral, Université Montpellier II, 1 Quai de la
Daurade, 34200 Sète, France; 1INRA, Station d’Hydrobio- A. OBWALLER, H SATTMANN1, R. KONECNY2,
logie, B.P. 511, F 74203 Thonon-les-Bains Cedex; C. HÖRWEG3, H. AUER, H. ASPÖCK
E-mail: silan@univ-montp2.fr
Department of Medical Parasitology, Clinical Institute of
For several years, an increase in the frequency of cercarial Hygiene, University of Vienna; 1Natural History Museum,
dermatitis caused by bird schistosomes has been observed Vienna, Austria; 2Institute of Ecology and Conservation
in certain French alpine lakes. This parasitological problem Biology, University of Vienna. Austria; 3Department of
identified in the lakes of Annecy and Le Bourget (Savoie Systematic Zoology, Institute of Zoology, University of
district). Vienna, Austria; E-mail: andreas.obwaller@univie.ac.at
The hosts implicated in the biological cycle of these trema-
todes have probably been present for a long time, but the Since the first detection of dermatitis causing cercariae in
abundance of the different species has obviously changed the Neusiedlersee in 1967, outbreaks of swimmer’s itch in
over several decades. The principal reasons favourable to various provinces have been observed during recent years.
the emergence of this problem are the following : i) a local Due to our rather fragmentary knowledge on the spectrum
eutrophication of this environment associated with an in- and biology of the parasites on the one hand and the in-
crease of urbanization, resulting in modifications of the creasing economical and medical relevance of cercarial
malacological fauna; ii) a progressive improvement of pro- dermatitis on the other, a concerted study including ecolo-
tective measures concerning the avifauna, favouring the gical (distribution of cercariae and snails), taxonomic (spe-
occupancy of anatidae during winter as well as summer; cies differentiation of cercariae and snails) and epidemio-
iii) a notable growth in summer tourist presence. logical (incidence of cercarial dermatitis) aspects, has been
However, the available data still does not allow to quantify started in 2001.
the problem in an epidemiological or a preventive perspec- Preliminary results show that not only species of Radix,
tive (nature and the importance of demographical flow). A Lymnaea and Stagnicola, but also Gyraulus parvus and
preliminary study was recently started in this direction and Aplexa hypnorum may act as intermediate hosts.
some results are presented. Furthermore, a specific PCR for the amplification of the
ITS regions and 5.8S rRNA gene from cercariae and spo-
rocysts in the digestive glands of snails has been establi-
Cercarial dermatitis in Italy shed. High sequence similarities of isolates within each
host species and significant dissimilarities between isolates
G. CANESTRI-TROTTI, M. L. FIORAVANTI1, of different host species could be determined.
S. PAMPIGLIONE1
Dip. Biologia Animale e dell’Uomo, Università di Torino, Identification of cercaria causing
Via Accademia Albertina 17, 10123 Torino, Italy; 1Dip.
Sanità Pubblica Veterinaria e Patologia Animale, Univer-
swimmers’ itch: preliminary observa-
sità di Bologna, Italy; E-mail: canestri@dba.unito.it tions on a skin lipid attachment assay
In Italy, rice-paddy dermatitis is known since the XVIIIth E. LINDER, C. THORS, A. JACKS
century (Asti, 1787). Firstly, Gianotti et al. (1956) recogni-
zed schistosome dermatitis in rice-paddy workers in Nort- Swedish Institute for Infectious Disease Control (SMI),
hern Italy. In Sardinia, Schistosoma bovis, has been report- Sweden; E-mail: ewert.linder@smi.ki.se
ed as causing human cercarial dermatitis (Carta, 1954).
More recently, cercarial dermatitis was studied in lake of The differentiation between cercarial species causing der-
Garda by Castellani et al. (1994) and Salmaso & Cordella matitis and those which are harmless for man is primarily
(1994). In the Venice lagoon, a survey was carried out on based on microscopical examination of distinctive morpho-
gastropods and bivalves with the purpose of ascertaining a logical features, notably presence of eye spots. However,
possible parasitological role in the aetiology of cases of this requires considerable skill and universal criteria are
dermatitis observed in people collecting marine molluscs generally lacking.
245
Our purpose was therefore to design an assay making this and internal structures of cercaria/schistosomula within 5
distinction in a practically useful way. The basis for such minutes of contact. Because it is minimally absorbed
an assay is the differential behaviour of pathogenic and through the skin Lipodeet can be loaded with 10-50 % of
non-pathogenic cercaria upon contact with components of DEET. Retention of the active ingredient in the superficial
human skin lipids in vitro. layers of the skin assures that any cercaria coming in
Cercaria causing swimmers’ itch are attracted by and at- contact or invading the skin will be killed. Given its low
tach to surfaces containing skin lipid. Typical swimming toxicity, poor absorption and remarkable activity against
movements in water change to crawling pattern of loco- the three major schistosomes of man, it is likely that Lipo-
motion at the surface. The cercarial body moves with the deet will have a broad spectrum of activity against other
aid of the two suckers along the surface. This involves de- schistosomes as well the bird schistosomes that cause cer-
position of water insoluble glycoconjugates which can be carial dermatitis. These studies thus suggest that Lipodeet
visualised e.g. with fluorochrome-labeled lectins. The may be a beneficial prophylactic agent against various
deposits, “kissing marks”, can be seen as regularly spaced forms of schistosomiasis in endemic areas.
paired dots marking the cercarial/schistosomular path
along the solid surface.
Various antibody markers for visualisation of “kissing Protection against cercarial
marks” were evaluated in addition to conjugated lectins.
An interesting possible marker for “kissing marks” is anti- penetration: use of dermatological
bodies recognising a carbohydrate epitope shared with key- preparations with 35/35
hole limpet haemocyanin (KLH). Possible direct visualisa-
tion methods are discussed. N. LEGER
We conclude that detecting water-insoluble glycoconjuga-
tes released upon contact with skin lipid may constitute the U.F.R. de Pharmacie F 51096 Reims Cedex; E-mail:
basis for an assay for the identification of pathogenic cer- nicole.leger@univ-reims.fr
caria.
Two formulations ( a gel and a dry oil ) have been tested
on:
Topical application of a long-acting, - the mice Schistosoma mansoni model
- volunteers with local applications of ocellated cerca-
safe, formulation of N, N-diethyl-m- riae from Lymnea peregra
toluamide (DEET) to prevent cercarial - beach workers on an infested area and swimmers du-
penetration through the skin ring a competition across Annecy Lake (France) on
the 15/8/01.
B. SALAFSKY, YI-XUN HE, JING LI, T. SHIBUYA, Mice have been protected against infection. Human experi-
R. KALYANASUNDARAM mentation, which is still in progress, will be presented and
discussed.
Department of Biomedical Sciences, University of Illinois,
College of Medicine, Rockford, IL, USA;
E-mail: BuzS@uic.edu In vitro emptying of penetration glands
in T. regenti and T. szidati cercariae.
Effect of a new long-acting formulation of DEET in a lipo-
some (Lipodeet) was evaluated for its ability to prevent Preliminary analysis of the products
cercarial penetration into the skin. A single application to
the skin of mice was 100 % effective in preventing pene- L. ZÍDKOVÁ, L. MIKEŠ
tration of cercariae of various species of schistosome
(Schistosoma mansoni, S. japonicum and S. hematobium). Deptartment of Parasitology, Charles University, Viničná
This protective effect of Lipodeet was not significantly im- 7, 12844 Prague 2, Czech Republic;
paired despite allowing mice to swim in water for 60 mi- E-mail: murfar@yahoo.com
nutes at room temperature or at 37 0C before infection. Ab-
sorption studies showed that Lipodeet is bound in the su- Cercariae of bird schistosomes Trichobilharzia regenti and
perficial layers of the skin resulting in minimal absorption T. szidati posses postacetabular and circumacetabular pe-
of DEET and thus avoiding any toxicity associated with netration glands. We stimulated both types of the glands to
systemic absorption of DEET. Because of its lipid com- empty their contents by incubating the cercariae with diffe-
position, Lipodeet is softer, smoother and more cosmeti- rent concentrations of praziquantel. The most effective
cally pleasing on the skin. In vitro studies showed that ex- concentration was 0.1 µg/ml. SDS-PAGE pattern of ES-
posure to 7.5 % DEET is highly toxic to cercariae of S. products differed among particular time periods of incuba-
mansoni resulting in ultra structural damage to tegument tion in which the products were collected, suggesting a dy-
246
namic nature of the emptying process. Using SDS-PAGE E-mail: KHradkova@seznam.cz
and zymographic analysis in polyacrylamide gels copoly-
merized with gelatine, we obtained protease activities Trichobilharzia regenti is a specific parasite of the central
around 30 kDa for T. regenti and 55kDa for T. szidati. nervous system (CNS). Cercariae penetrate the skin of
These activities were not inhibited by specific serine pro- birds and mammals, enter peripheral nerves of legs and use
tease inhibitors. Recent analyses indicate also a hyaluro- them as a route to CNS. In ducks (specific host) schisto-
nolytic activity in ES-products. In addition, ES-products somula were found in the spinal cord (2-15 days p. i.) and
were able to bind several carbohydrates, suggesting that brain (12-18 days p.i.), and in mice (nonspecific host) in
they contain some lectin-like molecule (s). In conclusion, the spinal cord of 3 inbred strains (2-21/24 days p. i.) and
ES-products contain enzymes like proteases or hyaluroni- brain of 2 inbred strains (3-24 days p. i.). A high affinity of
dases for disruption and degradation of the host’s connecti- T. regenti to the nervous system was proved also in vitro.
ve tissues. Besides these activities, ES-products are suspec- Characterization of the development in ducklings showed
ted to participate in host recognition and attachment to the that the most rapid growth of the body is probably 6-9 days
skin. Further experiments will be performed to increase the p. i. and after 15 days p. i. Concerning the inner organs,
purity of gland products by optimizing the recovery me- three phases of the intestinal development can be distingui-
thod, thus allowing further biochemical characterization. shed. The reproductive organs were detected from 9 days
p. i. The progress in parasite development was also chara-
cterized by lectin probes which showed -methyl-D-man-
Avian schistosomes and mammalian nose and -methyl-D-glucose to be probably the terminal
pathology saccharides of the surface and intestinal epithelium. Sub-
sequent characterization of parasite features within a non-
specific host may contribute to a better understanding of
C. BAYSSADE-DUFOUR
infection failure within mammals.
Muséum National, Biologie parasitaire, 61 rue Buffon,
75005 Paris, France; E-mail: trematod@mnhn.fr
Histopathological observation of the
A question is raised regarding ocellate furcocercariae res- mouse skin and CNS during the
ponsible for cutaneous dermatitis: are they dangerous for
humans? Recent investigations are reported in France, after primary- and reinfection by bird
accidental or experimental expositions of humans and mo- schistosome Trichobilharzia regenti
dels: ducks and Meriones unguiculatus (rodents), the fur-
cocercariae coming from naturally infected Lymnaea spp. P. KOUŘILOVÁ
In asthmatic children, pulmonary disorders increased dra-
matically. Adults, previously in good health, suffered se- Department of Tropical Medicine, 3rd Clinic of Infectious
vere immune complications. In volunteers, immunofluores- and Tropical Diseases, Faculty Hospital Bulovka,
cence of skin biopsies revealed IgG, IgM, C1q, C3, T Studničkova 7, 128 00 Prague 2, Czech Republic;
lymphocytes and mastocytes. Histology evidenced lym- E-mail: pkourilova@hotmail.com
phocytic vasculitis in derm. Ducks allowed to recover adult
worms of Trichobilharzia franki, T. regenti or Ornithobil- In order to evaluate the impact of the cellular immune res-
harzia sp. Pulmonary arteries and bronchial tree of M. un- ponse on further migration of the bird schistosome Tricho-
guiculatus sacrified 7 days after exposition (DAE), showed bilharzia regenti, histopathological changes in the skin and
alterations, near living worms. Lung and liver vessels of the central nervous system (CNS) following the primary-
M. unguiculatus sacrified 17 and 34 DAE displayed lym- and reinfections of immunocompetent and immunosup-
phocytic vasculitis. Do avian schistosomes migrate into pressed mice were studied.
human organs and develop pathology as in mammal mo- During the early phases primary infections - 4 hours and 1
dels? There is a body of presumptions. day p.i., infiltration of neutrophils and eosinophils around
the worms, respectively, were detected in BALB/c and
hr/hr mice strains. From day 2 p.i., no schistosomula were
Development and migration of detected in the mouse skin, however, most of the parasites
Trichobilharzia regenti were found in the thoracic spinal cord where a weak
inflammatory reaction surrounded the immature flukes. In
in ducks and mice the reinfected animals, extensive inflammatory deposits
with eosinophils as dominant cells surrounding the worms,
K. HRÁDKOVÁ probably, delimited the following migration of T. regenti
schistosomula into the CNS. Nevertheless, contrary to 10
Department of Parasitology, Charles University, Viničná 7, times reinfected animals in which no migrating flukes were
128 44 Prague 2, Czech Republic; detected, in case of the 5 times reinfected rodents few
247
worms escaped from the skin and invaded the CNS. In the Following the penetration into the skin of the nonspecific
immunosuppressed mice (SCID), different parts of the (mouse) host, the bird schistosome Trichobilharzia szidati
CNS were invaded by parasites. Observing the clinical cercariae transform to schistosomula and migrate to the
symptoms of the infections, contrary to the immunocompe- lungs, where they even feed on blood cells. In the lungs the
tent mice, in the immunosuppressed hosts the affection of parasites survive for relatively long, however, limited pe-
the CNS led to more severe neuromotor symptoms. riods. To date, factors influencing the parasite limited sur-
The investigation is supported by the Grant Agencies of vival in the organ are not known with reasonable accur-
the Czech Ministry of Health (o. NJ-6718-3) and Charles racy. Therefore, the aim of the study was to evaluate im-
University (38/2000/1LF). mune response against the parasites during various phases
of the pulmonary primary infections in a nonspecific host
(BALB/c mice).
Trematodes of the family Schistosomula were detected in host lungs during a period
of 1 to 7 days post-infection (p.i.). However, the living
Bilharziellidae in the fauna of schistosomula were found only until day 6 p.i.; 7 days p.i.
Uzbekistan only dead parasites were detected. A comparison of the
various lung schistosomula showed the parasite growth on-
E. B. SHAKARBAEV, D. A. AZIMOV ly till day 5 p.i.; no differences between found between 5-
and 6-days-old schistosomula. However, histological ob-
Institute of Zoology, Uzbek Academy of Sciences, A. servation showed that the timing of infection influenced
Niyazova street 1, Tashkent 700095, Uzbekistan; the intensity of pulmonary pathologies; the most intense
E-mail: uzzool@uzsci.net inflammatory reactions were detected around the older
worms. Except for the lungs, no parasites were found in
The family Bilharziellidae comprises 9 genera and 57 spe- any host organs.
cies, of which in fish-eating birds Bilharziella polonica, The retarded growth as well as an inflammatory reaction
Trichobilharzia ocellata, Dendritobilharzia loossi and Gi- around the pulmonary schistosomula suggests that the de-
gantobilharzia acotylea have been recorded. velopment of the parasites in the nonspecific host lungs is
These trematodes are widespread among ducks, geese and limited, probably, by lacking some nutritional substances
the other game in almost all regions of Uzbekistan. as well as by the stimulation of the host immune reaction.
Various species of fresh-water molluscs inhabiting water The investigation is supported by the Grant Agencies of
bodies in the basins of the rivers Syr Darya and Amu the Czech Ministry of Health (o. NJ-6718-3) and Chares
Darya take part in the life cycles of the trematodes the University (38/2000/1LF).
family Bilharziellidae. Hence, Lymnaea auricularia and L.
stagnalis are intermediate hosts of T. ocellata; Planorbis
planorbis and Anisus septemgyratus of B. polonica; A. New findings of schistosomes in
spirorbis of D. loossi; Physa fontinalis and A. spirorbis of
G. acotylea.
wildfowl and snails
The epizootic process at these trematodoses has an interpo-
pulation character: parasite - intermediate host - definitive J. RUDOLFOVÁ
host.
Department of Parasitology, Charles University, Viničná 7,
Thus, populations of bilharziellids interact with the compo-
128 44 Praha 2, Czech Republic;
nents of a specific biogeocenosis, which have been formed
E-mail: rudolfov@freemejl.cz
in the course of evolution of the system parasite-host for
the provision of vital needs of the parasites. The experimental definitive hosts of bird schistosomes are
often discovered, whereas the natural final hosts are un-
known. Our work proved the occurrence of nasal bird schi-
Pulmonary phase during a nonspecific stosomes of the genus Trichobilharzia in wild anatid birds
(Anas platyrhynchos, Aythya fuligula, A. ferina) in the
host primary infections by Czech Republic. Following experimental infections of Ra-
Trichobilharzia szidati dix peregra (an autochtonous snail species) and domestic
ducks affirmed that these parasites are able to complete
their life cycles under the conditions of Central Europe.
J. MORAVCOVÁ We also found a visceral bird schistosome in mute swan
(Cygnus olor). It occurs with rather high prevalence. In our
Department of Tropical Medicine, 3rd Clinic of Infectious view it belongs to Trichobilharzia filiformis (Szidat, 1939)
and Tropical Diseases, Charles University, Faculty Hospi- McMullen et Beaver, 1945, but this determination remains
tal Bulovka, Studničkova 7, 128 00 Prague 2, Czech Re- to be confirmed.
public; E-mail: jmora@lf1.cuni.cz The examination of physid and small planorbid snails
248
showed the presence of cercariae of bird schistosomes in Hebrew University, Hadassah Medical School, Jerusalem,
specimens of Anisus vortex, Gyraulus albus, Segmentina Israel; E-mail: jhertel@biologie.uni-erlangen.de
nitida (Planorbidae) and Physa fontinalis (Physidae). Ho-
wever, their prevalence is very low and their determination Up to now, the detection of bird schistosomes depends on
must be done. difficult microscopic examinations. The following DNA
markers, that base on a 396 bp tandem repeated DNA se-
quence (T1323), cloned from Trichobilharzia ocellata
Molecular analysis of European DNA, will make it easy for all laboratories to identify T.
ocellata, T. franki and T. regenti in snails and plankton
Trichobilharzia species probes. The T1323 sequence reperesents between 1 and 2
% (7000-14000 copies) of the genome of the 3 Trichobil-
J. DVOŘÁK harzia species. Signals with 25 pg to 100 pg Trichobilhar-
zia DNA occur by dot-blot hybridization, probed with the
Department of Parasitology, Charles University, Viničná 7, T1323 insert, while even 10 ng DNA of 9 other related or
CZ-12844 Prague 2, Czech Republic; sympatric trematode species are undetectable. PCR pri-
E-mail: hdvorak@natur.cuni.cz mers, based on the T1323 sequence, are much more sensi-
tive (less than 100 fg detectable) and also highly specific.
Trichobilharzia represents the largest genus of the family They are suitable to amplify specifically 1 cercaria in 0.5 g
Schistosomatidae with more than 40 species the validity of plankton and 2 cercariae in 0.5 g Lymnea stagnalis samp-
which is debatable. This taxonomic confusion is also les.
among the European Trichobilharzia species. In Europe,
only two clearly defined species (T. franki Müller et
Kimmig, 1994 and T. regenti Horák, Kolářová et Dvořák,
1998) exist. The third species T. szidati Neuhaus, 1952 is
Immunobiology of digenean parasite-
in an unclear taxonomical position. The name represents snail interactions
probably a junior synonym of T. ocellata (La Valette,
1855) Brumpt, 1931. The species determination of tricho- C. M. ADEMA
bilharzians is extremely difficult. Therefore, it is necessary
to describe the life cycle, developmental stages and host Biology, University of New Mexico, Albuquerque NM,
specificity. Because this effort is not sufficient in certain USA; E-mail: coenadem@unm.edu
cases, molecular data are required.
We sequenced internal transcribed spacers (ITS1 and Cercarial dermatitis can result from contact with water that
ITS2) and 5.8S ribosomal RNA gene of three European contains cercaria from avian schistosomes (digenean tre-
Trichobilharzia species (T. regenti, T. szidati and T. fran- matodes). These cercaria originate from snails that serve as
ki). Results showed that ITS1 and ITS2 sequences of the intermediate hosts in the life cycle of these parasites. Ho-
investigated trichobilharzians are useful for species identi- wever, snails are not passive hosts. Most pathogens are
fication. Repetitive elements in different number and eliminated by humoral and cellular components of the
length were found in ITS1 of all three Trichobilharzia spe- snail’s internal defense system. Upon recognition, invading
cies. The elements contained a sequence motif similar to trematodes are encapsulated by hemocytes (professional
the recombinational hot-spot sites of phage λ, Escherichia phagocytes) and killed by cell-mediated cytotoxicity. For
coli and Neurospora crassa. Phylogenetic study showed survival in such a potentially hostile environment, dige-
relation of the visceral species T. franki to the nasal T. re- neans employ molecular masking and mimicry to evade re-
genti, rather than to the visceral T. szidati. The newly de- cognition or interference to inhibit defense responses of the
signed primer, which is specific for T. regenti, might be snail host. Often, such survival strategies have a degree of
used as a tool for diagnosis of this potential neuropatho- specificity, and the resulting immunobiological compatibi-
gen. lity of digeneans and snail hosts may be restricted to spe-
cies or strain-level. Molecular techniques are used to study
the interactions between the digenean Echinostoma pa-
raensei and the snail Biomphalaria glabrata. Efforts to
Diagnostic markers for tandem characterize parasite-released factors that inhibit the fun-
repeated bird schistosome DNA ctioning of snail hemocytes are ongoing. Analysis of res-
ponse to infection has revealed a diverse gene family of
J. HERTEL, J. HAMBURGER1, B. HABERL, snail plasma lectins that bind to parasite antigens, the so-
W. HAAS called fibrinogen-related proteins (FREPs). Further immu-
nobiological study of digenean-snail associations may help
Department of Zoology I, University Erlangen-Nürnberg, explain the naturally occurring patterns of parasite-host
Germany; 1The Kuvin Centre for the Study of Infectious compatibility that contribute to the transmission of cerca-
and Tropical Diseases, Department of Parasitology, rial dermatitis.
249
Survey of trematode infections in Karyotypes of avian schistosomes
Spring Lake Regional Park, California,
M. ŠPAKULOVÁ
USA
Parasitological Institute, Slovak Academy of Sciences,
A.K. BEI, J. P. SALTER, K. C. LIM, Hlinkova 3, 040 01 Košice, Slovak Republic;
J. H. MCKERROW E-mail: spakulma@saske.sk
Department of Pathology, University of California, 513 A karyological comparison of 11 avian schistosome spe-
Parnassus, San Francisco, California 94143, United States cies - Austrobilharzia variglandis, Bilharziella polonica,
of America; E-mail: bei@fas.harvard.edu Gigantobilharzia huronensis, Ornithobilharzia canalicula-
ta (e.g. Short 1983; Baršiené 1993) with 7 Trichobilharzia
In the early summer of 2000, an outbreak of “swimmers’ spp., has been performed.
itch” disrupted a swimming hole at Spring Lake Regional The investigation showed that all the karyotypes revealed
Park in Santa Rosa, California, USA. The swimming la- some common features. Thus, chromosomes are relatively
goon, adjacent to the lake, was thought to be infested with large, measuring up to 13 µm; their diploid number is 16
Trichobilharzia, the causative agent of cercarial dermatitis, (except of 2 species with 18 chromosomes); chromosomes
or “swimmers’ itch”. The swimming lagoon was treated of the fifth autosomal pair are often satellited; the sex is
with copper sulphate and chlorinated in an attempt to kill determined by the ZZmale/ZWfemale mechanism. The
the snails carrying the parasite. Upon sampling from va- Z sex chromosome is the largest or the second largest ele-
rious regions of the lake over a course of two summers, ment of the set while the W chromosome is substantially
two trematodes were discovered in Physa snails: Echino- smaller.
paryphium and a furcocercous cercaria. Comparisons of Intergeneric differences relate to a gross morphology of
the cercariae to various Schistosomatidae were performed both autosomal and sex chromosomes. Visceral species of
using Alizarin Red staining, morphology analysis, and 28S the karyologically best known genus Trichobilharzia differ
ribosome sequence. The results suggest that the parasite is predominantly by the size and morphology of the sex chro-
not an avian schistosome, but rather of family Diplosto- mosomes Z and W. The nasal congeneric species T. regenti
matidae. These particular fork-tailed trematodes from both shows supernumerary B chromosomes which were detec-
2000 and 2001 are therefore not responsible for the out- ted for the first time in the group of both bird and mammal
break of cercarial dermatitis. schistosomes.
250